Sample records for account potential confounders

  1. Statin adherence and risk of acute cardiovascular events among women: a cohort study accounting for time-dependent confounding affected by previous adherence.

    PubMed

    Lavikainen, Piia; Helin-Salmivaara, Arja; Eerola, Mervi; Fang, Gang; Hartikainen, Juha; Huupponen, Risto; Korhonen, Maarit Jaana

    2016-06-03

    Previous studies on the effect of statin adherence on cardiovascular events in the primary prevention of cardiovascular disease have adjusted for time-dependent confounding, but potentially introduced bias into their estimates as adherence and confounders were measured simultaneously. We aimed to evaluate the effect when accounting for time-dependent confounding affected by previous adherence as well as time sequence between factors. Retrospective cohort study. Finnish healthcare registers. Women aged 45-64 years initiating statin use for primary prevention of cardiovascular disease in 2001-2004 (n=42 807). Acute cardiovascular event defined as a composite of acute coronary syndrome and acute ischaemic stroke was our primary outcome. Low-energy fractures were used as a negative control outcome to evaluate the healthy-adherer effect. During the 3-year follow-up, 474 women experienced the primary outcome event and 557 suffered a low-energy fracture. The causal HR estimated with marginal structural model for acute cardiovascular events for all the women who remained adherent (proportion of days covered ≥80%) to statin therapy during the previous adherence assessment year was 0.78 (95% CI: 0.65 to 0.94) when compared with everybody remaining non-adherent (proportion of days covered <80%). The result was robust against alternative model specifications. Statin adherers had a potentially reduced risk of experiencing low-energy fractures compared with non-adherers (HR 0.90, 95% CI 0.76 to 1.07). Our study, which took into account the time dependence of adherence and confounders, as well as temporal order between these factors, is support for the concept that adherence to statins in women in primary prevention decreases the risk of acute cardiovascular events by about one-fifth in comparison to non-adherence. However, part of the observed effect of statin adherence on acute cardiovascular events may be due to the healthy-adherer effect. Published by the BMJ Publishing

  2. Assessing Sensitivity to Unmeasured Confounding Using a Simulated Potential Confounder

    ERIC Educational Resources Information Center

    Carnegie, Nicole Bohme; Harada, Masataka; Hill, Jennifer L.

    2016-01-01

    A major obstacle to developing evidenced-based policy is the difficulty of implementing randomized experiments to answer all causal questions of interest. When using a nonexperimental study, it is critical to assess how much the results could be affected by unmeasured confounding. We present a set of graphical and numeric tools to explore the…

  3. The ACCE method: an approach for obtaining quantitative or qualitative estimates of residual confounding that includes unmeasured confounding

    PubMed Central

    Smith, Eric G.

    2015-01-01

    Background:  Nonrandomized studies typically cannot account for confounding from unmeasured factors.  Method:  A method is presented that exploits the recently-identified phenomenon of  “confounding amplification” to produce, in principle, a quantitative estimate of total residual confounding resulting from both measured and unmeasured factors.  Two nested propensity score models are constructed that differ only in the deliberate introduction of an additional variable(s) that substantially predicts treatment exposure.  Residual confounding is then estimated by dividing the change in treatment effect estimate between models by the degree of confounding amplification estimated to occur, adjusting for any association between the additional variable(s) and outcome. Results:  Several hypothetical examples are provided to illustrate how the method produces a quantitative estimate of residual confounding if the method’s requirements and assumptions are met.  Previously published data is used to illustrate that, whether or not the method routinely provides precise quantitative estimates of residual confounding, the method appears to produce a valuable qualitative estimate of the likely direction and general size of residual confounding. Limitations:  Uncertainties exist, including identifying the best approaches for: 1) predicting the amount of confounding amplification, 2) minimizing changes between the nested models unrelated to confounding amplification, 3) adjusting for the association of the introduced variable(s) with outcome, and 4) deriving confidence intervals for the method’s estimates (although bootstrapping is one plausible approach). Conclusions:  To this author’s knowledge, it has not been previously suggested that the phenomenon of confounding amplification, if such amplification is as predictable as suggested by a recent simulation, provides a logical basis for estimating total residual confounding. The method's basic approach is

  4. Overview of potential procedural and participant-related confounds for neuroimaging of the resting state

    PubMed Central

    Duncan, Niall W.; Northoff, Georg

    2013-01-01

    Studies of intrinsic brain activity in the resting state have become increasingly common. A productive discussion of what analysis methods are appropriate, of the importance of physiologic correction and of the potential interpretations of results has been ongoing. However, less attention has been paid to factors other than physiologic noise that may confound resting-state experiments. These range from straightforward factors, such as ensuring that participants are all instructed in the same manner, to more obscure participant-related factors, such as body weight. We provide an overview of such potentially confounding factors, along with some suggested approaches for minimizing their impact. A particular theme that emerges from the overview is the range of systematic differences between types of study groups (e.g., between patients and controls) that may influence resting-state study results. PMID:22964258

  5. Accounting for the Confound of Meninges in Segmenting Entorhinal and Perirhinal Cortices in T1-Weighted MRI.

    PubMed

    Xie, Long; Wisse, Laura E M; Das, Sandhitsu R; Wang, Hongzhi; Wolk, David A; Manjón, Jose V; Yushkevich, Paul A

    2016-10-01

    Quantification of medial temporal lobe (MTL) cortices, including entorhinal cortex (ERC) and perirhinal cortex (PRC), from in vivo MRI is desirable for studying the human memory system as well as in early diagnosis and monitoring of Alzheimer's disease. However, ERC and PRC are commonly over-segmented in T1-weighted (T1w) MRI because of the adjacent meninges that have similar intensity to gray matter in T1 contrast. This introduces errors in the quantification and could potentially confound imaging studies of ERC/PRC. In this paper, we propose to segment MTL cortices along with the adjacent meninges in T1w MRI using an established multi-atlas segmentation framework together with super-resolution technique. Experimental results comparing the proposed pipeline with existing pipelines support the notion that a large portion of meninges is segmented as gray matter by existing algorithms but not by our algorithm. Cross-validation experiments demonstrate promising segmentation accuracy. Further, agreement between the volume and thickness measures from the proposed pipeline and those from the manual segmentations increase dramatically as a result of accounting for the confound of meninges. Evaluated in the context of group discrimination between patients with amnestic mild cognitive impairment and normal controls, the proposed pipeline generates more biologically plausible results and improves the statistical power in discriminating groups in absolute terms comparing to other techniques using T1w MRI. Although the performance of the proposed pipeline is inferior to that using T2-weighted MRI, which is optimized to image MTL sub-structures, the proposed pipeline could still provide important utilities in analyzing many existing large datasets that only have T1w MRI available.

  6. Assessing Omitted Confounder Bias in Multilevel Mediation Models.

    PubMed

    Tofighi, Davood; Kelley, Ken

    2016-01-01

    To draw valid inference about an indirect effect in a mediation model, there must be no omitted confounders. No omitted confounders means that there are no common causes of hypothesized causal relationships. When the no-omitted-confounder assumption is violated, inference about indirect effects can be severely biased and the results potentially misleading. Despite the increasing attention to address confounder bias in single-level mediation, this topic has received little attention in the growing area of multilevel mediation analysis. A formidable challenge is that the no-omitted-confounder assumption is untestable. To address this challenge, we first analytically examined the biasing effects of potential violations of this critical assumption in a two-level mediation model with random intercepts and slopes, in which all the variables are measured at Level 1. Our analytic results show that omitting a Level 1 confounder can yield misleading results about key quantities of interest, such as Level 1 and Level 2 indirect effects. Second, we proposed a sensitivity analysis technique to assess the extent to which potential violation of the no-omitted-confounder assumption might invalidate or alter the conclusions about the indirect effects observed. We illustrated the methods using an empirical study and provided computer code so that researchers can implement the methods discussed.

  7. Multisample adjusted U-statistics that account for confounding covariates.

    PubMed

    Satten, Glen A; Kong, Maiying; Datta, Somnath

    2018-06-19

    Multisample U-statistics encompass a wide class of test statistics that allow the comparison of 2 or more distributions. U-statistics are especially powerful because they can be applied to both numeric and nonnumeric data, eg, ordinal and categorical data where a pairwise similarity or distance-like measure between categories is available. However, when comparing the distribution of a variable across 2 or more groups, observed differences may be due to confounding covariates. For example, in a case-control study, the distribution of exposure in cases may differ from that in controls entirely because of variables that are related to both exposure and case status and are distributed differently among case and control participants. We propose to use individually reweighted data (ie, using the stratification score for retrospective data or the propensity score for prospective data) to construct adjusted U-statistics that can test the equality of distributions across 2 (or more) groups in the presence of confounding covariates. Asymptotic normality of our adjusted U-statistics is established and a closed form expression of their asymptotic variance is presented. The utility of our approach is demonstrated through simulation studies, as well as in an analysis of data from a case-control study conducted among African-Americans, comparing whether the similarity in haplotypes (ie, sets of adjacent genetic loci inherited from the same parent) occurring in a case and a control participant differs from the similarity in haplotypes occurring in 2 control participants. Copyright © 2018 John Wiley & Sons, Ltd.

  8. The relationship between urinary tract infection during pregnancy and preeclampsia: causal, confounded or spurious?

    PubMed

    Karmon, Anatte; Sheiner, Eyal

    2008-06-01

    Preeclampsia is a major cause of maternal morbidity, although its precise etiology remains elusive. A number of studies suggest that urinary tract infection (UTI) during the course of gestation is associated with elevated risk for preeclampsia, while others have failed to prove such an association. In our medical center, pregnant women who were exposed to at least one UTI episode during pregnancy were 1.3 times more likely to have mild preeclampsia and 1.8 times more likely to have severe preeclampsia as compared to unexposed women. Our results are based on univariate analyses and are not adjusted for potential confounders. This editorial aims to discuss the relationship between urinary tract infection and preeclampsia, as well as examine the current problems regarding the interpretation of this association. Although the relationship between UTI and preeclampsia has been demonstrated in studies with various designs, carried-out in a variety of settings, the nature of this association is unclear. By taking into account timeline, dose-response effects, treatment influences, and potential confounders, as well as by neutralizing potential biases, future studies may be able to clarify the relationship between UTI and preeclampsia by determining if it is causal, confounded, or spurious.

  9. Reanalysis of mortality from lung cancer among diatomaceous earth industry workers, with consideration of potential confounding by asbestos exposure.

    PubMed Central

    Checkoway, H; Heyer, N J; Demers, P A; Gibbs, G W

    1996-01-01

    OBJECTIVE: To evaluate the potential for confounding from asbestos exposure, primarily chrysotile, on the relation between crystalline silica and mortality from lung cancer among diatomaceous earth (diatomite) workers. METHODS: A reanalysis of a cohort mortality study of diatomite workers was performed to take into account quantitative estimates of asbestos exposure. The reanalysis was limited to a subset of the original cohort, comprising 2266 white men for whom asbestos exposure could be reconstructed with greatest confidence. Comparisons between mortality from lung cancer (standardised mortality ratios (SMR)) were made between rates for 1942-87 for United States white men, and workers cross classified according to cumulative exposures to crystalline silica and asbestos. Comparisons of internal rates, involving Poisson regression modeling, were conducted for exposure to crystalline silica, with and without adjustment for asbestos exposure. Exposures were lagged by 15 years to take into account disease latency. RESULTS: There was an overall excess of lung cancer (SMR 1.41; 52 observed). The SMRs for four categories of increasing crystalline silica among the workers not exposed to asbestos were 1.13, 0.87, 2.14, 2.00. An SMR of 8.31 (three observed) was found for workers with the highest cumulative exposure to both dusts. Internal analysis, after adjustment for asbestos exposure, yielded rate ratios for categories of exposure to crystalline silica: 1.00 (reference), 1.37, 1.80, and 1.79. CONCLUSIONS: Asbestos exposure was not an important confounder of the association between crystalline silica and mortality from lung cancer in this cohort. Although based on a small number of deaths from lung cancer, the data suggest possible synergy between these exposures. An extended follow up of this cohort is in progress and should enable better assessments of independent and combined effects on risk of lung cancer. PMID:8882123

  10. Bayesian effect estimation accounting for adjustment uncertainty.

    PubMed

    Wang, Chi; Parmigiani, Giovanni; Dominici, Francesca

    2012-09-01

    Model-based estimation of the effect of an exposure on an outcome is generally sensitive to the choice of which confounding factors are included in the model. We propose a new approach, which we call Bayesian adjustment for confounding (BAC), to estimate the effect of an exposure of interest on the outcome, while accounting for the uncertainty in the choice of confounders. Our approach is based on specifying two models: (1) the outcome as a function of the exposure and the potential confounders (the outcome model); and (2) the exposure as a function of the potential confounders (the exposure model). We consider Bayesian variable selection on both models and link the two by introducing a dependence parameter, ω, denoting the prior odds of including a predictor in the outcome model, given that the same predictor is in the exposure model. In the absence of dependence (ω= 1), BAC reduces to traditional Bayesian model averaging (BMA). In simulation studies, we show that BAC, with ω > 1, estimates the exposure effect with smaller bias than traditional BMA, and improved coverage. We, then, compare BAC, a recent approach of Crainiceanu, Dominici, and Parmigiani (2008, Biometrika 95, 635-651), and traditional BMA in a time series data set of hospital admissions, air pollution levels, and weather variables in Nassau, NY for the period 1999-2005. Using each approach, we estimate the short-term effects of on emergency admissions for cardiovascular diseases, accounting for confounding. This application illustrates the potentially significant pitfalls of misusing variable selection methods in the context of adjustment uncertainty. © 2012, The International Biometric Society.

  11. Accounting for genetic and environmental confounds in associations between parent and child characteristics: a systematic review of children-of-twins studies.

    PubMed

    McAdams, Tom A; Neiderhiser, Jenae M; Rijsdijk, Fruhling V; Narusyte, Jurgita; Lichtenstein, Paul; Eley, Thalia C

    2014-07-01

    Parental psychopathology, parenting style, and the quality of intrafamilial relationships are all associated with child mental health outcomes. However, most research can say little about the causal pathways underlying these associations. This is because most studies are not genetically informative and are therefore not able to account for the possibility that associations are confounded by gene-environment correlation. That is, biological parents not only provide a rearing environment for their child, but also contribute 50% of their genes. Any associations between parental phenotype and child phenotype are therefore potentially confounded. One technique for disentangling genetic from environmental effects is the children-of-twins (COT) method. This involves using data sets comprising twin parents and their children to distinguish genetic from environmental associations between parent and child phenotypes. The COT technique has grown in popularity in the last decade, and we predict that this surge in popularity will continue. In the present article we explain the COT method for those unfamiliar with its use. We present the logic underlying this approach, discuss strengths and weaknesses, and highlight important methodological considerations for researchers interested in the COT method. We also cover variations on basic COT approaches, including the extended-COT method, capable of distinguishing forms of gene-environment correlation. We then present a systematic review of all the behavioral COT studies published to date. These studies cover such diverse phenotypes as psychosis, substance abuse, internalizing, externalizing, parenting, and marital difficulties. In reviewing this literature, we highlight past applications, identify emergent patterns, and suggest avenues for future research. PsycINFO Database Record (c) 2014 APA, all rights reserved.

  12. Addressing unmeasured confounding in comparative observational research.

    PubMed

    Zhang, Xiang; Faries, Douglas E; Li, Hu; Stamey, James D; Imbens, Guido W

    2018-04-01

    Observational pharmacoepidemiological studies can provide valuable information on the effectiveness or safety of interventions in the real world, but one major challenge is the existence of unmeasured confounder(s). While many analytical methods have been developed for dealing with this challenge, they appear under-utilized, perhaps due to the complexity and varied requirements for implementation. Thus, there is an unmet need to improve understanding the appropriate course of action to address unmeasured confounding under a variety of research scenarios. We implemented a stepwise search strategy to find articles discussing the assessment of unmeasured confounding in electronic literature databases. Identified publications were reviewed and characterized by the applicable research settings and information requirements required for implementing each method. We further used this information to develop a best practice recommendation to help guide the selection of appropriate analytical methods for assessing the potential impact of unmeasured confounding. Over 100 papers were reviewed, and 15 methods were identified. We used a flowchart to illustrate the best practice recommendation which was driven by 2 critical components: (1) availability of information on the unmeasured confounders; and (2) goals of the unmeasured confounding assessment. Key factors for implementation of each method were summarized in a checklist to provide further assistance to researchers for implementing these methods. When assessing comparative effectiveness or safety in observational research, the impact of unmeasured confounding should not be ignored. Instead, we suggest quantitatively evaluating the impact of unmeasured confounding and provided a best practice recommendation for selecting appropriate analytical methods. Copyright © 2018 John Wiley & Sons, Ltd.

  13. Cellular GFP Toxicity and Immunogenicity: Potential Confounders in in Vivo Cell Tracking Experiments.

    PubMed

    Ansari, Amir Mehdi; Ahmed, A Karim; Matsangos, Aerielle E; Lay, Frank; Born, Louis J; Marti, Guy; Harmon, John W; Sun, Zhaoli

    2016-10-01

    Green Fluorescent protein (GFP), used as a cellular tag, provides researchers with a valuable method of measuring gene expression and cell tracking. However, there is evidence to suggest that the immunogenicity and cytotoxicity of GFP potentially confounds the interpretation of in vivo experimental data. Studies have shown that GFP expression can deteriorate over time as GFP tagged cells are prone to death. Therefore, the cells that were originally marked with GFP do not survive and cannot be accurately traced over time. This review will present current evidence for the immunogenicity and cytotoxicity of GFP in in vivo studies by characterizing these responses.

  14. How Confounder Strength Can Affect Allocation of Resources in Electronic Health Records.

    PubMed

    Lynch, Kristine E; Whitcomb, Brian W; DuVall, Scott L

    2018-01-01

    When electronic health record (EHR) data are used, multiple approaches may be available for measuring the same variable, introducing potentially confounding factors. While additional information may be gleaned and residual confounding reduced through resource-intensive assessment methods such as natural language processing (NLP), whether the added benefits offset the added cost of the additional resources is not straightforward. We evaluated the implications of misclassification of a confounder when using EHRs. Using a combination of simulations and real data surrounding hospital readmission, we considered smoking as a potential confounder. We compared ICD-9 diagnostic code assignment, which is an easily available measure but has the possibility of substantial misclassification of smoking status, with NLP, a method of determining smoking status that more expensive and time-consuming than ICD-9 code assignment but has less potential for misclassification. Classification of smoking status with NLP consistently produced less residual confounding than the use of ICD-9 codes; however, when minimal confounding was present, differences between the approaches were small. When considerable confounding is present, investing in a superior measurement tool becomes advantageous.

  15. Understanding Confounding Effects in Linguistic Coordination: An Information-Theoretic Approach

    PubMed Central

    Gao, Shuyang; Ver Steeg, Greg; Galstyan, Aram

    2015-01-01

    We suggest an information-theoretic approach for measuring stylistic coordination in dialogues. The proposed measure has a simple predictive interpretation and can account for various confounding factors through proper conditioning. We revisit some of the previous studies that reported strong signatures of stylistic accommodation, and find that a significant part of the observed coordination can be attributed to a simple confounding effect—length coordination. Specifically, longer utterances tend to be followed by longer responses, which gives rise to spurious correlations in the other stylistic features. We propose a test to distinguish correlations in length due to contextual factors (topic of conversation, user verbosity, etc.) and turn-by-turn coordination. We also suggest a test to identify whether stylistic coordination persists even after accounting for length coordination and contextual factors. PMID:26115446

  16. Directed acyclic graphs (DAGs): an aid to assess confounding in dental research.

    PubMed

    Merchant, Anwar T; Pitiphat, Waranuch

    2002-12-01

    Confounding, a special type of bias, occurs when an extraneous factor is associated with the exposure and independently affects the outcome. In order to get an unbiased estimate of the exposure-outcome relationship, we need to identify potential confounders, collect information on them, design appropriate studies, and adjust for confounding in data analysis. However, it is not always clear which variables to collect information on and adjust for in the analyses. Inappropriate adjustment for confounding can even introduce bias where none existed. Directed acyclic graphs (DAGs) provide a method to select potential confounders and minimize bias in the design and analysis of epidemiological studies. DAGs have been used extensively in expert systems and robotics. Robins (1987) introduced the application of DAGs in epidemiology to overcome shortcomings of traditional methods to control for confounding, especially as they related to unmeasured confounding. DAGs provide a quick and visual way to assess confounding without making parametric assumptions. We introduce DAGs, starting with definitions and rules for basic manipulation, stressing more on applications than theory. We then demonstrate their application in the control of confounding through examples of observational and cross-sectional epidemiological studies.

  17. Evaluation of uncontrolled confounding in studies of environmental exposures and neurobehavioral testing in children.

    PubMed

    Mink, Pamela J; Goodman, Michael; Barraj, Leila M; Imrey, Harriet; Kelsh, Michael A; Yager, Janice

    2004-07-01

    Neurobehavioral tests are commonly used in studies of children exposed to low-level environmental concentrations of compounds known to be neurotoxic at higher levels. However, uncontrolled or incomplete control for confounding makes interpretation of results problematic because effects of confounders are often stronger than the effects of primary interest. We examined a priori the potential impact of confounding in a hypothetical study evaluating the association of a potentially neurotoxic environmental exposure with neurobehavioral function in children. We used 2 outcome measures: the Bayley Scales of Infant Development Mental Development Index and the Stanford-Binet Intelligence Scale Composite Score. We selected 3 potential confounders: maternal intelligence, home environment, and socioeconomic status as measured by years of parental education. We conducted 3 sets of analyses measuring the effect of each of the 3 confounding factors alone, 2 confounders acting simultaneously, and all 3 confounders acting simultaneously. Relatively small differences (0.5 standard deviations) in confounding variables between "exposed" and "unexposed" groups, if unmeasured and unaccounted for in the analysis, could produce spurious differences in cognitive test scores. The magnitude of this difference (3-10 points) has been suggested to have a meaningful impact in populations. The method of measuring confounders (eg, maternal intelligence) could also substantially affect the results. It is important to carefully consider the impact of potential confounders during the planning stages of an observational study. Study-to-study differences in neurobehavioral outcomes with similar environmental exposures could be partially explained by differences in the adjustment for confounding variables. Copyright 2004 Lippincott Williams and Wilkins

  18. Can statistic adjustment of OR minimize the potential confounding bias for meta-analysis of case-control study? A secondary data analysis.

    PubMed

    Liu, Tianyi; Nie, Xiaolu; Wu, Zehao; Zhang, Ying; Feng, Guoshuang; Cai, Siyu; Lv, Yaqi; Peng, Xiaoxia

    2017-12-29

    Different confounder adjustment strategies were used to estimate odds ratios (ORs) in case-control study, i.e. how many confounders original studies adjusted and what the variables are. This secondary data analysis is aimed to detect whether there are potential biases caused by difference of confounding factor adjustment strategies in case-control study, and whether such bias would impact the summary effect size of meta-analysis. We included all meta-analyses that focused on the association between breast cancer and passive smoking among non-smoking women, as well as each original case-control studies included in these meta-analyses. The relative deviations (RDs) of each original study were calculated to detect how magnitude the adjustment would impact the estimation of ORs, compared with crude ORs. At the same time, a scatter diagram was sketched to describe the distribution of adjusted ORs with different number of adjusted confounders. Substantial inconsistency existed in meta-analysis of case-control studies, which would influence the precision of the summary effect size. First, mixed unadjusted and adjusted ORs were used to combine individual OR in majority of meta-analysis. Second, original studies with different adjustment strategies of confounders were combined, i.e. the number of adjusted confounders and different factors being adjusted in each original study. Third, adjustment did not make the effect size of original studies trend to constringency, which suggested that model fitting might have failed to correct the systematic error caused by confounding. The heterogeneity of confounder adjustment strategies in case-control studies may lead to further bias for summary effect size in meta-analyses, especially for weak or medium associations so that the direction of causal inference would be even reversed. Therefore, further methodological researches are needed, referring to the assessment of confounder adjustment strategies, as well as how to take this kind

  19. The assessment of cortisol in human hair: associations with sociodemographic variables and potential confounders.

    PubMed

    Dettenborn, L; Tietze, A; Kirschbaum, C; Stalder, T

    2012-11-01

    To inform the future use of hair cortisol measurement, we have investigated influences of potential confounding variables (natural hair colour, frequency of hair washes, age, sex, oral contraceptive (OC) use and smoking status) on hair cortisol levels. The main study sample comprised 360 participants (172 women) covering a wide range of ages (1-91 years; mean = 25.95). In addition, to more closely examine influences of natural hair colour and young age on hair cortisol levels, two additional samples comprising 69 participants with natural blond or dark brown hair (hair colour sample) as well as 28 young children and 34 adults (young age sample) were recruited. Results revealed a lack of an effect for natural hair colour, OC use, and smoking status on hair cortisol levels (all p's >0.10). No influence of frequency of hair washes was seen for proximal hair segments (p = 0.335) but for the third hair segment indicating lower cortisol content (p = 0.008). We found elevated hair cortisol levels in young children and older adults (p < 0.001). Finally, men showed higher hair cortisol levels than women (p = 0.002). The present data indicate that hair cortisol measurement provides a useful tool in stress-related psychobiological research when applied with the consideration of possible confounders including age and sex.

  20. Gene × environment interaction studies have not properly controlled for potential confounders: the problem and the (simple) solution.

    PubMed

    Keller, Matthew C

    2014-01-01

    Candidate gene × environment (G × E) interaction research tests the hypothesis that the effects of some environmental variable (e.g., childhood maltreatment) on some outcome measure (e.g., depression) depend on a particular genetic polymorphism. Because this research is inherently nonexperimental, investigators have been rightly concerned that detected interactions could be driven by confounders (e.g., ethnicity, gender, age, socioeconomic status) rather than by the specified genetic or environmental variables per se. In an attempt to eliminate such alternative explanations for detected G × E interactions, investigators routinely enter the potential confounders as covariates in general linear models. However, this practice does not control for the effects these variables might have on the G × E interaction. Rather, to properly control for confounders, researchers need to enter the covariate × environment and the covariate × gene interaction terms in the same model that tests the G × E term. In this manuscript, I demonstrate this point analytically and show that the practice of improperly controlling for covariates is the norm in the G × E interaction literature to date. Thus, many alternative explanations for G × E findings that investigators had thought were eliminated have not been. © 2013 Society of Biological Psychiatry Published by Society of Biological Psychiatry All rights reserved.

  1. Influence of potentially confounding factors on sea urchin porewater toxicity tests

    USGS Publications Warehouse

    Carr, R.S.; Biedenbach, J.M.; Nipper, M.

    2006-01-01

    The influence of potentially confounding factors has been identified as a concern for interpreting sea urchin porewater toxicity test data. The results from >40 sediment-quality assessment surveys using early-life stages of the sea urchin Arbacia punctulata were compiled and examined to determine acceptable ranges of natural variables such as pH, ammonia, and dissolved organic carbon on the fertilization and embryological development endpoints. In addition, laboratory experiments were also conducted with A. punctulata and compared with information from the literature. Pore water with pH as low as 6.9 is an unlikely contributor to toxicity for the fertilization and embryological development tests with A. punctulata. Other species of sea urchin have narrower pH tolerance ranges. Ammonia is rarely a contributing factor in pore water toxicity tests using the fertilization endpoint, but the embryological development endpoint may be influenced by ammonia concentrations commonly found in porewater samples. Therefore, ammonia needs to be considered when interpreting results for the embryological development test. Humic acid does not affect sea urchin fertilization at saturation concentrations, but it could have an effect on the embryological development endpoint at near-saturation concentrations. There was no correlation between sediment total organic carbon concentrations and porewater dissolved organic carbon concentrations. Because of the potential for many varying substances to activate parthenogenesis in sea urchin eggs, it is recommended that a no-sperm control be included with every fertilization test treatment. ?? 2006 Springer Science+Business Media, Inc.

  2. Oxidative stress in drug-naïve first episode patients with schizophrenia and major depression: effects of disease acuity and potential confounders.

    PubMed

    Jordan, Wolfgang; Dobrowolny, Henrik; Bahn, Sabine; Bernstein, Hans-Gert; Brigadski, Tanja; Frodl, Thomas; Isermann, Berend; Lessmann, Volkmar; Pilz, Jürgen; Rodenbeck, Andrea; Schiltz, Kolja; Schwedhelm, Edzard; Tumani, Hayrettin; Wiltfang, Jens; Guest, Paul C; Steiner, Johann

    2018-03-01

    Oxidative stress and immune dysregulation have been linked to schizophrenia and depression. However, it is unknown whether these factors are related to the pathophysiology or whether they are an epiphenomenon. Inconsistent oxidative stress-related findings in previous studies may have resulted from the use of different biomarkers which show disparate aspects of oxidative stress. Additionally, disease severity, medication, smoking, endocrine stress axis activation and obesity are potential confounders. In order to address some of these shortcomings, we have analyzed a broader set of oxidative stress biomarkers in our exploratory study, including urinary 8-iso-prostaglandin F2α (8-iso-PGF2α), 8-OH-2-deoyxguanosine (8-OH-2-dG), and blood levels of malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione S-transferase (GST) in acutely ill drug-naïve first episode patients with schizophrenia (n = 22), major depression (n = 18), and controls (n = 43). Possible confounding factors were considered, and patients were followed-up after 6 weeks of treatment. No differences were observed regarding 8-OH-2-dG, MDA and GST. At baseline, 8-iso-PGF2α levels were higher in patients with schizophrenia (p = 0.004) and major depression (p = 0.037), with a trend toward higher SOD concentrations in schizophrenia (p = 0.053). After treatment, schizophrenia patients showed a further increase in 8-iso-PGF2α (p = 0.016). These results were not related to age, sex, disease severity, medication or adipose tissue mass. However, 8-iso-PGF2α was associated with smoking, endocrine stress axis activation, C-reactive protein levels and low plasma concentrations of brain-derived neurotrophic factor. This study suggests a role of lipid peroxidation particularly in drug-naïve acutely ill schizophrenia patients and highlights the importance of taking into account other confounding factors in biomarker studies.

  3. Confounding in statistical mediation analysis: What it is and how to address it.

    PubMed

    Valente, Matthew J; Pelham, William E; Smyth, Heather; MacKinnon, David P

    2017-11-01

    Psychology researchers are often interested in mechanisms underlying how randomized interventions affect outcomes such as substance use and mental health. Mediation analysis is a common statistical method for investigating psychological mechanisms that has benefited from exciting new methodological improvements over the last 2 decades. One of the most important new developments is methodology for estimating causal mediated effects using the potential outcomes framework for causal inference. Potential outcomes-based methods developed in epidemiology and statistics have important implications for understanding psychological mechanisms. We aim to provide a concise introduction to and illustration of these new methods and emphasize the importance of confounder adjustment. First, we review the traditional regression approach for estimating mediated effects. Second, we describe the potential outcomes framework. Third, we define what a confounder is and how the presence of a confounder can provide misleading evidence regarding mechanisms of interventions. Fourth, we describe experimental designs that can help rule out confounder bias. Fifth, we describe new statistical approaches to adjust for measured confounders of the mediator-outcome relation and sensitivity analyses to probe effects of unmeasured confounders on the mediated effect. All approaches are illustrated with application to a real counseling intervention dataset. Counseling psychologists interested in understanding the causal mechanisms of their interventions can benefit from incorporating the most up-to-date techniques into their mediation analyses. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  4. Genetic variation of loci potentially under selection confounds species-genetic diversity correlations in a fragmented habitat.

    PubMed

    Bertin, Angeline; Gouin, Nicolas; Baumel, Alex; Gianoli, Ernesto; Serratosa, Juan; Osorio, Rodomiro; Manel, Stephanie

    2017-01-01

    Positive species-genetic diversity correlations (SGDCs) are often thought to result from the parallel influence of neutral processes on genetic and species diversity. Yet, confounding effects of non-neutral mechanisms have not been explored. Here, we investigate the impact of non-neutral genetic diversity on SGDCs in high Andean wetlands. We compare correlations between plant species diversity and genetic diversity (GD) calculated with and without loci potentially under selection (outlier loci). The study system includes 2188 specimens from five species (three common aquatic macroinvertebrate and two dominant plant species) that were genotyped for 396 amplified fragment length polymorphism loci. We also appraise the importance of neutral processes on SGDCs by investigating the influence of habitat fragmentation features. Significant positive SGDCs were detected for all five species (mean SGDC = 0.52 ± 0.05). While only a few outlier loci were detected in each species, they resulted in significant decreases in GD and in SGDCs. This supports the hypothesis that neutral processes drive species-genetic diversity relationships in high Andean wetlands. Unexpectedly, the effects on genetic diversity GD of the habitat fragmentation characteristics in this study increased with the presence of outlier loci in two species. Overall, our results reveal pitfalls in using habitat features to infer processes driving SGDCs and show that a few loci potentially under selection are enough to cause a significant downward bias in SGDC. Investigating confounding effects of outlier loci thus represents a useful approach to evidence the contribution of neutral processes on species-genetic diversity relationships. © 2016 John Wiley & Sons Ltd.

  5. Resting-state FMRI confounds and cleanup

    PubMed Central

    Murphy, Kevin; Birn, Rasmus M.; Bandettini, Peter A.

    2013-01-01

    The goal of resting-state functional magnetic resonance imaging (FMRI) is to investigate the brain’s functional connections by using the temporal similarity between blood oxygenation level dependent (BOLD) signals in different regions of the brain “at rest” as an indicator of synchronous neural activity. Since this measure relies on the temporal correlation of FMRI signal changes between different parts of the brain, any non-neural activity-related process that affects the signals will influence the measure of functional connectivity, yielding spurious results. To understand the sources of these resting-state FMRI confounds, this article describes the origins of the BOLD signal in terms of MR physics and cerebral physiology. Potential confounds arising from motion, cardiac and respiratory cycles, arterial CO2 concentration, blood pressure/cerebral autoregulation, and vasomotion are discussed. Two classes of techniques to remove confounds from resting-state BOLD time series are reviewed: 1) those utilising external recordings of physiology and 2) data-based cleanup methods that only use the resting-state FMRI data itself. Further methods that remove noise from functional connectivity measures at a group level are also discussed. For successful interpretation of resting-state FMRI comparisons and results, noise cleanup is an often over-looked but essential step in the analysis pipeline. PMID:23571418

  6. An overview of confounding. Part 1: the concept and how to address it.

    PubMed

    Howards, Penelope P

    2018-04-01

    Confounding is an important source of bias, but it is often misunderstood. We consider how confounding occurs and how to address confounding using examples. Study results are confounded when the effect of the exposure on the outcome, mixes with the effects of other risk and protective factors for the outcome. This problem arises when these factors are present to different degrees among the exposed and unexposed study participants, but not all differences between the groups result in confounding. Thinking about an ideal study where all of the population of interest is exposed in one universe and is unexposed in a parallel universe helps to distinguish confounders from other differences. In an actual study, an observed unexposed population is chosen to stand in for the unobserved parallel universe. Differences between this substitute population and the parallel universe result in confounding. Confounding by identified factors can be addressed analytically and through study design, but only randomization has the potential to address confounding by unmeasured factors. Nevertheless, a given randomized study may still be confounded. Confounded study results can lead to incorrect conclusions about the effect of the exposure of interest on the outcome. © 2018 Nordic Federation of Societies of Obstetrics and Gynecology.

  7. Interpretational Confounding or Confounded Interpretations of Causal Indicators?

    ERIC Educational Resources Information Center

    Bainter, Sierra A.; Bollen, Kenneth A.

    2014-01-01

    In measurement theory, causal indicators are controversial and little understood. Methodological disagreement concerning causal indicators has centered on the question of whether causal indicators are inherently sensitive to interpretational confounding, which occurs when the empirical meaning of a latent construct departs from the meaning…

  8. Phenotypic variation as an indicator of pesticide stress in gudgeon: Accounting for confounding factors in the wild.

    PubMed

    Shinn, Cândida; Blanchet, Simon; Loot, Géraldine; Lek, Sovan; Grenouillet, Gaël

    2015-12-15

    The response of organisms to environmental stress is currently used in the assessment of ecosystem health. Morphological changes integrate the multiple effects of one or several stress factors upon the development of the exposed organisms. In a natural environment, many factors determine the patterns of morphological differentiation between individuals. However, few studies have sought to distinguish and measure the independent effect of these factors (genetic diversity and structure, spatial structuring of populations, physical-chemical conditions, etc.). Here we investigated the relationship between pesticide levels measured at 11 sites sampled in rivers of the Garonne river basin (SW France) and morphological changes of a freshwater fish species, the gudgeon (Gobio gobio). Each individual sampled was genotyped using 8 microsatellite markers and their phenotype characterized via 17 morphological traits. Our analysis detected a link between population genetic structure (revealed by a Bayesian method) and morphometry (linear discriminant analysis) of the studied populations. We then developed an original method based on general linear models using distance matrices, an extension of the partial Mantel test beyond 3 matrices. This method was used to test the relationship between contamination (toxicity index) and morphometry (PST of morphometric traits), taking into account (1) genetic differentiation between populations (FST), (2) geographical distances between sites, (3) site catchment area, and (4) various physical-chemical parameters for each sampling site. Upon removal of confounding effects, 3 of the 17 morphological traits studied were significantly correlated with pesticide toxicity, suggesting a response of these traits to the anthropogenic stress. These results underline the importance of taking into account the different sources of phenotypic variability between organisms when identifying the stress factors involved. The separation and quantification of

  9. An overview of confounding. Part 2: how to identify it and special situations.

    PubMed

    Howards, Penelope P

    2018-04-01

    Confounding biases study results when the effect of the exposure on the outcome mixes with the effects of other risk and protective factors for the outcome that are present differentially by exposure status. However, not all differences between the exposed and unexposed group cause confounding. Thus, sources of confounding must be identified before they can be addressed. Confounding is absent in an ideal study where all of the population of interest is exposed in one universe and is unexposed in a parallel universe. In an actual study, an observed unexposed population represents the unobserved parallel universe. Thinking about differences between this substitute population and the unexposed parallel universe helps identify sources of confounding. These differences can then be represented in a diagram that shows how risk and protective factors for the outcome are related to the exposure. Sources of confounding identified in the diagram should be addressed analytically and through study design. However, treating all factors that differ by exposure status as confounders without considering the structure of their relation to the exposure can introduce bias. For example, conditions affected by the exposure are not confounders. There are also special types of confounding, such as time-varying confounding and unfixable confounding. It is important to evaluate carefully whether factors of interest contribute to confounding because bias can be introduced both by ignoring potential confounders and by adjusting for factors that are not confounders. The resulting bias can result in misleading conclusions about the effect of the exposure of interest on the outcome. © 2018 Nordic Federation of Societies of Obstetrics and Gynecology.

  10. Identification of confounders in the assessment of the relationship between lead exposure and child development.

    PubMed

    Tong, I S; Lu, Y

    2001-01-01

    To explore the best approach to identify and adjust for confounders in epidemiologic practice. In the Port Pirie cohort study, the selection of covariates was based on both a priori and an empirical consideration. In an assessment of the relationship between exposure to environmental lead and child development, change-in-estimate (CE) and significance testing (ST) criteria were compared in identifying potential confounders. The Pearson correlation coefficients were used to evaluate the potential for collinearity between pairs of major quantitative covariates. In multivariate analyses, the effects of confounding factors were assessed with multiple linear regression models. The nature and number of covariates selected varied with different confounder selection criteria and different cutoffs. Four covariates (i.e., quality of home environment, socioeconomic status (SES), maternal intelligence, and parental smoking behaviour) met the conventional CE criterion (> or =10%), whereas 14 variables met the ST criterion (p < or = 0.25). However, the magnitude of the relationship between blood lead concentration and children's IQ differed slightly after adjustment for confounding, using either the CE (partial regression coefficient: -4.4; 95% confidence interval (CI): -0.5 to -8.3) or ST criterion (-4.3; 95% CI: -0.2 to -8.4). Identification and selection of confounding factors need to be viewed cautiously in epidemiologic studies. Either the CE (e.g., > or = 10%) or ST (e.g., p < or = 0.25) criterion may be implemented in identification of a potential confounder if a study sample is sufficiently large, and both the methods are subject to arbitrariness of selecting a cut-off point. In this study, the CE criterion (i.e., > or = 10%) appears to be more stringent than the ST method (i.e., p < or = 0.25) in the identification of confounders. However, the ST rule cannot be used to determine the trueness of confounding because it cannot reflect the causal relationship between the

  11. phMRI: methodological considerations for mitigating potential confounding factors

    PubMed Central

    Bourke, Julius H.; Wall, Matthew B.

    2015-01-01

    Pharmacological Magnetic Resonance Imaging (phMRI) is a variant of conventional MRI that adds pharmacological manipulations in order to study the effects of drugs, or uses pharmacological probes to investigate basic or applied (e.g., clinical) neuroscience questions. Issues that may confound the interpretation of results from various types of phMRI studies are briefly discussed, and a set of methodological strategies that can mitigate these problems are described. These include strategies that can be employed at every stage of investigation, from study design to interpretation of resulting data, and additional techniques suited for use with clinical populations are also featured. Pharmacological MRI is a challenging area of research that has both significant advantages and formidable difficulties, however with due consideration and use of these strategies many of the key obstacles can be overcome. PMID:25999812

  12. On the definition of a confounder

    PubMed Central

    VanderWeele, Tyler J.; Shpitser, Ilya

    2014-01-01

    Summary The causal inference literature has provided a clear formal definition of confounding expressed in terms of counterfactual independence. The causal inference literature has not, however, produced a clear formal definition of a confounder, as it has given priority to the concept of confounding over that of a confounder. We consider a number of candidate definitions arising from various more informal statements made in the literature. We consider the properties satisfied by each candidate definition, principally focusing on (i) whether under the candidate definition control for all “confounders” suffices to control for “confounding” and (ii) whether each confounder in some context helps eliminate or reduce confounding bias. Several of the candidate definitions do not have these two properties. Only one candidate definition of those considered satisfies both properties. We propose that a “confounder” be defined as a pre-exposure covariate C for which there exists a set of other covariates X such that effect of the exposure on the outcome is unconfounded conditional on (X, C) but such that for no proper subset of (X, C) is the effect of the exposure on the outcome unconfounded given the subset. A variable that helps reduce bias but not eliminate bias we propose referring to as a “surrogate confounder.” PMID:25544784

  13. Avoiding potential problems when selling accounts receivable.

    PubMed

    Ayers, D H; Kincaid, T J

    1996-05-01

    Accounts receivable financing is a potential tool for managing a provider organization's working capital needs. But before entering into a financing agreement, organizations need to consider and take steps to avoid serious problems that can arise from participation in an accounts receivable financing program. For example, the purchaser may cease purchasing the receivables, leaving the organization without funding needed for operations. Or, the financing program may be inordinately complex and unnecessarily costly to the organization. Sometimes the organization itself may fail to comply with the terms of the agreement under which the accounts receivable were sold, thus necessitating that restitution be made to the purchaser or provoking charges of fraud. These potential problems should be addressed as early as possible--before an organization enters into an accounts receivable financing program--in order to minimize time, effort, and expanse and maximize the benefits of the financing agreement.

  14. Modeling uranium(VI) adsorption onto montmorillonite under varying carbonate concentrations: A surface complexation model accounting for the spillover effect on surface potential

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tournassat, C.; Tinnacher, R. M.; Grangeon, S.

    The prediction of U(VI) adsorption onto montmorillonite clay is confounded by the complexities of: (1) the montmorillonite structure in terms of adsorption sites on basal and edge surfaces, and the complex interactions between the electrical double layers at these surfaces, and (2) U(VI) solution speciation, which can include cationic, anionic and neutral species. Previous U(VI)-montmorillonite adsorption and modeling studies have typically expanded classical surface complexation modeling approaches, initially developed for simple oxides, to include both cation exchange and surface complexation reactions. However, previous models have not taken into account the unique characteristics of electrostatic surface potentials that occur at montmorillonitemore » edge sites, where the electrostatic surface potential of basal plane cation exchange sites influences the surface potential of neighboring edge sites (‘spillover’ effect).« less

  15. Modeling uranium(VI) adsorption onto montmorillonite under varying carbonate concentrations: A surface complexation model accounting for the spillover effect on surface potential

    DOE PAGES

    Tournassat, C.; Tinnacher, R. M.; Grangeon, S.; ...

    2017-10-06

    The prediction of U(VI) adsorption onto montmorillonite clay is confounded by the complexities of: (1) the montmorillonite structure in terms of adsorption sites on basal and edge surfaces, and the complex interactions between the electrical double layers at these surfaces, and (2) U(VI) solution speciation, which can include cationic, anionic and neutral species. Previous U(VI)-montmorillonite adsorption and modeling studies have typically expanded classical surface complexation modeling approaches, initially developed for simple oxides, to include both cation exchange and surface complexation reactions. However, previous models have not taken into account the unique characteristics of electrostatic surface potentials that occur at montmorillonitemore » edge sites, where the electrostatic surface potential of basal plane cation exchange sites influences the surface potential of neighboring edge sites (‘spillover’ effect).« less

  16. Bias, Confounding, and Interaction: Lions and Tigers, and Bears, Oh My!

    PubMed

    Vetter, Thomas R; Mascha, Edward J

    2017-09-01

    Epidemiologists seek to make a valid inference about the causal effect between an exposure and a disease in a specific population, using representative sample data from a specific population. Clinical researchers likewise seek to make a valid inference about the association between an intervention and outcome(s) in a specific population, based upon their randomly collected, representative sample data. Both do so by using the available data about the sample variable to make a valid estimate about its corresponding or underlying, but unknown population parameter. Random error in an experiment can be due to the natural, periodic fluctuation or variation in the accuracy or precision of virtually any data sampling technique or health measurement tool or scale. In a clinical research study, random error can be due to not only innate human variability but also purely chance. Systematic error in an experiment arises from an innate flaw in the data sampling technique or measurement instrument. In the clinical research setting, systematic error is more commonly referred to as systematic bias. The most commonly encountered types of bias in anesthesia, perioperative, critical care, and pain medicine research include recall bias, observational bias (Hawthorne effect), attrition bias, misclassification or informational bias, and selection bias. A confounding variable is a factor associated with both the exposure of interest and the outcome of interest. A confounding variable (confounding factor or confounder) is a variable that correlates (positively or negatively) with both the exposure and outcome. Confounding is typically not an issue in a randomized trial because the randomized groups are sufficiently balanced on all potential confounding variables, both observed and nonobserved. However, confounding can be a major problem with any observational (nonrandomized) study. Ignoring confounding in an observational study will often result in a "distorted" or incorrect estimate of

  17. Confounding adjustment in comparative effectiveness research conducted within distributed research networks.

    PubMed

    Toh, Sengwee; Gagne, Joshua J; Rassen, Jeremy A; Fireman, Bruce H; Kulldorff, Martin; Brown, Jeffrey S

    2013-08-01

    A distributed research network (DRN) of electronic health care databases, in which data reside behind the firewall of each data partner, can support a wide range of comparative effectiveness research (CER) activities. An essential component of a fully functional DRN is the capability to perform robust statistical analyses to produce valid, actionable evidence without compromising patient privacy, data security, or proprietary interests. We describe the strengths and limitations of different confounding adjustment approaches that can be considered in observational CER studies conducted within DRNs, and the theoretical and practical issues to consider when selecting among them in various study settings. Several methods can be used to adjust for multiple confounders simultaneously, either as individual covariates or as confounder summary scores (eg, propensity scores and disease risk scores), including: (1) centralized analysis of patient-level data, (2) case-centered logistic regression of risk set data, (3) stratified or matched analysis of aggregated data, (4) distributed regression analysis, and (5) meta-analysis of site-specific effect estimates. These methods require different granularities of information be shared across sites and afford investigators different levels of analytic flexibility. DRNs are growing in use and sharing of highly detailed patient-level information is not always feasible in DRNs. Methods that incorporate confounder summary scores allow investigators to adjust for a large number of confounding factors without the need to transfer potentially identifiable information in DRNs. They have the potential to let investigators perform many analyses traditionally conducted through a centralized dataset with detailed patient-level information.

  18. Assessing mediation using marginal structural models in the presence of confounding and moderation

    PubMed Central

    Coffman, Donna L.; Zhong, Wei

    2012-01-01

    This paper presents marginal structural models (MSMs) with inverse propensity weighting (IPW) for assessing mediation. Generally, individuals are not randomly assigned to levels of the mediator. Therefore, confounders of the mediator and outcome may exist that limit causal inferences, a goal of mediation analysis. Either regression adjustment or IPW can be used to take confounding into account, but IPW has several advantages. Regression adjustment of even one confounder of the mediator and outcome that has been influenced by treatment results in biased estimates of the direct effect (i.e., the effect of treatment on the outcome that does not go through the mediator). One advantage of IPW is that it can properly adjust for this type of confounding, assuming there are no unmeasured confounders. Further, we illustrate that IPW estimation provides unbiased estimates of all effects when there is a baseline moderator variable that interacts with the treatment, when there is a baseline moderator variable that interacts with the mediator, and when the treatment interacts with the mediator. IPW estimation also provides unbiased estimates of all effects in the presence of non-randomized treatments. In addition, for testing mediation we propose a test of the null hypothesis of no mediation. Finally, we illustrate this approach with an empirical data set in which the mediator is continuous, as is often the case in psychological research. PMID:22905648

  19. Doubly robust matching estimators for high dimensional confounding adjustment.

    PubMed

    Antonelli, Joseph; Cefalu, Matthew; Palmer, Nathan; Agniel, Denis

    2018-05-11

    Valid estimation of treatment effects from observational data requires proper control of confounding. If the number of covariates is large relative to the number of observations, then controlling for all available covariates is infeasible. In cases where a sparsity condition holds, variable selection or penalization can reduce the dimension of the covariate space in a manner that allows for valid estimation of treatment effects. In this article, we propose matching on both the estimated propensity score and the estimated prognostic scores when the number of covariates is large relative to the number of observations. We derive asymptotic results for the matching estimator and show that it is doubly robust in the sense that only one of the two score models need be correct to obtain a consistent estimator. We show via simulation its effectiveness in controlling for confounding and highlight its potential to address nonlinear confounding. Finally, we apply the proposed procedure to analyze the effect of gender on prescription opioid use using insurance claims data. © 2018, The International Biometric Society.

  20. Why does early sexual intercourse predict subsequent maladjustment? Exploring potential familial confounds.

    PubMed

    Donahue, Kelly L; Lichtenstein, Paul; Långström, Niklas; D'Onofrio, Brian M

    2013-02-01

    Previous studies have found an association between early age at first sexual intercourse and subsequent psychosocial maladjustment. Using a quasi-experimental approach, we examined the extent to which this observed association may be due to familial confounds not explored in prior research. Using a population-based cohort of Swedish adult twins (ages 19-47; N = 12,126), we examined the nature of the association between early sexual intercourse (i.e., first intercourse occurring before age 16) and various outcomes reflecting psychosocial health, including substance use, depression, criminal convictions, and adolescent childbearing. We used two methods--discordant-twin analyses and bivariate twin modeling--to estimate the extent to which genetic and environmental confounds explained observed associations. Individuals who engaged in early intercourse were at greater risk for most of the adverse psychosocial health outcomes measured in this study. However, twin pairs discordant for engaging in early intercourse did not differ significantly in their risk for psychosocial maladjustment. Our results indicated that early age at first sexual intercourse and subsequent psychosocial maladjustment may be associated because of familial factors shared by twins. Early intercourse may be associated with poor psychosocial health largely due to shared familial influences rather than through a direct causal connection. Therefore, effective and efficient interventions should address other risk factors common to early intercourse and poor psychosocial health.

  1. Potential confounding in the association between short birth intervals and increased neonatal, infant, and child mortality

    PubMed Central

    Perin, Jamie; Walker, Neff

    2015-01-01

    Background Recent steep declines in child mortality have been attributed in part to increased use of contraceptives and the resulting change in fertility behaviour, including an increase in the time between births. Previous observational studies have documented strong associations between short birth spacing and an increase in the risk of neonatal, infant, and under-five mortality, compared to births with longer preceding birth intervals. In this analysis, we compare two methods to estimate the association between short birth intervals and mortality risk to better inform modelling efforts linking family planning and mortality in children. Objectives Our goal was to estimate the mortality risk for neonates, infants, and young children by preceding birth space using household survey data, controlling for mother-level factors and to compare the results to those from previous analyses with survey data. Design We assessed the potential for confounding when estimating the relative mortality risk by preceding birth interval and estimated mortality risk by birth interval in four categories: less than 18 months, 18–23 months, 24–35 months, and 36 months or longer. We estimated the relative risks among women who were 35 and older at the time of the survey with two methods: in a Cox proportional hazards regression adjusting for potential confounders and also by stratifying Cox regression by mother, to control for all factors that remain constant over a woman's childbearing years. We estimated the overall effects for birth spacing in a meta-analysis with random survey effects. Results We identified several factors known for their associations with neonatal, infant, and child mortality that are also associated with preceding birth interval. When estimating the effect of birth spacing on mortality, we found that regression adjustment for these factors does not substantially change the risk ratio for short birth intervals compared to an unadjusted mortality ratio. For birth

  2. Potential confounding in the association between short birth intervals and increased neonatal, infant, and child mortality.

    PubMed

    Perin, Jamie; Walker, Neff

    2015-01-01

    Recent steep declines in child mortality have been attributed in part to increased use of contraceptives and the resulting change in fertility behaviour, including an increase in the time between births. Previous observational studies have documented strong associations between short birth spacing and an increase in the risk of neonatal, infant, and under-five mortality, compared to births with longer preceding birth intervals. In this analysis, we compare two methods to estimate the association between short birth intervals and mortality risk to better inform modelling efforts linking family planning and mortality in children. Our goal was to estimate the mortality risk for neonates, infants, and young children by preceding birth space using household survey data, controlling for mother-level factors and to compare the results to those from previous analyses with survey data. We assessed the potential for confounding when estimating the relative mortality risk by preceding birth interval and estimated mortality risk by birth interval in four categories: less than 18 months, 18-23 months, 24-35 months, and 36 months or longer. We estimated the relative risks among women who were 35 and older at the time of the survey with two methods: in a Cox proportional hazards regression adjusting for potential confounders and also by stratifying Cox regression by mother, to control for all factors that remain constant over a woman's childbearing years. We estimated the overall effects for birth spacing in a meta-analysis with random survey effects. We identified several factors known for their associations with neonatal, infant, and child mortality that are also associated with preceding birth interval. When estimating the effect of birth spacing on mortality, we found that regression adjustment for these factors does not substantially change the risk ratio for short birth intervals compared to an unadjusted mortality ratio. For birth intervals less than 18 months, standard

  3. The alarming problems of confounding equivalence using logistic regression models in the perspective of causal diagrams.

    PubMed

    Yu, Yuanyuan; Li, Hongkai; Sun, Xiaoru; Su, Ping; Wang, Tingting; Liu, Yi; Yuan, Zhongshang; Liu, Yanxun; Xue, Fuzhong

    2017-12-28

    Confounders can produce spurious associations between exposure and outcome in observational studies. For majority of epidemiologists, adjusting for confounders using logistic regression model is their habitual method, though it has some problems in accuracy and precision. It is, therefore, important to highlight the problems of logistic regression and search the alternative method. Four causal diagram models were defined to summarize confounding equivalence. Both theoretical proofs and simulation studies were performed to verify whether conditioning on different confounding equivalence sets had the same bias-reducing potential and then to select the optimum adjusting strategy, in which logistic regression model and inverse probability weighting based marginal structural model (IPW-based-MSM) were compared. The "do-calculus" was used to calculate the true causal effect of exposure on outcome, then the bias and standard error were used to evaluate the performances of different strategies. Adjusting for different sets of confounding equivalence, as judged by identical Markov boundaries, produced different bias-reducing potential in the logistic regression model. For the sets satisfied G-admissibility, adjusting for the set including all the confounders reduced the equivalent bias to the one containing the parent nodes of the outcome, while the bias after adjusting for the parent nodes of exposure was not equivalent to them. In addition, all causal effect estimations through logistic regression were biased, although the estimation after adjusting for the parent nodes of exposure was nearest to the true causal effect. However, conditioning on different confounding equivalence sets had the same bias-reducing potential under IPW-based-MSM. Compared with logistic regression, the IPW-based-MSM could obtain unbiased causal effect estimation when the adjusted confounders satisfied G-admissibility and the optimal strategy was to adjust for the parent nodes of outcome, which

  4. Assessing mediation using marginal structural models in the presence of confounding and moderation.

    PubMed

    Coffman, Donna L; Zhong, Wei

    2012-12-01

    This article presents marginal structural models with inverse propensity weighting (IPW) for assessing mediation. Generally, individuals are not randomly assigned to levels of the mediator. Therefore, confounders of the mediator and outcome may exist that limit causal inferences, a goal of mediation analysis. Either regression adjustment or IPW can be used to take confounding into account, but IPW has several advantages. Regression adjustment of even one confounder of the mediator and outcome that has been influenced by treatment results in biased estimates of the direct effect (i.e., the effect of treatment on the outcome that does not go through the mediator). One advantage of IPW is that it can properly adjust for this type of confounding, assuming there are no unmeasured confounders. Further, we illustrate that IPW estimation provides unbiased estimates of all effects when there is a baseline moderator variable that interacts with the treatment, when there is a baseline moderator variable that interacts with the mediator, and when the treatment interacts with the mediator. IPW estimation also provides unbiased estimates of all effects in the presence of nonrandomized treatments. In addition, for testing mediation we propose a test of the null hypothesis of no mediation. Finally, we illustrate this approach with an empirical data set in which the mediator is continuous, as is often the case in psychological research. PsycINFO Database Record (c) 2013 APA, all rights reserved.

  5. Confounding by dietary pattern of the inverse association between alcohol consumption and type 2 diabetes risk

    USDA-ARS?s Scientific Manuscript database

    Epidemiology of dietary components and disease risk limits interpretability due to potential residual confounding by correlated dietary components. Dietary pattern analyses by factor analysis or partial least squares may overcome the limitation. To examine confounding by dietary pattern as well as ...

  6. Confounding by dietary patterns of the inverse association between alcohol consumption and type 2 diabetes risk

    USDA-ARS?s Scientific Manuscript database

    Epidemiology of dietary components and disease risk limits interpretability due to potential residual confounding by correlated dietary components. Dietary pattern analyses by factor analysis or partial least squares may overcome this limitation. To examine confounding by dietary pattern as well as ...

  7. Confounder Detection in High-Dimensional Linear Models Using First Moments of Spectral Measures.

    PubMed

    Liu, Furui; Chan, Laiwan

    2018-06-12

    In this letter, we study the confounder detection problem in the linear model, where the target variable [Formula: see text] is predicted using its [Formula: see text] potential causes [Formula: see text]. Based on an assumption of a rotation-invariant generating process of the model, recent study shows that the spectral measure induced by the regression coefficient vector with respect to the covariance matrix of [Formula: see text] is close to a uniform measure in purely causal cases, but it differs from a uniform measure characteristically in the presence of a scalar confounder. Analyzing spectral measure patterns could help to detect confounding. In this letter, we propose to use the first moment of the spectral measure for confounder detection. We calculate the first moment of the regression vector-induced spectral measure and compare it with the first moment of a uniform spectral measure, both defined with respect to the covariance matrix of [Formula: see text]. The two moments coincide in nonconfounding cases and differ from each other in the presence of confounding. This statistical causal-confounding asymmetry can be used for confounder detection. Without the need to analyze the spectral measure pattern, our method avoids the difficulty of metric choice and multiple parameter optimization. Experiments on synthetic and real data show the performance of this method.

  8. The impact of confounder selection in propensity scores when applied to prospective cohort studies in pregnancy.

    PubMed

    Xu, Ronghui; Hou, Jue; Chambers, Christina D

    2018-06-01

    Our work was motivated by small cohort studies on the risk of birth defects in infants born to pregnant women exposed to medications. We controlled for confounding using propensity scores (PS). The extremely rare events setting renders the matching or stratification infeasible. In addition, the PS itself may be formed via different approaches to select confounders from a relatively long list of potential confounders. We carried out simulation experiments to compare different combinations of approaches: IPW or regression adjustment, with 1) including all potential confounders without selection, 2) selection based on univariate association between the candidate variable and the outcome, 3) selection based on change in effects (CIE). The simulation showed that IPW without selection leads to extremely large variances in the estimated odds ratio, which help to explain the empirical data analysis results that we had observed. Copyright © 2018 Elsevier Inc. All rights reserved.

  9. Environmental confounding in gene-environment interaction studies.

    PubMed

    Vanderweele, Tyler J; Ko, Yi-An; Mukherjee, Bhramar

    2013-07-01

    We show that, in the presence of uncontrolled environmental confounding, joint tests for the presence of a main genetic effect and gene-environment interaction will be biased if the genetic and environmental factors are correlated, even if there is no effect of either the genetic factor or the environmental factor on the disease. When environmental confounding is ignored, such tests will in fact reject the joint null of no genetic effect with a probability that tends to 1 as the sample size increases. This problem with the joint test vanishes under gene-environment independence, but it still persists if estimating the gene-environment interaction parameter itself is of interest. Uncontrolled environmental confounding will bias estimates of gene-environment interaction parameters even under gene-environment independence, but it will not do so if the unmeasured confounding variable itself does not interact with the genetic factor. Under gene-environment independence, if the interaction parameter without controlling for the environmental confounder is nonzero, then there is gene-environment interaction either between the genetic factor and the environmental factor of interest or between the genetic factor and the unmeasured environmental confounder. We evaluate several recently proposed joint tests in a simulation study and discuss the implications of these results for the conduct of gene-environment interaction studies.

  10. Confounding, causality, and confusion: the role of intermediate variables in interpreting observational studies in obstetrics.

    PubMed

    Ananth, Cande V; Schisterman, Enrique F

    2017-08-01

    Prospective and retrospective cohorts and case-control studies are some of the most important study designs in epidemiology because, under certain assumptions, they can mimic a randomized trial when done well. These assumptions include, but are not limited to, properly accounting for 2 important sources of bias: confounding and selection bias. While not adjusting the causal association for an intermediate variable will yield an unbiased estimate of the exposure-outcome's total causal effect, it is often that obstetricians will want to adjust for an intermediate variable to assess if the intermediate is the underlying driver of the association. Such a practice must be weighed in light of the underlying research question and whether such an adjustment is necessary should be carefully considered. Gestational age is, by far, the most commonly encountered variable in obstetrics that is often mislabeled as a confounder when, in fact, it may be an intermediate. If, indeed, gestational age is an intermediate but if mistakenly labeled as a confounding variable and consequently adjusted in an analysis, the conclusions can be unexpected. The implications of this overadjustment of an intermediate as though it were a confounder can render an otherwise persuasive study downright meaningless. This commentary provides an exposition of confounding bias, collider stratification, and selection biases, with applications in obstetrics and perinatal epidemiology. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. Packet Randomized Experiments for Eliminating Classes of Confounders

    PubMed Central

    Pavela, Greg; Wiener, Howard; Fontaine, Kevin R.; Fields, David A.; Voss, Jameson D.; Allison, David B.

    2014-01-01

    Background Although randomization is considered essential for causal inference, it is often not possible to randomize in nutrition and obesity research. To address this, we develop a framework for an experimental design—packet randomized experiments (PREs), which improves causal inferences when randomization on a single treatment variable is not possible. This situation arises when subjects are randomly assigned to a condition (such as a new roommate) which varies in one characteristic of interest (such as weight), but also varies across many others. There has been no general discussion of this experimental design, including its strengths, limitations, and statistical properties. As such, researchers are left to develop and apply PREs on an ad hoc basis, limiting its potential to improve causal inferences among nutrition and obesity researchers. Methods We introduce PREs as an intermediary design between randomized controlled trials and observational studies. We review previous research that used the PRE design and describe its application in obesity-related research, including random roommate assignments, heterochronic parabiosis, and the quasi-random assignment of subjects to geographic areas. We then provide a statistical framework to control for potential packet-level confounders not accounted for by randomization. Results PREs have successfully been used to improve causal estimates of the effect of roommates, altitude, and breastfeeding on weight outcomes. When certain assumptions are met, PREs can asymptotically control for packet-level characteristics. This has the potential to statistically estimate the effect of a single treatment even when randomization to a single treatment did not occur. Conclusions Applying PREs to obesity-related research will improve decisions about clinical, public health, and policy actions insofar as it offers researchers new insight into cause and effect relationships among variables. PMID:25444088

  12. Mismeasurement and the resonance of strong confounders: correlated errors.

    PubMed

    Marshall, J R; Hastrup, J L; Ross, J S

    1999-07-01

    Confounding in epidemiology, and the limits of standard methods of control for an imperfectly measured confounder, have been understood for some time. However, most treatments of this problem are based on the assumption that errors of measurement in confounding and confounded variables are independent. This paper considers the situation in which a strong risk factor (confounder) and an inconsequential but suspected risk factor (confounded) are each measured with errors that are correlated; the situation appears especially likely to occur in the field of nutritional epidemiology. Error correlation appears to add little to measurement error as a source of bias in estimating the impact of a strong risk factor: it can add to, diminish, or reverse the bias induced by measurement error in estimating the impact of the inconsequential risk factor. Correlation of measurement errors can add to the difficulty involved in evaluating structures in which confounding and measurement error are present. In its presence, observed correlations among risk factors can be greater than, less than, or even opposite to the true correlations. Interpretation of multivariate epidemiologic structures in which confounding is likely requires evaluation of measurement error structures, including correlations among measurement errors.

  13. An independent component analysis confounding factor correction framework for identifying broad impact expression quantitative trait loci

    PubMed Central

    Ju, Jin Hyun; Crystal, Ronald G.

    2017-01-01

    Genome-wide expression Quantitative Trait Loci (eQTL) studies in humans have provided numerous insights into the genetics of both gene expression and complex diseases. While the majority of eQTL identified in genome-wide analyses impact a single gene, eQTL that impact many genes are particularly valuable for network modeling and disease analysis. To enable the identification of such broad impact eQTL, we introduce CONFETI: Confounding Factor Estimation Through Independent component analysis. CONFETI is designed to address two conflicting issues when searching for broad impact eQTL: the need to account for non-genetic confounding factors that can lower the power of the analysis or produce broad impact eQTL false positives, and the tendency of methods that account for confounding factors to model broad impact eQTL as non-genetic variation. The key advance of the CONFETI framework is the use of Independent Component Analysis (ICA) to identify variation likely caused by broad impact eQTL when constructing the sample covariance matrix used for the random effect in a mixed model. We show that CONFETI has better performance than other mixed model confounding factor methods when considering broad impact eQTL recovery from synthetic data. We also used the CONFETI framework and these same confounding factor methods to identify eQTL that replicate between matched twin pair datasets in the Multiple Tissue Human Expression Resource (MuTHER), the Depression Genes Networks study (DGN), the Netherlands Study of Depression and Anxiety (NESDA), and multiple tissue types in the Genotype-Tissue Expression (GTEx) consortium. These analyses identified both cis-eQTL and trans-eQTL impacting individual genes, and CONFETI had better or comparable performance to other mixed model confounding factor analysis methods when identifying such eQTL. In these analyses, we were able to identify and replicate a few broad impact eQTL although the overall number was small even when applying CONFETI. In

  14. An independent component analysis confounding factor correction framework for identifying broad impact expression quantitative trait loci.

    PubMed

    Ju, Jin Hyun; Shenoy, Sushila A; Crystal, Ronald G; Mezey, Jason G

    2017-05-01

    Genome-wide expression Quantitative Trait Loci (eQTL) studies in humans have provided numerous insights into the genetics of both gene expression and complex diseases. While the majority of eQTL identified in genome-wide analyses impact a single gene, eQTL that impact many genes are particularly valuable for network modeling and disease analysis. To enable the identification of such broad impact eQTL, we introduce CONFETI: Confounding Factor Estimation Through Independent component analysis. CONFETI is designed to address two conflicting issues when searching for broad impact eQTL: the need to account for non-genetic confounding factors that can lower the power of the analysis or produce broad impact eQTL false positives, and the tendency of methods that account for confounding factors to model broad impact eQTL as non-genetic variation. The key advance of the CONFETI framework is the use of Independent Component Analysis (ICA) to identify variation likely caused by broad impact eQTL when constructing the sample covariance matrix used for the random effect in a mixed model. We show that CONFETI has better performance than other mixed model confounding factor methods when considering broad impact eQTL recovery from synthetic data. We also used the CONFETI framework and these same confounding factor methods to identify eQTL that replicate between matched twin pair datasets in the Multiple Tissue Human Expression Resource (MuTHER), the Depression Genes Networks study (DGN), the Netherlands Study of Depression and Anxiety (NESDA), and multiple tissue types in the Genotype-Tissue Expression (GTEx) consortium. These analyses identified both cis-eQTL and trans-eQTL impacting individual genes, and CONFETI had better or comparable performance to other mixed model confounding factor analysis methods when identifying such eQTL. In these analyses, we were able to identify and replicate a few broad impact eQTL although the overall number was small even when applying CONFETI. In

  15. External adjustment sensitivity analysis for unmeasured confounding: an application to coronary stent outcomes, Pennsylvania 2004-2008.

    PubMed

    Huesch, Marco D

    2013-06-01

    Assessing the real-world comparative effectiveness of common interventions is challenged by unmeasured confounding. To determine whether the mortality benefit shown for drug-eluting stents (DES) over bare metal stents (BMS) in observational studies persists after controls for/tests for confounding. Retrospective observational study involving 38,019 patients, 65 years or older admitted for an index percutaneous coronary intervention receiving DES or BMS in Pennsylvania in 2004-2005 followed up for death through 3 years. Analysis was at the patient level. Mortality was analyzed with Cox proportional hazards models allowing for stratification by disease severity or DES use propensity, accounting for clustering of patients. Instrumental variables analysis used lagged physician stent usage to proxy for the focal stent type decision. A method originating in work by Cornfield and others in 1954 and popularized by Greenland in 1996 was used to assess robustness to confounding. DES was associated with a significantly lower adjusted risk of death at 3 years in Cox and in instrumented analyses. An implausibly strong hypothetical unobserved confounder would be required to fully explain these results. Confounding by indication can bias observational studies. No strong evidence of such selection biases was found in the reduced risk of death among elderly patients receiving DES instead of BMS in a Pennsylvanian state-wide population. © Health Research and Educational Trust.

  16. Wind turbines and idiopathic symptoms: The confounding effect of concurrent environmental exposures.

    PubMed

    Blanes-Vidal, Victoria; Schwartz, Joel

    2016-01-01

    Whether or not wind turbines pose a risk to human health is a matter of heated debate. Personal reactions to other environmental exposures occurring in the same settings as wind turbines may be responsible of the reported symptoms. However, these have not been accounted for in previous studies. We investigated whether there is an association between residential proximity to wind turbines and idiopathic symptoms, after controlling for personal reactions to other environmental co-exposures. We assessed wind turbine exposures in 454 residences as the distance to the closest wind turbine (Dw) and number of wind turbines <1000m (Nw1000). Information on symptoms, demographics and personal reactions to exposures was obtained by a blind questionnaire. We identified confounders using confounders' selection criteria and used adjusted logistic regression models to estimate associations. When controlling only for socio-demographic characteristics, log10Dw was associated with "unnatural fatigue" (ORadj=0.38, 95%CI=0.15-1.00) and "difficulty concentrating" (ORadj=0.26, 95%CI=0.08-0.83) and Nw1000 was associated with "unnatural fatigue" (ORadj=1.35, 95%CI=1.07-1.70) and "headache" (ORadj=1.26, 95%CI=1.00-1.58). After controlling for personal reactions to noise from sources different from wind turbines and agricultural odor exposure, we did not observe a significant relationship between residential proximity to wind turbines and symptoms and the parameter estimates were attenuated toward zero. Wind turbines-health associations can be confounded by personal reactions to other environmental co-exposures. Isolated associations reported in the literature may be due to confounding bias. Copyright © 2016 Elsevier Inc. All rights reserved.

  17. Diagnostics for Confounding of Time-varying and Other Joint Exposures.

    PubMed

    Jackson, John W

    2016-11-01

    The effects of joint exposures (or exposure regimes) include those of adhering to assigned treatment versus placebo in a randomized controlled trial, duration of exposure in a cohort study, interactions between exposures, and direct effects of exposure, among others. Unlike the setting of a single point exposure (e.g., propensity score matching), there are few tools to describe confounding for joint exposures or how well a method resolves it. Investigators need tools that describe confounding in ways that are conceptually grounded and intuitive for those who read, review, and use applied research to guide policy. We revisit the implications of exchangeability conditions that hold in sequentially randomized trials, and the bias structure that motivates the use of g-methods, such as marginal structural models. From these, we develop covariate balance diagnostics for joint exposures that can (1) describe time-varying confounding, (2) assess whether covariates are predicted by prior exposures given their past, the indication for g-methods, and (3) describe residual confounding after inverse probability weighting. For each diagnostic, we present time-specific metrics that encompass a wide class of joint exposures, including regimes of multivariate time-varying exposures in censored data, with multivariate point exposures as a special case. We outline how to estimate these directly or with regression and how to average them over person-time. Using a simulated example, we show how these metrics can be presented graphically. This conceptually grounded framework can potentially aid the transparent design, analysis, and reporting of studies that examine joint exposures. We provide easy-to-use tools to implement it.

  18. The Combined Effects of Measurement Error and Omitting Confounders in the Single-Mediator Model

    PubMed Central

    Fritz, Matthew S.; Kenny, David A.; MacKinnon, David P.

    2016-01-01

    Mediation analysis requires a number of strong assumptions be met in order to make valid causal inferences. Failing to account for violations of these assumptions, such as not modeling measurement error or omitting a common cause of the effects in the model, can bias the parameter estimates of the mediated effect. When the independent variable is perfectly reliable, for example when participants are randomly assigned to levels of treatment, measurement error in the mediator tends to underestimate the mediated effect, while the omission of a confounding variable of the mediator to outcome relation tends to overestimate the mediated effect. Violations of these two assumptions often co-occur, however, in which case the mediated effect could be overestimated, underestimated, or even, in very rare circumstances, unbiased. In order to explore the combined effect of measurement error and omitted confounders in the same model, the impact of each violation on the single-mediator model is first examined individually. Then the combined effect of having measurement error and omitted confounders in the same model is discussed. Throughout, an empirical example is provided to illustrate the effect of violating these assumptions on the mediated effect. PMID:27739903

  19. External radiation dose and cancer mortality among French nuclear workers: considering potential confounding by internal radiation exposure.

    PubMed

    Fournier, L; Laurent, O; Samson, E; Caër-Lorho, S; Laroche, P; Le Guen, B; Laurier, D; Leuraud, K

    2016-11-01

    French nuclear workers have detailed records of their occupational exposure to external radiation that have been used to examine associations with subsequent cancer mortality. However, some workers were also exposed to internal contamination by radionuclides. This study aims to assess the potential for bias due to confounding by internal contamination of estimates of associations between external radiation exposure and cancer mortality. A cohort of 59,004 workers employed for at least 1 year between 1950 and 1994 by CEA (Commissariat à l'Energie Atomique), AREVA NC, or EDF (Electricité de France) and badge-monitored for external radiation exposure were followed through 2004 to assess vital status and cause of death. A flag based on a workstation-exposure matrix defined four levels of potential for internal contamination. Standardized mortality ratios were assessed for each level of the internal contamination indicator. Poisson regression was used to quantify associations between external radiation exposure and cancer mortality, adjusting for potential internal contamination. For solid cancer, the mortality deficit tended to decrease as the levels of potential for internal contamination increased. For solid cancer and leukemia excluding chronic lymphocytic leukemia, adjusting the dose-response analysis on the internal contamination indicator did not markedly change the excess relative risk per Sievert of external radiation dose. This study suggests that in this cohort, neglecting information on internal dosimetry while studying the association between external dose and cancer mortality does not generate a substantial bias. To investigate more specifically the health effects of internal contamination, an effort is underway to estimate organ doses due to internal contamination.

  20. Insulin-Like Growth Factor 1 (IGF-1) in Parkinson's Disease: Potential as Trait-, Progression- and Prediction Marker and Confounding Factors.

    PubMed

    Bernhard, Felix P; Heinzel, Sebastian; Binder, Gerhard; Weber, Karin; Apel, Anja; Roeben, Benjamin; Deuschle, Christian; Maechtel, Mirjam; Heger, Tanja; Nussbaum, Susanne; Gasser, Thomas; Maetzler, Walter; Berg, Daniela

    2016-01-01

    Biomarkers indicating trait, progression and prediction of pathology and symptoms in Parkinson's disease (PD) often lack specificity or reliability. Investigating biomarker variance between individuals and over time and the effect of confounding factors is essential for the evaluation of biomarkers in PD, such as insulin-like growth factor 1 (IGF-1). IGF-1 serum levels were investigated in up to 8 biannual visits in 37 PD patients and 22 healthy controls (HC) in the longitudinal MODEP study. IGF-1 baseline levels and annual changes in IGF-1 were compared between PD patients and HC while accounting for baseline disease duration (19 early stage: ≤3.5 years; 18 moderate stage: >4 years), age, sex, body mass index (BMI) and common medical factors putatively modulating IGF-1. In addition, associations of baseline IGF-1 with annual changes of motor, cognitive and depressive symptoms and medication dose were investigated. PD patients in moderate (130±26 ng/mL; p = .004), but not early stages (115±19, p>.1), showed significantly increased baseline IGF-1 levels compared with HC (106±24 ng/mL; p = .017). Age had a significant negative correlation with IGF-1 levels in HC (r = -.47, p = .028) and no correlation in PD patients (r = -.06, p>.1). BMI was negatively correlated in the overall group (r = -.28, p = .034). The annual changes in IGF-1 did not differ significantly between groups and were not correlated with disease duration. Baseline IGF-1 levels were not associated with annual changes of clinical parameters. Elevated IGF-1 in serum might differentiate between patients in moderate PD stages and HC. However, the value of serum IGF-1 as a trait-, progression- and prediction marker in PD is limited as IGF-1 showed large inter- and intraindividual variability and may be modulated by several confounders.

  1. Everything that you have ever been told about assessment center ratings is confounded.

    PubMed

    Jackson, Duncan J R; Michaelides, George; Dewberry, Chris; Kim, Young-Jae

    2016-07-01

    Despite a substantial research literature on the influence of dimensions and exercises in assessment centers (ACs), the relative impact of these 2 sources of variance continues to raise uncertainties because of confounding. With confounded effects, it is not possible to establish the degree to which any 1 effect, including those related to exercises and dimensions, influences AC ratings. In the current study (N = 698) we used Bayesian generalizability theory to unconfound all of the possible effects contributing to variance in AC ratings. Our results show that ≤1.11% of the variance in AC ratings was directly attributable to behavioral dimensions, suggesting that dimension-related effects have no practical impact on the reliability of ACs. Even when taking aggregation level into consideration, effects related to general performance and exercises accounted for almost all of the reliable variance in AC ratings. The implications of these findings for recent dimension- and exercise-based perspectives on ACs are discussed. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

  2. Restricted spatial regression in practice: Geostatistical models, confounding, and robustness under model misspecification

    USGS Publications Warehouse

    Hanks, Ephraim M.; Schliep, Erin M.; Hooten, Mevin B.; Hoeting, Jennifer A.

    2015-01-01

    In spatial generalized linear mixed models (SGLMMs), covariates that are spatially smooth are often collinear with spatially smooth random effects. This phenomenon is known as spatial confounding and has been studied primarily in the case where the spatial support of the process being studied is discrete (e.g., areal spatial data). In this case, the most common approach suggested is restricted spatial regression (RSR) in which the spatial random effects are constrained to be orthogonal to the fixed effects. We consider spatial confounding and RSR in the geostatistical (continuous spatial support) setting. We show that RSR provides computational benefits relative to the confounded SGLMM, but that Bayesian credible intervals under RSR can be inappropriately narrow under model misspecification. We propose a posterior predictive approach to alleviating this potential problem and discuss the appropriateness of RSR in a variety of situations. We illustrate RSR and SGLMM approaches through simulation studies and an analysis of malaria frequencies in The Gambia, Africa.

  3. Radon-induced lung cancer deaths may be overestimated due to failure to account for confounding by exposure to diesel engine exhaust in BEIR VI miner studies.

    PubMed

    Cao, Xiaodong; MacNaughton, Piers; Laurent, Jose Cedeno; Allen, Joseph G

    2017-01-01

    EPA reported that radon is the second leading cause of lung cancer in the United States, killing 21,100 people per year. EPA relies on the BEIR VI models, based on an evaluation of radon exposure and lung cancer risk in studies of miners. But these models did not account for co-exposure to diesel exhaust, a known human carcinogen recently classified by IARC. It is probable then that a portion of the lung cancer deaths in the miner cohorts are originally attributable to the exposure to diesel rather than radon. To re-evaluate EPA's radon attributable lung cancer estimates accounting for diesel exposure information in the miner cohorts. We used estimates of historical diesel concentrations, combined with diesel exposure-response functions, to estimate the risks of lung cancer attributable to diesel engine exhaust (DEE) exposure in the miner studies. We re-calculated the fatal lung cancer risk attributable to radon after accounting for risk from diesel and re-estimated the number of U.S. deaths associated with radon in the U.S. using EPA's methodology. Considering the probable confounding with DEE exposure and using the same estimate of baseline mortality from 1989-91 that the EPA currently uses in their calculations, we estimate that radon-induced lung cancer deaths per year are 15,600 (95% CI: 14,300, 17,000)- 19,300 (95% CI: 18,800, 20,000) in the U.S. population, a reduction of 9%-26%. The death estimates would be 12,900-15,900 using 2014 baseline vital statistics. We recommend further research on re-evaluating the health effects of exposure to radon that accounts for new information on diesel exhaust carcinogenicity in BEIR VI models, up-to-date vital statistics and new epidemiological evidence from residential studies.

  4. Radon-induced lung cancer deaths may be overestimated due to failure to account for confounding by exposure to diesel engine exhaust in BEIR VI miner studies

    PubMed Central

    MacNaughton, Piers; Laurent, Jose Cedeno; Allen, Joseph G.

    2017-01-01

    Background EPA reported that radon is the second leading cause of lung cancer in the United States, killing 21,100 people per year. EPA relies on the BEIR VI models, based on an evaluation of radon exposure and lung cancer risk in studies of miners. But these models did not account for co-exposure to diesel exhaust, a known human carcinogen recently classified by IARC. It is probable then that a portion of the lung cancer deaths in the miner cohorts are originally attributable to the exposure to diesel rather than radon. Objective To re-evaluate EPA’s radon attributable lung cancer estimates accounting for diesel exposure information in the miner cohorts. Methods We used estimates of historical diesel concentrations, combined with diesel exposure-response functions, to estimate the risks of lung cancer attributable to diesel engine exhaust (DEE) exposure in the miner studies. We re-calculated the fatal lung cancer risk attributable to radon after accounting for risk from diesel and re-estimated the number of U.S. deaths associated with radon in the U.S. using EPA’s methodology. Results Considering the probable confounding with DEE exposure and using the same estimate of baseline mortality from 1989–91 that the EPA currently uses in their calculations, we estimate that radon-induced lung cancer deaths per year are 15,600 (95% CI: 14,300, 17,000)– 19,300 (95% CI: 18,800, 20,000) in the U.S. population, a reduction of 9%–26%. The death estimates would be 12,900–15,900 using 2014 baseline vital statistics. Conclusions We recommend further research on re-evaluating the health effects of exposure to radon that accounts for new information on diesel exhaust carcinogenicity in BEIR VI models, up-to-date vital statistics and new epidemiological evidence from residential studies. PMID:28886109

  5. Mismeasurement and the resonance of strong confounders: uncorrelated errors.

    PubMed

    Marshall, J R; Hastrup, J L

    1996-05-15

    Greenland first documented (Am J Epidemiol 1980; 112:564-9) that error in the measurement of a confounder could resonate--that it could bias estimates of other study variables, and that the bias could persist even with statistical adjustment for the confounder as measured. An important question is raised by this finding: can such bias be more than trivial within the bounds of realistic data configurations? The authors examine several situations involving dichotomous and continuous data in which a confounder and a null variable are measured with error, and they assess the extent of resultant bias in estimates of the effect of the null variable. They show that, with continuous variables, measurement error amounting to 40% of observed variance in the confounder could cause the observed impact of the null study variable to appear to alter risk by as much as 30%. Similarly, they show, with dichotomous independent variables, that 15% measurement error in the form of misclassification could lead the null study variable to appear to alter risk by as much as 50%. Such bias would result only from strong confounding. Measurement error would obscure the evidence that strong confounding is a likely problem. These results support the need for every epidemiologic inquiry to include evaluations of measurement error in each variable considered.

  6. A flexible, interpretable framework for assessing sensitivity to unmeasured confounding.

    PubMed

    Dorie, Vincent; Harada, Masataka; Carnegie, Nicole Bohme; Hill, Jennifer

    2016-09-10

    When estimating causal effects, unmeasured confounding and model misspecification are both potential sources of bias. We propose a method to simultaneously address both issues in the form of a semi-parametric sensitivity analysis. In particular, our approach incorporates Bayesian Additive Regression Trees into a two-parameter sensitivity analysis strategy that assesses sensitivity of posterior distributions of treatment effects to choices of sensitivity parameters. This results in an easily interpretable framework for testing for the impact of an unmeasured confounder that also limits the number of modeling assumptions. We evaluate our approach in a large-scale simulation setting and with high blood pressure data taken from the Third National Health and Nutrition Examination Survey. The model is implemented as open-source software, integrated into the treatSens package for the R statistical programming language. © 2016 The Authors. Statistics in Medicine Published by John Wiley & Sons Ltd. © 2016 The Authors. Statistics in Medicine Published by John Wiley & Sons Ltd.

  7. Evaluating Public Health Interventions: 3. The Two-Stage Design for Confounding Bias Reduction-Having Your Cake and Eating It Two.

    PubMed

    Spiegelman, Donna; Rivera-Rodriguez, Claudia L; Haneuse, Sebastien

    2016-07-01

    In public health evaluations, confounding bias in the estimate of the intervention effect will typically threaten the validity of the findings. It is a common misperception that the only way to avoid this bias is to measure detailed, high-quality data on potential confounders for every intervention participant, but this strategy for adjusting for confounding bias is often infeasible. Rather than ignoring confounding altogether, the two-phase design and analysis-in which detailed high-quality confounding data are obtained among a small subsample-can be considered. We describe the two-stage design and analysis approach, and illustrate its use in the evaluation of an intervention conducted in Dar es Salaam, Tanzania, of an enhanced community health worker program to improve antenatal care uptake.

  8. Assessment of Confounders in Comparative Effectiveness Studies From Secondary Databases.

    PubMed

    Franklin, Jessica M; Schneeweiss, Sebastian; Solomon, Daniel H

    2017-03-15

    Secondary clinical databases are an important and growing source of data for comparative effectiveness research (CER) studies. However, measurement of confounders, such as biomarker values or patient-reported health status, in secondary clinical databases may not align with the initiation of a new treatment. In many published CER analyses of registry data, investigators assessed confounders based on the first questionnaire in which the new exposure was recorded. However, it is known that adjustment for confounders measured after the start of exposure can lead to biased treatment effect estimates. In the present study, we conducted simulations to compare assessment strategies for a dynamic clinical confounder in a registry-based comparative effectiveness study of 2 therapies. As expected, we found that adjustment for the confounder value at the time of the first questionnaire after the start of exposure creates a biased estimate the total effect of exposure choice on outcome when the confounder mediates part of the effect. However, adjustment for the prior value can also be badly biased when measured long before exposure initiation. Thus, investigators should carefully consider the timing of confounder measurements relative to exposure initiation and the rate of change in the confounder in order to choose the most relevant measure for each patient. © The Author 2017. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  9. Interpretational confounding is due to misspecification, not to type of indicator: comment on Howell, Breivik, and Wilcox (2007).

    PubMed

    Bollen, Kenneth A

    2007-06-01

    R. D. Howell, E. Breivik, and J. B. Wilcox (2007) have argued that causal (formative) indicators are inherently subject to interpretational confounding. That is, they have argued that using causal (formative) indicators leads the empirical meaning of a latent variable to be other than that assigned to it by a researcher. Their critique of causal (formative) indicators rests on several claims: (a) A latent variable exists apart from the model when there are effect (reflective) indicators but not when there are causal (formative) indicators, (b) causal (formative) indicators need not have the same consequences, (c) causal (formative) indicators are inherently subject to interpretational confounding, and (d) a researcher cannot detect interpretational confounding when using causal (formative) indicators. This article shows that each claim is false. Rather, interpretational confounding is more a problem of structural misspecification of a model combined with an underidentified model that leaves these misspecifications undetected. Interpretational confounding does not occur if the model is correctly specified whether a researcher has causal (formative) or effect (reflective) indicators. It is the validity of a model not the type of indicator that determines the potential for interpretational confounding. Copyright 2007 APA, all rights reserved.

  10. Methods to control for unmeasured confounding in pharmacoepidemiology: an overview.

    PubMed

    Uddin, Md Jamal; Groenwold, Rolf H H; Ali, Mohammed Sanni; de Boer, Anthonius; Roes, Kit C B; Chowdhury, Muhammad A B; Klungel, Olaf H

    2016-06-01

    Background Unmeasured confounding is one of the principal problems in pharmacoepidemiologic studies. Several methods have been proposed to detect or control for unmeasured confounding either at the study design phase or the data analysis phase. Aim of the Review To provide an overview of commonly used methods to detect or control for unmeasured confounding and to provide recommendations for proper application in pharmacoepidemiology. Methods/Results Methods to control for unmeasured confounding in the design phase of a study are case only designs (e.g., case-crossover, case-time control, self-controlled case series) and the prior event rate ratio adjustment method. Methods that can be applied in the data analysis phase include, negative control method, perturbation variable method, instrumental variable methods, sensitivity analysis, and ecological analysis. A separate group of methods are those in which additional information on confounders is collected from a substudy. The latter group includes external adjustment, propensity score calibration, two-stage sampling, and multiple imputation. Conclusion As the performance and application of the methods to handle unmeasured confounding may differ across studies and across databases, we stress the importance of using both statistical evidence and substantial clinical knowledge for interpretation of the study results.

  11. Educational gains in cause-specific mortality: Accounting for cognitive ability and family-level confounders using propensity score weighting.

    PubMed

    Bijwaard, Govert E; Myrskylä, Mikko; Tynelius, Per; Rasmussen, Finn

    2017-07-01

    A negative educational gradient has been found for many causes of death. This association may be partly explained by confounding factors that affect both educational attainment and mortality. We correct the cause-specific educational gradient for observed individual background and unobserved family factors using an innovative method based on months lost due to a specific cause of death re-weighted by the probability of attaining a higher educational level. We use data on men with brothers from the Swedish Military Conscription Registry (1951-1983), linked to administrative registers. This dataset of some 700,000 men allows us to distinguish between five education levels and many causes of death. The empirical results reveal that raising the educational level from primary to tertiary would result in an additional 20 months of survival between ages 18 and 63. This improvement in mortality is mainly attributable to fewer deaths from external causes. The highly educated gain more than nine months due to the reduction in deaths from external causes, but gain only two months due to the reduction in cancer mortality and four months due to the reduction in cardiovascular mortality. Ignoring confounding would lead to an underestimation of the gains by educational attainment, especially for the less educated. Our results imply that if the education distribution of 50,000 Swedish men from the 1951 cohort were replaced with that of the corresponding 1983 cohort, 22% of the person-years that were lost to death between ages 18 and 63 would have been saved for this cohort. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Insulin-Like Growth Factor 1 (IGF-1) in Parkinson's Disease: Potential as Trait-, Progression- and Prediction Marker and Confounding Factors

    PubMed Central

    Binder, Gerhard; Weber, Karin; Apel, Anja; Roeben, Benjamin; Deuschle, Christian; Maechtel, Mirjam; Heger, Tanja; Nussbaum, Susanne; Gasser, Thomas; Maetzler, Walter; Berg, Daniela

    2016-01-01

    Introduction Biomarkers indicating trait, progression and prediction of pathology and symptoms in Parkinson's disease (PD) often lack specificity or reliability. Investigating biomarker variance between individuals and over time and the effect of confounding factors is essential for the evaluation of biomarkers in PD, such as insulin-like growth factor 1 (IGF-1). Materials and Methods IGF-1 serum levels were investigated in up to 8 biannual visits in 37 PD patients and 22 healthy controls (HC) in the longitudinal MODEP study. IGF-1 baseline levels and annual changes in IGF-1 were compared between PD patients and HC while accounting for baseline disease duration (19 early stage: ≤3.5 years; 18 moderate stage: >4 years), age, sex, body mass index (BMI) and common medical factors putatively modulating IGF-1. In addition, associations of baseline IGF-1 with annual changes of motor, cognitive and depressive symptoms and medication dose were investigated. Results PD patients in moderate (130±26 ng/mL; p = .004), but not early stages (115±19, p>.1), showed significantly increased baseline IGF-1 levels compared with HC (106±24 ng/mL; p = .017). Age had a significant negative correlation with IGF-1 levels in HC (r = -.47, p = .028) and no correlation in PD patients (r = -.06, p>.1). BMI was negatively correlated in the overall group (r = -.28, p = .034). The annual changes in IGF-1 did not differ significantly between groups and were not correlated with disease duration. Baseline IGF-1 levels were not associated with annual changes of clinical parameters. Discussion Elevated IGF-1 in serum might differentiate between patients in moderate PD stages and HC. However, the value of serum IGF-1 as a trait-, progression- and prediction marker in PD is limited as IGF-1 showed large inter- and intraindividual variability and may be modulated by several confounders. PMID:26967642

  13. Task-independent effects are potential confounders in longitudinal imaging studies of learning in schizophrenia.

    PubMed

    Korostil, Michele; Fatima, Zainab; Kovacevic, Natasha; Menon, Mahesh; McIntosh, Anthony Randal

    2016-01-01

    Learning impairment is a core deficit in schizophrenia that impacts on real-world functioning and yet, elucidating its underlying neural basis remains a challenge. A key issue when interpreting learning-task experiments is that task-independent changes may confound interpretation of task-related signal changes in neuroimaging studies. The nature of these task-independent changes in schizophrenia is unknown. Therefore, we examined task-independent "time effects" in a group of participants with schizophrenia contrasted with healthy participants in a longitudinal fMRI learning-experiment designed to allow for examination of non-specific effects of time. Flanking the learning portions of the experiment with a task-of-no-interest allowed us to extract task-independent BOLD changes. Task-independent effects occurred in both groups, but were more robust in the schizophrenia group. There was a significant interaction effect between group and time in a distributed activity pattern that included inferior and superior temporal regions, frontal areas (left anterior insula and superior medial gyri), and parietal areas (posterior cingulate cortices and precuneus). This pattern showed task-independent linear decrease in BOLD amplitude over the two scanning sessions for the schizophrenia group, but showed either opposite effect or no activity changes for the control group. There was a trend towards a correlation between task-independent effects and the presence of more negative symptoms in the schizophrenia group. The strong interaction between group and time suggests that both the scanning experience as a whole and the transition between task-types evokes a different response in persons with schizophrenia and may confound interpretation of learning-related longitudinal imaging experiments if not explicitly considered.

  14. Task-independent effects are potential confounders in longitudinal imaging studies of learning in schizophrenia

    PubMed Central

    Korostil, Michele; Fatima, Zainab; Kovacevic, Natasha; Menon, Mahesh; McIntosh, Anthony Randal

    2015-01-01

    Learning impairment is a core deficit in schizophrenia that impacts on real-world functioning and yet, elucidating its underlying neural basis remains a challenge. A key issue when interpreting learning-task experiments is that task-independent changes may confound interpretation of task-related signal changes in neuroimaging studies. The nature of these task-independent changes in schizophrenia is unknown. Therefore, we examined task-independent “time effects” in a group of participants with schizophrenia contrasted with healthy participants in a longitudinal fMRI learning-experiment designed to allow for examination of non-specific effects of time. Flanking the learning portions of the experiment with a task-of-no-interest allowed us to extract task-independent BOLD changes. Task-independent effects occurred in both groups, but were more robust in the schizophrenia group. There was a significant interaction effect between group and time in a distributed activity pattern that included inferior and superior temporal regions, frontal areas (left anterior insula and superior medial gyri), and parietal areas (posterior cingulate cortices and precuneus). This pattern showed task-independent linear decrease in BOLD amplitude over the two scanning sessions for the schizophrenia group, but showed either opposite effect or no activity changes for the control group. There was a trend towards a correlation between task-independent effects and the presence of more negative symptoms in the schizophrenia group. The strong interaction between group and time suggests that both the scanning experience as a whole and the transition between task-types evokes a different response in persons with schizophrenia and may confound interpretation of learning-related longitudinal imaging experiments if not explicitly considered. PMID:26759790

  15. The ad-libitum alcohol 'taste test': secondary analyses of potential confounds and construct validity.

    PubMed

    Jones, Andrew; Button, Emily; Rose, Abigail K; Robinson, Eric; Christiansen, Paul; Di Lemma, Lisa; Field, Matt

    2016-03-01

    Motivation to drink alcohol can be measured in the laboratory using an ad-libitum 'taste test', in which participants rate the taste of alcoholic drinks whilst their intake is covertly monitored. Little is known about the construct validity of this paradigm. The objective of this study was to investigate variables that may compromise the validity of this paradigm and its construct validity. We re-analysed data from 12 studies from our laboratory that incorporated an ad-libitum taste test. We considered time of day and participants' awareness of the purpose of the taste test as potential confounding variables. We examined whether gender, typical alcohol consumption, subjective craving, scores on the Alcohol Use Disorders Identification Test and perceived pleasantness of the drinks predicted ad-libitum consumption (construct validity). We included 762 participants (462 female). Participant awareness and time of day were not related to ad-libitum alcohol consumption. Males drank significantly more alcohol than females (p < 0.001), and individual differences in typical alcohol consumption (p = 0.04), craving (p < 0.001) and perceived pleasantness of the drinks (p = 0.04) were all significant predictors of ad-libitum consumption. We found little evidence that time of day or participant awareness influenced alcohol consumption. The construct validity of the taste test was supported by relationships between ad-libitum consumption and typical alcohol consumption, craving and pleasantness ratings of the drinks. The ad-libitum taste test is a valid method for the assessment of alcohol intake in the laboratory.

  16. Coping with confounds in multivoxel pattern analysis: what should we do about reaction time differences? A comment on Todd, Nystrom & Cohen 2013.

    PubMed

    Woolgar, Alexandra; Golland, Polina; Bode, Stefan

    2014-09-01

    Multivoxel pattern analysis (MVPA) is a sensitive and increasingly popular method for examining differences between neural activation patterns that cannot be detected using classical mass-univariate analysis. Recently, Todd et al. ("Confounds in multivariate pattern analysis: Theory and rule representation case study", 2013, NeuroImage 77: 157-165) highlighted a potential problem for these methods: high sensitivity to confounds at the level of individual participants due to the use of directionless summary statistics. Unlike traditional mass-univariate analyses where confounding activation differences in opposite directions tend to approximately average out at group level, group level MVPA results may be driven by any activation differences that can be discriminated in individual participants. In Todd et al.'s empirical data, factoring out differences in reaction time (RT) reduced a classifier's ability to distinguish patterns of activation pertaining to two task rules. This raises two significant questions for the field: to what extent have previous multivoxel discriminations in the literature been driven by RT differences, and by what methods should future studies take RT and other confounds into account? We build on the work of Todd et al. and compare two different approaches to remove the effect of RT in MVPA. We show that in our empirical data, in contrast to that of Todd et al., the effect of RT on rule decoding is negligible, and results were not affected by the specific details of RT modelling. We discuss the meaning of and sensitivity for confounds in traditional and multivoxel approaches to fMRI analysis. We observe that the increased sensitivity of MVPA comes at a price of reduced specificity, meaning that these methods in particular call for careful consideration of what differs between our conditions of interest. We conclude that the additional complexity of the experimental design, analysis and interpretation needed for MVPA is still not a reason to

  17. Accounting for context in studies of health inequalities: a review and comparison of analytic approaches.

    PubMed

    Schempf, Ashley H; Kaufman, Jay S

    2012-10-01

    A common epidemiologic objective is to evaluate the contribution of residential context to individual-level disparities by race or socioeconomic position. We reviewed analytic strategies to account for the total (observed and unobserved factors) contribution of environmental context to health inequalities, including conventional fixed effects (FE) and hybrid FE implemented within a random effects (RE) or a marginal model. To illustrate results and limitations of the various analytic approaches of accounting for the total contextual component of health disparities, we used data on births nested within neighborhoods as an applied example of evaluating neighborhood confounding of racial disparities in gestational age at birth, including both a continuous and a binary outcome. Ordinary and RE models provided disparity estimates that can be substantially biased in the presence of neighborhood confounding. Both FE and hybrid FE models can account for cluster level confounding and provide disparity estimates unconfounded by neighborhood, with the latter having greater flexibility in allowing estimation of neighborhood-level effects and intercept/slope variability when implemented in a RE specification. Given the range of models that can be implemented in a hybrid approach and the frequent goal of accounting for contextual confounding, this approach should be used more often. Published by Elsevier Inc.

  18. Using expert opinion to quantify unmeasured confounding bias parameters.

    PubMed

    Navadeh, Soodabeh; Mirzazadeh, Ali; McFarland, Willi; Woolf-King, Sarah; Mansournia, Mohammad Ali

    2016-06-27

    To develop and apply a method to quantify bias parameters in the case example of the association between alcohol use and HIV-serodiscordant condomless anal sex with potential confounding by sensation seeking among men who have sex with men (MSM), using expert opinion as an external data source. Through an online survey, we sought the input of 41 epidemiologist and behavioural scientists to quantify six parameters in the population of MSM: the proportion of high sensation seeking among heavy-drinking MSM, the proportion of sensation seeking among low-level drinking MSM, and the risk ratio (RR) of the association between sensation seeking and condomless anal sex, for HIV-positive and HIV-negative MSM. Eleven experts responded. For HIV-positive heavy drinkers, the proportion of high sensation seeking was 53.6% (beta distribution [α=5.50, β=4.78]), and 41.1% (beta distribution [α=3.10, β=4.46]) in HIV-negative heavy drinkers. In HIV-positive low-level alcohol drinkers, high sensation seeking was 26.9% (beta distribution [α=1.81, β=4.92]), similar to high sensation seeking among HIV-negative low-level alcohol drinkers (25.3%) (beta distribution [α=2.00, β=5.89]). The lnRR for the association between sensation seeking and condomless anal sex was ln(2.4) (normal distribution [μ=0.889, σ=0.438]) in HIV-positive and ln(1.5) (normal distribution [μ=0.625, σ=0.391]) in HIV-negative MSM. Expert opinion can be a simple and efficient method for deriving bias parameters to quantify and adjust for hypothesized confounding. In this test case, expert opinion confirmed sensation seeking as a confounder for the effect of alcohol on condomless anal sex and provided the parameters necessary for probabilistic bias analysis.

  19. Controlling for unmeasured confounding and spatial misalignment in long-term air pollution and health studies.

    PubMed

    Lee, Duncan; Sarran, Christophe

    2015-11-01

    The health impact of long-term exposure to air pollution is now routinely estimated using spatial ecological studies, owing to the recent widespread availability of spatial referenced pollution and disease data. However, this areal unit study design presents a number of statistical challenges, which if ignored have the potential to bias the estimated pollution-health relationship. One such challenge is how to control for the spatial autocorrelation present in the data after accounting for the known covariates, which is caused by unmeasured confounding. A second challenge is how to adjust the functional form of the model to account for the spatial misalignment between the pollution and disease data, which causes within-area variation in the pollution data. These challenges have largely been ignored in existing long-term spatial air pollution and health studies, so here we propose a novel Bayesian hierarchical model that addresses both challenges and provide software to allow others to apply our model to their own data. The effectiveness of the proposed model is compared by simulation against a number of state-of-the-art alternatives proposed in the literature and is then used to estimate the impact of nitrogen dioxide and particulate matter concentrations on respiratory hospital admissions in a new epidemiological study in England in 2010 at the local authority level. © 2015 The Authors. Environmetrics published by John Wiley & Sons Ltd.

  20. Poppers, Kaposi's sarcoma, and HIV infection: empirical example of a strong confounding effect?

    PubMed

    Morabia, A

    1995-01-01

    Are there empirical examples of strong confounding effects? Textbooks usually show examples of weak confounding or use hypothetical examples of strong confounding to illustrate the paradoxical consequences of not separating out the effect of the studied exposure from that of second factor acting as a confounder. HIV infection is a candidate strong confounder of the spuriously high association reported between consumption of poppers, a sexual stimulant, and risk of Kaposi's sarcoma in the early phase of the AIDS epidemic. To examine this hypothesis, assumptions must be made on the prevalence of HIV infection among cases of Kaposi's sarcoma and on the prevalence of heavy popper consumption according to HIV infection in cases and controls. Results show that HIV infection may have confounded the poppers-Kaposi's sarcoma association. However, it cannot be ruled out that HIV did not qualify as a confounder because it was either an intermediate variable or an effect modifier of the association between popper inhalation and Kaposi's sarcoma. This example provides a basis to discuss the mechanism by which confounding occurs as well as the practical importance of confounding in epidemiologic research.

  1. LD Score Regression Distinguishes Confounding from Polygenicity in Genome-Wide Association Studies

    PubMed Central

    Bulik-Sullivan, Brendan K.; Loh, Po-Ru; Finucane, Hilary; Ripke, Stephan; Yang, Jian; Patterson, Nick; Daly, Mark J.; Price, Alkes L.; Neale, Benjamin M.

    2015-01-01

    Both polygenicity (i.e., many small genetic effects) and confounding biases, such as cryptic relatedness and population stratification, can yield an inflated distribution of test statistics in genome-wide association studies (GWAS). However, current methods cannot distinguish between inflation from true polygenic signal and bias. We have developed an approach, LD Score regression, that quantifies the contribution of each by examining the relationship between test statistics and linkage disequilibrium (LD). The LD Score regression intercept can be used to estimate a more powerful and accurate correction factor than genomic control. We find strong evidence that polygenicity accounts for the majority of test statistic inflation in many GWAS of large sample size. PMID:25642630

  2. Controlling for seasonal patterns and time varying confounders in time-series epidemiological models: a simulation study.

    PubMed

    Perrakis, Konstantinos; Gryparis, Alexandros; Schwartz, Joel; Le Tertre, Alain; Katsouyanni, Klea; Forastiere, Francesco; Stafoggia, Massimo; Samoli, Evangelia

    2014-12-10

    An important topic when estimating the effect of air pollutants on human health is choosing the best method to control for seasonal patterns and time varying confounders, such as temperature and humidity. Semi-parametric Poisson time-series models include smooth functions of calendar time and weather effects to control for potential confounders. Case-crossover (CC) approaches are considered efficient alternatives that control seasonal confounding by design and allow inclusion of smooth functions of weather confounders through their equivalent Poisson representations. We evaluate both methodological designs with respect to seasonal control and compare spline-based approaches, using natural splines and penalized splines, and two time-stratified CC approaches. For the spline-based methods, we consider fixed degrees of freedom, minimization of the partial autocorrelation function, and general cross-validation as smoothing criteria. Issues of model misspecification with respect to weather confounding are investigated under simulation scenarios, which allow quantifying omitted, misspecified, and irrelevant-variable bias. The simulations are based on fully parametric mechanisms designed to replicate two datasets with different mortality and atmospheric patterns. Overall, minimum partial autocorrelation function approaches provide more stable results for high mortality counts and strong seasonal trends, whereas natural splines with fixed degrees of freedom perform better for low mortality counts and weak seasonal trends followed by the time-season-stratified CC model, which performs equally well in terms of bias but yields higher standard errors. Copyright © 2014 John Wiley & Sons, Ltd.

  3. An assessment of the possible extent of confounding in epidemiological studies of lung cancer risk among roofers

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mundt, D.J.; van Wijngaarden, E.; Mundt, K.A.

    2007-07-01

    We evaluated the likelihood and extent to which the observed increased risk of lung cancer may be due to confounding (a mixing of effects of multiple exposures) by co-exposure to other potential carcinogens present in roofing or to lifestyle variables. We conducted a review of the epidemiological and industrial hygiene literature of asphalt-exposed workers. Peer-reviewed epidemiological studies of asphalt fumes, related occupational exposures, and confounding factors were identified from MEDLINE (1966 early 2004). Industrial hygiene studies of asphalt workers were identified through MEDLINE, publicly available government documents, and asphalt industry documents. Using well established statistical methods, we quantified the extentmore » to which lung cancer relative risk estimates among roofers reflect confounding from other exposures, using different prevalence and risk scenarios. The relative risk of lung cancer varied from 1.2 to 5.0 in 13 epidemiological studies of roofers; most studies reported a relative risk between 1.2 and 1.4. Smoking, asbestos and coal tar were the most likely confounders, but the prevalence of these factors varied over time. The results of the study indicate that much of the observed risk reported in epidemiological studies of cancer among roofers is well within the range of what may have resulted from confounding by reasonable and expected levels of smoking, asbestos or coal tar. This may be particularly true for those studies that did not adjust for these confounders and where the exposure was defined as employment in the roofing industry. In addition to poorly defined asphalt exposure, uncontrolled confounding cannot reliably be ruled out in studies of lung cancer among asphalt-exposed roofers. Therefore, it is not possible to conclude whether roofers are at increased risk of lung cancer due to asphalt exposure.« less

  4. Examining the role of unmeasured confounding in mediation analysis with genetic and genomic applications.

    PubMed

    Lutz, Sharon M; Thwing, Annie; Schmiege, Sarah; Kroehl, Miranda; Baker, Christopher D; Starling, Anne P; Hokanson, John E; Ghosh, Debashis

    2017-07-19

    In mediation analysis if unmeasured confounding is present, the estimates for the direct and mediated effects may be over or under estimated. Most methods for the sensitivity analysis of unmeasured confounding in mediation have focused on the mediator-outcome relationship. The Umediation R package enables the user to simulate unmeasured confounding of the exposure-mediator, exposure-outcome, and mediator-outcome relationships in order to see how the results of the mediation analysis would change in the presence of unmeasured confounding. We apply the Umediation package to the Genetic Epidemiology of Chronic Obstructive Pulmonary Disease (COPDGene) study to examine the role of unmeasured confounding due to population stratification on the effect of a single nucleotide polymorphism (SNP) in the CHRNA5/3/B4 locus on pulmonary function decline as mediated by cigarette smoking. Umediation is a flexible R package that examines the role of unmeasured confounding in mediation analysis allowing for normally distributed or Bernoulli distributed exposures, outcomes, mediators, measured confounders, and unmeasured confounders. Umediation also accommodates multiple measured confounders, multiple unmeasured confounders, and allows for a mediator-exposure interaction on the outcome. Umediation is available as an R package at https://github.com/SharonLutz/Umediation A tutorial on how to install and use the Umediation package is available in the Additional file 1.

  5. On the Confounding Effect of Temperature on Chemical Shift-Encoded Fat Quantification

    PubMed Central

    Hernando, Diego; Sharma, Samir D.; Kramer, Harald; Reeder, Scott B.

    2014-01-01

    Purpose To characterize the confounding effect of temperature on chemical shift-encoded (CSE) fat quantification. Methods The proton resonance frequency of water, unlike triglycerides, depends on temperature. This leads to a temperature dependence of the spectral models of fat (relative to water) that are commonly used by CSE-MRI methods. Simulation analysis was performed for 1.5 Tesla CSE fat–water signals at various temperatures and echo time combinations. Oil–water phantoms were constructed and scanned at temperatures between 0 and 40°C using spectroscopy and CSE imaging at three echo time combinations. An explanted human liver, rejected for transplantation due to steatosis, was scanned using spectroscopy and CSE imaging. Fat–water reconstructions were performed using four different techniques: magnitude and complex fitting, with standard or temperature-corrected signal modeling. Results In all experiments, magnitude fitting with standard signal modeling resulted in large fat quantification errors. Errors were largest for echo time combinations near TEinit ≈ 1.3 ms, ΔTE ≈ 2.2 ms. Errors in fat quantification caused by temperature-related frequency shifts were smaller with complex fitting, and were avoided using a temperature-corrected signal model. Conclusion Temperature is a confounding factor for fat quantification. If not accounted for, it can result in large errors in fat quantifications in phantom and ex vivo acquisitions. PMID:24123362

  6. Which Propensity Score Method Best Reduces Confounder Imbalance? An Example From a Retrospective Evaluation of a Childhood Obesity Intervention.

    PubMed

    Schroeder, Krista; Jia, Haomiao; Smaldone, Arlene

    Propensity score (PS) methods are increasingly being employed by researchers to reduce bias arising from confounder imbalance when using observational data to examine intervention effects. The purpose of this study was to examine PS theory and methodology and compare application of three PS methods (matching, stratification, weighting) to determine which best improves confounder balance. Baseline characteristics of a sample of 20,518 school-aged children with severe obesity (of whom 1,054 received an obesity intervention) were assessed prior to PS application. Three PS methods were then applied to the data to determine which showed the greatest improvement in confounder balance between the intervention and control group. The effect of each PS method on the outcome variable-body mass index percentile change at one year-was also examined. SAS 9.4 and Comprehensive Meta-analysis statistical software were used for analyses. Prior to PS adjustment, the intervention and control groups differed significantly on seven of 11 potential confounders. PS matching removed all differences. PS stratification and weighting both removed one difference but created two new differences. Sensitivity analyses did not change these results. Body mass index percentile at 1 year decreased in both groups. The size of the decrease was smaller in the intervention group, and the estimate of the decrease varied by PS method. Selection of a PS method should be guided by insight from statistical theory and simulation experiments, in addition to observed improvement in confounder balance. For this data set, PS matching worked best to correct confounder imbalance. Because each method varied in correcting confounder imbalance, we recommend that multiple PS methods be compared for ability to improve confounder balance before implementation in evaluating treatment effects in observational data.

  7. Structural confounding of area-level deprivation and segreation: an empirical example

    EPA Science Inventory

    The neighborhood effects literature has grown, but its utility is limited by the lack of attention paid to non-random selection into neighborhoods. Confounding occurs when an exposure and an outcome share an underlying common cause. Confounding resulting from differential allocat...

  8. Breast milk and cognitive development—the role of confounders: a systematic review

    PubMed Central

    Walfisch, Asnat; Sermer, Corey; Cressman, Alex; Koren, Gideon

    2013-01-01

    Objectives The association between breastfeeding and child cognitive development is conflicted by studies reporting positive and null effects. This relationship may be confounded by factors associated with breastfeeding, specifically maternal socioeconomic class and IQ. Design Systematic review of the literature. Setting and participants Any prospective or retrospective study, in any language, evaluating the association between breastfeeding and cognitive development using a validated method in healthy term infants, children or adults, was included. Primary and secondary outcome measures Extracted data included the study design, target population and sample size, breastfeeding exposure, cognitive development assessment tool used and participants’ age, summary of the results prior to, and following, adjustment for confounders, and all confounders adjusted for. Study quality was assessed as well. Results 84 studies met our inclusion criteria (34 rated as high quality, 26 moderate and 24 low quality). Critical assessment of accepted studies revealed the following associations: 21 null, 28 positive, 18 null after adjusting for confounders and 17 positive—diminished after adjusting for confounders. Directionality of effect did not correlate with study quality; however, studies showing a decreased effect after multivariate analysis were of superior quality compared with other study groupings (14/17 high quality, 82%). Further, studies that showed null or diminished effect after multivariate analysis corrected for significantly more confounders (7.7±3.4) as compared with those that found no change following adjustment (5.6±4.5, p=0.04). The majority of included studies were carried out during childhood (75%) and set in high-income countries (85.5%). Conclusions Much of the reported effect of breastfeeding on child neurodevelopment is due to confounding. It is unlikely that additional work will change the current synthesis. Future studies should attempt to rigorously

  9. Comorbidity of intellectual disability confounds ascertainment of autism: implications for genetic diagnosis.

    PubMed

    Polyak, Andrew; Kubina, Richard M; Girirajan, Santhosh

    2015-10-01

    While recent studies suggest a converging role for genetic factors towards risk for nosologically distinct disorders including autism, intellectual disability (ID), and epilepsy, current estimates of autism prevalence fail to take into account the impact of comorbidity of these disorders on autism diagnosis. We aimed to assess the effect of comorbidity on the diagnosis and prevalence of autism by analyzing 11 years (2000-2010) of special education enrollment data on approximately 6.2 million children per year. We found a 331% increase in the prevalence of autism from 2000 to 2010 within special education, potentially due to a diagnostic recategorization from frequently comorbid features such as ID. The decrease in ID prevalence equaled an average of 64.2% of the increase of autism prevalence for children aged 3-18 years. The proportion of ID cases potentially undergoing recategorization to autism was higher (P = 0.007) among older children (75%) than younger children (48%). Some US states showed significant negative correlations between the prevalence of autism compared to that of ID while others did not, suggesting state-specific health policy to be a major factor in categorizing autism. Further, a high frequency of autistic features was observed when individuals with classically defined genetic syndromes were evaluated for autism using standardized instruments. Our results suggest that current ascertainment practices are based on a single facet of autism-specific clinical features and do not consider associated comorbidities that may confound diagnosis. Longitudinal studies with detailed phenotyping and deep molecular genetic analyses are necessary to completely understand the cause of this complex disorder. © 2015 Wiley Periodicals, Inc.

  10. Assessment of the Potential for Human Resource Accounting in Venezuelan Navy Management Decision Making.

    DTIC Science & Technology

    1981-12-01

    Accounting Association, 1957, op. cit, p. 6. 23. Horngren , Charles, " Cost Accounting : A Managerial Emphasis," Solutions Manual, Prentice-Hall...Model," Management Accounting , December 1977. Savich, R. S . and Ehrenreich, K. E., " Cost /Benefits Analysis of Human Resource Accounting Alternatives...A0A112 T40 NAVAL POSTGRADUATE SCHOOL MONTEREY CA F/ S S / ASSESS1ENT OF THE POTENTIAL FOR HUMAN RESOURCE ACCOUNTING IN VE-ETC(Ul EC GS K FI MARN

  11. Confounding by dietary patterns of the inverse association between alcohol consumption and type 2 diabetes risk.

    PubMed

    Imamura, Fumiaki; Lichtenstein, Alice H; Dallal, Gerard E; Meigs, James B; Jacques, Paul F

    2009-07-01

    The ability to interpret epidemiologic observations is limited because of potential residual confounding by correlated dietary components. Dietary pattern analyses by factor analysis or partial least squares may overcome the limitation. To examine confounding by dietary pattern as well as standard risk factors and selected nutrients, the authors modeled the longitudinal association between alcohol consumption and 7-year risk of type 2 diabetes mellitus in 2,879 healthy adults enrolled in the Framingham Offspring Study (1991-2001) by Cox proportional hazard models. After adjustment for standard risk factors, consumers of > or =9.0 drinks/week had a significantly lower risk of type 2 diabetes mellitus compared with abstainers (hazard ratio = 0.47, 95% confidence interval (CI): 0.27, 0.81). Adjustment for selected nutrients had little effect on the hazard ratio, whereas adjustment for dietary pattern variables by factor analysis significantly shifted the hazard ratio away from null (hazard ratio = 0.33, 95% CI: 0.17, 0.64) by 40.0% (95% CI: 16.8, 57.0; P = 0.002). Dietary pattern variables by partial least squares showed similar results. Therefore, the observed inverse association, consistent with past studies, was confounded by dietary patterns, and this confounding was not captured by individual nutrient adjustment. The data suggest that alcohol intake, not dietary patterns associated with alcohol intake, is responsible for the observed inverse association with type 2 diabetes mellitus risk.

  12. Clinical and evoked pain, personality traits, and emotional states: can familial confounding explain the associations?

    PubMed

    Strachan, Eric; Poeschla, Brian; Dansie, Elizabeth; Succop, Annemarie; Chopko, Laura; Afari, Niloofar

    2015-01-01

    Pain is a complex phenomenon influenced by context and person-specific factors. Affective dimensions of pain involve both enduring personality traits and fleeting emotional states. We examined how personality traits and emotional states are linked with clinical and evoked pain in a twin sample. 99 female twin pairs were evaluated for clinical and evoked pain using the McGill Pain Questionnaire (MPQ) and dolorimetry, and completed the 120-item International Personality Item Pool (IPIP), the Positive and Negative Affect Scale (PANAS), and ratings of stress and mood. Using a co-twin control design we examined a) the relationship of personality traits and emotional states with clinical and evoked pain and b) whether genetics and common environment (i.e. familial factors) may account for the associations. Neuroticism was associated with the sensory component of the MPQ; this relationship was not confounded by familial factors. None of the emotional state measures was associated with the MPQ. PANAS negative affect was associated with lower evoked pressure pain threshold and tolerance; these associations were confounded by familial factors. There were no associations between IPIP traits and evoked pain. A relationship exists between neuroticism and clinical pain that is not confounded by familial factors. There is no similar relationship between negative emotional states and clinical pain. In contrast, the relationship between negative emotional states and evoked pain is strong while the relationship with enduring personality traits is weak. The relationship between negative emotional states and evoked pain appears to be non-causal and due to familial factors. Copyright © 2014 Elsevier Inc. All rights reserved.

  13. Quantification of confounding factors in MRI-based dose calculations as applied to prostate IMRT

    NASA Astrophysics Data System (ADS)

    Maspero, Matteo; Seevinck, Peter R.; Schubert, Gerald; Hoesl, Michaela A. U.; van Asselen, Bram; Viergever, Max A.; Lagendijk, Jan J. W.; Meijer, Gert J.; van den Berg, Cornelis A. T.

    2017-02-01

    Magnetic resonance (MR)-only radiotherapy treatment planning requires pseudo-CT (pCT) images to enable MR-based dose calculations. To verify the accuracy of MR-based dose calculations, institutions interested in introducing MR-only planning will have to compare pCT-based and computer tomography (CT)-based dose calculations. However, interpreting such comparison studies may be challenging, since potential differences arise from a range of confounding factors which are not necessarily specific to MR-only planning. Therefore, the aim of this study is to identify and quantify the contribution of factors confounding dosimetric accuracy estimation in comparison studies between CT and pCT. The following factors were distinguished: set-up and positioning differences between imaging sessions, MR-related geometric inaccuracy, pCT generation, use of specific calibration curves to convert pCT into electron density information, and registration errors. The study comprised fourteen prostate cancer patients who underwent CT/MRI-based treatment planning. To enable pCT generation, a commercial solution (MRCAT, Philips Healthcare, Vantaa, Finland) was adopted. IMRT plans were calculated on CT (gold standard) and pCTs. Dose difference maps in a high dose region (CTV) and in the body volume were evaluated, and the contribution to dose errors of possible confounding factors was individually quantified. We found that the largest confounding factor leading to dose difference was the use of different calibration curves to convert pCT and CT into electron density (0.7%). The second largest factor was the pCT generation which resulted in pCT stratified into a fixed number of tissue classes (0.16%). Inter-scan differences due to patient repositioning, MR-related geometric inaccuracy, and registration errors did not significantly contribute to dose differences (0.01%). The proposed approach successfully identified and quantified the factors confounding accurate MRI-based dose calculation in

  14. Teacher Quality at the High-School Level: The Importance of Accounting for Tracks. Working Paper 17722. Revised

    ERIC Educational Resources Information Center

    Jackson, C. Kirabo

    2013-01-01

    Unlike in elementary school, high-school teacher effects may be confounded with both selection to tracks and unobserved track-level treatments. I document sizable confounding track effects, and show that traditional tests for the existence of teacher effects are likely biased. After accounting for these biases, high-school algebra and English…

  15. Are attractive men's faces masculine or feminine? The importance of controlling confounds in face stimuli.

    PubMed

    DeBruine, Lisa M; Jones, Benedict C; Smith, Finlay G; Little, Anthony C

    2010-06-01

    Women's preferences for male masculinity are highly variable. Although many researchers explain this variability as reflecting systematic individual differences in how women resolve the tradeoff between the costs and benefits of choosing a masculine partner, others suggest that methodological differences between studies are responsible. A recent study found general femininity preferences for judgments of faces that were manipulated in sexual dimorphism of shape but general masculinity preferences for judgments of faces that were based on perceived masculinity. Using the original stimuli, we replicated these previous results but found equivalent general femininity preferences for both types of faces when nonface confounds in the stimuli (e.g. hairstyle) were eliminated through masking. We conclude that care must be taken to control potential confounds in stimuli and that the influence of nonface cues on preferences for facial masculinity deserves further study.

  16. The Problem of Confounding in Studies of the Effect of Maternal Drug Use on Pregnancy Outcome

    PubMed Central

    Källén, Bengt

    2012-01-01

    In most epidemilogical studies, the problem of confounding adds to the uncertainty in conclusions drawn. This is also true for studies on the effect of maternal drug use on birth defect risks. This paper describes various types of such confounders and discusses methods to identify and adjust for them. Such confounders can be found in maternal characteristics like age, parity, smoking, use of alcohol, and body mass index, subfertility, and previous pregnancies including previous birth of a malformed child, socioeconomy, race/ethnicity, or country of birth. Confounding by concomitant maternal drug use may occur. A geographical or seasonal confounding can exist. In rare instances, infant sex and multiple birth can appear as confounders. The most difficult problem to solve is often confounding by indication. The problem of confounding is less important for congenital malformations than for many other pregnancy outcomes. PMID:22190949

  17. Handling stress may confound murine gut microbiota studies.

    PubMed

    Allen-Blevins, Cary R; You, Xiaomeng; Hinde, Katie; Sela, David A

    2017-01-01

    Accumulating evidence indicates interactions between human milk composition, particularly sugars (human milk oligosaccharides or HMO), the gut microbiota of human infants, and behavioral effects. Some HMO secreted in human milk are unable to be endogenously digested by the human infant but are able to be metabolized by certain species of gut microbiota, including Bifidobacterium longum subsp. infantis (B. infantis) , a species sensitive to host stress (Bailey & Coe, 2004). Exposure to gut bacteria like B. infantis during critical neurodevelopment windows in early life appears to have behavioral consequences; however, environmental, physical, and social stress during this period can also have behavioral and microbial consequences. While rodent models are a useful method for determining causal relationships between HMO, gut microbiota, and behavior, murine studies of gut microbiota usually employ oral gavage, a technique stressful to the mouse. Our aim was to develop a less-invasive technique for HMO administration to remove the potential confound of gavage stress. Under the hypothesis that stress affects gut microbiota, particularly B. infantis , we predicted the pups receiving a prebiotic solution in a less-invasive manner would have the highest amount of Bifidobacteria in their gut. This study was designed to test two methods, active and passive, of solution administration to mice and the effects on their gut microbiome. Neonatal C57BL/6J mice housed in a specific-pathogen free facility received increasing doses of fructooligosaccharide (FOS) solution or deionized, distilled water. Gastrointestinal (GI) tracts were collected from five dams, six sires, and 41 pups over four time points. Seven fecal pellets from unhandled pups and two pellets from unhandled dams were also collected. Qualitative real-time polymerase chain reaction (qRT-PCR) was used to quantify and compare the amount of Bifidobacterium , Bacteroides , Bacteroidetes, and Firmicutes. Our results

  18. Modeling uranium(VI) adsorption onto montmorillonite under varying carbonate concentrations: A surface complexation model accounting for the spillover effect on surface potential

    NASA Astrophysics Data System (ADS)

    Tournassat, C.; Tinnacher, R. M.; Grangeon, S.; Davis, J. A.

    2018-01-01

    The prediction of U(VI) adsorption onto montmorillonite clay is confounded by the complexities of: (1) the montmorillonite structure in terms of adsorption sites on basal and edge surfaces, and the complex interactions between the electrical double layers at these surfaces, and (2) U(VI) solution speciation, which can include cationic, anionic and neutral species. Previous U(VI)-montmorillonite adsorption and modeling studies have typically expanded classical surface complexation modeling approaches, initially developed for simple oxides, to include both cation exchange and surface complexation reactions. However, previous models have not taken into account the unique characteristics of electrostatic surface potentials that occur at montmorillonite edge sites, where the electrostatic surface potential of basal plane cation exchange sites influences the surface potential of neighboring edge sites ('spillover' effect). A series of U(VI) - Na-montmorillonite batch adsorption experiments was conducted as a function of pH, with variable U(VI), Ca, and dissolved carbonate concentrations. Based on the experimental data, a new type of surface complexation model (SCM) was developed for montmorillonite, that specifically accounts for the spillover effect using the edge surface speciation model by Tournassat et al. (2016a). The SCM allows for a prediction of U(VI) adsorption under varying chemical conditions with a minimum number of fitting parameters, not only for our own experimental results, but also for a number of published data sets. The model agreed well with many of these datasets without introducing a second site type or including the formation of ternary U(VI)-carbonato surface complexes. The model predictions were greatly impacted by utilizing analytical measurements of dissolved inorganic carbon (DIC) concentrations in individual sample solutions rather than assuming solution equilibration with a specific partial pressure of CO2, even when the gas phase was

  19. Evaluation in medical education: A topical review of target parameters, data collection tools and confounding factors.

    PubMed

    Schiekirka, Sarah; Feufel, Markus A; Herrmann-Lingen, Christoph; Raupach, Tobias

    2015-01-01

    Evaluation is an integral part of education in German medical schools. According to the quality standards set by the German Society for Evaluation, evaluation tools must provide an accurate and fair appraisal of teaching quality. Thus, data collection tools must be highly reliable and valid. This review summarises the current literature on evaluation of medical education with regard to the possible dimensions of teaching quality, the psychometric properties of survey instruments and potential confounding factors. We searched Pubmed, PsycINFO and PSYNDEX for literature on evaluation in medical education and included studies published up until June 30, 2011 as well as articles identified in the "grey literature". RESULTS are presented as a narrative review. We identified four dimensions of teaching quality: structure, process, teacher characteristics, and outcome. Student ratings are predominantly used to address the first three dimensions, and a number of reliable tools are available for this purpose. However, potential confounders of student ratings pose a threat to the validity of these instruments. Outcome is usually operationalised in terms of student performance on examinations, but methodological problems may limit the usability of these data for evaluation purposes. In addition, not all examinations at German medical schools meet current quality standards. The choice of tools for evaluating medical education should be guided by the dimension that is targeted by the evaluation. Likewise, evaluation results can only be interpreted within the context of the construct addressed by the data collection tool that was used as well as its specific confounding factors.

  20. Accounting for Time-Varying Confounding in the Relationship Between Obesity and Coronary Heart Disease: Analysis With G-Estimation: The ARIC Study.

    PubMed

    Shakiba, Maryam; Mansournia, Mohammad Ali; Salari, Arsalan; Soori, Hamid; Mansournia, Nasrin; Kaufman, Jay S

    2018-06-01

    In longitudinal studies, standard analysis may yield biased estimates of exposure effect in the presence of time-varying confounders that are also intermediate variables. We aimed to quantify the relationship between obesity and coronary heart disease (CHD) by appropriately adjusting for time-varying confounders. This study was performed in a subset of participants from the Atherosclerosis Risk in Communities (ARIC) Study (1987-2010), a US study designed to investigate risk factors for atherosclerosis. General obesity was defined as body mass index (weight (kg)/height (m)2) ≥30, and abdominal obesity (AOB) was defined according to either waist circumference (≥102 cm in men and ≥88 cm in women) or waist:hip ratio (≥0.9 in men and ≥0.85 in women). The association of obesity with CHD was estimated by G-estimation and compared with results from accelerated failure-time models using 3 specifications. The first model, which adjusted for baseline covariates, excluding metabolic mediators of obesity, showed increased risk of CHD for all obesity measures. Further adjustment for metabolic mediators in the second model and time-varying variables in the third model produced negligible changes in the hazard ratios. The hazard ratios estimated by G-estimation were 1.15 (95% confidence interval (CI): 0.83, 1.47) for general obesity, 1.65 (95% CI: 1.35, 1.92) for AOB based on waist circumference, and 1.38 (95% CI: 1.13, 1.99) for AOB based on waist:hip ratio, suggesting that AOB increased the risk of CHD. The G-estimated hazard ratios for both measures were further from the null than those derived from standard models.

  1. A Comprehensive Analysis of the SRS-Schwab Adult Spinal Deformity Classification and Confounding Variables: A Prospective, Non-US Cross-sectional Study in 292 Patients.

    PubMed

    Hallager, Dennis Winge; Hansen, Lars Valentin; Dragsted, Casper Rokkjær; Peytz, Nina; Gehrchen, Martin; Dahl, Benny

    2016-05-01

    Cross-sectional analyses on a consecutive, prospective cohort. To evaluate the ability of the Scoliosis Research Society (SRS)-Schwab Adult Spinal Deformity Classification to group patients by widely used health-related quality-of-life (HRQOL) scores and examine possible confounding variables. The SRS-Schwab Adult Spinal Deformity Classification includes sagittal modifiers considered important for HRQOL and the clinical impact of the classification has been validated in patients from the International Spine Study Group database; however, equivocal results were reported for the Pelvic Tilt modifier and potential confounding variables were not evaluated. Between March 2013 and May 2014, all adult spinal deformity patients from our outpatient clinic with sufficient radiographs were prospectively enrolled. Analyses of HRQOL variance and post hoc analyses were performed for each SRS-Schwab modifier. Age, history of spine surgery, and aetiology of spinal deformity were considered potential confounders and their influence on the association between SRS-Schwab modifiers and aggregated Oswestry Disability Index (ODI) scores was evaluated with multivariate proportional odds regressions. P values were adjusted for multiple testing. Two hundred ninety-two of 460 eligible patients were included for analyses. The SRS-Schwab Classification significantly discriminated HRQOL scores between normal and abnormal sagittal modifier classifications. Individual grade comparisons showed equivocal results; however, Pelvic Tilt grade + versus +  + did not discriminate patients according to any HRQOL score. All modifiers showed significant proportional odds for worse aggregated ODI scores with increasing grade levels and the effects were robust to confounding. However, age group and aetiology had individual significant effects. The SRS-Schwab sagittal modifiers reliably grouped patients graded 0 versus + / +  + according to the most widely used HRQOL scores and the

  2. Associations between lifestyle and air pollution exposure: Potential for confounding in large administrative data cohorts.

    PubMed

    Strak, Maciej; Janssen, Nicole; Beelen, Rob; Schmitz, Oliver; Karssenberg, Derek; Houthuijs, Danny; van den Brink, Carolien; Dijst, Martin; Brunekreef, Bert; Hoek, Gerard

    2017-07-01

    Cohorts based on administrative data have size advantages over individual cohorts in investigating air pollution risks, but often lack in-depth information on individual risk factors related to lifestyle. If there is a correlation between lifestyle and air pollution, omitted lifestyle variables may result in biased air pollution risk estimates. Correlations between lifestyle and air pollution can be induced by socio-economic status affecting both lifestyle and air pollution exposure. Our overall aim was to assess potential confounding by missing lifestyle factors on air pollution mortality risk estimates. The first aim was to assess associations between long-term exposure to several air pollutants and lifestyle factors. The second aim was to assess whether these associations were sensitive to adjustment for individual and area-level socioeconomic status (SES), and whether they differed between subgroups of the population. Using the obtained air pollution-lifestyle associations and indirect adjustment methods, our third aim was to investigate the potential bias due to missing lifestyle information on air pollution mortality risk estimates in administrative cohorts. We used a recent Dutch national health survey of 387,195 adults to investigate the associations of PM 10 , PM 2.5 , PM 2.5-10 , PM 2.5 absorbance, OP DTT, OP ESR and NO 2 annual average concentrations at the residential address from land use regression models with individual smoking habits, alcohol consumption, physical activity and body mass index. We assessed the associations with and without adjustment for neighborhood and individual SES characteristics typically available in administrative data cohorts. We illustrated the effect of including lifestyle information on the air pollution mortality risk estimates in administrative cohort studies using a published indirect adjustment method. Current smoking and alcohol consumption were generally positively associated with air pollution. Physical activity

  3. Comorbidities, confounders, and the white matter transcriptome in chronic alcoholism.

    PubMed

    Sutherland, Greg T; Sheedy, Donna; Sheahan, Pam J; Kaplan, Warren; Kril, Jillian J

    2014-04-01

    Alcohol abuse is the world's third leading cause of disease and disability, and one potential sequel of chronic abuse is alcohol-related brain damage (ARBD). This clinically manifests as cognitive dysfunction and pathologically as atrophy of white matter (WM) in particular. The mechanism linking chronic alcohol intoxication with ARBD remains largely unknown but it is also complicated by common comorbidities such as liver damage and nutritional deficiencies. Liver cirrhosis, in particular, often leads to hepatic encephalopathy (HE), a primary glial disease. In a novel transcriptomic study, we targeted the WM only of chronic alcoholics in an attempt to tease apart the pathogenesis of ARBD. Specifically, in alcoholics with and without HE, we explored both the prefrontal and primary motor cortices, 2 regions that experience differential levels of neuronal loss. Our results suggest that HE, along with 2 confounders, gray matter contamination, and low RNA quality are major drivers of gene expression in ARBD. All 3 exceeded the effects of alcohol itself. In particular, low-quality RNA samples were characterized by an up-regulation of translation machinery, while HE was associated with a down-regulation of mitochondrial energy metabolism pathways. The findings in HE alcoholics are consistent with the metabolic acidosis seen in this condition. In contrast non-HE alcoholics had widespread but only subtle changes in gene expression in their WM. Notwithstanding the latter result, this study demonstrates that significant confounders in transcriptomic studies of human postmortem brain tissue can be identified, quantified, and "removed" to reveal disease-specific signals. Copyright © 2014 by the Research Society on Alcoholism.

  4. Cardiovascular health, traffic-related air pollution and noise: are associations mutually confounded? A systematic review.

    PubMed

    Tétreault, Louis-François; Perron, Stéphane; Smargiassi, Audrey

    2013-10-01

    This review assessed the confounding effect of one traffic-related exposure (noise or air pollutants) on the association between the other exposure and cardiovascular outcomes. A systematic review was conducted with the databases Medline and Embase. The confounding effects in studies were assessed by using change in the estimate with a 10 % cutoff point. The influence on the change in the estimate of the quality of the studies, the exposure assessment methods and the correlation between road noise and air pollutions were also assessed. Nine publications were identified. For most studies, the specified confounders produced changes in estimates <10 %. The correlation between noise and pollutants, the quality of the study and of the exposure assessment do not seem to influence the confounding effects. Results from this review suggest that confounding of cardiovascular effects by noise or air pollutants is low, though with further improvements in exposure assessment, the situation may change. More studies using pollution indicators specific to road traffic are needed to properly assess if noise and air pollution are subjected to confounding.

  5. Examining the Error of Mis-Specifying Nonlinear Confounding Effect With Application on Accelerometer-Measured Physical Activity.

    PubMed

    Lee, Paul H

    2017-06-01

    Some confounders are nonlinearly associated with dependent variables, but they are often adjusted using a linear term. The purpose of this study was to examine the error of mis-specifying the nonlinear confounding effect. We carried out a simulation study to investigate the effect of adjusting for a nonlinear confounder in the estimation of a causal relationship between the exposure and outcome in 3 ways: using a linear term, binning into 5 equal-size categories, or using a restricted cubic spline of the confounder. Continuous, binary, and survival outcomes were simulated. We examined the confounder across varying measurement error. In addition, we performed a real data analysis examining the 3 strategies to handle the nonlinear effects of accelerometer-measured physical activity in the National Health and Nutrition Examination Survey 2003-2006 data. The mis-specification of a nonlinear confounder had little impact on causal effect estimation for continuous outcomes. For binary and survival outcomes, this mis-specification introduced bias, which could be eliminated using spline adjustment only when there is small measurement error of the confounder. Real data analysis showed that the associations between high blood pressure, high cholesterol, and diabetes and mortality adjusted for physical activity with restricted cubic spline were about 3% to 11% larger than their counterparts adjusted with a linear term. For continuous outcomes, confounders with nonlinear effects can be adjusting with a linear term. Spline adjustment should be used for binary and survival outcomes on confounders with small measurement error.

  6. Comparison of Statistical Approaches Dealing with Time-dependent Confounding in Drug Effectiveness Studies

    PubMed Central

    Karim, Mohammad Ehsanul; Petkau, John; Gustafson, Paul; Platt, Robert W.; Tremlett, Helen

    2017-01-01

    In longitudinal studies, if the time-dependent covariates are affected by the past treatment, time-dependent confounding may be present. For a time-to-event response, marginal structural Cox models (MSCMs) are frequently used to deal with such confounding. To avoid some of the problems of fitting MSCM, the sequential Cox approach has been suggested as an alternative. Although the estimation mechanisms are different, both approaches claim to estimate the causal effect of treatment by appropriately adjusting for time-dependent confounding. We carry out simulation studies to assess the suitability of the sequential Cox approach for analyzing time-to-event data in the presence of a time-dependent covariate that may or may not be a time-dependent confounder. Results from these simulations revealed that the sequential Cox approach is not as effective as MSCM in addressing the time-dependent confounding. The sequential Cox approach was also found to be inadequate in the presence of a time-dependent covariate. We propose a modified version of the sequential Cox approach that correctly estimates the treatment effect in both of the above scenarios. All approaches are applied to investigate the impact of beta-interferon treatment in delaying disability progression in the British Columbia Multiple Sclerosis cohort (1995 – 2008). PMID:27659168

  7. Comparison of statistical approaches dealing with time-dependent confounding in drug effectiveness studies.

    PubMed

    Karim, Mohammad Ehsanul; Petkau, John; Gustafson, Paul; Platt, Robert W; Tremlett, Helen

    2018-06-01

    In longitudinal studies, if the time-dependent covariates are affected by the past treatment, time-dependent confounding may be present. For a time-to-event response, marginal structural Cox models are frequently used to deal with such confounding. To avoid some of the problems of fitting marginal structural Cox model, the sequential Cox approach has been suggested as an alternative. Although the estimation mechanisms are different, both approaches claim to estimate the causal effect of treatment by appropriately adjusting for time-dependent confounding. We carry out simulation studies to assess the suitability of the sequential Cox approach for analyzing time-to-event data in the presence of a time-dependent covariate that may or may not be a time-dependent confounder. Results from these simulations revealed that the sequential Cox approach is not as effective as marginal structural Cox model in addressing the time-dependent confounding. The sequential Cox approach was also found to be inadequate in the presence of a time-dependent covariate. We propose a modified version of the sequential Cox approach that correctly estimates the treatment effect in both of the above scenarios. All approaches are applied to investigate the impact of beta-interferon treatment in delaying disability progression in the British Columbia Multiple Sclerosis cohort (1995-2008).

  8. Associations of Perfluoroalkyl Substances (PFAS) with Lower Birth Weight: An Evaluation of Potential Confounding by Glomerular Filtration Rate Using a Physiologically Based Pharmacokinetic Model (PBPK)

    PubMed Central

    Loccisano, Anne E.; Morken, Nils-Halvdan; Yoon, Miyoung; Wu, Huali; McDougall, Robin; Maisonet, Mildred; Marcus, Michele; Kishi, Reiko; Miyashita, Chihiro; Chen, Mei-Huei; Hsieh, Wu-Shiun; Andersen, Melvin E.; Clewell, Harvey J.; Longnecker, Matthew P.

    2015-01-01

    Dougall R, Maisonet M, Marcus M, Kishi R, Miyashita C, Chen MH, Hsieh WS, Andersen ME, Clewell HJ III, Longnecker MP. 2015. Associations of perfluoroalkyl substances (PFAS) with lower birth weight: an evaluation of potential confounding by glomerular filtration rate using a physiologically based pharmacokinetic model (PBPK). Environ Health Perspect 123:1317–1324; http://dx.doi.org/10.1289/ehp.1408837 PMID:26008903

  9. "A Bayesian sensitivity analysis to evaluate the impact of unmeasured confounding with external data: a real world comparative effectiveness study in osteoporosis".

    PubMed

    Zhang, Xiang; Faries, Douglas E; Boytsov, Natalie; Stamey, James D; Seaman, John W

    2016-09-01

    Observational studies are frequently used to assess the effectiveness of medical interventions in routine clinical practice. However, the use of observational data for comparative effectiveness is challenged by selection bias and the potential of unmeasured confounding. This is especially problematic for analyses using a health care administrative database, in which key clinical measures are often not available. This paper provides an approach to conducting a sensitivity analyses to investigate the impact of unmeasured confounding in observational studies. In a real world osteoporosis comparative effectiveness study, the bone mineral density (BMD) score, an important predictor of fracture risk and a factor in the selection of osteoporosis treatments, is unavailable in the data base and lack of baseline BMD could potentially lead to significant selection bias. We implemented Bayesian twin-regression models, which simultaneously model both the observed outcome and the unobserved unmeasured confounder, using information from external sources. A sensitivity analysis was also conducted to assess the robustness of our conclusions to changes in such external data. The use of Bayesian modeling in this study suggests that the lack of baseline BMD did have a strong impact on the analysis, reversing the direction of the estimated effect (odds ratio of fracture incidence at 24 months: 0.40 vs. 1.36, with/without adjusting for unmeasured baseline BMD). The Bayesian twin-regression models provide a flexible sensitivity analysis tool to quantitatively assess the impact of unmeasured confounding in observational studies. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  10. A New Method for Partial Correction of Residual Confounding in Time-Series and Other Observational Studies.

    PubMed

    Flanders, W Dana; Strickland, Matthew J; Klein, Mitchel

    2017-05-15

    Methods exist to detect residual confounding in epidemiologic studies. One requires a negative control exposure with 2 key properties: 1) conditional independence of the negative control and the outcome (given modeled variables) absent confounding and other model misspecification, and 2) associations of the negative control with uncontrolled confounders and the outcome. We present a new method to partially correct for residual confounding: When confounding is present and our assumptions hold, we argue that estimators from models that include a negative control exposure with these 2 properties tend to be less biased than those from models without it. Using regression theory, we provide theoretical arguments that support our claims. In simulations, we empirically evaluated the approach using a time-series study of ozone effects on asthma emergency department visits. In simulations, effect estimators from models that included the negative control exposure (ozone concentrations 1 day after the emergency department visit) had slightly or modestly less residual confounding than those from models without it. Theory and simulations show that including the negative control can reduce residual confounding, if our assumptions hold. Our method differs from available methods because it uses a regression approach involving an exposure-based indicator rather than a negative control outcome to partially correct for confounding. © The Author 2017. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  11. Using instrumental variables to estimate a Cox's proportional hazards regression subject to additive confounding

    PubMed Central

    Tosteson, Tor D.; Morden, Nancy E.; Stukel, Therese A.; O'Malley, A. James

    2014-01-01

    The estimation of treatment effects is one of the primary goals of statistics in medicine. Estimation based on observational studies is subject to confounding. Statistical methods for controlling bias due to confounding include regression adjustment, propensity scores and inverse probability weighted estimators. These methods require that all confounders are recorded in the data. The method of instrumental variables (IVs) can eliminate bias in observational studies even in the absence of information on confounders. We propose a method for integrating IVs within the framework of Cox's proportional hazards model and demonstrate the conditions under which it recovers the causal effect of treatment. The methodology is based on the approximate orthogonality of an instrument with unobserved confounders among those at risk. We derive an estimator as the solution to an estimating equation that resembles the score equation of the partial likelihood in much the same way as the traditional IV estimator resembles the normal equations. To justify this IV estimator for a Cox model we perform simulations to evaluate its operating characteristics. Finally, we apply the estimator to an observational study of the effect of coronary catheterization on survival. PMID:25506259

  12. Using instrumental variables to estimate a Cox's proportional hazards regression subject to additive confounding.

    PubMed

    MacKenzie, Todd A; Tosteson, Tor D; Morden, Nancy E; Stukel, Therese A; O'Malley, A James

    2014-06-01

    The estimation of treatment effects is one of the primary goals of statistics in medicine. Estimation based on observational studies is subject to confounding. Statistical methods for controlling bias due to confounding include regression adjustment, propensity scores and inverse probability weighted estimators. These methods require that all confounders are recorded in the data. The method of instrumental variables (IVs) can eliminate bias in observational studies even in the absence of information on confounders. We propose a method for integrating IVs within the framework of Cox's proportional hazards model and demonstrate the conditions under which it recovers the causal effect of treatment. The methodology is based on the approximate orthogonality of an instrument with unobserved confounders among those at risk. We derive an estimator as the solution to an estimating equation that resembles the score equation of the partial likelihood in much the same way as the traditional IV estimator resembles the normal equations. To justify this IV estimator for a Cox model we perform simulations to evaluate its operating characteristics. Finally, we apply the estimator to an observational study of the effect of coronary catheterization on survival.

  13. Sensitivity analysis for direct and indirect effects in the presence of exposure-induced mediator-outcome confounders

    PubMed Central

    Chiba, Yasutaka

    2014-01-01

    Questions of mediation are often of interest in reasoning about mechanisms, and methods have been developed to address these questions. However, these methods make strong assumptions about the absence of confounding. Even if exposure is randomized, there may be mediator-outcome confounding variables. Inference about direct and indirect effects is particularly challenging if these mediator-outcome confounders are affected by the exposure because in this case these effects are not identified irrespective of whether data is available on these exposure-induced mediator-outcome confounders. In this paper, we provide a sensitivity analysis technique for natural direct and indirect effects that is applicable even if there are mediator-outcome confounders affected by the exposure. We give techniques for both the difference and risk ratio scales and compare the technique to other possible approaches. PMID:25580387

  14. Examining the Error of Mis-Specifying Nonlinear Confounding Effect with Application on Accelerometer-Measured Physical Activity

    ERIC Educational Resources Information Center

    Lee, Paul H.

    2017-01-01

    Purpose: Some confounders are nonlinearly associated with dependent variables, but they are often adjusted using a linear term. The purpose of this study was to examine the error of mis-specifying the nonlinear confounding effect. Methods: We carried out a simulation study to investigate the effect of adjusting for a nonlinear confounder in the…

  15. Birth weight and mortality: causality or confounding?

    PubMed

    Basso, Olga; Wilcox, Allen J; Weinberg, Clarice R

    2006-08-15

    The association between birth weight and mortality is among the strongest seen in epidemiology. While preterm delivery causes both small babies and high mortality, it does not explain this association. Fetal growth restriction has also been proposed, although its features are unclear because it lacks a definition independent of weight. If, as some postulate, birth weight is not itself on the causal path to mortality, its relation with mortality would have to be explained by confounding factors that decrease birth weight and increase mortality. In this paper, the authors explore the characteristics such confounders would require in order to achieve the observed association between birth weight and mortality. Through a simple simulation, they found that the observed steep gradient of risk for small babies at term can be produced by a rare condition or conditions (with a total prevalence of 0.5%) having profound effects on both fetal growth (-1.7 standard deviations) and mortality (relative risk = 160). Candidate conditions might include malformations, fetal or placental aneuploidy, infections, or imprinting disorders. If such rare factors underlie the association of birth weight with mortality, it would have broad implications for the study of fetal growth restriction and birth weight, and for the prevention of infant mortality.

  16. Instrumental variables as bias amplifiers with general outcome and confounding.

    PubMed

    Ding, P; VanderWeele, T J; Robins, J M

    2017-06-01

    Drawing causal inference with observational studies is the central pillar of many disciplines. One sufficient condition for identifying the causal effect is that the treatment-outcome relationship is unconfounded conditional on the observed covariates. It is often believed that the more covariates we condition on, the more plausible this unconfoundedness assumption is. This belief has had a huge impact on practical causal inference, suggesting that we should adjust for all pretreatment covariates. However, when there is unmeasured confounding between the treatment and outcome, estimators adjusting for some pretreatment covariate might have greater bias than estimators without adjusting for this covariate. This kind of covariate is called a bias amplifier, and includes instrumental variables that are independent of the confounder, and affect the outcome only through the treatment. Previously, theoretical results for this phenomenon have been established only for linear models. We fill in this gap in the literature by providing a general theory, showing that this phenomenon happens under a wide class of models satisfying certain monotonicity assumptions. We further show that when the treatment follows an additive or multiplicative model conditional on the instrumental variable and the confounder, these monotonicity assumptions can be interpreted as the signs of the arrows of the causal diagrams.

  17. Correction of confounding bias in non-randomized studies by appropriate weighting.

    PubMed

    Schmoor, Claudia; Gall, Christine; Stampf, Susanne; Graf, Erika

    2011-03-01

    In non-randomized studies, the assessment of a causal effect of treatment or exposure on outcome is hampered by possible confounding. Applying multiple regression models including the effects of treatment and covariates on outcome is the well-known classical approach to adjust for confounding. In recent years other approaches have been promoted. One of them is based on the propensity score and considers the effect of possible confounders on treatment as a relevant criterion for adjustment. Another proposal is based on using an instrumental variable. Here inference relies on a factor, the instrument, which affects treatment but is thought to be otherwise unrelated to outcome, so that it mimics randomization. Each of these approaches can basically be interpreted as a simple reweighting scheme, designed to address confounding. The procedures will be compared with respect to their fundamental properties, namely, which bias they aim to eliminate, which effect they aim to estimate, and which parameter is modelled. We will expand our overview of methods for analysis of non-randomized studies to methods for analysis of randomized controlled trials and show that analyses of both study types may target different effects and different parameters. The considerations will be illustrated using a breast cancer study with a so-called Comprehensive Cohort Study design, including a randomized controlled trial and a non-randomized study in the same patient population as sub-cohorts. This design offers ideal opportunities to discuss and illustrate the properties of the different approaches. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Negative affectivity: moderator or confound in emotional dissonance-outcome relationships?

    PubMed

    Abraham, R

    1999-01-01

    This study was an examination of the impact of negative affectivity on relationships between emotional dissonance, job satisfaction, and emotional exhaustion. Negative affectivity is the predisposition to view life in negative terms. Emotional dissonance originates from the conflict between expressed and experienced emotions. In organizations that require the expression of positive emotions, high negative affectivity individuals may experience conflict between expressed, positive emotions and felt, negative emotions. A moderator effect exists when high negative affectivity individuals experience greater job dissatisfaction and emotional exhaustion. Alternatively, negative affectivity may exert a confounding effect through its relationship to both emotional dissonance and its outcomes. Empirical tests showed that negative affectivity moderated the emotional dissonance-job satisfaction relationship and confounded the emotional dissonance-emotional exhaustion relationship.

  19. Distinguishing prostate cancer from benign confounders via a cascaded classifier on multi-parametric MRI

    NASA Astrophysics Data System (ADS)

    Litjens, G. J. S.; Elliott, R.; Shih, N.; Feldman, M.; Barentsz, J. O.; Hulsbergen-van de Kaa, C. A.; Kovacs, I.; Huisman, H. J.; Madabhushi, A.

    2014-03-01

    Learning how to separate benign confounders from prostate cancer is important because the imaging characteristics of these confounders are poorly understood. Furthermore, the typical representations of the MRI parameters might not be enough to allow discrimination. The diagnostic uncertainty this causes leads to a lower diagnostic accuracy. In this paper a new cascaded classifier is introduced to separate prostate cancer and benign confounders on MRI in conjunction with specific computer-extracted features to distinguish each of the benign classes (benign prostatic hyperplasia (BPH), inflammation, atrophy or prostatic intra-epithelial neoplasia (PIN). In this study we tried to (1) calculate different mathematical representations of the MRI parameters which more clearly express subtle differences between different classes, (2) learn which of the MRI image features will allow to distinguish specific benign confounders from prostate cancer, and (2) find the combination of computer-extracted MRI features to best discriminate cancer from the confounding classes using a cascaded classifier. One of the most important requirements for identifying MRI signatures for adenocarcinoma, BPH, atrophy, inflammation, and PIN is accurate mapping of the location and spatial extent of the confounder and cancer categories from ex vivo histopathology to MRI. Towards this end we employed an annotated prostatectomy data set of 31 patients, all of whom underwent a multi-parametric 3 Tesla MRI prior to radical prostatectomy. The prostatectomy slides were carefully co-registered to the corresponding MRI slices using an elastic registration technique. We extracted texture features from the T2-weighted imaging, pharmacokinetic features from the dynamic contrast enhanced imaging and diffusion features from the diffusion-weighted imaging for each of the confounder classes and prostate cancer. These features were selected because they form the mainstay of clinical diagnosis. Relevant features for

  20. Use of instrumental variables in the analysis of generalized linear models in the presence of unmeasured confounding with applications to epidemiological research.

    PubMed

    Johnston, K M; Gustafson, P; Levy, A R; Grootendorst, P

    2008-04-30

    A major, often unstated, concern of researchers carrying out epidemiological studies of medical therapy is the potential impact on validity if estimates of treatment are biased due to unmeasured confounders. One technique for obtaining consistent estimates of treatment effects in the presence of unmeasured confounders is instrumental variables analysis (IVA). This technique has been well developed in the econometrics literature and is being increasingly used in epidemiological studies. However, the approach to IVA that is most commonly used in such studies is based on linear models, while many epidemiological applications make use of non-linear models, specifically generalized linear models (GLMs) such as logistic or Poisson regression. Here we present a simple method for applying IVA within the class of GLMs using the generalized method of moments approach. We explore some of the theoretical properties of the method and illustrate its use within both a simulation example and an epidemiological study where unmeasured confounding is suspected to be present. We estimate the effects of beta-blocker therapy on one-year all-cause mortality after an incident hospitalization for heart failure, in the absence of data describing disease severity, which is believed to be a confounder. 2008 John Wiley & Sons, Ltd

  1. Why Do Thin People Have Elevated All-Cause Mortality? Evidence on Confounding and Reverse Causality in the Association of Adiposity and COPD from the British Women’s Heart and Health Study

    PubMed Central

    Dale, Caroline; Nüesch, Eveline; Prieto-Merino, David; Choi, Minkyoung; Amuzu, Antoinette; Ebrahim, Shah; Casas, Juan P.; Davey-Smith, George

    2015-01-01

    Low adiposity has been linked to elevated mortality from several causes including respiratory disease. However, this could arise from confounding or reverse causality. We explore the association between two measures of adiposity (BMI and WHR) with COPD in the British Women’s Heart and Health Study including a detailed assessment of the potential for confounding and reverse causality for each adiposity measure. Low BMI was found to be associated with increased COPD risk while low WHR was not (OR = 2.2; 95% CI 1.3 – 3.1 versus OR = 1.2; 95% CI 0.7 – 1.6). Potential confounding variables (e.g. smoking) and markers of ill-health (e.g. unintentional weight loss) were found to be higher in low BMI but not in low WHR. Women with low BMI have a detrimental profile across a broad range of health markers compared to women with low WHR, and women with low WHR do not appear to have an elevated COPD risk, lending support to the hypothesis that WHR is a less confounded measure of adiposity than BMI. Low adiposity does not in itself appear to increase the risk of respiratory disease, and the apparent adverse consequences of low BMI may be due to reverse causation and confounding. PMID:25884834

  2. The “Dry-Run” Analysis: A Method for Evaluating Risk Scores for Confounding Control

    PubMed Central

    Wyss, Richard; Hansen, Ben B.; Ellis, Alan R.; Gagne, Joshua J.; Desai, Rishi J.; Glynn, Robert J.; Stürmer, Til

    2017-01-01

    Abstract A propensity score (PS) model's ability to control confounding can be assessed by evaluating covariate balance across exposure groups after PS adjustment. The optimal strategy for evaluating a disease risk score (DRS) model's ability to control confounding is less clear. DRS models cannot be evaluated through balance checks within the full population, and they are usually assessed through prediction diagnostics and goodness-of-fit tests. A proposed alternative is the “dry-run” analysis, which divides the unexposed population into “pseudo-exposed” and “pseudo-unexposed” groups so that differences on observed covariates resemble differences between the actual exposed and unexposed populations. With no exposure effect separating the pseudo-exposed and pseudo-unexposed groups, a DRS model is evaluated by its ability to retrieve an unconfounded null estimate after adjustment in this pseudo-population. We used simulations and an empirical example to compare traditional DRS performance metrics with the dry-run validation. In simulations, the dry run often improved assessment of confounding control, compared with the C statistic and goodness-of-fit tests. In the empirical example, PS and DRS matching gave similar results and showed good performance in terms of covariate balance (PS matching) and controlling confounding in the dry-run analysis (DRS matching). The dry-run analysis may prove useful in evaluating confounding control through DRS models. PMID:28338910

  3. Developing hazelnut tissue culture medium free of ion confounding

    USDA-ARS?s Scientific Manuscript database

    The general approach for tissue culture medium optimization is to use salts as factors in experimental design and analysis. However, using salts as factors leads to ion confounding, making it difficult to detect the effects of individual ions on particular growth responses. This study focused on tes...

  4. Air pollutants and health outcomes: Assessment of confounding by influenza

    NASA Astrophysics Data System (ADS)

    Thach, Thuan-Quoc; Wong, Chit-Ming; Chan, King-Pan; Chau, Yuen-Kwan; Neil Thomas, G.; Ou, Chun-Quan; Yang, Lin; Peiris, Joseph S. M.; Lam, Tai-Hing; Hedley, Anthony J.

    2010-04-01

    We assessed confounding of associations between short-term effects of air pollution and health outcomes by influenza using Hong Kong mortality and hospitalization data for 1996-2002. Three measures of influenza were defined: (i) intensity: weekly proportion of positive influenza viruses, (ii) epidemic: weekly number of positive influenza viruses ≥4% of the annual number for ≥2 consecutive weeks, and (iii) predominance: an epidemic period with co-circulation of respiratory syncytial virus <2% of the annual positive isolates for ≥2 consecutive weeks. We examined effects of influenza on associations between nitrogen dioxide (NO 2), sulfur dioxide (SO 2), particulate matter with aerodynamic diameter ≤10 μm (PM 10) and ozone (O 3) and health outcomes including all natural causes mortality, cardiorespiratory mortality and hospitalization. Generalized additive Poisson regression model with natural cubic splines was fitted to control for time-varying covariates to estimate air pollution health effects. Confounding with influenza was assessed using an absolute difference of >0.1% between unadjusted and adjusted excess risks (ER%). Without adjustment, pollutants were associated with positive ER% for all health outcomes except asthma and stroke hospitalization with SO 2 and stroke hospitalization with O 3. Following adjustment, changes in ER% for all pollutants were <0.1% for all natural causes mortality, but >0.1% for mortality from stroke with NO 2 and SO 2, cardiac or heart disease with NO 2, PM 10 and O 3, lower respiratory infections with NO 2 and O 3 and mortality from chronic obstructive pulmonary disease with all pollutants. Changes >0.1% were seen for acute respiratory disease hospitalization with NO 2, SO 2 and O 3 and acute lower respiratory infections hospitalization with PM 10. Generally, influenza does not confound the observed associations of air pollutants with all natural causes mortality and cardiovascular hospitalization, but for some pollutants

  5. Effects of heat waves on mortality: effect modification and confounding by air pollutants.

    PubMed

    Analitis, Antonis; Michelozzi, Paola; D'Ippoliti, Daniela; De'Donato, Francesca; Menne, Bettina; Matthies, Franziska; Atkinson, Richard W; Iñiguez, Carmen; Basagaña, Xavier; Schneider, Alexandra; Lefranc, Agnès; Paldy, Anna; Bisanti, Luigi; Katsouyanni, Klea

    2014-01-01

    Heat waves and air pollution are both associated with increased mortality. Their joint effects are less well understood. We explored the role of air pollution in modifying the effects of heat waves on mortality, within the EuroHEAT project. Daily mortality, meteorologic, and air pollution data from nine European cities for the years 1990-2004 were assembled. We defined heat waves by taking both intensity and duration into account. The city-specific effects of heat wave episodes were estimated using generalized estimating equation models, adjusting for potential confounders with and without inclusion of air pollutants (particles, ozone, nitrogen dioxide, sulphur dioxide, carbon monoxide). To investigate effect modification, we introduced an interaction term between heat waves and each single pollutant in the models. Random effects meta-analysis was used to summarize the city-specific results. The increase in the number of daily deaths during heat wave episodes was 54% higher on high ozone days compared with low, among people age 75-84 years. The heat wave effect on high PM10 days was increased by 36% and 106% in the 75-84 year and 85+ year age groups, respectively. A similar pattern was observed for effects on cardiovascular mortality. Effect modification was less evident for respiratory mortality, although the heat wave effect itself was greater for this cause of death. The heat wave effect was smaller (15-30%) after adjustment for ozone or PM10. The heat wave effect on mortality was larger during high ozone or high PM10 days. When assessing the effect of heat waves on mortality, lack of adjustment for ozone and especially PM10 overestimates effect parameters. This bias has implications for public health policy.

  6. Causal diagrams and multivariate analysis III: confound it!

    PubMed

    Jupiter, Daniel C

    2015-01-01

    This commentary concludes my series concerning inclusion of variables in multivariate analyses. We take up the issues of confounding and effect modification and summarize the work we have thus far done. Finally, we provide a rough algorithm to help guide us through the maze of possibilities that we have outlined. Copyright © 2015 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

  7. Effectiveness and confounding factors of penetrating astigmatic keratotomy in clinical practice

    PubMed Central

    Yen, Chu-Yu; Tseng, Gow-Lieng

    2018-01-01

    Abstract Rationale: Penetrating astigmatic keratotomy (penetrating AK) is a well-known method to correct corneal astigmatism but rarely be performed nowadays. This article reevaluated the clinical effectiveness and confounding factors of penetrating AK. Patient concerns: Penetrating AK has been introduced to serve as one alternative operation for astigmatism correction, and is thought to have the potential advantage of being more affordable and easy to perform. The purpose of our study is to evaluate the effectiveness and confounding factors of penetrating AK. Diagnoses: The chart of 95 patients with corneal astigmatism (range: 0.75–3.25 diopters [D]) who received penetrating AK from January 2014 to December 2016 was collected. The corneal astigmatism were measured by an autokeratometer (Topcon KR8100PA topographer-autorefractor), and repeated with manual keratometer in low reproducibility cases. Interventions: All patients received penetrating AK by an experienced ophthalmologist (Dr. Gow-Lieng Tseng, MD, PHD) in the operation room. Among which, 66 patients received penetrating AK with phacoemulsification simultaneously (group A), whereas 29 patients received penetrating AK at least 3 months after phacoemulsification (group B). After excluding the patients combined with other procedures or lost followed up, 79 patients are remaining for analysis. The outcome was evaluated by net correction, the difference between preoperative corneal astigmatism (PCA) and residual corneal astigmatism (RCA). Two sample t tests and Pearson test were used for effectiveness evaluation. For confounding factors, multivariate linear regression was used for statistical analysis. Outcomes: The mean preoperative and postoperative refractive cylinders were 1.97 ± 0.77 and 1.08 ± 0.64 D, respectively, in group A and 2.62 ± 1.05 and 1.51 ± 0.89 D in group B. There were no statistically significant differences in net correction between these two groups (0.9 ± 0.66 vs

  8. Examining confounding by diet in the association between perfluoroalkyl acids and serum cholesterol in pregnancy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Skuladottir, Margret; Ramel, Alfons; Unit for Nutrition Research, Landspitali National University Hospital, Reykjavik

    Background: Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) have consistently been associated with higher cholesterol levels in cross sectional studies. Concerns have, however, been raised about potential confounding by diet and clinical relevance. Objective: To examine the association between concentrations of PFOS and PFOA and total cholesterol in serum during pregnancy taking into considerations confounding by diet. Methods: 854 Danish women who gave birth in 1988–89 and provided a blood sample and reported their diet in week 30 of gestation. Results: Mean serum PFOS, PFOA and total cholesterol concentrations were 22.3 ng/mL, 4.1 ng/mL and 7.3 mmol/L, respectively. Maternal dietmore » was a significant predictor of serum PFOS and PFOA concentrations. In particular intake of meat and meat products was positively associated while intake of vegetables was inversely associated (P for trend <0.01) with relative difference between the highest and lowest quartile in PFOS and PFOA concentrations ranging between 6% and 25% of mean values. After adjustment for dietary factors both PFOA and PFOS were positively and similarly associated with serum cholesterol (P for trend ≤0.01). For example, the mean increase in serum cholesterol was 0.39 mmol/L (95%CI: 0.09, 0.68) when comparing women in the highest to lowest quintile of PFOA concentrations. In comparison the mean increase in serum cholesterol was 0.61 mmol/L (95%CI: 0.17, 1.05) when comparing women in the highest to lowest quintile of saturated fat intake. Conclusion: In this study associations between PFOS and PFOA with serum cholesterol appeared unrelated to dietary intake and were similar in magnitude as the associations between saturated fat intake and serum cholesterol. - Highlights: • PFOS and PFOA have consistently been linked with raised serum cholesterol • Clinical relevance remains uncertain and confounding by diet has been suggested • The aim of this study was to address these

  9. Control selection and confounding factors: A lesson from a Japanese case-control study to examine acellular pertussis vaccine effectiveness.

    PubMed

    Ohfuji, Satoko; Okada, Kenji; Nakano, Takashi; Ito, Hiroaki; Hara, Megumi; Kuroki, Haruo; Hirota, Yoshio

    2017-08-24

    When using a case-control study design to examine vaccine effectiveness, both the selection of control subjects and the consideration of potential confounders must be the important issues to ensure accurate results. In this report, we described our experience from a case-control study conducted to evaluate the effectiveness of acellular pertussis vaccine combined with diphtheria-tetanus toxoids (DTaP vaccine). Newly diagnosed pertussis cases and age- and sex-matched friend-controls were enrolled, and the history of DTaP vaccination was compared between groups. Logistic regression models were used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) of vaccination for development of pertussis. After adjustment for potential confounders, four doses of DTaP vaccination showed a lower OR for pediatrician-diagnosed pertussis (OR=0.11, 95% CI, 0.01-0.99). In addition, the decreasing OR of four doses vaccination was more pronounced for laboratory-confirmed pertussis (OR=0.07, 95%CI, 0.01-0.82). Besides, positive association with pertussis was observed in subjects with a history of steroid treatment (OR=5.67) and those with a recent contact with a lasting cough (OR=4.12). When using a case-control study to evaluate the effectiveness of vaccines, particularly those for uncommon infectious diseases such as pertussis, the use of friend-controls may be optimal due to the fact that they shared a similar experience for exposure to the pathogen as the cases. In addition, to assess vaccine effectiveness as accurately as possible, the effects of confounding should be adequately controlled with a matching or analysis technique. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.

  10. Effect decomposition in the presence of an exposure-induced mediator-outcome confounder

    PubMed Central

    VanderWeele, Tyler J.; Vansteelandt, Stijn; Robins, James M.

    2014-01-01

    Methods from causal mediation analysis have generalized the traditional approach to direct and indirect effects in the epidemiologic and social science literature by allowing for interaction and non-linearities. However, the methods from the causal inference literature have themselves been subject to a major limitation in that the so-called natural direct and indirect effects that are employed are not identified from data whenever there is a variable that is affected by the exposure, which also confounds the relationship between the mediator and the outcome. In this paper we describe three alternative approaches to effect decomposition that give quantities that can be interpreted as direct and indirect effects, and that can be identified from data even in the presence of an exposure-induced mediator-outcome confounder. We describe a simple weighting-based estimation method for each of these three approaches, illustrated with data from perinatal epidemiology. The methods described here can shed insight into pathways and questions of mediation even when an exposure-induced mediator-outcome confounder is present. PMID:24487213

  11. Analyzing partially missing confounder information in comparative effectiveness and safety research of therapeutics.

    PubMed

    Toh, Sengwee; García Rodríguez, Luis A; Hernán, Miguel A

    2012-05-01

    Electronic healthcare databases are commonly used in comparative effectiveness and safety research of therapeutics. Many databases now include additional confounder information in a subset of the study population through data linkage or data collection. We described and compared existing methods for analyzing such datasets. Using data from The Health Improvement Network and the relation between non-steroidal anti-inflammatory drugs and upper gastrointestinal bleeding as an example, we employed several methods to handle partially missing confounder information. The crude odds ratio (OR) of upper gastrointestinal bleeding was 1.50 (95% confidence interval: 0.98, 2.28) among selective cyclo-oxygenase-2 inhibitor initiators (n = 43 569) compared with traditional non-steroidal anti-inflammatory drug initiators (n = 411 616). The OR dropped to 0.81 (0.52, 1.27) upon adjustment for confounders recorded for all patients. When further considering three additional variables missing in 22% of the study population (smoking, alcohol consumption, body mass index), the OR was between 0.80 and 0.83 for the missing-category approach, the missing-indicator approach, single imputation by the most common category, multiple imputation by chained equations, and propensity score calibration. The OR was 0.65 (0.39, 1.09) and 0.67 (0.38, 1.16) for the unweighted and the inverse probability weighted complete-case analysis, respectively. Existing methods for handling partially missing confounder data require different assumptions and may produce different results. The unweighted complete-case analysis, the missing-category/indicator approach, and single imputation require often unrealistic assumptions and should be avoided. In this study, differences across methods were not substantial, likely due to relatively low proportion of missingness and weak confounding effect by the three additional variables upon adjustment for other variables. Copyright © 2012 John Wiley & Sons, Ltd.

  12. Effects of categorization method, regression type, and variable distribution on the inflation of Type-I error rate when categorizing a confounding variable.

    PubMed

    Barnwell-Ménard, Jean-Louis; Li, Qing; Cohen, Alan A

    2015-03-15

    The loss of signal associated with categorizing a continuous variable is well known, and previous studies have demonstrated that this can lead to an inflation of Type-I error when the categorized variable is a confounder in a regression analysis estimating the effect of an exposure on an outcome. However, it is not known how the Type-I error may vary under different circumstances, including logistic versus linear regression, different distributions of the confounder, and different categorization methods. Here, we analytically quantified the effect of categorization and then performed a series of 9600 Monte Carlo simulations to estimate the Type-I error inflation associated with categorization of a confounder under different regression scenarios. We show that Type-I error is unacceptably high (>10% in most scenarios and often 100%). The only exception was when the variable categorized was a continuous mixture proxy for a genuinely dichotomous latent variable, where both the continuous proxy and the categorized variable are error-ridden proxies for the dichotomous latent variable. As expected, error inflation was also higher with larger sample size, fewer categories, and stronger associations between the confounder and the exposure or outcome. We provide online tools that can help researchers estimate the potential error inflation and understand how serious a problem this is. Copyright © 2014 John Wiley & Sons, Ltd.

  13. A two-stage model in a Bayesian framework to estimate a survival endpoint in the presence of confounding by indication.

    PubMed

    Bellera, Carine; Proust-Lima, Cécile; Joseph, Lawrence; Richaud, Pierre; Taylor, Jeremy; Sandler, Howard; Hanley, James; Mathoulin-Pélissier, Simone

    2018-04-01

    Background Biomarker series can indicate disease progression and predict clinical endpoints. When a treatment is prescribed depending on the biomarker, confounding by indication might be introduced if the treatment modifies the marker profile and risk of failure. Objective Our aim was to highlight the flexibility of a two-stage model fitted within a Bayesian Markov Chain Monte Carlo framework. For this purpose, we monitored the prostate-specific antigens in prostate cancer patients treated with external beam radiation therapy. In the presence of rising prostate-specific antigens after external beam radiation therapy, salvage hormone therapy can be prescribed to reduce both the prostate-specific antigens concentration and the risk of clinical failure, an illustration of confounding by indication. We focused on the assessment of the prognostic value of hormone therapy and prostate-specific antigens trajectory on the risk of failure. Methods We used a two-stage model within a Bayesian framework to assess the role of the prostate-specific antigens profile on clinical failure while accounting for a secondary treatment prescribed by indication. We modeled prostate-specific antigens using a hierarchical piecewise linear trajectory with a random changepoint. Residual prostate-specific antigens variability was expressed as a function of prostate-specific antigens concentration. Covariates in the survival model included hormone therapy, baseline characteristics, and individual predictions of the prostate-specific antigens nadir and timing and prostate-specific antigens slopes before and after the nadir as provided by the longitudinal process. Results We showed positive associations between an increased prostate-specific antigens nadir, an earlier changepoint and a steeper post-nadir slope with an increased risk of failure. Importantly, we highlighted a significant benefit of hormone therapy, an effect that was not observed when the prostate-specific antigens trajectory was

  14. Ultrasound Elastography and MR Elastography for Assessing Liver Fibrosis: Part 2, Diagnostic Performance, Confounders, and Future Directions

    PubMed Central

    Tang, An; Cloutier, Guy; Szeverenyi, Nikolaus M.; Sirlin, Claude B.

    2016-01-01

    OBJECTIVE The purpose of the article is to review the diagnostic performance of ultrasound and MR elastography techniques for detection and staging of liver fibrosis, the main current clinical applications of elastography in the abdomen. CONCLUSION Technical and instrument-related factors and biologic and patient-related factors may constitute potential confounders of stiffness measurements for assessment of liver fibrosis. Future developments may expand the scope of elastography for monitoring liver fibrosis and predict complications of chronic liver disease. PMID:25905762

  15. Rainfall and temperatures changes have confounding impacts on Phytophthora cinnamomi occurrence risk in the southwestern USA under climate change scenarios.

    PubMed

    Thompson, Sally E; Levin, Simon; Rodriguez-Iturbe, Ignacio

    2014-04-01

    Global change will simultaneously impact many aspects of climate, with the potential to exacerbate the risks posed by plant pathogens to agriculture and the natural environment; yet, most studies that explore climate impacts on plant pathogen ranges consider individual climatic factors separately. In this study, we adopt a stochastic modeling approach to address multiple pathways by which climate can constrain the range of the generalist plant pathogen Phytophthora cinnamomi (Pc): through changing winter soil temperatures affecting pathogen survival; spring soil temperatures and thus pathogen metabolic rates; and changing spring soil moisture conditions and thus pathogen growth rates through host root systems. We apply this model to the southwestern USA for contemporary and plausible future climate scenarios and evaluate the changes in the potential range of Pc. The results indicate that the plausible range of this pathogen in the southwestern USA extends over approximately 200,000 km(2) under contemporary conditions. While warming temperatures as projected by the IPCC A2 and B1 emissions scenarios greatly expand the range over which the pathogen can survive winter, projected reductions in spring rainfall reduce its feasible habitat, leading to spatially complex patterns of changing risk. The study demonstrates that temperature and rainfall changes associated with possible climate futures in the southwestern USA have confounding impacts on the range of Pc, suggesting that projections of future pathogen dynamics and ranges should account for multiple pathways of climate-pathogen interaction. © 2014 John Wiley & Sons Ltd.

  16. The confounded effects of age and exposure history in response to influenza vaccination

    PubMed Central

    Höpping, Ana Mosterín; McElhaney, Janet; Fonville, Judith M.; Powers, Douglas C.; Beyer, Walter E.P.; Smith, Derek J.

    2016-01-01

    Numerous studies have explored whether the antibody response to influenza vaccination in elderly adults is as strong as it is in young adults. Results vary, but tend to indicate lower post-vaccination titers (antibody levels) in the elderly, supporting the concept of immunosenescence – the weakening of the immunological response related to age. Because the elderly in such studies typically have been vaccinated against influenza before enrollment, a confounding of effects occurs between age, and previous exposures, as a potential extrinsic reason for immunosenescence. We conducted a four-year study of serial annual immunizations with inactivated trivalent influenza vaccines in 136 young adults (16 to 39 years) and 122 elderly adults (62 to 92 years). Compared to data sets of previously published studies, which were designed to investigate the effect of age, this detailed longitudinal study with multiple vaccinations allowed us to also study the effect of prior vaccination history on the response to a vaccine. In response to the first vaccination, young adults produced higher post-vaccination titers, accounting for pre-vaccination titers, than elderly adults. However, upon subsequent vaccinations the difference in response to vaccination between the young and elderly age groups declined rapidly. Although age is an important factor when modeling the outcome of the first vaccination, this term lost its relevance with successive vaccinations. In fact, when we examined the data with the assumption that the elderly group had received (on average) as few as two vaccinations prior to our study, the difference due to age disappeared. Our analyses therefore show that the initial difference between the two age groups in their response to vaccination may not be uniquely explained by immunosenescence due to ageing of the immune system, but could equally be the result of the different pre-study vaccination and infection histories in the elderly. PMID:26667611

  17. Confounding and Statistical Significance of Indirect Effects: Childhood Adversity, Education, Smoking, and Anxious and Depressive Symptomatology.

    PubMed

    Sheikh, Mashhood Ahmed

    2017-01-01

    association between childhood adversity and ADS in adulthood. However, when education was excluded as a mediator-response confounding variable, the indirect effect of childhood adversity on ADS in adulthood was statistically significant ( p < 0.05). This study shows that a careful inclusion of potential confounding variables is important when assessing mediation.

  18. Confounding and Statistical Significance of Indirect Effects: Childhood Adversity, Education, Smoking, and Anxious and Depressive Symptomatology

    PubMed Central

    Sheikh, Mashhood Ahmed

    2017-01-01

    association between childhood adversity and ADS in adulthood. However, when education was excluded as a mediator-response confounding variable, the indirect effect of childhood adversity on ADS in adulthood was statistically significant (p < 0.05). This study shows that a careful inclusion of potential confounding variables is important when assessing mediation. PMID:28824498

  19. Pattern classification of brain activation during emotional processing in subclinical depression: psychosis proneness as potential confounding factor.

    PubMed

    Modinos, Gemma; Mechelli, Andrea; Pettersson-Yeo, William; Allen, Paul; McGuire, Philip; Aleman, Andre

    2013-01-01

    We used Support Vector Machine (SVM) to perform multivariate pattern classification based on brain activation during emotional processing in healthy participants with subclinical depressive symptoms. Six-hundred undergraduate students completed the Beck Depression Inventory II (BDI-II). Two groups were subsequently formed: (i) subclinical (mild) mood disturbance (n = 17) and (ii) no mood disturbance (n = 17). Participants also completed a self-report questionnaire on subclinical psychotic symptoms, the Community Assessment of Psychic Experiences Questionnaire (CAPE) positive subscale. The functional magnetic resonance imaging (fMRI) paradigm entailed passive viewing of negative emotional and neutral scenes. The pattern of brain activity during emotional processing allowed correct group classification with an overall accuracy of 77% (p = 0.002), within a network of regions including the amygdala, insula, anterior cingulate cortex and medial prefrontal cortex. However, further analysis suggested that the classification accuracy could also be explained by subclinical psychotic symptom scores (correlation with SVM weights r = 0.459, p = 0.006). Psychosis proneness may thus be a confounding factor for neuroimaging studies in subclinical depression.

  20. Viral contacts confound studies of childhood leukemia and high-voltage transmission lines.

    PubMed

    Sahl, J D

    1994-05-01

    Studies of childhood leukemia have reported a link with residential proximity to electric utility facilities. This paper elaborates on the hypothesis that residential proximity to electric utility transmission-systems is a surrogate for viral contacts, a potential confounder in these studies. While the causal implications of increased viral contacts is not established, the assumption made here is that a significant component of childhood leukemia has an infectious etiology. Increased viral contacts can result from residential mobility, being first born, or use of community childcare facilities. Re-analysis of existing studies should look specifically for the interaction between childhood leukemia, markers for viral contacts (e.g., residential mobility, birth order, use of outside childcare facilities), and residential proximity to high-voltage transmission lines. New study designs should include parameters to test directly for a virus-related infectious model for childhood leukemia.

  1. Residential proximity to electromagnetic field sources and birth weight: Minimizing residual confounding using multiple imputation and propensity score matching.

    PubMed

    de Vocht, Frank; Lee, Brian

    2014-08-01

    Studies have suggested that residential exposure to extremely low frequency (50 Hz) electromagnetic fields (ELF-EMF) from high voltage cables, overhead power lines, electricity substations or towers are associated with reduced birth weight and may be associated with adverse birth outcomes or even miscarriages. We previously conducted a study of 140,356 singleton live births between 2004 and 2008 in Northwest England, which suggested that close residential proximity (≤ 50 m) to ELF-EMF sources was associated with reduced average birth weight of 212 g (95%CI: -395 to -29 g) but not with statistically significant increased risks for other adverse perinatal outcomes. However, the cohort was limited by missing data for most potentially confounding variables including maternal smoking during pregnancy, which was only available for a small subgroup, while also residual confounding could not be excluded. This study, using the same cohort, was conducted to minimize the effects of these problems using multiple imputation to address missing data and propensity score matching to minimize residual confounding. Missing data were imputed using multiple imputation using chained equations to generate five datasets. For each dataset 115 exposed women (residing ≤ 50 m from a residential ELF-EMF source) were propensity score matched to 1150 unexposed women. After doubly robust confounder adjustment, close proximity to a residential ELF-EMF source remained associated with a reduction in birth weight of -116 g (95% confidence interval: -224:-7 g). No effect was found for proximity ≤ 100 m compared to women living further away. These results indicate that although the effect size was about half of the effect previously reported, close maternal residential proximity to sources of ELF-EMF remained associated with suboptimal fetal growth. Copyright © 2014 Elsevier Ltd. All rights reserved.

  2. Homophily and Contagion Are Generically Confounded in Observational Social Network Studies

    PubMed Central

    Shalizi, Cosma Rohilla; Thomas, Andrew C.

    2012-01-01

    The authors consider processes on social networks that can potentially involve three factors: homophily, or the formation of social ties due to matching individual traits; social contagion, also known as social influence; and the causal effect of an individual’s covariates on his or her behavior or other measurable responses. The authors show that generically, all of these are confounded with each other. Distinguishing them from one another requires strong assumptions on the parametrization of the social process or on the adequacy of the covariates used (or both). In particular the authors demonstrate, with simple examples, that asymmetries in regression coefficients cannot identify causal effects and that very simple models of imitation (a form of social contagion) can produce substantial correlations between an individual’s enduring traits and his or her choices, even when there is no intrinsic affinity between them. The authors also suggest some possible constructive responses to these results. PMID:22523436

  3. Breath biomarkers for lung cancer detection and assessment of smoking related effects--confounding variables, influence of normalization and statistical algorithms.

    PubMed

    Kischkel, Sabine; Miekisch, Wolfram; Sawacki, Annika; Straker, Eva M; Trefz, Phillip; Amann, Anton; Schubert, Jochen K

    2010-11-11

    Up to now, none of the breath biomarkers or marker sets proposed for cancer recognition has reached clinical relevance. Possible reasons are the lack of standardized methods of sampling, analysis and data processing and effects of environmental contaminants. Concentration profiles of endogenous and exogenous breath markers were determined in exhaled breath of 31 lung cancer patients, 31 smokers and 31 healthy controls by means of SPME-GC-MS. Different correcting and normalization algorithms and a principal component analysis were applied to the data. Differences of exhalation profiles in cancer and non-cancer patients did not persist if physiology and confounding variables were taken into account. Smoking history, inspired substance concentrations, age and gender were recognized as the most important confounding variables. Normalization onto PCO2 or BSA or correction for inspired concentrations only partially solved the problem. In contrast, previous smoking behaviour could be recognized unequivocally. Exhaled substance concentrations may depend on a variety of parameters other than the disease under investigation. Normalization and correcting parameters have to be chosen with care as compensating effects may be different from one substance to the other. Only well-founded biomarker identification, normalization and data processing will provide clinically relevant information from breath analysis. 2010 Elsevier B.V. All rights reserved.

  4. The Relationship between Patient Satisfaction with Service Quality and Survival in Non-Small Cell Lung Cancer - Is Self-Rated Health a Potential Confounder?

    PubMed

    Lis, Christopher G; Patel, Kamal; Gupta, Digant

    2015-01-01

    Previously we reported that higher patient satisfaction (PS) with service quality is associated with favorable survival outcomes in a variety of cancers. However, we cautioned the readers that patients with greater satisfaction might be the ones with better self-rated health (SRH), a well-established prognosticator of cancer survival. In other words, SRH could potentially confound the PS and survival relationship. We investigated this hypothesis in non-small cell lung cancer (NSCLC). 778 NSCLC patients (327 males and 451 females; mean age 58.8 years) treated at 4 Cancer Treatment Centers of America hospitals between July 2011 and March 2013. PS was measured on a 7-point scale ranging from "completely dissatisfied" to "completely satisfied". SRH was measured on a 7-point scale ranging from "very poor" to "excellent". Both were dichotomized into 2 categories: top box response (7) versus all others (1-6). Patient survival was the primary end point. Cox regression was used to evaluate the association between PS and survival controlling for covariates. 74, 70, 232 and 391 patients had stage I, II, III and IV disease respectively. 631 (81.1%) patients were "completely satisfied". 184 (23.7%) patients had "excellent" SRH. There was a weak but significant correlation between overall PS and SRH (Kendall's tau b = 0.19; p<0.001). On univariate analysis, "completely satisfied" patients had a significantly lower risk of mortality (HR = 0.75; 95% CI: 0.57 to 0.99; p = 0.04). Similarly, patients with "excellent" SRH had a significantly lower risk of mortality (HR = 0.61; 95% CI: 0.46 to 0.81; p = 0.001). On multivariate analysis controlling for stage at diagnosis, treatment history and gender, SRH was found to be a significant predictor of survival (HR = 0.67; 95% CI: 0.50 to 0.89; p = 0.007) while PS was not (HR = 0.86; 95% CI: 0.64 to 1.2; p = 0.32). Among the individual PS items, the only significant independent predictor of survival was "teams communicating with each other

  5. Confounder summary scores when comparing the effects of multiple drug exposures.

    PubMed

    Cadarette, Suzanne M; Gagne, Joshua J; Solomon, Daniel H; Katz, Jeffrey N; Stürmer, Til

    2010-01-01

    Little information is available comparing methods to adjust for confounding when considering multiple drug exposures. We compared three analytic strategies to control for confounding based on measured variables: conventional multivariable, exposure propensity score (EPS), and disease risk score (DRS). Each method was applied to a dataset (2000-2006) recently used to examine the comparative effectiveness of four drugs. The relative effectiveness of risedronate, nasal calcitonin, and raloxifene in preventing non-vertebral fracture, were each compared to alendronate. EPSs were derived both by using multinomial logistic regression (single model EPS) and by three separate logistic regression models (separate model EPS). DRSs were derived and event rates compared using Cox proportional hazard models. DRSs derived among the entire cohort (full cohort DRS) was compared to DRSs derived only among the referent alendronate (unexposed cohort DRS). Less than 8% deviation from the base estimate (conventional multivariable) was observed applying single model EPS, separate model EPS or full cohort DRS. Applying the unexposed cohort DRS when background risk for fracture differed between comparison drug exposure cohorts resulted in -7 to + 13% deviation from our base estimate. With sufficient numbers of exposed and outcomes, either conventional multivariable, EPS or full cohort DRS may be used to adjust for confounding to compare the effects of multiple drug exposures. However, our data also suggest that unexposed cohort DRS may be problematic when background risks differ between referent and exposed groups. Further empirical and simulation studies will help to clarify the generalizability of our findings.

  6. Using ecological propensity score to adjust for missing confounders in small area studies.

    PubMed

    Wang, Yingbo; Pirani, Monica; Hansell, Anna L; Richardson, Sylvia; Blangiardo, Marta

    2017-11-09

    Small area ecological studies are commonly used in epidemiology to assess the impact of area level risk factors on health outcomes when data are only available in an aggregated form. However, the resulting estimates are often biased due to unmeasured confounders, which typically are not available from the standard administrative registries used for these studies. Extra information on confounders can be provided through external data sets such as surveys or cohorts, where the data are available at the individual level rather than at the area level; however, such data typically lack the geographical coverage of administrative registries. We develop a framework of analysis which combines ecological and individual level data from different sources to provide an adjusted estimate of area level risk factors which is less biased. Our method (i) summarizes all available individual level confounders into an area level scalar variable, which we call ecological propensity score (EPS), (ii) implements a hierarchical structured approach to impute the values of EPS whenever they are missing, and (iii) includes the estimated and imputed EPS into the ecological regression linking the risk factors to the health outcome. Through a simulation study, we show that integrating individual level data into small area analyses via EPS is a promising method to reduce the bias intrinsic in ecological studies due to unmeasured confounders; we also apply the method to a real case study to evaluate the effect of air pollution on coronary heart disease hospital admissions in Greater London. © The Author 2017. Published by Oxford University Press.

  7. The Association Between Headaches and Temporomandibular Disorders is Confounded by Bruxism and Somatic Symptoms.

    PubMed

    van der Meer, Hedwig A; Speksnijder, Caroline M; Engelbert, Raoul H H; Lobbezoo, Frank; Nijhuis-van der Sanden, Maria W G; Visscher, Corine M

    2017-09-01

    The objective of this observational study was to establish the possible presence of confounders on the association between temporomandibular disorders (TMD) and headaches in a patient population from a TMD and Orofacial Pain Clinic. Several subtypes of headaches have been diagnosed: self-reported headache, (probable) migraine, (probable) tension-type headache, and secondary headache attributed to TMD. The presence of TMD was subdivided into 2 subtypes: painful TMD and function-related TMD. The associations between the subtypes of TMD and headaches were evaluated by single regression models. To study the influence of possible confounding factors on this association, the regression models were extended with age, sex, bruxism, stress, depression, and somatic symptoms. Of the included patients (n=203), 67.5% experienced headaches. In the subsample of patients with a painful TMD (n=58), the prevalence of self-reported headaches increased to 82.8%. The associations found between self-reported headache and (1) painful TMD and (2) function-related TMD were confounded by the presence of somatic symptoms. For probable migraine, both somatic symptoms and bruxism confounded the initial association found with painful TMD. The findings of this study imply that there is a central working mechanism overlapping TMD and headache. Health care providers should not regard these disorders separately, but rather look at the bigger picture to appreciate the complex nature of the diagnostic and therapeutic process.

  8. Combating Unmeasured Confounding in Cross-Sectional Studies: Evaluating Instrumental-Variable and Heckman Selection Models

    PubMed Central

    DeMaris, Alfred

    2014-01-01

    Unmeasured confounding is the principal threat to unbiased estimation of treatment “effects” (i.e., regression parameters for binary regressors) in nonexperimental research. It refers to unmeasured characteristics of individuals that lead them both to be in a particular “treatment” category and to register higher or lower values than others on a response variable. In this article, I introduce readers to 2 econometric techniques designed to control the problem, with a particular emphasis on the Heckman selection model (HSM). Both techniques can be used with only cross-sectional data. Using a Monte Carlo experiment, I compare the performance of instrumental-variable regression (IVR) and HSM to that of ordinary least squares (OLS) under conditions with treatment and unmeasured confounding both present and absent. I find HSM generally to outperform IVR with respect to mean-square-error of treatment estimates, as well as power for detecting either a treatment effect or unobserved confounding. However, both HSM and IVR require a large sample to be fully effective. The use of HSM and IVR in tandem with OLS to untangle unobserved confounding bias in cross-sectional data is further demonstrated with an empirical application. Using data from the 2006–2010 General Social Survey (National Opinion Research Center, 2014), I examine the association between being married and subjective well-being. PMID:25110904

  9. Duration perception of emotional stimuli: Using evaluative conditioning to avoid sensory confounds.

    PubMed

    Kliegl, Katrin M; Watrin, Luc; Huckauf, Anke

    2015-01-01

    It has been found that emotional pictures are estimated to last longer than neutral ones. However, emotional and neutral stimuli often differ in their physical characteristics, too. Since this might also affect time perception, we present a method disentangling a possible confounding regarding the processing of physically different stimulus material. In the evaluative condition paradigm, participants, at first, learnt the association of neutral images with a certain Landolt ring and of emotional images with another Landolt ring with a different gap position. The conditioned Landolt rings were subsequently used in a temporal bisection task. In two experiments, the results revealed a temporal overestimation of Landolt rings conditioned with emotional pictures compared to neutral pictures showing that the temporal overestimation of emotional stimuli cannot be attributed to perceptual differences between neutral and emotional stimuli. The method provides the potential for investigating emotional effects on various perceptual processes.

  10. Species-specific responses to ocean acidification should account for local adaptation and adaptive plasticity.

    PubMed

    Vargas, Cristian A; Lagos, Nelson A; Lardies, Marco A; Duarte, Cristian; Manríquez, Patricio H; Aguilera, Victor M; Broitman, Bernardo; Widdicombe, Steve; Dupont, Sam

    2017-03-13

    Global stressors, such as ocean acidification, constitute a rapidly emerging and significant problem for marine organisms, ecosystem functioning and services. The coastal ecosystems of the Humboldt Current System (HCS) off Chile harbour a broad physical-chemical latitudinal and temporal gradient with considerable patchiness in local oceanographic conditions. This heterogeneity may, in turn, modulate the specific tolerances of organisms to climate stress in species with populations distributed along this environmental gradient. Negative response ratios are observed in species models (mussels, gastropods and planktonic copepods) exposed to changes in the partial pressure of CO 2 (pCO2) far from the average and extreme pCO2 levels experienced in their native habitats. This variability in response between populations reveals the potential role of local adaptation and/or adaptive phenotypic plasticity in increasing resilience of species to environmental change. The growing use of standard ocean acidification scenarios and treatment levels in experimental protocols brings with it a danger that inter-population differences are confounded by the varying environmental conditions naturally experienced by different populations. Here, we propose the use of a simple index taking into account the natural pCO2 variability, for a better interpretation of the potential consequences of ocean acidification on species inhabiting variable coastal ecosystems. Using scenarios that take into account the natural variability will allow understanding of the limits to plasticity across organismal traits, populations and species.

  11. Metformin and Cancer Risk and Mortality: A Systematic Review and Meta-Analysis taking into account Biases and Confounders

    PubMed Central

    Gandini, Sara; Puntoni, Matteo; Heckman-Stoddard, Brandy M; Dunn, Barbara K; Ford, Leslie; DeCensi, Andrea; Szabo, Eva

    2014-01-01

    Previous meta-analyses have shown that the anti-diabetic agent metformin is associated with reduced cancer incidence and mortality. However, this effect has not been consistently demonstrated in animal models and recent epidemiological studies. We performed a meta-analysis with a focus on confounders and biases, including BMI, study type, and time related biases. We identified 71 articles published between January 1, 1966 to May 31, 2013 through Pubmed, ISI Web of Science (Science Citation Index Expanded), Embase, and the Cochrane library that were related to metformin and cancer incidence or mortality. Study characteristics and outcomes were abstracted for each study that met inclusion criteria. We included estimates from 47 independent studies and 65,540 cancer cases in diabetic patients. Overall cancer incidence was reduced by 31% (SRR=0.69, 95%CI: 0.52–0.90), although between-study heterogeneity was considerable (I2=88%). Cancer mortality was reduced by 34% (SRR=0.66, 95%CI: 0.54–0.81; I2=21%). BMI-adjusted studies and studies without time-related biases also showed significant reduction in cancer incidence (SRR=0.82, 95%CI: 0.70–0.96 with I2=76% and SRR=0.90; 95%CI: 0.89–0.91 with I2=56%, respectively), albeit with lesser magnitude (18% and 10% reduction, respectively). However, studies of cancer mortality and individual organ sites did not consistently show significant reductions across all types of analyses. Although these associations may not be causal, our results show that metformin may reduce cancer incidence and mortality in diabetic patients. However the reduction seems to be of modest magnitude and not affecting all populations equally. Clinical trials are needed to determine if these observations apply to non-diabetic populations and to specific organ sites. PMID:24985407

  12. Small intestinal permeability is increased in diarrhoea predominant IBS, while alterations in gastroduodenal permeability in all IBS subtypes are largely attributable to confounders.

    PubMed

    Mujagic, Z; Ludidi, S; Keszthelyi, D; Hesselink, M A M; Kruimel, J W; Lenaerts, K; Hanssen, N M J; Conchillo, J M; Jonkers, D M A E; Masclee, A A M

    2014-08-01

    Intestinal permeability has been studied in small groups of IBS patients with contrasting findings. To assess intestinal permeability at different sites of the GI tract in different subtypes of well-characterised IBS patients and healthy controls (HC), and to assess potential confounding factors. IBS patients and HC underwent a multi-sugar test to assess site-specific intestinal permeability. Sucrose excretion and lactulose/rhamnose ratio in 0-5 h urine indicated gastroduodenal and small intestinal permeability, respectively. Sucralose/erythritol ratio in 0-24 h and 5-24 h urine indicated whole gut and colonic permeability, respectively. Linear regression analysis was used to assess the association between IBS groups and intestinal permeability and to adjust for age, sex, BMI, anxiety or depression, smoking, alcohol intake and use of medication. Ninety-one IBS patients, i.e. 37% IBS-D, 23% IBS-C, 33% IBS-M and 7% IBS-U and 94 HC were enrolled. Urinary sucrose excretion was significantly increased in the total IBS group [μmol, median (Q1;Q3): 5.26 (1.82;11.03) vs. 2.44 (0.91;5.85), P < 0.05], as well as in IBS-C and IBS-D vs. HC. However, differences attenuated when adjusting for confounders. The lactulose/rhamnose ratio was increased in IBS-D vs. HC [0.023 (0.013;0.038) vs. 0.014 (0.008;0.025), P < 0.05], which remained significant after adjustment for confounders. No difference was found in 0-24 and 5-24 h sucralose/erythritol ratio between groups. Small intestinal permeability is increased in patients with IBS-D compared to healthy controls, irrespective of confounding factors. Adjustment for confounders is necessary when studying intestinal permeability, especially in a heterogeneous disorder such as IBS. © 2014 John Wiley & Sons Ltd.

  13. KIR Genotypic Diversity Can Track Ancestries in Heterogeneous Populations: A Potential Confounder for Disease Association Studies

    PubMed Central

    Singh, Komal Manpreet; Phung, Yume T.; Kohla, Mohamed S.; Lan, Billy Y-A; Chan, Sharon; Suen, Diana L.; Murad, Sahar; Rheault, Shana; Davidson, Peter; Evans, Jennifer; Singh, Manpreet; Dohil, Sofie; Osorio, Robert W.; Wakil, Adil E.; Page, Kimberly; Feng, Sandy; Cooper, Stewart L.

    2014-01-01

    Killer cell immunoglobulin-like receptors (KIR) are encoded by highly polymorphic genes that regulate the activation of natural killer (NK) cells and other lymphocyte subsets, and likely play key roles in innate and adaptive immunity. Association studies increasingly implicate KIR in disease predisposition and outcome but could be confounded by unknown KIR genetic structure in heterogeneous populations. To examine this we characterized the diversity of 16 KIR genes in 712 Northern Californians (NC) stratified by selfassigned ethnicities, and compared the profiles of KIR polymorphism with other US and global populations using a reference database. Sixty-eight distinct KIR genotypes were characterized: 58 in 457 Caucasians (NCC); 17 in 47 African Americans (NCAA); 21 in 80 Asians (NCA); 20 in 74 Hispanics (NCH) and 18 in 54 “other” ethnicities (NCO). KIR genotype patterns and frequencies in the 4 defined ethnicities were compared with each other and with 34 global populations by phylogenetic analysis. Although there were no population-specific genotypes, the KIR genotype frequency patterns faithfully traced the ancestry of NCC, NCAA and NCA but not of NCH whose ancestries are known to be more heterogeneous. KIR genotype frequencies can therefore track ethnic ancestries in modern urban populations. Our data emphasize the importance of selecting ethnically matched controls in KIR based studies to avert spurious associations. PMID:21898189

  14. Adjusting for Confounding in Early Postlaunch Settings: Going Beyond Logistic Regression Models.

    PubMed

    Schmidt, Amand F; Klungel, Olaf H; Groenwold, Rolf H H

    2016-01-01

    Postlaunch data on medical treatments can be analyzed to explore adverse events or relative effectiveness in real-life settings. These analyses are often complicated by the number of potential confounders and the possibility of model misspecification. We conducted a simulation study to compare the performance of logistic regression, propensity score, disease risk score, and stabilized inverse probability weighting methods to adjust for confounding. Model misspecification was induced in the independent derivation dataset. We evaluated performance using relative bias confidence interval coverage of the true effect, among other metrics. At low events per coefficient (1.0 and 0.5), the logistic regression estimates had a large relative bias (greater than -100%). Bias of the disease risk score estimates was at most 13.48% and 18.83%. For the propensity score model, this was 8.74% and >100%, respectively. At events per coefficient of 1.0 and 0.5, inverse probability weighting frequently failed or reduced to a crude regression, resulting in biases of -8.49% and 24.55%. Coverage of logistic regression estimates became less than the nominal level at events per coefficient ≤5. For the disease risk score, inverse probability weighting, and propensity score, coverage became less than nominal at events per coefficient ≤2.5, ≤1.0, and ≤1.0, respectively. Bias of misspecified disease risk score models was 16.55%. In settings with low events/exposed subjects per coefficient, disease risk score methods can be useful alternatives to logistic regression models, especially when propensity score models cannot be used. Despite better performance of disease risk score methods than logistic regression and propensity score models in small events per coefficient settings, bias, and coverage still deviated from nominal.

  15. Antipsychotics and mortality: adjusting for mortality risk scores to address confounding by terminal illness.

    PubMed

    Park, Yoonyoung; Franklin, Jessica M; Schneeweiss, Sebastian; Levin, Raisa; Crystal, Stephen; Gerhard, Tobias; Huybrechts, Krista F

    2015-03-01

    To determine whether adjustment for prognostic indices specifically developed for nursing home (NH) populations affect the magnitude of previously observed associations between mortality and conventional and atypical antipsychotics. Cohort study. A merged data set of Medicaid, Medicare, Minimum Data Set (MDS), Online Survey Certification and Reporting system, and National Death Index for 2001 to 2005. Dual-eligible individuals aged 65 and older who initiated antipsychotic treatment in a NH (N=75,445). Three mortality risk scores (Mortality Risk Index Score, Revised MDS Mortality Risk Index, Advanced Dementia Prognostic Tool) were derived for each participant using baseline MDS data, and their performance was assessed using c-statistics and goodness-of-fit tests. The effect of adjusting for these indices in addition to propensity scores (PSs) on the association between antipsychotic medication and mortality was evaluated using Cox models with and without adjustment for risk scores. Each risk score showed moderate discrimination for 6-month mortality, with c-statistics ranging from 0.61 to 0.63. There was no evidence of lack of fit. Imbalances in risk scores between conventional and atypical antipsychotic users, suggesting potential confounding, were much lower within PS deciles than the imbalances in the full cohort. Accounting for each score in the Cox model did not change the relative risk estimates: 2.24 with PS-only adjustment versus 2.20, 2.20, and 2.22 after further adjustment for the three risk scores. Although causality cannot be proven based on nonrandomized studies, this study adds to the body of evidence rejecting explanations other than causality for the greater mortality risk associated with conventional antipsychotics than with atypical antipsychotics. © 2015, Copyright the Authors Journal compilation © 2015, The American Geriatrics Society.

  16. Infection with parasitic nematodes confounds vaccination efficacy

    PubMed Central

    Urban, Joseph F.; Steenhard, Nina R.; Solano-Aguilar, Gloria I.; Dawson, Harry D.; Iweala, Onyinye I.; Nagler, Cathryn R.; Noland, Gregory S.; Kumar, Nirbhay; Anthony, Robert M.; Shea-Donohue, Terez; Weinstock, Joel; Gause, William C.

    2007-01-01

    T helper (Th) cells produce signature cytokine patterns, induced largely by intracellular versus extracellular pathogens that provide the cellular and molecular basis for counter regulatory expression of protective immunity during concurrent infections. The production of IL-12 and IFN-γ, for example, resulting from exposure to many bacterial, viral, and protozoan pathogens is responsible for Th1-derived protective responses that also can inhibit development of Th2-cells expressing IL-4-dependent immunity to extracellular helminth parasites and vice versa. In a similar manner, concurrent helminth infection alters optimal vaccine-induced responses in humans and livestock; however, the consequences of this condition have not been adequately studied especially in the context of a challenge infection following vaccination. Demands for new and effective vaccines to control chronic and emerging diseases, and the need for rapid deployment of vaccines for bio security concerns requires a systematic evaluation of confounding factors that limit vaccine efficacy. One common albeit overlooked confounder is the presence of gastrointestinal nematode parasites in populations of humans and livestock targeted for vaccination. This is particularly important in areas of the world were helminth infections are prevalent, but the interplay between parasites and emerging diseases that can be transmitted worldwide make this a global issue. In addition, it is not clear if the epidemic in allergic disease in industrialized countries substitutes for geohelminth infection to interfere with effective vaccination regimens. This presentation will focus on recent vaccination studies in mice experimentally infected with Heligmosomoides polygyrus to model the condition of gastrointestinal parasite infestation in mammalian populations targeted for vaccination. In addition, a large animal vaccination and challenge model against Mycoplasma hyopneumonia in swine exposed to Ascaris suum will provide a

  17. State Assessment (Accountability): Potential for Becoming a Friend or Foe?

    ERIC Educational Resources Information Center

    Buchmiller, Archie A.

    A summary of legislation concerning educational accountability reveals that 13 States hope to find greater accountability in testing or assessment programs, 7 in planning, programming, budgeting systems, 4 in uniform accounting system, 8 in the evaluation of professional employees, 2 in management information systems, and 1 in performance…

  18. The diurnal course of salivary alpha-amylase in nurses: an investigation of potential confounders and associations with stress.

    PubMed

    Wingenfeld, Katja; Schulz, Michael; Damkroeger, Annika; Philippsen, Christine; Rose, Matthias; Driessen, Martin

    2010-09-01

    In psychoneuroendocrinology research, salivary measures have become increasingly important. While several studies focus on determinants of salivary cortisol such as age, gender, and gynaecological variables, less research has focused on confounding variables of salivary alpha-amylase (sAA). In a large sample of nurses (N=215) we analyzed the impact of age, gender, intake of oral contraceptives, smoking, coffee consumption as well as psychological parameters, such as work stress and burnout, on basal diurnal sAA release. Saliva was collected at 07:00 h, 11:30 h, 17:30 h, and 20:00 h on a working day during early shift. Only gender could be identified to have an impact on sAA, with females having a more pronounced sAA increase over the course of the day. Whereas depression, anxiety, work stress and burnout were not associated with sAA, a small negative correlation between social difficulties, measured with the Chronic Stress Screening Scale, and sAA could be identified. Copyright (c) 2010 Elsevier B.V. All rights reserved.

  19. A Harmonious Accounting Duo?

    ERIC Educational Resources Information Center

    Schapperle, Robert F.; Hardiman, Patrick F.

    1992-01-01

    Accountants have urged "harmonization" of standards between the Governmental Accounting Standards Board and the Financial Accounting Standards Board, recommending similar reporting of like transactions. However, varying display of similar accounting events does not necessarily indicate disharmony. The potential for problems because of…

  20. Job Strain and the Cortisol Diurnal Cycle in MESA: Accounting for Between- and Within-Day Variability

    PubMed Central

    Rudolph, Kara E.; Sánchez, Brisa N.; Stuart, Elizabeth A.; Greenberg, Benjamin; Fujishiro, Kaori; Wand, Gary S.; Shrager, Sandi; Seeman, Teresa; Diez Roux, Ana V.; Golden, Sherita H.

    2016-01-01

    Evidence of the link between job strain and cortisol levels has been inconsistent. This could be due to failure to account for cortisol variability leading to underestimated standard errors. Our objective was to model the relationship between job strain and the whole cortisol curve, accounting for sources of cortisol variability. Our functional mixed-model approach incorporated all available data—18 samples over 3 days—and uncertainty in estimated relationships. We used employed participants from the Multi-Ethnic Study of Atherosclerosis Stress I Study and data collected between 2002 and 2006. We used propensity score matching on an extensive set of variables to control for sources of confounding. We found that job strain was associated with lower salivary cortisol levels and lower total area under the curve. We found no relationship between job strain and the cortisol awakening response. Our findings differed from those of several previous studies. It is plausible that our results were unique to middle- to older-aged racially, ethnically, and occupationally diverse adults and were therefore not inconsistent with previous research among younger, mostly white samples. However, it is also plausible that previous findings were influenced by residual confounding and failure to propagate uncertainty (i.e., account for the multiple sources of variability) in estimating cortisol features. PMID:26905339

  1. On negative outcome control of unobserved confounding as a generalization of difference-in-differences

    PubMed Central

    Sofer, Tamar; Richardson, David B.; Colicino, Elena; Schwartz, Joel; Tchetgen Tchetgen, Eric J.

    2016-01-01

    The difference-in-differences (DID) approach is a well known strategy for estimating the effect of an exposure in the presence of unobserved confounding. The approach is most commonly used when pre-and post-exposure outcome measurements are available, and one can assume that the association of the unobserved confounder with the outcome is equal in the two exposure groups, and constant over time. Then, one recovers the treatment effect by regressing the change in outcome over time on the exposure. In this paper, we interpret the difference-in-differences as a negative outcome control (NOC) approach. We show that the pre-exposure outcome is a negative control outcome, as it cannot be influenced by the subsequent exposure, and it is affected by both observed and unobserved confounders of the exposure-outcome association of interest. The relation between DID and NOC provides simple conditions under which negative control outcomes can be used to detect and correct for confounding bias. However, for general negative control outcomes, the DID-like assumption may be overly restrictive and rarely credible, because it requires that both the outcome of interest and the control outcome are measured on the same scale. Thus, we present a scale-invariant generalization of the DID that may be used in broader NOC contexts. The proposed approach is demonstrated in simulations and on a Normative Aging Study data set, in which Body Mass Index is used for NOC of the relationship between air pollution and inflammatory outcomes. PMID:28239233

  2. Using instrumental variables to disentangle treatment and placebo effects in blinded and unblinded randomized clinical trials influenced by unmeasured confounders

    NASA Astrophysics Data System (ADS)

    Chaibub Neto, Elias

    2016-11-01

    Clinical trials traditionally employ blinding as a design mechanism to reduce the influence of placebo effects. In practice, however, it can be difficult or impossible to blind study participants and unblinded trials are common in medical research. Here we show how instrumental variables can be used to quantify and disentangle treatment and placebo effects in randomized clinical trials comparing control and active treatments in the presence of confounders. The key idea is to use randomization to separately manipulate treatment assignment and psychological encouragement conversations/interactions that increase the participants’ desire for improved symptoms. The proposed approach is able to improve the estimation of treatment effects in blinded studies and, most importantly, opens the doors to account for placebo effects in unblinded trials.

  3. Cryptic confounding compounds: A brief consideration of the influences of anthropogenic contaminants on courtship and mating behavior

    PubMed Central

    Blocker, Tomica D.; Ophir, Alexander G.

    2012-01-01

    Contaminants, like pesticides, polychlorinated biphenyls (PCBs), dioxins and metals, are persistent and ubiquitous and are known to threaten the environment. Traditionally, scientists have considered the direct physiological risks that these contaminants pose. However, scientists have just begun to integrate ethology and toxicology to investigate the effects that contaminants have on behavior. This review considers the potential for contaminant effects on mating behavior. Here we assess the growing body of research concerning disruptions in sexual differentiation, courtship, sexual receptivity, arousal, and mating. We discuss the implications of these disruptions on conservation efforts and highlight the importance of recognizing the potential for environmental stressors to affect behavioral experimentation. More specifically, we consider the negative implications for anthropogenic contaminants to affect the immediate behavior of animals, and their potential to have cascading and/or long-term effects on the behavioral ecology and evolution of populations. Overall, we aim to raise awareness of the confounding influence that contaminants can have, and promote caution when interpreting results where the potential for cryptic affects are possible. PMID:24244068

  4. The confounded effects of age and exposure history in response to influenza vaccination.

    PubMed

    Mosterín Höpping, Ana; McElhaney, Janet; Fonville, Judith M; Powers, Douglas C; Beyer, Walter E P; Smith, Derek J

    2016-01-20

    Numerous studies have explored whether the antibody response to influenza vaccination in elderly adults is as strong as it is in young adults. Results vary, but tend to indicate lower post-vaccination titers (antibody levels) in the elderly, supporting the concept of immunosenescence-the weakening of the immunological response related to age. Because the elderly in such studies typically have been vaccinated against influenza before enrollment, a confounding of effects occurs between age, and previous exposures, as a potential extrinsic reason for immunosenescence. We conducted a four-year study of serial annual immunizations with inactivated trivalent influenza vaccines in 136 young adults (16 to 39 years) and 122 elderly adults (62 to 92 years). Compared to data sets of previously published studies, which were designed to investigate the effect of age, this detailed longitudinal study with multiple vaccinations allowed us to also study the effect of prior vaccination history on the response to a vaccine. In response to the first vaccination, young adults produced higher post-vaccination titers, accounting for pre-vaccination titers, than elderly adults. However, upon subsequent vaccinations the difference in response to vaccination between the young and elderly age groups declined rapidly. Although age is an important factor when modeling the outcome of the first vaccination, this term lost its relevance with successive vaccinations. In fact, when we examined the data with the assumption that the elderly group had received (on average) as few as two vaccinations prior to our study, the difference due to age disappeared. Our analyses therefore show that the initial difference between the two age groups in their response to vaccination may not be uniquely explained by immunosenescence due to ageing of the immune system, but could equally be the result of the different pre-study vaccination and infection histories in the elderly. Copyright © 2015 The Authors

  5. Association between obesity and glomerular hyperfiltration: the confounding effect of smoking and sodium and protein intakes.

    PubMed

    Ogna, Adam; Forni Ogna, Valentina; Bochud, Murielle; Guessous, Idris; Paccaud, Fred; Burnier, Michel; Wuerzner, Gregoire

    2016-04-01

    Glomerular hyperfiltration has been suggested as a possible mechanism linking obesity and chronic kidney disease (CKD), independently of classical risk factors. We explored the association of overweight and obesity with glomerular hyperfiltration in a large sample of the Swiss adult population, accounting for several confounders including dietary factors. Data from a 2010 to 2012 cross-sectional population-based survey in Switzerland were used. Creatinine clearance (CrCl) was determined from 24-h urine collection; CrCl > 140 ml/min was used to define glomerular hyperfiltration. Participants were categorized into lean (<25 kg/m(2)), overweight (25-29.9 kg/m(2)) and obese (≥30 kg/m(2)) according to body mass index (BMI). A total of 1339 participants were included in the analysis [median (IQR) age 49.4 (34.3-63.5) years, 48.9 % men]. The prevalences of overweight and obesity were 32.2 and 14.2 %, respectively. Median CrCl was 102[84-121] ml/min in lean, 110 [87-136] ml/min in overweight and 124 [97-150] ml/min in obese participants (p < 0.001). The prevalence of glomerular hyperfiltration increased across BMI categories (10.4, 20.8 and 34.7 %, respectively; p < 0.001). This positive association remained significant after adjusting for age, sex, hypertension, diabetes, smoking and dietary factors (sodium and protein intakes): odds ratio [95 %CI] 2.39 [1.52-3.76] (p < 0.001) for overweight versus lean and 4.10[2.31-7.27] (p < 0.001) for obesity versus lean. BMI categories and glomerular hyperfiltration are positively associated, independently of other known CKD risk factors and dietary confounders, suggesting that glomerular hyperfiltration may represent an early renal phenotype in obesity. Our observations confirm the significant association of glomerular hyperfiltration with sodium and protein intakes and identify sodium intake as an important modifying factor of the association between hyperfiltration and obesity.

  6. Confronting ‘confounding by health system use’ in Medicare Part D: Comparative effectiveness of propensity score approaches to confounding adjustment

    PubMed Central

    Polinski, Jennifer M.; Schneeweiss, Sebastian; Glynn, Robert J.; Lii, Joyce; Rassen, Jeremy

    2012-01-01

    Purpose Under Medicare Part D, patient characteristics influence plan choice, which in turn influences Part D coverage gap entry. We compared pre-defined propensity score (PS) and high-dimensional propensity score (hdPS) approaches to address such ‘confounding by health system use’ in assessing whether coverage gap entry is associated with cardiovascular events or death. Methods We followed 243,079 Medicare patients aged 65+ with linked prescription, medical, and plan-specific data in 2005–2007. Patients reached the coverage gap and were followed until an event or year’s end. Exposed patients were responsible for drug costs in the gap; unexposed patients (patients with non-Part D drug insurance and Part D patients receiving a low-income subsidy (LIS)) received financial assistance. Exposed patients were 1:1 PS- or hdPS-matched to unexposed patients. The PS model included 52 predefined covariates; the hdPS model added 400 empirically identified covariates. Hazard ratios for death and any of five cardiovascular outcomes were compared. In sensitivity analyses, we explored residual confounding using only LIS patients in the unexposed group. Results In unadjusted analyses, exposed patients had no greater hazard of death (HR=1.00; 95% CI, 0.84–1.20) or other outcomes. PS- (HR=1.29;0.99–1.66) and hdPS- (HR=1.11;0.86–1.42) matched analyses showed elevated but non-significant hazards of death. In sensitivity analyses, the PS analysis showed a protective effect (HR=0.78;0.61–0.98), while the hdPS analysis (HR=1.06;0.82–1.37) confirmed the main hdPS findings. Conclusion Although the PS-matched analysis suggested elevated though non-significant hazards of death among patients with no financial assistance during the gap, the hdPS analysis produced lower estimates that were stable across sensitivity analyses. PMID:22552984

  7. Is it patience or motivation? On motivational confounds in intertemporal choice tasks.

    PubMed

    Paglieri, Fabio; Addessi, Elsa; Sbaffi, Agnese; Tasselli, Maria Isabella; Delfino, Alexia

    2015-01-01

    Intertemporal choices create a tension between amount maximization, which would favor the larger and later option (LL), and delay minimization, which would promote the smaller and sooner reward (SS). Two common interpretations of intertemporal choice behavior are discussed: looking at LL responses as indicative of self-control, and using intertemporal choices to assess delay aversion. We argue that both interpretations need to take into account motivational confounds, in order to be warranted by data. In intertemporal choices with prepotent, salient stimuli (e.g., food amounts, typically used with nonhuman primates), LL responses could also be indicative of failed inhibition of a "go for more" impulsive response-the opposite of self-control. Similarly, intertemporal choices can be used to measure delay aversion only with respect to the subject's baseline motivation to maximize the reinforcer in question, and this baseline is not always assessed in current experimental protocols. This concern is especially crucial in comparing intertemporal choices across different groups or manipulation. We focus in particular on the effects of reward types on intertemporal choices, presenting two experimental studies where the difference in behavior with monetary versus food rewards is the product of different baseline motivation, rather than variations in delay aversion. We conclude discussing the implications of these and other similar recent findings, which are far-reaching. © Society for the Experimental Analysis of Behavior.

  8. Arnica montana experimental studies: confounders and biases?

    PubMed

    Bellavite, Paolo; Marzotto, Marta; Bonafini, Clara

    2018-03-01

    Arnica montana is a popular traditional remedy widely used in complementary and alternative medicine, in part for its wound-healing properties. The authors recently showed that this plant extract and several of its homeopathic dilutions are able to modify the expression of a series of genes involved in inflammation and connective tissue regeneration. Their studies opened a debate, including criticisms to the "errors" in the methods used and the "confounders and biases". Here the authors show that the criticisms raised on methodology and statistics are not consistent and cannot be considered pertinent. The present comment also updates and reviews information concerning the action of A. montana dilutions in human macrophage cells while summarizing the major experimental advances reported on this interesting medicinal plant. Copyright © 2018. Published by Elsevier B.V.

  9. Assessing moderated mediation in linear models requires fewer confounding assumptions than assessing mediation.

    PubMed

    Loeys, Tom; Talloen, Wouter; Goubert, Liesbet; Moerkerke, Beatrijs; Vansteelandt, Stijn

    2016-11-01

    It is well known from the mediation analysis literature that the identification of direct and indirect effects relies on strong no unmeasured confounding assumptions of no unmeasured confounding. Even in randomized studies the mediator may still be correlated with unobserved prognostic variables that affect the outcome, in which case the mediator's role in the causal process may not be inferred without bias. In the behavioural and social science literature very little attention has been given so far to the causal assumptions required for moderated mediation analysis. In this paper we focus on the index for moderated mediation, which measures by how much the mediated effect is larger or smaller for varying levels of the moderator. We show that in linear models this index can be estimated without bias in the presence of unmeasured common causes of the moderator, mediator and outcome under certain conditions. Importantly, one can thus use the test for moderated mediation to support evidence for mediation under less stringent confounding conditions. We illustrate our findings with data from a randomized experiment assessing the impact of being primed with social deception upon observer responses to others' pain, and from an observational study of individuals who ended a romantic relationship assessing the effect of attachment anxiety during the relationship on mental distress 2 years after the break-up. © 2016 The British Psychological Society.

  10. Drug induced liver injury with analysis of alternative causes as confounding variables.

    PubMed

    Teschke, Rolf; Danan, Gaby

    2018-04-01

    Drug-induced liver injury (DILI) is rare compared to the worldwide frequent acute or chronic liver diseases. Therefore, patients included in series of suspected DILI are at high risk of not having DILI, whereby alternative causes may confound the DILI diagnosis. The aim of this review is to evaluate published case series of DILI for alternative causes. Relevant studies were identified using a computerized search of the Medline database for publications from 1993 through 30 October 2017. We used the following terms: drug hepatotoxicity, drug induced liver injury, hepatotoxic drugs combined with diagnosis, causality assessment and alternative causes. Alternative causes as variables confounding the DILI diagnosis emerged in 22 published DILI case series, ranging from 4 to 47%. Among 13 335 cases of suspected DILI, alternative causes were found to be more likely in 4555 patients (34.2%), suggesting that the suspected DILI was probably not DILI. Biliary diseases such as biliary obstruction, cholangitis, choledocholithiasis, primary biliary cholangitis and primary sclerosing cholangitis were among the most missed diagnoses. Alternative causes included hepatitis B, C and E, cytomegalovirus, Epstein-Barr virus, ischemic hepatitis, cardiac hepatopathy, autoimmune hepatitis, nonalcoholic fatty liver disease, nonalcoholic steatohepatitis, and alcoholic liver disease. In more than one-third of published global DILI case series, alternative causes as published in these reports confounded the DILI diagnosis. In the future, published DILI case series should include only patients with secured DILI diagnosis, preferentially established by prospective use of scored items provided by robust diagnostic algorithms such as the updated Roussel Uclaf causality assessment method. © 2018 The British Pharmacological Society.

  11. A powerful and efficient set test for genetic markers that handles confounders

    PubMed Central

    Listgarten, Jennifer; Lippert, Christoph; Kang, Eun Yong; Xiang, Jing; Kadie, Carl M.; Heckerman, David

    2013-01-01

    Motivation: Approaches for testing sets of variants, such as a set of rare or common variants within a gene or pathway, for association with complex traits are important. In particular, set tests allow for aggregation of weak signal within a set, can capture interplay among variants and reduce the burden of multiple hypothesis testing. Until now, these approaches did not address confounding by family relatedness and population structure, a problem that is becoming more important as larger datasets are used to increase power. Results: We introduce a new approach for set tests that handles confounders. Our model is based on the linear mixed model and uses two random effects—one to capture the set association signal and one to capture confounders. We also introduce a computational speedup for two random-effects models that makes this approach feasible even for extremely large cohorts. Using this model with both the likelihood ratio test and score test, we find that the former yields more power while controlling type I error. Application of our approach to richly structured Genetic Analysis Workshop 14 data demonstrates that our method successfully corrects for population structure and family relatedness, whereas application of our method to a 15 000 individual Crohn’s disease case–control cohort demonstrates that it additionally recovers genes not recoverable by univariate analysis. Availability: A Python-based library implementing our approach is available at http://mscompbio.codeplex.com. Contact: jennl@microsoft.com or lippert@microsoft.com or heckerma@microsoft.com Supplementary information: Supplementary data are available at Bioinformatics online. PMID:23599503

  12. A causal examination of the effects of confounding factors on multimetric indices

    USGS Publications Warehouse

    Schoolmaster, Donald R.; Grace, James B.; Schweiger, E. William; Mitchell, Brian R.; Guntenspergen, Glenn R.

    2013-01-01

    The development of multimetric indices (MMIs) as a means of providing integrative measures of ecosystem condition is becoming widespread. An increasingly recognized problem for the interpretability of MMIs is controlling for the potentially confounding influences of environmental covariates. Most common approaches to handling covariates are based on simple notions of statistical control, leaving the causal implications of covariates and their adjustment unstated. In this paper, we use graphical models to examine some of the potential impacts of environmental covariates on the observed signals between human disturbance and potential response metrics. Using simulations based on various causal networks, we show how environmental covariates can both obscure and exaggerate the effects of human disturbance on individual metrics. We then examine from a causal interpretation standpoint the common practice of adjusting ecological metrics for environmental influences using only the set of sites deemed to be in reference condition. We present and examine the performance of an alternative approach to metric adjustment that uses the whole set of sites and models both environmental and human disturbance effects simultaneously. The findings from our analyses indicate that failing to model and adjust metrics can result in a systematic bias towards those metrics in which environmental covariates function to artificially strengthen the metric–disturbance relationship resulting in MMIs that do not accurately measure impacts of human disturbance. We also find that a “whole-set modeling approach” requires fewer assumptions and is more efficient with the given information than the more commonly applied “reference-set” approach.

  13. ADC Quantification of the Vertebral Bone Marrow Water Component: Removing the Confounding Effect of Residual Fat.

    PubMed

    Dieckmeyer, Michael; Ruschke, Stefan; Eggers, Holger; Kooijman, Hendrik; Rummeny, Ernst J; Kirschke, Jan S; Baum, Thomas; Karampinos, Dimitrios C

    2017-10-01

    To remove the confounding effect of unsuppressed fat on the imaging-based apparent diffusion coefficient (ADC) of the vertebral bone marrow water component when using spectrally selective fat suppression and to compare and validate the proposed quantification strategy against diffusion-weighted magnetic resonance spectroscopy (DW-MRS). Twelve subjects underwent diffusion-weighted imaging (DWI) and DW-MRS of the vertebral bone marrow. A theoretical model was developed to take into account and correct the effects of residual fat on ADC, incorporating additional measurements for proton density fat fraction (PDFF) and water T 2 (T 2w ). Uncorrected and corrected DWI-based ADC was compared with DW-MRS-based ADC using the Bland-Altman method. There was a systematic bias equal to 0.118 ± 0.116 × 10 -3 mm 2 /s between DWI and DW-MRS when no correction was performed. Taking into account measured PDFF and constant T 2w reduced the bias to 0.006 ± 0.128 × 10 -3 mm 2 /s. Using the proposed approach with both individually measured PDFF and T 2w reduced both the bias and the limits of agreement between DWI and DW-MRS (0.018 ± 0.065 × 10 -3 mm 2 /s). By taking into account the presence of residual fat in a modified signal model that incorporates additional individual measurements of PDFF and T 2w , good agreement of imaging-based ADC with MRS-based ADC can be achieved in vertebral bone marrow. Magn Reson Med 78:1432-1441, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

  14. Reactive Aggression and Peer Victimization from Pre-Kindergarten to First Grade: Accounting for Hyperactivity and Teacher-Child Conflict

    ERIC Educational Resources Information Center

    Runions, Kevin C.

    2014-01-01

    Background: The role of reactive aggression in the development of peer victimization remains unclear due in part to a failure to account for confounding problems of behavioural undercontrol (e.g., hyperactivity). As well, the school social context has rarely been examined to see whether these risks are mediated by relationships with teachers.…

  15. How "accountable" are accountable care organizations?

    PubMed

    Addicott, Rachael; Shortell, Stephen M

    2014-01-01

    The establishment of accountable care organizations (ACOs) in the Affordable Care Act (ACA) was intended to support both cost savings and high-quality care. However, a key challenge will be to ensure that governance and accountability mechanisms are sufficient to support those twin ambitions. This exploratory study considers how recently developed ACOs have established governance structures and accountability mechanisms, particularly focusing on attempts at collaborative accountability and shared governance arrangements. Four case studies of ACOs across the United States were undertaken, with data collected throughout 2012. These involved 34 semistructured interviews with ACO administrative and clinical leaders, observation of nine meetings, and a review of documentary materials from each ACO. We identified very few examples of physicians being held to account as a collective and therefore only limited evidence of collaborative accountability impacting on behavior change. However, ACO leaders do have many mechanisms available to stimulate change across physicians. The challenge is to determine governance structure(s) and accountability mechanisms that facilitate the most effective combination of approaches, measures, incentives, and sanctions to achieve the goals of more accountable care. Accountability structures and processes will need to be tailored to local membership composition, historical evolution, and current stage of development. There are also some common lessons to be drawn. Shared goals and incentives should be reflected through performance criteria. It is important to align measures and thresholds across payers to ensure ACOs are not unnecessarily burdened or compromised by reporting on different and potentially disjointed measures. Finally, emphasis needs to be placed on the importance of credible, transparent data. This exploratory study provides early evidence regarding how ACOs are establishing their governance and accountability arrangements and

  16. Deterrents to Accountability.

    ERIC Educational Resources Information Center

    Hencley, Stephen P.

    This speech assesses potential deterrents to the implementation of accountability in education. The author divides these deterrents into (1) philosophical-ideological; humanist-behaviorist conflicts, individuality versus "techno-urban fascism," and accountability systems tied to the achievement of cognitive objectives at the lower end of Bloom's…

  17. Biosolids impact soil phosphorus accountability, fractionation, and potential environmental risk.

    PubMed

    Ippolito, J A; Barbarick, K A; Norvell, K L

    2007-01-01

    Biosolids land application rates are typically based on crop N requirements but can lead to soil P accumulation. The Littleton/Englewood, Colorado, wastewater treatment facility has supported biosolids beneficial-use on a dryland wheat-fallow agroecosystem site since 1982, with observable soil P concentration increases as biyearly repeated biosolids applications increased from 0, 6.7, 13, 27, to 40 Mg ha(-1). The final study year was 2003, after which P accountability, fractionation, and potential environmental risk were assessed. Between 93 and 128% of biosolids-P added was accounted for when considering conventional tillage soil displacement, grain removal, and soil adsorption. The Fe-P fraction dominated all soil surface P fractions, likely due to an increase in amorphous Fe-oxide because Fe2(SO4)3 was added at the wastewater treatment facility inflow for digester H2S reduction. The Ca-P phase dominated all soil subsurface P fractions due to calcareous soil conditions. A combination of conventional tillage, drought from 1999 to 2003, and repeated and increasing biosolids application rates may have forced soil surface microorganism dormancy, reduction, or mortality; thus, biomass P reduction was evident. Subsurface biomass P was greater than surface biomass, possibly due to protection against environmental and anthropogenic variables or to increased dissolved organic carbon inputs. Even given years of biosolids application, the soil surface had the ability to sorb additional P as determined by shaking the soil in an excessive P solution. Biosolids-application regulations based on the Colorado Phosphorus Index would not impede current site practices. Proper monitoring, management, and addition of other best management practices are needed for continued assurance that P movement off-site does not become a major issue.

  18. Education and smoking: confounding or effect modification by phenotypic personality traits?

    PubMed

    Chapman, Benjamin; Fiscella, Kevin; Duberstein, Paul; Kawachi, Ichiro

    2009-12-01

    Little is known about whether educational gradients in smoking patterns can be explained by financial measures of socioeconomic status (SES) and/or personality traits. To assess whether the relationship of education to (1) never smoking and (2) having quit smoking would be confounded by financial measures of SES or by personality; whether lower Neuroticism and higher Conscientiousness would be associated with having abstained from or quit smoking; and whether education effects were modified by personality. Using data from the Midlife Development in the US National Survey, 2,429 individuals were classified as current (n = 695), former (n = 999), or never (n = 735) smokers. Multinomial logistic regressions examined study questions. Greater education was strongly associated with both never and former smoking, with no confounding by financial status and personality. Never smoking was associated with lower Openness and higher Conscientiousness, while have quit was associated with higher Neuroticism. Education interacted additively with Conscientiousness to increase and with Openness to decrease the probability of never smoking. Education and personality should be considered unconfounded smoking risks in epidemiologic and clinical studies. Educational associations with smoking may vary by personality dispositions, and prevention and intervention programs should consider both sets of factors.

  19. Confounding of the Association between Radiation Exposure from CT Scans and Risk of Leukemia and Brain Tumors by Cancer Susceptibility Syndromes.

    PubMed

    Meulepas, Johanna M; Ronckers, Cécile M; Merks, Johannes; Weijerman, Michel E; Lubin, Jay H; Hauptmann, Michael

    2016-01-01

    Recent studies linking radiation exposure from pediatric computed tomography (CT) to increased risks of leukemia and brain tumors lacked data to control for cancer susceptibility syndromes (CSS). These syndromes might be confounders because they are associated with an increased cancer risk and may increase the likelihood of CT scans performed in children. We identify CSS predisposing to leukemia and brain tumors through a systematic literature search and summarize prevalence and risk estimates. Because there is virtually no empirical evidence in published literature on patterns of CT use for most types of CSS, we estimate confounding bias of relative risks (RR) for categories of radiation exposure based on expert opinion about the current and previous patterns of CT scans among CSS patients. We estimate that radiation-related RRs for leukemia are not meaningfully confounded by Down syndrome, Noonan syndrome, or other CSS. In contrast, RRs for brain tumors may be overestimated due to confounding by tuberous sclerosis complex (TSC) while von Hippel-Lindau disease, neurofibromatosis type 1, or other CSS do not meaningfully confound. Empirical data on the use of CT scans among CSS patients are urgently needed. Our assessment indicates that associations with leukemia reported in previous studies are unlikely to be substantially confounded by unmeasured CSS, whereas brain tumor risks might have been overestimated due to confounding by TSC. Future studies should identify TSC patients in order to avoid overestimation of brain tumor risks due to radiation exposure from CT scans. ©2015 American Association for Cancer Research.

  20. A stratification approach using logit-based models for confounder adjustment in the study of continuous outcomes.

    PubMed

    Tan, Chuen Seng; Støer, Nathalie C; Chen, Ying; Andersson, Marielle; Ning, Yilin; Wee, Hwee-Lin; Khoo, Eric Yin Hao; Tai, E-Shyong; Kao, Shih Ling; Reilly, Marie

    2017-01-01

    The control of confounding is an area of extensive epidemiological research, especially in the field of causal inference for observational studies. Matched cohort and case-control study designs are commonly implemented to control for confounding effects without specifying the functional form of the relationship between the outcome and confounders. This paper extends the commonly used regression models in matched designs for binary and survival outcomes (i.e. conditional logistic and stratified Cox proportional hazards) to studies of continuous outcomes through a novel interpretation and application of logit-based regression models from the econometrics and marketing research literature. We compare the performance of the maximum likelihood estimators using simulated data and propose a heuristic argument for obtaining the residuals for model diagnostics. We illustrate our proposed approach with two real data applications. Our simulation studies demonstrate that our stratification approach is robust to model misspecification and that the distribution of the estimated residuals provides a useful diagnostic when the strata are of moderate size. In our applications to real data, we demonstrate that parity and menopausal status are associated with percent mammographic density, and that the mean level and variability of inpatient blood glucose readings vary between medical and surgical wards within a national tertiary hospital. Our work highlights how the same class of regression models, available in most statistical software, can be used to adjust for confounding in the study of binary, time-to-event and continuous outcomes.

  1. An education gradient in health, a health gradient in education, or a confounded gradient in both?

    PubMed

    Lynch, Jamie L; von Hippel, Paul T

    2016-04-01

    There is a positive gradient associating educational attainment with health, yet the explanation for this gradient is not clear. Does higher education improve health (causation)? Do the healthy become highly educated (selection)? Or do good health and high educational attainment both result from advantages established early in the life course (confounding)? This study evaluates these competing explanations by tracking changes in educational attainment and Self-rated Health (SRH) from age 15 to age 31 in the National Longitudinal Study of Youth, 1997 cohort. Ordinal logistic regression confirms that high-SRH adolescents are more likely to become highly educated. This is partly because adolescent SRH is associated with early advantages including adolescents' academic performance, college plans, and family background (confounding); however, net of these confounders adolescent SRH still predicts adult educational attainment (selection). Fixed-effects longitudinal regression shows that educational attainment has little causal effect on SRH at age 31. Completion of a high school diploma or associate's degree has no effect on SRH, while completion of a bachelor's or graduate degree have effects that, though significant, are quite small (less than 0.1 points on a 5-point scale). While it is possible that educational attainment would have greater effect on health at older ages, at age 31 what we see is a health gradient in education, shaped primarily by selection and confounding rather than by a causal effect of education on health. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Ace Your Accounting Classes: 12 Hints to Maximize Your Potential

    ERIC Educational Resources Information Center

    Albrecht, W. David

    2008-01-01

    Many students experience difficulties when they try to get good grades in their accounting classes, and they are searching for answers. There is no single answer. Getting a good grade in an accounting class results from a process. If you know and understand the process--and can apply it--then your chances are much improved for getting a good…

  3. Syphilis may be a confounding factor, not a causative agent, in syphilitic ALS.

    PubMed

    Tuk, Bert

    2016-01-01

    Based upon a review of published clinical observations regarding syphilitic amyotrophic lateral sclerosis (ALS), I hypothesize that syphilis is actually a confounding factor, not a causative factor, in syphilitic ALS. Moreover, I propose that the successful treatment of ALS symptoms in patients with syphilitic ALS using penicillin G and hydrocortisone is an indirect consequence of the treatment regimen and is not due to the treatment of syphilis. Specifically, I propose that the observed effect is due to the various pharmacological activities of penicillin G ( e.g ., a GABA receptor antagonist) and/or the multifaceted pharmacological activity of hydrocortisone. The notion that syphilis may be a confounding factor in syphilitic ALS is highly relevant, as it suggests that treating ALS patients with penicillin G and hydrocortisone-regardless of whether they present with syphilitic ALS or non-syphilitic ALS-may be effective at treating this rapidly progressive, highly devastating disease.

  4. Enhancing the estimation of blood pressure using pulse arrival time and two confounding factors.

    PubMed

    Baek, Hyun Jae; Kim, Ko Keun; Kim, Jung Soo; Lee, Boreom; Park, Kwang Suk

    2010-02-01

    A new method of blood pressure (BP) estimation using multiple regression with pulse arrival time (PAT) and two confounding factors was evaluated in clinical and unconstrained monitoring situations. For the first analysis with clinical data, electrocardiogram (ECG), photoplethysmogram (PPG) and invasive BP signals were obtained by a conventional patient monitoring device during surgery. In the second analysis, ECG, PPG and non-invasive BP were measured using systems developed to obtain data under conditions in which the subject was not constrained. To enhance the performance of BP estimation methods, heart rate (HR) and arterial stiffness were considered as confounding factors in regression analysis. The PAT and HR were easily extracted from ECG and PPG signals. For arterial stiffness, the duration from the maximum derivative point to the maximum of the dicrotic notch in the PPG signal, a parameter called TDB, was employed. In two experiments that normally cause BP variation, the correlation between measured BP and the estimated BP was investigated. Multiple-regression analysis with the two confounding factors improved correlation coefficients for diastolic blood pressure and systolic blood pressure to acceptable confidence levels, compared to existing methods that consider PAT only. In addition, reproducibility for the proposed method was determined using constructed test sets. Our results demonstrate that non-invasive, non-intrusive BP estimation can be obtained using methods that can be applied in both clinical and daily healthcare situations.

  5. Pot binding as a variable confounding plant phenotype: theoretical derivation and experimental observations.

    PubMed

    Sinclair, Thomas R; Manandhar, Anju; Shekoofa, Avat; Rosas-Anderson, Pablo; Bagherzadi, Laleh; Schoppach, Remy; Sadok, Walid; Rufty, Thomas W

    2017-04-01

    Theoretical derivation predicted growth retardation due to pot water limitations, i.e., pot binding. Experimental observations were consistent with these limitations. Combined, these results indicate a need for caution in high-throughput screening and phenotyping. Pot experiments are a mainstay in many plant studies, including the current emphasis on developing high-throughput, phenotyping systems. Pot studies can be vulnerable to decreased physiological activity of the plants particularly when pot volume is small, i.e., "pot binding". It is necessary to understand the conditions under which pot binding may exist to avoid the confounding influence of pot binding in interpreting experimental results. In this paper, a derivation is offered that gives well-defined conditions for the occurrence of pot binding based on restricted water availability. These results showed that not only are pot volume and plant size important variables, but the potting media is critical. Artificial potting mixtures used in many studies, including many high-throughput phenotyping systems, are particularly susceptible to the confounding influences of pot binding. Experimental studies for several crop species are presented that clearly show the existence of thresholds of plant leaf area at which various pot sizes and potting media result in the induction of pot binding even though there may be no immediate, visual plant symptoms. The derivation and experimental results showed that pot binding can readily occur in plant experiments if care is not given to have sufficiently large pots, suitable potting media, and maintenance of pot water status. Clear guidelines are provided for avoiding the confounding effects of water-limited pot binding in studying plant phenotype.

  6. Job Strain and the Cortisol Diurnal Cycle in MESA: Accounting for Between- and Within-Day Variability.

    PubMed

    Rudolph, Kara E; Sánchez, Brisa N; Stuart, Elizabeth A; Greenberg, Benjamin; Fujishiro, Kaori; Wand, Gary S; Shrager, Sandi; Seeman, Teresa; Diez Roux, Ana V; Golden, Sherita H

    2016-03-01

    Evidence of the link between job strain and cortisol levels has been inconsistent. This could be due to failure to account for cortisol variability leading to underestimated standard errors. Our objective was to model the relationship between job strain and the whole cortisol curve, accounting for sources of cortisol variability. Our functional mixed-model approach incorporated all available data-18 samples over 3 days-and uncertainty in estimated relationships. We used employed participants from the Multi-Ethnic Study of Atherosclerosis Stress I Study and data collected between 2002 and 2006. We used propensity score matching on an extensive set of variables to control for sources of confounding. We found that job strain was associated with lower salivary cortisol levels and lower total area under the curve. We found no relationship between job strain and the cortisol awakening response. Our findings differed from those of several previous studies. It is plausible that our results were unique to middle- to older-aged racially, ethnically, and occupationally diverse adults and were therefore not inconsistent with previous research among younger, mostly white samples. However, it is also plausible that previous findings were influenced by residual confounding and failure to propagate uncertainty (i.e., account for the multiple sources of variability) in estimating cortisol features. © The Author 2016. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  7. Distance to high-voltage power lines and risk of childhood leukemia--an analysis of confounding by and interaction with other potential risk factors.

    PubMed

    Pedersen, Camilla; Bräuner, Elvira V; Rod, Naja H; Albieri, Vanna; Andersen, Claus E; Ulbak, Kaare; Hertel, Ole; Johansen, Christoffer; Schüz, Joachim; Raaschou-Nielsen, Ole

    2014-01-01

    We investigated whether there is an interaction between distance from residence at birth to nearest power line and domestic radon and traffic-related air pollution, respectively, in relation to childhood leukemia risk. Further, we investigated whether adjusting for potential confounders alters the association between distance to nearest power line and childhood leukemia. We included 1024 cases aged <15, diagnosed with leukemia during 1968-1991, from the Danish Cancer Registry and 2048 controls randomly selected from the Danish childhood population and individually matched by gender and year of birth. We used geographical information systems to determine the distance between residence at birth and the nearest 132-400 kV overhead power line. Concentrations of domestic radon and traffic-related air pollution (NOx at the front door) were estimated using validated models. We found a statistically significant interaction between distance to nearest power line and domestic radon regarding risk of childhood leukemia (p = 0.01) when using the median radon level as cut-off point but not when using the 75th percentile (p = 0.90). We found no evidence of an interaction between distance to nearest power line and traffic-related air pollution (p = 0.73). We found almost no change in the estimated association between distance to power line and risk of childhood leukemia when adjusting for socioeconomic status of the municipality, urbanization, maternal age, birth order, domestic radon and traffic-related air pollution. The statistically significant interaction between distance to nearest power line and domestic radon was based on few exposed cases and controls and sensitive to the choice of exposure categorization and might, therefore, be due to chance.

  8. Confounding of the association between radiation exposure from CT scans and risk of leukemia and brain tumors by cancer susceptibility syndromes.

    PubMed

    Meulepas, Johanna M; Ronckers, Cécile M; Merks, Johannes; Weijerman, Michel E; Lubin, Jay H; Hauptmann, Michael

    2016-12-01

    Recent studies linking radiation exposure from pediatric computed tomography (CT) to increased risks of leukemia and brain tumors lacked data to control for cancer susceptibility syndromes (CSS). These syndromes might be confounders because they are associated with an increased cancer risk and may increase the likelihood of pediatric CT scans. We identify CSS predisposing to leukemia and brain tumors through a systematic literature search and summarize prevalence and risk. Since empirical evidence is lacking in published literature on patterns of CT use for most types of CSS, we estimate confounding bias of relative risks (RR) for categories of radiation exposure based on expert opinion about patterns of CT scans among CSS patients. We estimate that radiation-related RRs for leukemia are not meaningfully confounded by Down syndrome, Noonan syndrome and other CSS. Moreover, tuberous sclerosis complex, von Hippel-Lindau disease, neurofibromatosis type 1 and other CSS do not meaningfully confound RRs for brain tumors. Empirical data on the use of CT scans among CSS patients is urgently needed. Our assessment indicates that associations with radiation exposure from pediatric CT scans and leukemia or brain tumors reported in previous studies are unlikely to be substantially confounded by unmeasured CSS.

  9. Assessing Mediation Using Marginal Structural Models in the Presence of Confounding and Moderation

    ERIC Educational Resources Information Center

    Coffman, Donna L.; Zhong, Wei

    2012-01-01

    This article presents marginal structural models with inverse propensity weighting (IPW) for assessing mediation. Generally, individuals are not randomly assigned to levels of the mediator. Therefore, confounders of the mediator and outcome may exist that limit causal inferences, a goal of mediation analysis. Either regression adjustment or IPW…

  10. Drug safety analyses in a rheumatoid arthritis registry: application of different approaches regarding timing of exposure and confounder measurement.

    PubMed

    Solomon, Daniel H; Shadick, Nancy A; Weinblatt, Michael E; Zak, Agnes; Frits, Michelle; Franklin, Jessica M

    2017-06-13

    Patient registry data serves an increasing role in drug safety and comparative effectiveness research, but registry databases often do not contain confounder information measured at the same time that treatments begin. This study evaluated a set of approaches for estimating confounder values at treatment initiation using actual data from a rheumatoid arthritis (RA) registry to examine the risk of infection associated with different biologic DMARDs (bDMARDs). We examined the risk of infection associated with starting a TNF inhibitor (TNFi) versus any of the other non-TNFi bDMARDs. Different confounder assessment approaches were tested. All approaches were tested in Cox proportional hazard regression models that used a propensity score (PS). The confounder of interest was the disease activity score (DAS28-CRP). The confounder assessment approaches utilized different temporal relationships between the DAS28-CRP measurement and the start of the treatments of interest. We included 219 subjects with RA with 269 initiations of either a TNFi or a different bDMARD or both. Among this group, 305 infections were reported and confirmed through chart review. The hazard ratio (HR) for the risk of infection associated with use of a non-TNFi bDMARD ranged from 1.17 to 3.03 using 13 different approaches; only the approach with the highest HR produced results significantly different than one, but this approach included the fewest subjects and infections. The relative risk of infection for TNFi and other non-TNFi bDMARDs was similar using various approaches regarding which DAS28-CRP score should be used as the baseline measure in adjusted analyses.

  11. Accounting for measurement reliability to improve the quality of inference in dental microhardness research: a worked example.

    PubMed

    Sever, Ivan; Klaric, Eva; Tarle, Zrinka

    2016-07-01

    Dental microhardness experiments are influenced by unobserved factors related to the varying tooth characteristics that affect measurement reproducibility. This paper explores the appropriate analytical tools for modeling different sources of unobserved variability to reduce the biases encountered and increase the validity of microhardness studies. The enamel microhardness of human third molars was measured by Vickers diamond. The effects of five bleaching agents-10, 16, and 30 % carbamide peroxide, and 25 and 38 % hydrogen peroxide-were examined, as well as the effect of artificial saliva and amorphous calcium phosphate. To account for both between- and within-tooth heterogeneity in evaluating treatment effects, the statistical analysis was performed in the mixed-effects framework, which also included the appropriate weighting procedure to adjust for confounding. The results were compared to those of the standard ANOVA model usually applied. The weighted mixed-effects model produced the parameter estimates of different magnitude and significance than the standard ANOVA model. The results of the former model were more intuitive, with more precise estimates and better fit. Confounding could seriously bias the study outcomes, highlighting the need for more robust statistical procedures in dental research that account for the measurement reliability. The presented framework is more flexible and informative than existing analytical techniques and may improve the quality of inference in dental research. Reported results could be misleading if underlying heterogeneity of microhardness measurements is not taken into account. The confidence in treatment outcomes could be increased by applying the framework presented.

  12. Is the association between general cognitive ability and violent crime caused by family-level confounders?

    PubMed

    Frisell, Thomas; Pawitan, Yudi; Långström, Niklas

    2012-01-01

    Research has consistently found lower cognitive ability to be related to increased risk for violent and other antisocial behaviour. Since this association has remained when adjusting for childhood socioeconomic position, ethnicity, and parental characteristics, it is often assumed to be causal, potentially mediated through school adjustment problems and conduct disorder. Socioeconomic differences are notoriously difficult to quantify, however, and it is possible that the association between intelligence and delinquency suffer substantial residual confounding. We linked longitudinal Swedish total population registers to study the association of general cognitive ability (intelligence) at age 18 (the Conscript Register, 1980-1993) with the incidence proportion of violent criminal convictions (the Crime Register, 1973-2009), among all men born in Sweden 1961-1975 (N = 700,514). Using probit regression, we controlled for measured childhood socioeconomic variables, and further employed sibling comparisons (family pedigree data from the Multi-Generation Register) to adjust for shared familial characteristics. Cognitive ability in early adulthood was inversely associated to having been convicted of a violent crime (β = -0.19, 95% CI: -0.19; -0.18), the association remained when adjusting for childhood socioeconomic factors (β = -0.18, 95% CI: -0.18; -0.17). The association was somewhat lower within half-brothers raised apart (β = -0.16, 95% CI: -0.18; -0.14), within half-brothers raised together (β = -0.13, 95% CI: (-0.15; -0.11), and lower still in full-brother pairs (β = -0.10, 95% CI: -0.11; -0.09). The attenuation among half-brothers raised together and full brothers was too strong to be attributed solely to attenuation from measurement error. Our results suggest that the association between general cognitive ability and violent criminality is confounded partly by factors shared by brothers. However, most of the association remains even

  13. Multiorgan Involvement Confounding the Diagnosis of Bartonella henselae Infective Endocarditis in Children With Congenital Heart Disease.

    PubMed

    Ouellette, Christopher P; Joshi, Sarita; Texter, Karen; Jaggi, Preeti

    2017-05-01

    Two children with congenital heart disease status post surgical correction presented with prolonged constitutional symptoms, hepatosplenomegaly and pancytopenia. Concern for malignancy prompted bone marrow biopsies that were without evidence thereof. In case 1, echocardiography identified a multilobulated vegetation on the conduit valve. In case 2, transthoracic, transesophageal and intracardiac echocardiography were performed and were without evidence of cardiac vegetations; however, pulmonic emboli raised concern for infective endocarditis. Both patients underwent surgical resection of the infected material and had histopathologic evidence of infective endocarditis. Further diagnostics identified elevated cytoplasmic antineutrophil cytoplasmic antibodies and antiproteinase 3 antibodies in addition to acute kidney injury with crescentic glomerulonephritis on renal biopsy. Serologic evidence of infection with Bartonella henselae was observed in both patients. These 2 cases highlight the potential multiorgan involvement that may confound the diagnosis of culture-negative infective endocarditis caused by B. henselae.

  14. Who really gets strep sore throat? Confounding and effect modification of a time-varying exposure on recurrent events.

    PubMed

    Follmann, Dean; Huang, Chiung-Yu; Gabriel, Erin

    2016-10-30

    Unmeasured confounding is the fundamental obstacle to drawing causal conclusions about the impact of an intervention from observational data. Typically, covariates are measured to eliminate or ameliorate confounding, but they may be insufficient or unavailable. In the special setting where a transient intervention or exposure varies over time within each individual and confounding is time constant, a different tack is possible. The key idea is to condition on either the overall outcome or the proportion of time in the intervention. These measures can eliminate the unmeasured confounding either by conditioning or by use of a proxy covariate. We evaluate existing methods and develop new models from which causal conclusions can be drawn from such observational data even if no baseline covariates are measured. Our motivation for this work was to determine the causal effect of Streptococcus bacteria in the throat on pharyngitis (sore throat) in Indian schoolchildren. Using our models, we show that existing methods can be badly biased and that sick children who are rarely colonized have a high probability that the Streptococcus bacteria are causing their disease. Published 2016. This article is a U.S. Government work and is in the public domain in the USA. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

  15. Comorbidities confounding the outcomes of surgery for third window syndrome: Outlier analysis

    PubMed Central

    Mackay‐Promitas, Heather T.; Demirel, Shaban; Gianoli, Gerard J.; Gizzi, Martin S.; Carter, Dale M.; Siker, David A.

    2017-01-01

    Objective Patients with third window syndrome and superior semicircular canal dehiscence (SSCD) symptoms whose surgical outcomes placed them as outliers were systematically studied to determine comorbidities that were responsible for their poor outcomes due to these confounding factors. Study Design Observational analytic case‐control study in a tertiary referral center. Methods Twelve adult patients with clinical SSCD syndrome underwent surgical management and had outcomes that did not resolve all of their subjective symptoms. In addition to one of the neurotologists, 2 neurologists (one specializing in migraine and the other a neuro‐ophthalmologist), and a psychologist clinician‐investigator completed comprehensive evaluations. Neuropsychology test batteries included: the Millon Behavioral Medicine Diagnostic; Patient Health Questionnaire (PHQ‐9) and Generalized Anxiety Disorder Screener (GAD‐7); Adverse Childhood Experiences Scale; the Wide Range Assessment of Memory and Learning, including the 3 domains of verbal memory, visual memory, and attention/concentration; Wechsler Adult Intelligence Scale; and the Delis‐Kaplan Executive Function System. The control cohort was comprised of 17 participants who previously underwent surgery for third window syndrome that resulted in the expected outcomes of resolution of their third window syndrome symptoms and cognitive dysfunction. Results There was a high rate of psychological comorbidity (n = 6) in the outlier cohort; multiple traumatic brain injuries were also a confounding element (n = 10). One patient had elevated cerebrospinal fluid (CSF) pressure requiring ventriculoperitoneal shunting to control the recurrence of dehiscence and one patient with a drug‐induced Parkinson‐like syndrome and idiopathic progressive neurological degenerative process. Conclusions Components of the Millon Behavioral Medicine Diagnostic, PHQ‐9 and GAD‐7 results suggest that these instruments would be useful as

  16. On the use and misuse of scalar scores of confounders in design and analysis of observational studies.

    PubMed

    Pfeiffer, R M; Riedl, R

    2015-08-15

    We assess the asymptotic bias of estimates of exposure effects conditional on covariates when summary scores of confounders, instead of the confounders themselves, are used to analyze observational data. First, we study regression models for cohort data that are adjusted for summary scores. Second, we derive the asymptotic bias for case-control studies when cases and controls are matched on a summary score, and then analyzed either using conditional logistic regression or by unconditional logistic regression adjusted for the summary score. Two scores, the propensity score (PS) and the disease risk score (DRS) are studied in detail. For cohort analysis, when regression models are adjusted for the PS, the estimated conditional treatment effect is unbiased only for linear models, or at the null for non-linear models. Adjustment of cohort data for DRS yields unbiased estimates only for linear regression; all other estimates of exposure effects are biased. Matching cases and controls on DRS and analyzing them using conditional logistic regression yields unbiased estimates of exposure effect, whereas adjusting for the DRS in unconditional logistic regression yields biased estimates, even under the null hypothesis of no association. Matching cases and controls on the PS yield unbiased estimates only under the null for both conditional and unconditional logistic regression, adjusted for the PS. We study the bias for various confounding scenarios and compare our asymptotic results with those from simulations with limited sample sizes. To create realistic correlations among multiple confounders, we also based simulations on a real dataset. Copyright © 2015 John Wiley & Sons, Ltd.

  17. Weight Loss and Coronary Heart Disease: Sensitivity Analysis for Unmeasured Confounding by Undiagnosed Disease.

    PubMed

    Danaei, Goodarz; Robins, James M; Young, Jessica G; Hu, Frank B; Manson, JoAnn E; Hernán, Miguel A

    2016-03-01

    Evidence for the effect of weight loss on coronary heart disease (CHD) or mortality has been mixed. The effect estimates can be confounded due to undiagnosed diseases that may affect weight loss. We used data from the Nurses' Health Study to estimate the 26-year risk of CHD under several hypothetical weight loss strategies. We applied the parametric g-formula and implemented a novel sensitivity analysis for unmeasured confounding due to undiagnosed disease by imposing a lag time for the effect of weight loss on chronic disease. Several sensitivity analyses were conducted. The estimated 26-year risk of CHD did not change under weight loss strategies using lag times from 0 to 18 years. For a 6-year lag time, the risk ratios of CHD for weight loss compared with no weight loss ranged from 1.00 (0.99, 1.02) to 1.02 (0.99, 1.05) for different degrees of weight loss with and without restricting the weight loss strategy to participants with no major chronic disease. Similarly, no protective effect of weight loss was estimated for mortality risk. In contrast, we estimated a protective effect of weight loss on risk of type 2 diabetes. We estimated that maintaining or losing weight after becoming overweight or obese does not reduce the risk of CHD or death in this cohort of middle-age US women. Unmeasured confounding, measurement error, and model misspecification are possible explanations but these did not prevent us from estimating a beneficial effect of weight loss on diabetes.

  18. Use of Self-Matching to Control for Stable Patient Characteristics While Addressing Time-Varying Confounding on Treatment Effect: A Case Study of Older Intensive Care Patients.

    PubMed

    Han, Ling; Pisani, M A; Araujo, K L B; Allore, Heather G

    Exposure-crossover design offers a non-experimental option to control for stable baseline confounding through self-matching while examining causal effect of an exposure on an acute outcome. This study extends this approach to longitudinal data with repeated measures of exposure and outcome using data from a cohort of 340 older medical patients in an intensive care unit (ICU). The analytic sample included 92 patients who received ≥1 dose of haloperidol, an antipsychotic medication often used for patients with delirium. Exposure-crossover design was implemented by sampling the 3-day time segments prior ( Induction) and posterior ( Subsequent) to each treatment episode of receiving haloperidol. In the full cohort, there was a trend of increasing delirium severity scores (Mean±SD: 4.4±1.7) over the course of the ICU stay. After exposure-crossover sampling, the delirium severity score decreased from the Induction (4.9) to the Subsequent (4.1) intervals, with the treatment episode falling in-between (4.5). Based on a GEE Poisson model accounting for self-matching and within-subject correlation, the unadjusted mean delirium severity scores was -0.55 (95% CI: -1.10, -0.01) points lower for the Subsequent than the Induction intervals. The association diminished by 32% (-0.38, 95%CI: -0.99, 0.24) after adjusting only for ICU confounding, while being slightly increased by 7% (-0.60, 95%CI: -1.15, -0.04) when adjusting only for baseline characteristics. These results suggest that longitudinal exposure-crossover design is feasible and capable of partially removing stable baseline confounding through self-matching. Loss of power due to eliminating treatment-irrelevant person-time and uncertainty around allocating person-time to comparison intervals remain methodological challenges.

  19. Distance to High-Voltage Power Lines and Risk of Childhood Leukemia – an Analysis of Confounding by and Interaction with Other Potential Risk Factors

    PubMed Central

    Pedersen, Camilla; Bräuner, Elvira V.; Rod, Naja H.; Albieri, Vanna; Andersen, Claus E.; Ulbak, Kaare; Hertel, Ole; Johansen, Christoffer; Schüz, Joachim; Raaschou-Nielsen, Ole

    2014-01-01

    We investigated whether there is an interaction between distance from residence at birth to nearest power line and domestic radon and traffic-related air pollution, respectively, in relation to childhood leukemia risk. Further, we investigated whether adjusting for potential confounders alters the association between distance to nearest power line and childhood leukemia. We included 1024 cases aged <15, diagnosed with leukemia during 1968–1991, from the Danish Cancer Registry and 2048 controls randomly selected from the Danish childhood population and individually matched by gender and year of birth. We used geographical information systems to determine the distance between residence at birth and the nearest 132–400 kV overhead power line. Concentrations of domestic radon and traffic-related air pollution (NOx at the front door) were estimated using validated models. We found a statistically significant interaction between distance to nearest power line and domestic radon regarding risk of childhood leukemia (p = 0.01) when using the median radon level as cut-off point but not when using the 75th percentile (p = 0.90). We found no evidence of an interaction between distance to nearest power line and traffic-related air pollution (p = 0.73). We found almost no change in the estimated association between distance to power line and risk of childhood leukemia when adjusting for socioeconomic status of the municipality, urbanization, maternal age, birth order, domestic radon and traffic-related air pollution. The statistically significant interaction between distance to nearest power line and domestic radon was based on few exposed cases and controls and sensitive to the choice of exposure categorization and might, therefore, be due to chance. PMID:25259740

  20. 'Mechanical restraint-confounders, risk, alliance score': testing the clinical validity of a new risk assessment instrument.

    PubMed

    Deichmann Nielsen, Lea; Bech, Per; Hounsgaard, Lise; Alkier Gildberg, Frederik

    2017-08-01

    Unstructured risk assessment, as well as confounders (underlying reasons for the patient's risk behaviour and alliance), risk behaviour, and parameters of alliance, have been identified as factors that prolong the duration of mechanical restraint among forensic mental health inpatients. To clinically validate a new, structured short-term risk assessment instrument called the Mechanical Restraint-Confounders, Risk, Alliance Score (MR-CRAS), with the intended purpose of supporting the clinicians' observation and assessment of the patient's readiness to be released from mechanical restraint. The content and layout of MR-CRAS and its user manual were evaluated using face validation by forensic mental health clinicians, content validation by an expert panel, and pilot testing within two, closed forensic mental health inpatient units. The three sub-scales (Confounders, Risk, and a parameter of Alliance) showed excellent content validity. The clinical validations also showed that MR-CRAS was perceived and experienced as a comprehensible, relevant, comprehensive, and useable risk assessment instrument. MR-CRAS contains 18 clinically valid items, and the instrument can be used to support the clinical decision-making regarding the possibility of releasing the patient from mechanical restraint. The present three studies have clinically validated a short MR-CRAS scale that is currently being psychometrically tested in a larger study.

  1. The Coming Accounting Crisis

    ERIC Educational Resources Information Center

    Eaton, Tim V.

    2007-01-01

    The accounting profession is facing a potential crisis not only from the overall shortage of accounting faculty driven by smaller numbers of new faculty entering the profession as many existing faculty retire but also from changes that have been less well documented. This includes: (1) changes in attitude towards the roles of teaching, service and…

  2. Risk of bias and confounding of observational studies of Zika virus infection: A scoping review of research protocols

    PubMed Central

    Haby, Michelle M.; Martínez-Vega, Ruth; Pinzón-Flores, Carlos E.; Smith, Emma; Pinart, Mariona; Broutet, Nathalie; Becerra-Posada, Francisco; Aldighieri, Sylvain; Van Kerkhove, Maria D.

    2017-01-01

    Introduction Given the severity and impact of the current Zika virus (ZIKV) outbreak in the Americas, numerous countries have rushed to develop research studies to assess ZIKV and its potential health consequences. In an effort to ensure that studies are comprehensive, both internally and externally valid, and with reliable results, the World Health Organization, the Pan American Health Organization, Institut Pasteur, the networks of Fiocruz, the Consortia for the Standardization of Influenza Seroepidemiology (CONSISE) and the International Severe Acute Respiratory and Emerging Infection Consortium (ISARIC) have generated six standardized clinical and epidemiological research protocols and questionnaires to address key public health questions on ZIKV. Methods We conducted a systematic search of ongoing study protocols related to ZIKV research. We analyzed the content of protocols of 32 cohort studies and 13 case control studies for systematic bias that could produce erroneous results. Additionally we aimed to characterize the risks of bias and confounding in observational studies related to ZIKV and to propose ways to minimize them, including the use of six newly standardized research protocols. Results Observational studies of ZIKV face an array of challenges, including measurement of exposure and outcomes (microcephaly and Guillain-Barré Syndrome). Potential confounders need to be measured where known and controlled for in the analysis. Selection bias due to non-random selection is a significant issue, particularly in the case-control design, and losses to follow-up is equally important for the cohort design. Conclusion Observational research seeking to answer key questions on the ZIKV should consider these restrictions and take precautions to minimize bias in an effort to provide reliable and valid results. Utilization of the standardized research protocols developed by the WHO, PAHO, Institut Pasteur, and CONSISE will harmonize the key methodological aspects

  3. Risk of bias and confounding of observational studies of Zika virus infection: A scoping review of research protocols.

    PubMed

    Reveiz, Ludovic; Haby, Michelle M; Martínez-Vega, Ruth; Pinzón-Flores, Carlos E; Elias, Vanessa; Smith, Emma; Pinart, Mariona; Broutet, Nathalie; Becerra-Posada, Francisco; Aldighieri, Sylvain; Van Kerkhove, Maria D

    2017-01-01

    Given the severity and impact of the current Zika virus (ZIKV) outbreak in the Americas, numerous countries have rushed to develop research studies to assess ZIKV and its potential health consequences. In an effort to ensure that studies are comprehensive, both internally and externally valid, and with reliable results, the World Health Organization, the Pan American Health Organization, Institut Pasteur, the networks of Fiocruz, the Consortia for the Standardization of Influenza Seroepidemiology (CONSISE) and the International Severe Acute Respiratory and Emerging Infection Consortium (ISARIC) have generated six standardized clinical and epidemiological research protocols and questionnaires to address key public health questions on ZIKV. We conducted a systematic search of ongoing study protocols related to ZIKV research. We analyzed the content of protocols of 32 cohort studies and 13 case control studies for systematic bias that could produce erroneous results. Additionally we aimed to characterize the risks of bias and confounding in observational studies related to ZIKV and to propose ways to minimize them, including the use of six newly standardized research protocols. Observational studies of ZIKV face an array of challenges, including measurement of exposure and outcomes (microcephaly and Guillain-Barré Syndrome). Potential confounders need to be measured where known and controlled for in the analysis. Selection bias due to non-random selection is a significant issue, particularly in the case-control design, and losses to follow-up is equally important for the cohort design. Observational research seeking to answer key questions on the ZIKV should consider these restrictions and take precautions to minimize bias in an effort to provide reliable and valid results. Utilization of the standardized research protocols developed by the WHO, PAHO, Institut Pasteur, and CONSISE will harmonize the key methodological aspects of each study design to minimize bias at

  4. Associations of Perfluoroalkyl Substances (PFAS) with Lower Birth Weight: An Evaluation of Potential Confounding by Glomerular Filtration Rate Using a Physiologically Based Pharmacokinetic Model (PBPK).

    PubMed

    Verner, Marc-André; Loccisano, Anne E; Morken, Nils-Halvdan; Yoon, Miyoung; Wu, Huali; McDougall, Robin; Maisonet, Mildred; Marcus, Michele; Kishi, Reiko; Miyashita, Chihiro; Chen, Mei-Huei; Hsieh, Wu-Shiun; Andersen, Melvin E; Clewell, Harvey J; Longnecker, Matthew P

    2015-12-01

    Prenatal exposure to perfluoroalkyl substances (PFAS) has been associated with lower birth weight in epidemiologic studies. This association could be attributable to glomerular filtration rate (GFR), which is related to PFAS concentration and birth weight. We used a physiologically based pharmacokinetic (PBPK) model of pregnancy to assess how much of the PFAS-birth weight association observed in epidemiologic studies might be attributable to GFR. We modified a PBPK model to reflect the association of GFR with birth weight (estimated from three studies of GFR and birth weight) and used it to simulate PFAS concentrations in maternal and cord plasma. The model was run 250,000 times, with variation in parameters, to simulate a population. Simulated data were analyzed to evaluate the association between PFAS levels and birth weight due to GFR. We compared simulated estimates with those from a meta-analysis of epidemiologic data. The reduction in birth weight for each 1-ng/mL increase in simulated cord plasma for perfluorooctane sulfonate (PFOS) was 2.72 g (95% CI: -3.40, -2.04), and for perfluorooctanoic acid (PFOA) was 7.13 g (95% CI: -8.46, -5.80); results based on maternal plasma at term were similar. Results were sensitive to variations in PFAS level distributions and the strength of the GFR-birth weight association. In comparison, our meta-analysis of epidemiologic studies suggested that each 1-ng/mL increase in prenatal PFOS and PFOA levels was associated with 5.00 g (95% CI: -21.66, -7.78) and 14.72 g (95% CI: -8.92, -1.09) reductions in birth weight, respectively. Results of our simulations suggest that a substantial proportion of the association between prenatal PFAS and birth weight may be attributable to confounding by GFR and that confounding by GFR may be more important in studies with sample collection later in pregnancy.

  5. Interpreting large-scale experiments on effects of trawling on benthic fauna: an empirical test of the potential effects of spatial confounding in experiments without replicated control and trawled areas.

    PubMed

    Lindegarth; Valentinsson; Hansson; Ulmestrand

    2000-03-15

    Disturbances due to trawling and dredging is a serious threat to assemblages of benthic marine animals. We tested hypotheses about effects of trawling on benthic assemblages in a manipulative field experiment, using gear and intensities relevant to future management of trawling in a Swedish fjord. Three trawled and three control sites were sampled at several times before and after trawling was initiated. This paper describes how conclusions about effects of trawling might differ between experiments involving replicate sites and experiments using only one trawled and one control site, as in several recent studies. Analyses of selected taxa showed that abundances of many species changed differently among control sites. Differences in temporal change between pairs of single trawled and control sites were also frequent. Neither the quantitative nor the qualitative nature of differences between treatments could, however, be coherently interpreted among the different combinations of trawled and control sites. This is consistent with results obtained from analyses using all sites, which showed no consistent effects of trawling on any of these taxa. These results provide empirical evidence that spatial confounding may cause serious problems to formal interpretation of experiments, which use only one control and one trawled area. Such potential problems can best be solved by ensuring that the study incorporates more than one control site.

  6. Increased Public Accountability for Hospital Nonprofit Status: Potential Impacts on Residency Positions.

    PubMed

    Raffoul, Melanie C; Phillips, Robert L

    2017-01-01

    could be potentially strategic mechanisms to assess community needs as well as GME accountability in light of community needs and to guide GME expansion more strategically. Internal Revenue Service guidance regarding CHNAs could include workforce needs assessment and intervention requirements. Preference for future Medicaid or Medicare GME funding expansion could potentially favor states that use CHNAs or RHPs to identify workforce needs and track outcomes of related interventions. © Copyright 2017 by the American Board of Family Medicine.

  7. Is the Association of Subjective SES and Self-Rated Health Confounded by Negative Mood? An Experimental Approach

    PubMed Central

    Kraus, Michael W.; Adler, Nancy; David Chen, Teh-Way

    2012-01-01

    Objective Lower subjective socioeconomic status (SSS) consistently shows associations with poorer health with the strongest relationships emerging with global self-rated health. Though often interpreted as reflecting the impact of low SSS on health, the association could also arise from confounding SSS with negative affect. In this research we sought to determine if negative affect confounds, or alternatively, is on the causal pathway linking SSS to self-rated health. Methods 300 adult participants—recruited from throughout the United States—were randomized to experience sadness, shame, or a neutral mood induction wherein they wrote about and visualized a particularly emotionally evocative event. Participants subsequently completed measures of SSS, self-rated health, depression, and negative mood. Results Consistent with predictions, neither SSS scores nor the association of SSS with self-rated health, depression, and chronic negative affect differed by mood induction condition, controlling for demographic factors that covary with SSS (e.g., age, gender, education, income). Moreover, chronic negative affect partially explained the relationship between SSS and self-rated health, independent of manipulated mood. Conclusions These findings support the utility of the measurement of SSS, and provide evidence suggesting that chronic negative affect is a likely mediator of the SSS association with global health rather than a confounder. PMID:22329426

  8. Harnessing Facebook for Student Engagement in Accounting Education: Guiding Principles for Accounting Students and Educators

    ERIC Educational Resources Information Center

    Stone, Gerard; Fiedler, Brenton Andrew; Kandunias, Chris

    2014-01-01

    This paper proposes principles to guide accounting students' and accounting educators' use of Facebook as an educational resource to engage students with their learning. A body of cross-disciplinary research has investigated potential applications of Facebook to invigorate student engagement. Generic guidelines for educators who are contemplating…

  9. Is the Association between General Cognitive Ability and Violent Crime Caused by Family-Level Confounders?

    PubMed Central

    Frisell, Thomas; Pawitan, Yudi; Långström, Niklas

    2012-01-01

    Background Research has consistently found lower cognitive ability to be related to increased risk for violent and other antisocial behaviour. Since this association has remained when adjusting for childhood socioeconomic position, ethnicity, and parental characteristics, it is often assumed to be causal, potentially mediated through school adjustment problems and conduct disorder. Socioeconomic differences are notoriously difficult to quantify, however, and it is possible that the association between intelligence and delinquency suffer substantial residual confounding. Methods We linked longitudinal Swedish total population registers to study the association of general cognitive ability (intelligence) at age 18 (the Conscript Register, 1980–1993) with the incidence proportion of violent criminal convictions (the Crime Register, 1973–2009), among all men born in Sweden 1961–1975 (N = 700,514). Using probit regression, we controlled for measured childhood socioeconomic variables, and further employed sibling comparisons (family pedigree data from the Multi-Generation Register) to adjust for shared familial characteristics. Results Cognitive ability in early adulthood was inversely associated to having been convicted of a violent crime (β = −0.19, 95% CI: −0.19; −0.18), the association remained when adjusting for childhood socioeconomic factors (β = −0.18, 95% CI: −0.18; −0.17). The association was somewhat lower within half-brothers raised apart (β = −0.16, 95% CI: −0.18; −0.14), within half-brothers raised together (β = −0.13, 95% CI: (−0.15; −0.11), and lower still in full-brother pairs (β = −0.10, 95% CI: −0.11; −0.09). The attenuation among half-brothers raised together and full brothers was too strong to be attributed solely to attenuation from measurement error. Discussion Our results suggest that the association between general cognitive ability and violent criminality is confounded partly by

  10. Residual confounding explains the association between high parity and child mortality.

    PubMed

    Kozuki, Naoko; Sonneveldt, Emily; Walker, Neff

    2013-01-01

    This study used data from recent Demographic and Health Surveys (DHS) to examine the impact of high parity on under-five and neonatal mortality. The analyses used various techniques to attempt eliminating selection issues, including stratification of analyses by mothers' completed fertility. We analyzed DHS datasets from 47 low- and middle-income countries. We only used data from women who were age 35 or older at the time of survey to have a measure of their completed fertility. We ran log-binominal regression by country to calculate relative risk between parity and both under-five and neonatal mortality, controlled for wealth quintile, maternal education, urban versus rural residence, maternal age at first birth, calendar year (to control for possible time trends), and birth interval. We then controlled for maternal background characteristics even further by using mothers' completed fertility as a proxy measure. We found a statistically significant association between high parity and child mortality. However, this association is most likely not physiological, and can be largely attributed to the difference in background characteristics of mothers who complete reproduction with high fertility versus low fertility. Children of high completed fertility mothers have statistically significantly increased risk of death compared to children of low completed fertility mothers at every birth order, even after controlling for available confounders (i.e. among children of birth order 1, adjusted RR of under-five mortality 1.58, 95% CI: 1.42, 1.76). There appears to be residual confounders that put children of high completed fertility mothers at higher risk, regardless of birth order. When we examined the association between parity and under-five mortality among mothers with high completed fertility, it remained statistically significant, but negligible in magnitude (i.e. adjusted RR of under-five mortality 1.03, 95% CI: 1.02-1.05). Our analyses strongly suggest that the

  11. Second-generation corneal deformation signal waveform analysis in normal, forme fruste keratoconic, and manifest keratoconic corneas after statistical correction for potentially confounding factors.

    PubMed

    Zhang, Lijun; Danesh, Jennifer; Tannan, Anjali; Phan, Vivian; Yu, Fei; Hamilton, D Rex

    2015-10-01

    To evaluate the difference in corneal biomechanical waveform parameters between manifest keratoconus, forme fruste keratoconus, and healthy eyes with a second-generation biomechanical waveform analyzer (Ocular Response Analyzer 2). Jules Stein Eye Institute, University of California, Los Angeles, California, USA. Retrospective chart review. The biomechanical waveform analyzer was used to obtain corneal hysteresis (CH), corneal resistance factor (CRF), and 37 biomechanical waveform parameters in manifest keratoconus eyes, forme fruste keratoconus eyes, and healthy eyes. Useful distinguishing parameters were found using t tests and a multivariable logistic regression model with stepwise variable selection. Potential confounders were controlled for. The study included 68 manifest keratoconus eyes, 64 forme fruste keratoconus eyes, and 249 healthy eyes. There was a statistical difference in the mean CRF between the normal group (10.2 mm Hg ± 1.7 [SD]) and keratoconus group (6.3 ± 1.9 mm Hg) (P = .003), and between the normal group and the forme fruste keratoconus group (7.8 ± 1.4 mm Hg) (P < .0001). There was no statistical difference in the mean CH between the normal group and the keratoconus group or the forme fruste keratoconus group. The CRF, height of peak 1 (P1) (P = .001), downslope of P1 (dslope1) (P = .027), upslope of peak 2 (P2) (P = .004), and downslope of P2 (P = .006) distinguished the normal group from the keratoconus groups. The CRF, downslope of P2 derived from upper 50% of applanation peak (P = .035), dslope1 (P = .014), and upslope of P1 (P = .008) distinguished the normal group from the forme fruste keratoconus group. Differences in multiple biomechanical waveform parameters can differentiate between healthy and diseased conditions and might improve early diagnosis of keratoconus and forme fruste keratoconus. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by

  12. Confounding factors in the detection of species responses to habitat fragmentation.

    PubMed

    Ewers, Robert M; Didham, Raphael K

    2006-02-01

    genetic structure of fragment-dwelling populations. Again, the matrix habitat is a strong determinant of fragmentation effects within remnants because of its role in regulating dispersal and dispersal-related mortality, the provision of spatial subsidies and the potential mediation of edge-related microclimatic gradients. We show that confounding factors can mask many fragmentation effects. For instance, there are multiple ways in which species traits like trophic level, dispersal ability and degree of habitat specialisation influence species-level responses. The temporal scale of investigation may have a strong influence on the results of a study, with short-term crowding effects eventually giving way to long-term extinction debts. Moreover, many fragmentation effects like changes in genetic, morphological or behavioural traits of species require time to appear. By contrast, synergistic interactions of fragmentation with climate change, human-altered disturbance regimes, species interactions and other drivers of population decline may magnify the impacts of fragmentation. To conclude, we emphasise that anthropogenic fragmentation is a recent phenomenon in evolutionary time and suggest that the final, long-term impacts of habitat fragmentation may not yet have shown themselves.

  13. Neuropsychological functioning in older people with type 2 diabetes: the effect of controlling for confounding factors.

    PubMed

    Asimakopoulou, K G; Hampson, S E; Morrish, N J

    2002-04-01

    Neuropsychological functioning was examined in a group of 33 older (mean age 62.40 +/- 9.62 years) people with Type 2 diabetes (Group 1) and 33 non-diabetic participants matched with Group 1 on age, sex, premorbid intelligence and presence of hypertension and cardio/cerebrovascular conditions (Group 2). Data statistically corrected for confounding factors obtained from the diabetic group were compared with the matched control group. The results suggested small cognitive deficits in diabetic people's verbal memory and mental flexibility (Logical Memory A and SS7). No differences were seen between the two samples in simple and complex visuomotor attention, sustained complex visual attention, attention efficiency, mental double tracking, implicit memory, and self-reported memory problems. These findings indicate minimal cognitive impairment in relatively uncomplicated Type 2 diabetes and demonstrate the importance of control and matching for confounding factors.

  14. JIM-13-0560 R1: Propensity scores for confounder adjustment when assessing the effects of medical interventions using non-experimental study designs

    PubMed Central

    Stürmer, Til; Wyss, Richard; Glynn, Robert J.; Brookhart, M. Alan

    2014-01-01

    Treatment effects, especially when comparing two or more therapeutic alternatives as in comparative effectiveness research, are likely to be heterogeneous across age, gender, co-morbidities, and co-medications. Propensity scores (PSs), an alternative to multivariable outcome models to control for measured confounding, have specific advantages in the presence of heterogeneous treatment effects. Implementing PSs using matching or weighting allows us to estimate different overall treatment effects in differently defined populations. Heterogeneous treatment effects can also be due to unmeasured confounding concentrated in those treated contrary to prediction. Sensitivity analyses based on PSs can help to assess such unmeasured confounding. PSs should be considered a primary or secondary analytic strategy in non-experimental medical research, including pharmacoepidemiology and non-experimental comparative effectiveness research. PMID:24520806

  15. Clinical and methodological confounders in assessing the cerebellar cognitive affective syndrome in adult patients with posterior fossa tumours.

    PubMed

    Omar, Dashne; Ryan, Tracy; Carson, Alan; Bak, Thomas H; Torrens, Lorna; Whittle, Ian

    2014-12-01

    The cerebellar cognitive affective syndrome (CCAS) was first described by Schmahmann and Sherman as a constellation of symptoms including dysexecutive syndrome, spatial cognitive deficit, linguistic deficits and behavioural abnormalities in patients with a lesion in the cerebellum with otherwise normal brain. Neurosurgical patients with cerebellar tumours constitute one of the cohorts in which the CCAS has been described. In this paper, we present a critical review of the literature of this syndrome in neurosurgical patients. Thereafter, we present a prospective clinical study of 10 patients who underwent posterior fossa tumour resection and had a detailed post-operative neuropsychological, neuropsychiatric and neuroradiological assessment. Because our findings revealed a large number of perioperative neuroradiological confounding variables, we reviewed the neuroimaging of a further 20 patients to determine their prevalence. Our literature review revealed that study design, methodological quality and sometimes both diagnostic criteria and findings were inconsistent. The neuroimaging study (pre-operative, n = 10; post-operative, n = 10) showed very frequent neuroradiological confounding complications (e.g. hydrocephalus; brainstem compression; supratentorial lesions and post-operative subdural hygroma); the impact of such features had largely been ignored in the literature. Findings from our clinical study showed various degree of deficits in neuropsychological testing (n = 1, memory; n = 3, verbal fluency; n = 3, attention; n = 2, spatial cognition deficits; and n = 1, behavioural changes), but no patient had full-blown features of CCAS. Our study, although limited, finds no robust evidence of the CCAS following surgery. This and our literature review highlight a need for guidelines regarding study design and methodology when attempting to evaluate neurosurgical cases with regard to the potential CCAS.

  16. Student Academic Performance in Undergraduate Managerial-Accounting Courses

    ERIC Educational Resources Information Center

    Al-Twaijry, Abdulrahman Ali

    2010-01-01

    The author's purpose was to identify potential factors possibly affecting student performance in three sequential management-accounting courses: Managerial Accounting (MA), Cost Accounting (CA), and Advanced Managerial Accounting (AMA) within the Saudi Arabian context. The sample, which was used to test the developed hypotheses, included 312…

  17. Biomechanical and psychosocial exposures are independent risk factors for carpal tunnel syndrome: assessment of confounding using causal diagrams.

    PubMed

    Harris-Adamson, Carisa; Eisen, Ellen A; Neophytou, Andreas; Kapellusch, Jay; Garg, Arun; Hegmann, Kurt T; Thiese, Matthew S; Dale, Ann Marie; Evanoff, Bradley; Bao, Stephen; Silverstein, Barbara; Gerr, Fred; Burt, Susan; Rempel, David

    2016-11-01

    Between 2001 and 2010, six research groups conducted coordinated prospective studies of carpal tunnel syndrome (CTS) incidence among US workers from various industries to estimate exposure-response relationships. This analysis examined the presence and magnitude of confounding between biomechanical and workplace psychosocial factors and incidence of dominant-hand CTS. 1605 participants, without CTS at enrolment, were followed for up to 3.5 years (2471 person-years). Demographic information, medical history and workplace psychosocial stress measures were collected at baseline. Individual workplace biomechanical exposures were collected for each task and combined across the workweek using time-weighted averaging (TWA). CTS case criteria were based on symptoms and results of electrophysiological testing. HRs were estimated with Cox proportional hazard models. Confounding was assessed using causal diagrams and an empirical criterion of 10% or greater change in effect estimate magnitude. There were 109 incident CTS cases (IR=4.41/100 person-years; 6.7% cumulative incidence). The relationships between CTS and forceful repetition rate, % time forceful hand exertion and the Threshold Limit Value for Hand Activity Level (TLV-HAL) were slightly confounded by decision latitude with effect estimates being attenuated towards the null (10-14% change) after adjustment. The risk of CTS among participants reporting high job strain was attenuated towards the null by 14% after adjusting for the HAL Scale or the % time forceful hand exertions. Although attenuation of the relationships between CTS and some biomechanical and work psychosocial exposures was observed after adjusting for confounding, the magnitudes were small and confirmed biomechanical and work psychosocial exposures as independent risk factors for incident CTS. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

  18. Innovations in an Accounting Information Systems Course.

    ERIC Educational Resources Information Center

    Shaoul, Jean

    A new approach to teaching an introductory accounting information systems course is outlined and the potential of this approach for integrating computers into the accounting curriculum at Manchester University (England) is demonstrated. Specifically, the use of a small inventory recording system and database in an accounting information course is…

  19. Reported association of air pollution and suicide rate could be confounded.

    PubMed

    Afshari, R

    2017-02-28

    A statistical association between ambient air pollution and suicide mortality has been recently reported in Environmental Health, which seems not to be scientifically supported by their data.In this article, very low (unrealistic) suicide rate is reported, which is subjected to selection bias. Their justification is also flawed as high exposure to ambient air pollution in rural areas is lower as compared to urban residents. Weekends, holidays, time of death … are also both air pollution and suicide rate related. Reported statistical association of air pollution and suicide in this study is heavily confound.Please see article under discussion: https://ehjournal.biomedcentral.com/articles/10.1186/s12940-016-0177-1 .

  20. Review of methods for handling confounding by cluster and informative cluster size in clustered data

    PubMed Central

    Seaman, Shaun; Pavlou, Menelaos; Copas, Andrew

    2014-01-01

    Clustered data are common in medical research. Typically, one is interested in a regression model for the association between an outcome and covariates. Two complications that can arise when analysing clustered data are informative cluster size (ICS) and confounding by cluster (CBC). ICS and CBC mean that the outcome of a member given its covariates is associated with, respectively, the number of members in the cluster and the covariate values of other members in the cluster. Standard generalised linear mixed models for cluster-specific inference and standard generalised estimating equations for population-average inference assume, in general, the absence of ICS and CBC. Modifications of these approaches have been proposed to account for CBC or ICS. This article is a review of these methods. We express their assumptions in a common format, thus providing greater clarity about the assumptions that methods proposed for handling CBC make about ICS and vice versa, and about when different methods can be used in practice. We report relative efficiencies of methods where available, describe how methods are related, identify a previously unreported equivalence between two key methods, and propose some simple additional methods. Unnecessarily using a method that allows for ICS/CBC has an efficiency cost when ICS and CBC are absent. We review tools for identifying ICS/CBC. A strategy for analysis when CBC and ICS are suspected is demonstrated by examining the association between socio-economic deprivation and preterm neonatal death in Scotland. PMID:25087978

  1. Pixel-based absorption correction for dual-tracer fluorescence imaging of receptor binding potential

    PubMed Central

    Kanick, Stephen C.; Tichauer, Kenneth M.; Gunn, Jason; Samkoe, Kimberley S.; Pogue, Brian W.

    2014-01-01

    Ratiometric approaches to quantifying molecular concentrations have been used for decades in microscopy, but have rarely been exploited in vivo until recently. One dual-tracer approach can utilize an untargeted reference tracer to account for non-specific uptake of a receptor-targeted tracer, and ultimately estimate receptor binding potential quantitatively. However, interpretation of the relative dynamic distribution kinetics is confounded by differences in local tissue absorption at the wavelengths used for each tracer. This study simulated the influence of absorption on fluorescence emission intensity and depth sensitivity at typical near-infrared fluorophore wavelength bands near 700 and 800 nm in mouse skin in order to correct for these tissue optical differences in signal detection. Changes in blood volume [1-3%] and hemoglobin oxygen saturation [0-100%] were demonstrated to introduce substantial distortions to receptor binding estimates (error > 30%), whereas sampled depth was relatively insensitive to wavelength (error < 6%). In response, a pixel-by-pixel normalization of tracer inputs immediately post-injection was found to account for spatial heterogeneities in local absorption properties. Application of the pixel-based normalization method to an in vivo imaging study demonstrated significant improvement, as compared with a reference tissue normalization approach. PMID:25360349

  2. Covariance between predation risk and nutritional preferences confound interpretations of giving-up density experiments.

    PubMed

    McMahon, Jordan D; Lashley, Marcus A; Brooks, Christopher P; Barton, Brandon T

    2018-04-26

    Giving-up density (GUD) experiments have been a foundational method to evaluate perceived predation risk, but rely on the assumption that food preferences are absolute, so that areas with higher GUDs can be interpreted as having higher risk. However, nutritional preferences are context dependent and can change with risk. We used spiders and grasshoppers to test the hypothesis that covariance in nutritional preferences and risk may confound the interpretation of GUD experiments. We presented grasshoppers with carbohydrate-rich and protein-rich diets, in the presence and absence of spider predators. Predators reduced grasshopper preference for the protein-rich food, but increased their preference for the carbohydrate-rich food. We then measured GUDs with both food types under different levels of risk (spider density, 0 - 5). As expected, GUDs increased with spider density indicating increasing risk, but only when using protein-rich food. With carbohydrate-rich food, GUD was independent of predation risk. Our results demonstrate that predation risk and nutritional preferences covary and can confound interpretation of GUD experiments. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  3. Neurophysiological mechanism of possibly confounding peripheral activation of the facial nerve during corticobulbar tract monitoring.

    PubMed

    Téllez, Maria J; Ulkatan, Sedat; Urriza, Javier; Arranz-Arranz, Beatriz; Deletis, Vedran

    2016-02-01

    To improve the recognition and possibly prevent confounding peripheral activation of the facial nerve caused by leaking transcranial electrical stimulation (TES) current during corticobulbar tract monitoring. We applied a single stimulus and a short train of electrical stimuli directly to the extracranial portion of the facial nerve. We compared the peripherally elicited compound muscle action potential (CMAP) of the facial nerve with the responses elicited by TES during intraoperative monitoring of the corticobulbar tract. A single stimulus applied directly to the facial nerve at subthreshold intensities did not evoke a CMAP, whereas short trains of subthreshold stimuli repeatedly evoked CMAPs. This is due to the phenomenon of sub- or near-threshold super excitability of the cranial nerve. Therefore, the facial responses evoked by short trains TES, when the leaked current reaches the facial nerve at sub- or near-threshold intensity, could lead to false interpretation. Our results revealed a potential pitfall in the current methodology for facial corticobulbar tract monitoring that is due to the activation of the facial nerve by subthreshold trains of stimuli. This study proposes a new criterion to exclude peripheral activation during corticobulbar tract monitoring. The failure to recognize and avoid facial nerve activation due to leaking current in the peripheral portion of the facial nerve during TES decreases the reliability of corticobulbar tract monitoring by increasing the possibility of false interpretation. Copyright © 2015 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

  4. Do time-invariant confounders explain away the association between job stress and workers' mental health? Evidence from Japanese occupational panel data.

    PubMed

    Oshio, Takashi; Tsutsumi, Akizumi; Inoue, Akiomi

    2015-02-01

    It is well known that job stress is negatively related to workers' mental health, but most recent studies have not controlled for unobserved time-invariant confounders. In the current study, we attempted to validate previous observations on the association between job stress and workers' mental health, by removing the effects of unobserved time-invariant confounders. We used data from three to four waves of an occupational Japanese cohort survey, focusing on 31,382 observations of 9741 individuals who participated in at least two consecutive waves. We estimated mean-centered fixed effects models to explain psychological distress in terms of the Kessler 6 (K6) scores (range: 0-24) by eight job stress indicators related to the job demands-control, effort-reward imbalance, and organizational injustice models. Mean-centered fixed effects models reduced the magnitude of the association between jobs stress and K6 scores to 44.8-54.2% of those observed from pooled ordinary least squares. However, the association remained highly significant even after controlling for unobserved time-invariant confounders for all job stress indicators. In addition, alternatively specified models showed the robustness of the results. In all, we concluded that the validity of major job stress models, which link job stress and workers' mental health, was robust, although unobserved time-invariant confounders led to an overestimation of the association. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. On causal interpretation of race in regressions adjusting for confounding and mediating variables

    PubMed Central

    VanderWeele, Tyler J.; Robinson, Whitney R.

    2014-01-01

    We consider several possible interpretations of the “effect of race” when regressions are run with race as an exposure variable, controlling also for various confounding and mediating variables. When adjustment is made for socioeconomic status early in a person’s life, we discuss under what contexts the regression coefficients for race can be interpreted as corresponding to the extent to which a racial inequality would remain if various socioeconomic distributions early in life across racial groups could be equalized. When adjustment is also made for adult socioeconomic status, we note how the overall racial inequality can be decomposed into the portion that would be eliminated by equalizing adult socioeconomic status across racial groups and the portion of the inequality that would remain even if adult socioeconomic status across racial groups were equalized. We also discuss a stronger interpretation of the “effect of race” (stronger in terms of assumptions) involving the joint effects of race-associated physical phenotype (e.g. skin color), parental physical phenotype, genetic background and cultural context when such variables are thought to be hypothetically manipulable and if adequate control for confounding were possible. We discuss some of the challenges with such an interpretation. Further discussion is given as to how the use of selected populations in examining racial disparities can additionally complicate the interpretation of the effects. PMID:24887159

  6. Assessment of the number of eye symptoms and the impact of some confounding variables for office staff in non-air-conditioned buildings.

    PubMed

    Doughty, Michael J; Blades, Kenneth A; Ibrahim, Nassim

    2002-03-01

    The goal of this study was both to assess the frequency of self-reported eye symptoms for employees in a non-air-conditioned office building complex, and to specifically assess whether confounding variables (contact lens wear, medicines use, and provoking stimuli) had a discernible impact on the characteristics of this reporting. A questionnaire was distributed, in the winter months, to office employees in a building complex within a city-located University site, consisting of non-air-conditioned rooms with some mechanical ventilation. The questionnaire asked respondents to identify any eye symptoms experienced (foreign body sensation, soreness, dryness, grittiness, itchiness, stinging, intense burning), the frequency of their occurrence, details of any conditions provoking eye symptoms (such as changes in the microenvironment), their medication use and if they were contact lens wearers. The proportion of respondents for various categories was calculated, along with the total number of symptoms. If 'eye irritation' is considered as reporting any symptoms experienced at any time, then 63% of 292 respondents (median age 42.5 years) reported an average of 1.83 symptoms. However, the identification of contact lens wearers, medication use (especially for seasonal allergies) and provoking stimuli reduced this prevalence to just 29% (with the average number of symptoms being 1.51). If the frequency of experiencing symptoms was also taken into account (never, sometimes, often, and constantly), then only 12.3% of the respondents indicated symptoms often or constantly, i.e. could be considered to have significant symptoms. In all categories, men were more likely to report eye symptoms compared with women. The results confirm that office employees are likely to have some ocular symptoms, but that even a simple consideration of possible confounding variables can greatly change the reported prevalence of eye irritation that might be specifically associated with the workplace

  7. Accounting for Selectivity Bias and Correlation Across the Sequence From Elevated Blood Pressure to Hypertension Diagnosis and Treatment.

    PubMed

    Gordon-Larsen, Penny; Attard, Samantha M; Howard, Annie Green; Popkin, Barry M; Zhang, Bing; Du, Shufa; Guilkey, David K

    2017-12-08

    It is unknown whether efforts to reduce hypertension burden in countries with very high prevalence, would be more effective if directed at hypertension diagnosis vs. treatment. Most analyses do not address bias and correlation across the sequence from elevated blood pressure (BP) to hypertension diagnosis and treatment, leading to potentially misleading findings. Using data spanning 18 years of the China Health and Nutrition Survey (n = 18,926; ages 18-75 years), we used an innovative 3-step, integrated system of equations to predict the sequence from: (i) elevated BP (systolic/diastolic BP ≥ 140/90 mm Hg) to (ii) diagnosed hypertension conditional on elevated BP, and to (iii) treatment (medication use) conditional on diagnosis, accounting for measured and unmeasured individual- and community-level confounders at each of the 3 steps. We compared results to separate traditional logistic regression models without control for unmeasured confounding. Using our 3-step model, elevated BP increased from 12.6% and 8.5% (1991) to 36.8% and 29% (2009) in men and women, respectively, but diagnosis remained under 50%. We found widening disparities in hypertension diagnosis (higher hypertension at lower vs. higher education (difference of 2% in 1991 that widened to 5% in 2009)) and narrowing disparities in education (difference of 6% in 1991 to 4% in 2009) and insurance status (difference of 7% in 1991 to 2% in 2009) for treatment. Our 3-step model improved model fit over traditionally used models. Our findings highlight serious barriers to hypertension diagnosis in Chinese adults, particularly among men and individuals of low attained education. © American Journal of Hypertension, Ltd 2017. All rights reserved. For Permissions, please email: journals.permissions@oup.com

  8. Controlling for confounding variables in MS-omics protocol: why modularity matters.

    PubMed

    Smith, Rob; Ventura, Dan; Prince, John T

    2014-09-01

    As the field of bioinformatics research continues to grow, more and more novel techniques are proposed to meet new challenges and improvements upon solutions to long-standing problems. These include data processing techniques and wet lab protocol techniques. Although the literature is consistently thorough in experimental detail and variable-controlling rigor for wet lab protocol techniques, bioinformatics techniques tend to be less described and less controlled. As the validation or rejection of hypotheses rests on the experiment's ability to isolate and measure a variable of interest, we urge the importance of reducing confounding variables in bioinformatics techniques during mass spectrometry experimentation. © The Author 2013. Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.

  9. Defining Ecosystem Assets for Natural Capital Accounting

    PubMed Central

    Hein, Lars; Bagstad, Ken; Edens, Bram; Obst, Carl; de Jong, Rixt; Lesschen, Jan Peter

    2016-01-01

    In natural capital accounting, ecosystems are assets that provide ecosystem services to people. Assets can be measured using both physical and monetary units. In the international System of Environmental-Economic Accounting, ecosystem assets are generally valued on the basis of the net present value of the expected flow of ecosystem services. In this paper we argue that several additional conceptualisations of ecosystem assets are needed to understand ecosystems as assets, in support of ecosystem assessments, ecosystem accounting and ecosystem management. In particular, we define ecosystems’ capacity and capability to supply ecosystem services, as well as the potential supply of ecosystem services. Capacity relates to sustainable use levels of multiple ecosystem services, capability involves prioritising the use of one ecosystem service over a basket of services, and potential supply considers the ability of ecosystems to generate services regardless of demand for these services. We ground our definitions in the ecosystem services and accounting literature, and illustrate and compare the concepts of flow, capacity, capability, and potential supply with a range of conceptual and real-world examples drawn from case studies in Europe and North America. Our paper contributes to the development of measurement frameworks for natural capital to support environmental accounting and other assessment frameworks. PMID:27828969

  10. Defining ecosystem assets for natural capital accounting

    USGS Publications Warehouse

    Hein, Lars; Bagstad, Kenneth J.; Edens, Bram; Obst, Carl; de Jong, Rixt; Lesschen, Jan Peter

    2016-01-01

    In natural capital accounting, ecosystems are assets that provide ecosystem services to people. Assets can be measured using both physical and monetary units. In the international System of Environmental-Economic Accounting, ecosystem assets are generally valued on the basis of the net present value of the expected flow of ecosystem services. In this paper we argue that several additional conceptualisations of ecosystem assets are needed to understand ecosystems as assets, in support of ecosystem assessments, ecosystem accounting and ecosystem management. In particular, we define ecosystems’ capacity and capability to supply ecosystem services, as well as the potential supply of ecosystem services. Capacity relates to sustainable use levels of multiple ecosystem services, capability involves prioritising the use of one ecosystem service over a basket of services, and potential supply considers the ability of ecosystems to generate services regardless of demand for these services. We ground our definitions in the ecosystem services and accounting literature, and illustrate and compare the concepts of flow, capacity, capability, and potential supply with a range of conceptual and real-world examples drawn from case studies in Europe and North America. Our paper contributes to the development of measurement frameworks for natural capital to support environmental accounting and other assessment frameworks.

  11. Defining Ecosystem Assets for Natural Capital Accounting.

    PubMed

    Hein, Lars; Bagstad, Ken; Edens, Bram; Obst, Carl; de Jong, Rixt; Lesschen, Jan Peter

    2016-01-01

    In natural capital accounting, ecosystems are assets that provide ecosystem services to people. Assets can be measured using both physical and monetary units. In the international System of Environmental-Economic Accounting, ecosystem assets are generally valued on the basis of the net present value of the expected flow of ecosystem services. In this paper we argue that several additional conceptualisations of ecosystem assets are needed to understand ecosystems as assets, in support of ecosystem assessments, ecosystem accounting and ecosystem management. In particular, we define ecosystems' capacity and capability to supply ecosystem services, as well as the potential supply of ecosystem services. Capacity relates to sustainable use levels of multiple ecosystem services, capability involves prioritising the use of one ecosystem service over a basket of services, and potential supply considers the ability of ecosystems to generate services regardless of demand for these services. We ground our definitions in the ecosystem services and accounting literature, and illustrate and compare the concepts of flow, capacity, capability, and potential supply with a range of conceptual and real-world examples drawn from case studies in Europe and North America. Our paper contributes to the development of measurement frameworks for natural capital to support environmental accounting and other assessment frameworks.

  12. Accounting for sampling patterns reverses the relative importance of trade and climate for the global sharing of exotic plants

    USGS Publications Warehouse

    Sofaer, Helen R.; Jarnevich, Catherine S.

    2017-01-01

    AimThe distributions of exotic species reflect patterns of human-mediated dispersal, species climatic tolerances and a suite of other biotic and abiotic factors. The relative importance of each of these factors will shape how the spread of exotic species is affected by ongoing economic globalization and climate change. However, patterns of trade may be correlated with variation in scientific sampling effort globally, potentially confounding studies that do not account for sampling patterns.LocationGlobal.Time periodMuseum records, generally from the 1800s up to 2015.Major taxa studiedPlant species exotic to the United States.MethodsWe used data from the Global Biodiversity Information Facility (GBIF) to summarize the number of plant species with exotic occurrences in the United States that also occur in each other country world-wide. We assessed the relative importance of trade and climatic similarity for explaining variation in the number of shared species while evaluating several methods to account for variation in sampling effort among countries.ResultsAccounting for variation in sampling effort reversed the relative importance of trade and climate for explaining numbers of shared species. Trade was strongly correlated with numbers of shared U.S. exotic plants between the United States and other countries before, but not after, accounting for sampling variation among countries. Conversely, accounting for sampling effort strengthened the relationship between climatic similarity and species sharing. Using the number of records as a measure of sampling effort provided a straightforward approach for the analysis of occurrence data, whereas species richness estimators and rarefaction were less effective at removing sampling bias.Main conclusionsOur work provides support for broad-scale climatic limitation on the distributions of exotic species, illustrates the need to account for variation in sampling effort in large biodiversity databases, and highlights the

  13. Brief Communication: Latent toxoplasmosis and salivary testosterone concentration--important confounding factors in second to fourth digit ratio studies.

    PubMed

    Flegr, Jaroslav; Lindová, Jitka; Pivoñková, Vera; Havlícek, Jan

    2008-12-01

    A sexually dimorphic characteristic, the second to fourth digit ratio (2D:4D ratio), has been shown to reflect the prenatal concentration of sex steroid hormones and to correlate with many personality, physiological, and life history traits. The correlations are usually stronger for the right than the left hand. Most studies have shown that the 2D:4D ratio does not vary with age or postnatal concentration of sex steroid hormones. Recently, a strong association between left hand 2D:4D ratio and infection with a common human parasite Toxoplasma has been reported. We hypothesized that the confounding effect of Toxoplasma infection on left hand 2D:4D ratio could be responsible for the stronger association between different traits and right hand rather than left hand 2D:4D ratio. This confounding effect of toxoplasmosis could also be responsible for the difficulty in finding an association between 2D:4D ratio and age or postnatal steroid hormone concentration. To test this hypothesis, we analyzed the association between sex and age and 2D:4D ratio in a population of 194 female and 106 male students with and without controlling for the confounding variables of Toxoplasma infection and testosterone concentration. Our results showed that the relationship between age and sex and 2D:4D ratio increased sharply when Toxoplasma infection and testosterone concentration were controlled. These results suggest that left hand 2D:4D ratio is more susceptible to postnatal influences and that the confounding factors of Toxoplasma infection, testosterone concentration and possibly also age, should be controlled in future 2D:4D ratio studies. Because of a stronger 2D:4D dimorphism in Toxoplasma-infected than Toxoplasma-free subjects, we predict that 2D:4D ratio dimorphism as well as right hand/left hand 2D:4D ratio dimorphism will be higher in countries with a high prevalence of Toxoplasma infection than in those with a low prevalence. (c) 2008 Wiley-Liss, Inc.

  14. Indoor biofuel air pollution and respiratory health: the role of confounding factors among women in highland Guatemala.

    PubMed

    Bruce, N; Neufeld, L; Boy, E; West, C

    1998-06-01

    A number of studies have reported associations between indoor biofuel air pollution in developing countries and chronic obstructive lung disease (COLD) in adults and acute lower respiratory infection (ALRI) in children. Most of these studies have used indirect measures of exposure and generally dealt inadequately with confounding. More reliable, quantified information about this presumed effect is an important pre-requisite for prevention, not least because of the technical, economic and cultural barriers to achieving substantial exposure reductions in the world's poorest households, where ambient pollution levels are typically between ten and a hundred times higher than recommended standards. This study was carried out as part of a programme of research designed to inform the development of intervention studies capable of providing quantified estimates of health benefits. The association between respiratory symptoms and the use of open fires and chimney woodstoves ('planchas'), and the distribution of confounding factors, were examined in a cross-sectional study of 340 women aged 15-45 years, living in a poor rural area in the western highlands of Guatemala. The prevalence of reported cough and phlegm was significantly higher for three of six symptom measures among women using open fires. Although this finding is consistent with a number of other studies, none has systematically examined the extent to which strong associations with confounding variables in these settings limit the ability of observational studies to define the effect of indoor air pollution adequately. Very strong associations (P < 0.0001) were found between the type of fire and a number of household and socioeconomic factors including the arrangement of rooms, floor type, and possession of a radio and television. The spouse's economic activity type was also significantly associated (P < 0.05). Thus, while 82% of open fire users had dirt floors and only 18% cement or tile floors, the situation was

  15. Grandparental help in Indonesia is directed preferentially towards needier descendants: a potential confounder when exploring grandparental influences on child health.

    PubMed

    Snopkowski, Kristin; Sear, Rebecca

    2015-03-01

    A considerable body of evidence has now demonstrated positive correlations between grandparental presence and child health outcomes. It is typically assumed that such correlations exist because grandparental investment in their grandchildren improves child health and wellbeing. However, less is known about how grandparents allocate help to adult children and grandchildren, particularly in lower income contexts. Here we use detailed quantitative data from the longitudinal Indonesia Family Life Survey (data collected in 1993, 1997, 2000, 2007; n = 16,250) to examine grandparental help in a society transitioning both demographically and economically. We test the hypothesis that grandparents direct help preferentially towards those adult children and grandchildren most in need of help. This hypothesis was supported for help provided by married grandparents and single grandmothers, who tended to: provide more help to their adult children when this generation had young children themselves, provide financial help if their adult children were poorer, and provide more household help if their adult daughters worked outside the home. One unexpected result was that help from maternal and paternal grandparents is positively correlated; if one set of grandparents is helping the other set is more likely to help, counter to our predictions. These results provide support for the hypothesis that grandparents preferentially invest in some descendants over others, where married grandparents and single grandmothers tend to invest in those adult children and grandchildren with the most need. Investigating the effect of grandparents on child health outcomes may therefore be confounded by grandparent's preferential investment in needier descendants. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Refining adverse drug reaction signals by incorporating interaction variables identified using emergent pattern mining.

    PubMed

    Reps, Jenna M; Aickelin, Uwe; Hubbard, Richard B

    2016-02-01

    To develop a framework for identifying and incorporating candidate confounding interaction terms into a regularised cox regression analysis to refine adverse drug reaction signals obtained via longitudinal observational data. We considered six drug families that are commonly associated with myocardial infarction in observational healthcare data, but where the causal relationship ground truth is known (adverse drug reaction or not). We applied emergent pattern mining to find itemsets of drugs and medical events that are associated with the development of myocardial infarction. These are the candidate confounding interaction terms. We then implemented a cohort study design using regularised cox regression that incorporated and accounted for the candidate confounding interaction terms. The methodology was able to account for signals generated due to confounding and a cox regression with elastic net regularisation correctly ranking the drug families known to be true adverse drug reactions above those that are not. This was not the case without the inclusion of the candidate confounding interaction terms, where confounding leads to a non-adverse drug reaction being ranked highest. The methodology is efficient, can identify high-order confounding interactions and does not require expert input to specify outcome specific confounders, so it can be applied for any outcome of interest to quickly refine its signals. The proposed method shows excellent potential to overcome some forms of confounding and therefore reduce the false positive rate for signal analysis using longitudinal data. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. [Instruments of management accounting in german hospitals - potentials for competitive advantage and status quo].

    PubMed

    Berens, W; Lachmann, M; Wömpener, A

    2011-03-01

    The aim of this study is to provide an analysis of the status quo for the usage of instruments of management accounting in German hospitals. 600 managing directors of German hospitals were asked to answer a questionnaire about the usage of management accounting instruments in their hospitals. We obtained 121 usable datasets, which are evaluated in this study. A significant increase in the usage of management accounting instruments can be observed over time. The respondents have an overall positive perception of the usage of these instruments. Cost accounting and information systems are among the most widely used instruments, while widely discussed concepts like the balanced scorecard or clinical pathways show surprisingly low usage rates. © Georg Thieme Verlag KG Stuttgart · New York.

  18. Local Field Potentials: Myths and Misunderstandings

    PubMed Central

    Herreras, Oscar

    2016-01-01

    The intracerebral local field potential (LFP) is a measure of brain activity that reflects the highly dynamic flow of information across neural networks. This is a composite signal that receives contributions from multiple neural sources, yet interpreting its nature and significance may be hindered by several confounding factors and technical limitations. By and large, the main factor defining the amplitude of LFPs is the geometry of the current sources, over and above the degree of synchronization or the properties of the media. As such, similar levels of activity may result in potentials that differ in several orders of magnitude in different populations. The geometry of these sources has been experimentally inaccessible until intracerebral high density recordings enabled the co-activating sources to be revealed. Without this information, it has proven difficult to interpret a century's worth of recordings that used temporal cues alone, such as event or spike related potentials and frequency bands. Meanwhile, a collection of biophysically ill-founded concepts have been considered legitimate, which can now be corrected in the light of recent advances. The relationship of LFPs to their sources is often counterintuitive. For instance, most LFP activity is not local but remote, it may be larger further from rather than close to the source, the polarity does not define its excitatory or inhibitory nature, and the amplitude may increase when source's activity is reduced. As technological developments foster the use of LFPs, the time is now ripe to raise awareness of the need to take into account spatial aspects of these signals and of the errors derived from neglecting to do so. PMID:28018180

  19. Selection bias and patterns of confounding in cohort studies: the case of the NINFEA web-based birth cohort.

    PubMed

    Pizzi, Costanza; De Stavola, Bianca L; Pearce, Neil; Lazzarato, Fulvio; Ghiotti, Paola; Merletti, Franco; Richiardi, Lorenzo

    2012-11-01

    Several studies have examined the effects of sample selection on the exposure-outcome association estimates in cohort studies, but the reasons why this selection may induce bias have not been fully explored. To investigate how sample selection of the web-based NINFEA birth cohort may change the confounding patterns present in the source population. The characteristics of the NINFEA participants (n=1105) were compared with those of the wider source population-the Piedmont Birth Registry (PBR)-(n=36 092), and the association of two exposures (parity and educational level) with two outcomes (low birth weight and birth by caesarean section), while controlling for other risk factors, was studied. Specifically the associations among measured risk factors within each dataset were examined and the exposure-outcome estimates compared in terms of relative ORs. The associations of educational level with the other risk factors (alcohol consumption, folic acid intake, maternal age, pregnancy weight gain, previous miscarriages) partly differed between PBR and NINFEA. This was not observed for parity. Overall, the exposure-outcome estimates derived from NINFEA only differed moderately from those obtained in PBR, with relative ORs ranging between 0.74 and 1.03. Sample selection in cohort studies may alter the confounding patterns originally present in the general population. However, this does not necessarily introduce selection bias in the exposure-outcome estimates, as sample selection may reduce some of the residual confounding present in the general population.

  20. Detection rates of geckos in visual surveys: Turning confounding variables into useful knowledge

    USGS Publications Warehouse

    Lardner, Bjorn; Rodda, Gordon H.; Yackel Adams, Amy A.; Savidge, Julie A.; Reed, Robert N.

    2016-01-01

    Transect surveys without some means of estimating detection probabilities generate population size indices prone to bias because survey conditions differ in time and space. Knowing what causes such bias can help guide the collection of relevant survey covariates, correct the survey data, anticipate situations where bias might be unacceptably large, and elucidate the ecology of target species. We used negative binomial regression to evaluate confounding variables for gecko (primarily Hemidactylus frenatus and Lepidodactylus lugubris) counts on 220-m-long transects surveyed at night, primarily for snakes, on 9,475 occasions. Searchers differed in gecko detection rates by up to a factor of six. The worst and best headlamps differed by a factor of at least two. Strong winds had a negative effect potentially as large as those of searchers or headlamps. More geckos were seen during wet weather conditions, but the effect size was small. Compared with a detection nadir during waxing gibbous (nearly full) moons above the horizon, we saw 28% more geckos during waning crescent moons below the horizon. A sine function suggested that we saw 24% more geckos at the end of the wet season than at the end of the dry season. Fluctuations on a longer timescale also were verified. Disturbingly, corrected data exhibited strong short-term fluctuations that covariates apparently failed to capture. Although some biases can be addressed with measured covariates, others will be difficult to eliminate as a significant source of error in longterm monitoring programs.

  1. Reactive aggression and peer victimization from pre-kindergarten to first grade: accounting for hyperactivity and teacher-child conflict.

    PubMed

    Runions, Kevin C

    2014-12-01

    The role of reactive aggression in the development of peer victimization remains unclear due in part to a failure to account for confounding problems of behavioural undercontrol (e.g., hyperactivity). As well, the school social context has rarely been examined to see whether these risks are mediated by relationships with teachers. This study tests the prospective relations between reactive aggression, hyperactivity, victimization, and teacher-child (T-C) relationship, to determine whether conflict mediates the relationships between externalizing problems and victimization. A sample of 1,114 Australian students were followed from pre-kindergarten through first grade. Cross-lagged path analyses were conducted, with comparison of gender-moderating models and autocorrelation models. Full-information maximum likelihood was deployed to account for missingness. Best fitting models found that the relationship of early externalizing problems to later victimization was mediated by T-C conflict. No evidence of victimization increasing externalizing problems nor gender differences were observed. T-C conflict in kindergarten predicted subsequent increases in victimization, reactive aggression, and hyperactivity. Understanding the processes whereby externalizing problems confer risk of victimization involves understanding the whole social context of classrooms, including relationships with teachers. Finer-grained research is needed to better understand how peer dynamics may be influenced by observation of T-C relationships. Pre-service teacher education needs to ensure a focus on the potential social impact of teacher's relationships with students. © 2014 The British Psychological Society.

  2. Is the Relation Between Ozone and Mortality Confounded by Chemical Components of Particulate Matter? Analysis of 7 Components in 57 US Communities

    PubMed Central

    Anderson, G. Brooke; Krall, Jenna R.; Peng, Roger D.; Bell, Michelle L.

    2012-01-01

    Epidemiologic studies have linked tropospheric ozone pollution and human mortality. Although research has shown that this relation is not confounded by particulate matter when measured by mass, little scientific evidence exists on whether confounding exists by chemical components of the particle mixture. Using mortality and particulate matter with aerodynamic diameter ≤2.5 µm (PM2.5) component data from 57 US communities (2000–2005), the authors investigate whether the ozone-mortality relation is confounded by 7 components of PM2.5: sulfate, nitrate, silicon, elemental carbon, organic carbon matter, sodium ion, and ammonium. Together, these components constitute most PM2.5 mass in the United States. Estimates of the effect of ozone on mortality were almost identical before and after controlling for the 7 components of PM2.5 considered (mortality increase/10-ppb ozone increase, before and after controlling: ammonium, 0.34% vs. 0.35%; elemental carbon, 0.36% vs. 0.37%; nitrate, 0.27% vs. 0.26%; organic carbon matter, 0.34% vs. 0.31%; silicon, 0.36% vs. 0.37%; sodium ion, 0.21% vs. 0.18%; and sulfate, 0.35% vs. 0.38%). Additionally, correlations were weak between ozone and each particulate component across all communities. Previous research found that the ozone-mortality relation is not confounded by particulate matter measured by mass; this national study indicates that the relation is also robust to control for specific components of PM2.5. PMID:23043133

  3. Determining Confounding Sensitivities In Eddy Current Thin Film Measurements

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gros, Ethan; Udpa, Lalita; Smith, James A.

    Determining Confounding Sensitivities In Eddy Current Thin Film Measurements Ethan Gros, Lalita Udpa, Electrical Engineering, Michigan State University, East Lansing MI 48824 James A. Smith, Experiment Analysis, Idaho National Laboratory, Idaho Falls ID 83415 Eddy current (EC) techniques are widely used in industry to measure the thickness of non-conductive films on a metal substrate. This is done using a system whereby a coil carrying a high-frequency alternating current is used to create an alternating magnetic field at the surface of the instrument's probe. When the probe is brought near a conductive surface, the alternating magnetic field will induce ECs inmore » the conductor. The substrate characteristics and the distance of the probe from the substrate (the coating thickness) affect the magnitude of the ECs. The induced currents load the probe coil affecting the terminal impedance of the coil. The measured probe impedance is related to the lift off between coil and conductor as well as conductivity of the test sample. For a known conductivity sample, the probe impedance can be converted into an equivalent film thickness value. The EC measurement can be confounded by a number of measurement parameters. It is the goal of this research to determine which physical properties of the measurement set-up and sample can adversely affect the thickness measurement. The eddy current testing is performed using a commercially available, hand held eddy current probe (ETA3.3H spring loaded eddy probe running at 8 MHz) that comes with a stand to hold the probe. The stand holds the probe and adjusts the probe on the z-axis to help position the probe in the correct area as well as make precise measurements. The signal from the probe is sent to a hand held readout, where the results are recorded directly in terms of liftoff or film thickness. Understanding the effect of certain factors on the measurements of film thickness, will help to evaluate how accurate the ETA3.3H

  4. Depression and Physical Inactivity as Confounding the Effect of Obesity on Atrial Fibrillation.

    PubMed

    Garimella, Roja S; Sears, Samuel F; Gehi, Anil K

    2016-06-01

    Obesity is associated with an increased likelihood for the development of atrial fibrillation (AF) and with worsened AF symptom severity. However, other factors that are correlated with obesity may confound or mediate the relation of obesity with AF symptom severity. The purpose of this study was to determine if depression and physical inactivity may confound the association of obesity and AF symptom severity. Health status and demographic data were captured by questionnaire for 332 outpatients with documented AF. Weight/height was measured and body mass index (kg/m(2)) calculated. Recent depression symptom severity was assessed using the Patient Health Questionnaire-9 questionnaire. Physical activity during the last month was assessed by questionnaire. AF symptom severity was assessed using the University of Toronto AF Severity scale. Multivariate linear regression was used to evaluate which factors were associated with AF symptom severity. Obesity in patients with AF is associated with increased depression severity. In bivariate analysis, increasing body mass index (p = 0.001), lower levels of physical activity (p <0.001), and more severe depression (p <0.001) were associated with worsened AF symptom severity. In multivariate analysis, only physical activity and depression persisted as significant predictors of AF symptom severity. In conclusion, although obesity likely contributes to the substrate predisposing to the development of AF, other factors may contribute to or mediate the worsened AF symptoms associated with obesity. Depression symptoms and physical inactivity, factors closely correlated with obesity, may exacerbate symptoms in patients with AF. Copyright © 2016 Elsevier Inc. All rights reserved.

  5. A Bayesian Framework to Account for Complex Non-Genetic Factors in Gene Expression Levels Greatly Increases Power in eQTL Studies

    PubMed Central

    Durbin, Richard; Winn, John

    2010-01-01

    Gene expression measurements are influenced by a wide range of factors, such as the state of the cell, experimental conditions and variants in the sequence of regulatory regions. To understand the effect of a variable of interest, such as the genotype of a locus, it is important to account for variation that is due to confounding causes. Here, we present VBQTL, a probabilistic approach for mapping expression quantitative trait loci (eQTLs) that jointly models contributions from genotype as well as known and hidden confounding factors. VBQTL is implemented within an efficient and flexible inference framework, making it fast and tractable on large-scale problems. We compare the performance of VBQTL with alternative methods for dealing with confounding variability on eQTL mapping datasets from simulations, yeast, mouse, and human. Employing Bayesian complexity control and joint modelling is shown to result in more precise estimates of the contribution of different confounding factors resulting in additional associations to measured transcript levels compared to alternative approaches. We present a threefold larger collection of cis eQTLs than previously found in a whole-genome eQTL scan of an outbred human population. Altogether, 27% of the tested probes show a significant genetic association in cis, and we validate that the additional eQTLs are likely to be real by replicating them in different sets of individuals. Our method is the next step in the analysis of high-dimensional phenotype data, and its application has revealed insights into genetic regulation of gene expression by demonstrating more abundant cis-acting eQTLs in human than previously shown. Our software is freely available online at http://www.sanger.ac.uk/resources/software/peer/. PMID:20463871

  6. The relationship between type D personality and chronic heart failure is not confounded by disease severity as assessed by BNP.

    PubMed

    Pelle, Aline J; van den Broek, Krista C; Szabó, Balázs; Kupper, Nina

    2010-11-05

    Psychological factors, like Type D personality (i.e., the tendency to experience negative emotions and to inhibit emotional distress) have been linked to impaired health outcomes. Criticism on the role of psychological factors in cardiac disease has postulated that such constructs may be confounded by disease severity. Hence, we examined whether Type D personality is associated with brain natriuretic peptide (BNP), a sensitive marker of disease severity in chronic heart failure (CHF), in 202 consecutive CHF outpatients. No differences in logBNP levels were found between Type D and non-Type D patients (t(200) = -1.03, p = .30). After adjusting for demographic and clinical confounders, Type D personality remained unassociated with logBNP levels (β=.04, p = .55), whereas older age (β = .27, p<.001), being prescribed beta-blockers (β = .15, p = .02), lower left ventricular ejection fraction (β = -.38, p<.0001), and kidney dysfunction (β = .17, p = .01) were associated with higher logBNP. To conclude, Type D personality was not associated with BNP in CHF outpatients, whereas clinical variables were associated with BNP. These findings oppose the suggestion that Type D personality is confounded by indicators of disease severity. Copyright © 2009 Elsevier Ireland Ltd. All rights reserved.

  7. Factors confounding impedance catheter volume measurements in vitro.

    PubMed

    Bielefeld, M R; Cabreriza, S E; Spotnitz, H M

    1993-06-01

    The impedance catheter allows continuous measurement of ventricular volume. External influences have been described as causing parallel shifts in impedance-measured volumes; however, factors affecting impedance measurements in a nonparallel manner have not been fully characterized. Accordingly, an impedance catheter was placed inside a latex balloon into which known volumes of normal saline solution were injected. Conductive and nonconductive materials were individually placed within the balloon. Impedance was measured with materials touching (T) or not touching (NT) the catheter. Impedance-measured volumes were plotted versus actual volumes. Compared with the line of identity (LID), a statistical difference (p < 0.05) was found in the slopes in the presence of metallic objects only. These included a pacing lead (T, NT) (mT = 1.32m mNT = 1.29 versus mLID = 1.00), titanium (T) (mT = 1.68 versus mLID = 1.00), and aluminum (NT) (mNT = 0.72 versus mLID = 1.00). These changes in slope indicate nonparallel effects on impedance that confound the ability of the impedance catheter to determine volumes in vitro. These observations imply that serial calibration of both the slope constant (alpha) and the intercept (parallel conductance) of impedance may be necessary for in vivo measurements of ventricular volume based on impedance in the presence of metallic objects.

  8. Accounting Issues: An Essay Series Part VII--Liabilities

    ERIC Educational Resources Information Center

    Laux, Judy

    2008-01-01

    This article, the seventh in the series, presents accounting for liabilities along with some related conceptual and measurement issues. Additional coverage is devoted to potential ethical dilemmas and both theoretical and empirical literature related to this set of accounting elements.

  9. Offspring ADHD as a risk factor for parental marital problems: controls for genetic and environmental confounds.

    PubMed

    Schermerhorn, Alice C; D'Onofrio, Brian M; Slutske, Wendy S; Emery, Robert E; Turkheimer, Eric; Harden, K Paige; Heath, Andrew C; Martin, Nicholas G

    2012-12-01

    Previous studies have found that child attention-deficit/hyperactivity disorder (ADHD) is associated with more parental marital problems. However, the reasons for this association are unclear. The association might be due to genetic or environmental confounds that contribute to both marital problems and ADHD. Data were drawn from the Australian Twin Registry, including 1,296 individual twins, their spouses, and offspring. We studied adult twins who were discordant for offspring ADHD.Using a discordant twin pairs design, we examined the extent to which genetic and environmental confounds,as well as measured parental and offspring characteristics, explain the ADHD-marital problems association. Offspring ADHD predicted parental divorce and marital conflict. The associations were also robust when comparing differentially exposed identical twins to control for unmeasured genetic and environmental factors, when controlling for measured maternal and paternal psychopathology,when restricting the sample based on timing of parental divorce and ADHD onset, and when controlling for other forms of offspring psychopathology. Each of these controls rules out alternative explanations for the association. The results of the current study converge with those of prior research in suggesting that factors directly associated with offspring ADHD increase parental marital problems.

  10. Offspring ADHD as a Risk Factor for Parental Marital Problems: Controls for Genetic and Environmental Confounds

    PubMed Central

    Schermerhorn, Alice C.; D’Onofrio, Brian M.; Slutske, Wendy S.; Emery, Robert E.; Turkheimer, Eric; Harden, K. Paige; Heath, Andrew C.; Martin, Nicholas G.

    2013-01-01

    Background Previous studies have found that child attention-deficit/hyperactivity disorder (ADHD) is associated with more parental marital problems. The reasons for this association are unclear, however. The association might be due to genetic or environmental confounds that contribute to both marital problems and ADHD. Method Data were drawn from the Australian Twin Registry, including 1296 individual twins, their spouses, and offspring. We studied adult twins who were discordant for offspring ADHD. Using a discordant twin pairs design, we examined the extent to which genetic and environmental confounds, as well as measured parental and offspring characteristics, explain the ADHD-marital problems association. Results Offspring ADHD predicted parental divorce and marital conflict. The associations were also robust when comparing differentially exposed identical twins to control for unmeasured genetic and environmental factors, when controlling for measured maternal and paternal psychopathology, when restricting the sample based on timing of parental divorce and ADHD onset, and when controlling for other forms of offspring psychopathology. Each of these controls rules out alternative explanations for the association. Conclusion The results of the current study converge with those of prior research in suggesting that factors directly associated with offspring ADHD increase parental marital problems. PMID:22958575

  11. Analysis of Longitudinal Studies With Repeated Outcome Measures: Adjusting for Time-Dependent Confounding Using Conventional Methods.

    PubMed

    Keogh, Ruth H; Daniel, Rhian M; VanderWeele, Tyler J; Vansteelandt, Stijn

    2018-05-01

    Estimation of causal effects of time-varying exposures using longitudinal data is a common problem in epidemiology. When there are time-varying confounders, which may include past outcomes, affected by prior exposure, standard regression methods can lead to bias. Methods such as inverse probability weighted estimation of marginal structural models have been developed to address this problem. However, in this paper we show how standard regression methods can be used, even in the presence of time-dependent confounding, to estimate the total effect of an exposure on a subsequent outcome by controlling appropriately for prior exposures, outcomes, and time-varying covariates. We refer to the resulting estimation approach as sequential conditional mean models (SCMMs), which can be fitted using generalized estimating equations. We outline this approach and describe how including propensity score adjustment is advantageous. We compare the causal effects being estimated using SCMMs and marginal structural models, and we compare the two approaches using simulations. SCMMs enable more precise inferences, with greater robustness against model misspecification via propensity score adjustment, and easily accommodate continuous exposures and interactions. A new test for direct effects of past exposures on a subsequent outcome is described.

  12. Diagnostic confounders of chronic widespread pain: not always fibromyalgia

    PubMed Central

    Häuser, Winfried; Perrot, Serge; Sommer, Claudia; Shir, Yoram; Fitzcharles, Mary-Ann

    2017-01-01

    Abstract Introduction: Chronic widespread pain (CWP) is the defining feature of fibromyalgia (FM), a worldwide prevalent condition. Chronic widespread pain is, however, not pathognomonic of FM, and other conditions may present similarly with CWP, requiring consideration of a differential diagnosis. Objectives: To conduct a literature search to identify medical conditions that may mimic FM and have highlighted features that may differentiate these various conditions from FM. Methods: A comprehensive literature search from 1990 through September 2016 was conducted to identify conditions characterized by CWP. Results: Conditions that may mimic FM may be categorized as musculoskeletal, neurological, endocrine/metabolic, psychiatric/psychological, and medication related. Characteristics pertaining to the most commonly identified confounding diagnoses within each category are discussed; clues to enable clinical differentiation from FM are presented; and steps towards a diagnostic algorithm for mimicking conditions are presented. Conclusion: Although the most likely reason for a complaint of CWP is FM, this pain complaint can be a harbinger of illness other than FM, prompting consideration of a differential diagnosis. This review should sensitize physicians to a broad spectrum of conditions that can mimic FM. PMID:29392213

  13. The contribution of fetal drug exposure to temperament: potential teratogenic effects on neuropsychiatric risk.

    PubMed

    Weiss, Sandra J; St Jonn-Seed, Mary; Harris-Muchell, Carolyn

    2007-08-01

    Preliminary evidence indicates that fetal drug exposure may be associated with alterations in temperament. However, studies often do not dissociate the potential effects of drug exposure from other perinatal or environmental factors that could influence temperament phenotypes. High risk children (n = 120) were followed from birth to 6 months of age to determine the effects of fetal drug exposure on temperament, after controlling for the child's gender, gestational age, medical morbidity, ethnicity, and maltreatment as well as the mother's stress, income adequacy, and quality of caregiving. Methods included medical chart review, questionnaires, and videotapes of mother-child interaction. Preliminary analyses indicated that fetal drug exposure was associated with both distractibility and intensity of children's responses to the environment at 6 months of age. After adjusting for potentially confounding variables, drug exposure accounted for 12% of the variance in distractibility but was not a significant predictor in the regression model for intensity. Findings suggest that drug-exposed children may experience difficulty sustaining their focus of attention and be more easily distracted by environmental stimuli than non-drug-exposed children. Results converge with previous research to implicate cortical hyperarousal, stemming from teratogenic effects on the dopaminergic system during fetal development.

  14. Muscle thickness measurements of the lower trapezius with rehabilitative ultrasound imaging are confounded by scapular dyskinesis.

    PubMed

    Seitz, Amee L; Baxter, Caralyn J; Benya, Kristen

    2015-08-01

    Alterations in scapular muscle activity have been theorized to contribute to abnormal scapular motion and shoulder pain, but pose challenges to quantify in the clinic. Rehabilitative Ultrasound Imaging (RUSI) has proved useful identifying dysfunction of lumbar regional stabilizing muscle activity, specifically contractile behavior. Although, recent examinations of scapular stabilizing trapezius muscle function using RUSI did not detect alterations individuals with shoulder pain or differences in muscle thickness between varying external loads in asymptomatic individuals, a potential confounder to prior results, scapular dyskinesis has not been controlled. It is unknown if dyskinesis alters scapular muscle thickness during activation measured with RUSI. Thus, the purpose of this study was to compare change in scapular muscle thickness between individuals with and without scapular dyskinesis. Thirty-nine asymptomatic adults with (n = 19) and without (n = 20) scapular dyskinesis, defined with a reliable and validated method, participated. Two separate ultrasound images of the serratus anterior (SA) and lower trapezius (LT) were captured under two randomized conditions, rest and isometric contraction against gravity, and saved for blinded measurement. Change in thickness with contraction was calculated and expressed as a percentage. The dyskinesis group demonstrated a greater increase (p = 0.005) in LT thickness with the isometric contraction than the group without (mean difference = 31.6%; 95%CI = 10.3, 53.0). No differences in SA or resting thickness of either muscle were found between groups. The presence of scapular dyskinesis alters thickness changes of the lower trapezius during activation. Furthermore, potential underlying reasons beyond muscle contractile behavior must be considered. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. On Estimation of the Survivor Average Causal Effect in Observational Studies when Important Confounders are Missing Due to Death

    PubMed Central

    Egleston, Brian L.; Scharfstein, Daniel O.; MacKenzie, Ellen

    2008-01-01

    We focus on estimation of the causal effect of treatment on the functional status of individuals at a fixed point in time t* after they have experienced a catastrophic event, from observational data with the following features: (1) treatment is imposed shortly after the event and is non-randomized, (2) individuals who survive to t* are scheduled to be interviewed, (3) there is interview non-response, (4) individuals who die prior to t* are missing information on pre-event confounders, (5) medical records are abstracted on all individuals to obtain information on post-event, pre-treatment confounding factors. To address the issue of survivor bias, we seek to estimate the survivor average causal effect (SACE), the effect of treatment on functional status among the cohort of individuals who would survive to t* regardless of whether or not assigned to treatment. To estimate this effect from observational data, we need to impose untestable assumptions, which depend on the collection of all confounding factors. Since pre-event information is missing on those who die prior to t*, it is unlikely that these data are missing at random (MAR). We introduce a sensitivity analysis methodology to evaluate the robustness of SACE inferences to deviations from the MAR assumption. We apply our methodology to the evaluation of the effect of trauma center care on vitality outcomes using data from the National Study on Costs and Outcomes of Trauma Care. PMID:18759833

  16. Cascaded discrimination of normal, abnormal, and confounder classes in histopathology: Gleason grading of prostate cancer

    PubMed Central

    2012-01-01

    Background Automated classification of histopathology involves identification of multiple classes, including benign, cancerous, and confounder categories. The confounder tissue classes can often mimic and share attributes with both the diseased and normal tissue classes, and can be particularly difficult to identify, both manually and by automated classifiers. In the case of prostate cancer, they may be several confounding tissue types present in a biopsy sample, posing as major sources of diagnostic error for pathologists. Two common multi-class approaches are one-shot classification (OSC), where all classes are identified simultaneously, and one-versus-all (OVA), where a “target” class is distinguished from all “non-target” classes. OSC is typically unable to handle discrimination of classes of varying similarity (e.g. with images of prostate atrophy and high grade cancer), while OVA forces several heterogeneous classes into a single “non-target” class. In this work, we present a cascaded (CAS) approach to classifying prostate biopsy tissue samples, where images from different classes are grouped to maximize intra-group homogeneity while maximizing inter-group heterogeneity. Results We apply the CAS approach to categorize 2000 tissue samples taken from 214 patient studies into seven classes: epithelium, stroma, atrophy, prostatic intraepithelial neoplasia (PIN), and prostate cancer Gleason grades 3, 4, and 5. A series of increasingly granular binary classifiers are used to split the different tissue classes until the images have been categorized into a single unique class. Our automatically-extracted image feature set includes architectural features based on location of the nuclei within the tissue sample as well as texture features extracted on a per-pixel level. The CAS strategy yields a positive predictive value (PPV) of 0.86 in classifying the 2000 tissue images into one of 7 classes, compared with the OVA (0.77 PPV) and OSC approaches (0.76 PPV

  17. Applying new AICPA accounting rules on special reports.

    PubMed

    Reinstein, A; Dery, R J

    1998-04-01

    Two new standards on agreed-upon procedures, issued by the American Institute of Certified Public Accountants, provide healthcare organizations and associated decision makers with new flexibility in acquiring professional accounting services. Effective January 1, 1996, these procedures allow organizations to target the type and volume of services performed by accountants and potentially avoid the time and expense involved in completing a full financial statement audit. As with any other accounting engagement, both the healthcare organization and the accounting firm need to establish what procedures will be conducted, who will be allowed to use the resulting report, and how the procedures will be conducted.

  18. Familial confounding of the association between maternal smoking during pregnancy and offspring substance use and problems.

    PubMed

    D'Onofrio, Brian M; Rickert, Martin E; Langström, Niklas; Donahue, Kelly L; Coyne, Claire A; Larsson, Henrik; Ellingson, Jarrod M; Van Hulle, Carol A; Iliadou, Anastasia N; Rathouz, Paul J; Lahey, Benjamin B; Lichtenstein, Paul

    2012-11-01

    Previous epidemiological, animal, and human cognitive neuroscience research suggests that maternal smoking during pregnancy (SDP) causes increased risk of substance use/problems in offspring. To determine the extent to which the association between SDP and offspring substance use/problems depends on confounded familial background factors by using a quasi-experimental design. We used 2 separate samples from the United States and Sweden. The analyses prospectively predicted multiple indices of substance use and problems while controlling for statistical covariates and comparing differentially exposed siblings to minimize confounding. Offspring of a representative sample of women in the United States (sample 1) and the total Swedish population born during the period from January 1, 1983, to December 31, 1995 (sample 2). Adolescent offspring of the women in the National Longitudinal Survey of Youth 1979 (n = 6904) and all offspring born in Sweden during the 13-year period (n = 1,187,360). Self-reported adolescent alcohol, cigarette, and marijuana use and early onset (before 14 years of age) of each substance (sample 1) and substance-related convictions and hospitalizations for an alcohol- or other drug-related problem (sample 2). The same pattern emerged for each index of substance use/problems across the 2 samples. At the population level, maternal SDP predicted every measure of offspring substance use/problems in both samples, ranging from adolescent alcohol use (hazard ratio [HR](moderate), 1.32 [95% CI, 1.22-1.43]; HR(high), 1.33 [1.17-1.53]) to a narcotics-related conviction (HR(moderate), 2.23 [2.14-2.31]; HR(high), 2.97 [2.86-3.09]). When comparing differentially exposed siblings to minimize genetic and environmental confounds, however, the association between SDP and each measure of substance use/problems was minimal and not statistically significant. The association between maternal SDP and offspring substance use/problems is likely due to familial background

  19. Efficient and accurate causal inference with hidden confounders from genome-transcriptome variation data

    PubMed Central

    2017-01-01

    Mapping gene expression as a quantitative trait using whole genome-sequencing and transcriptome analysis allows to discover the functional consequences of genetic variation. We developed a novel method and ultra-fast software Findr for higly accurate causal inference between gene expression traits using cis-regulatory DNA variations as causal anchors, which improves current methods by taking into consideration hidden confounders and weak regulations. Findr outperformed existing methods on the DREAM5 Systems Genetics challenge and on the prediction of microRNA and transcription factor targets in human lymphoblastoid cells, while being nearly a million times faster. Findr is publicly available at https://github.com/lingfeiwang/findr. PMID:28821014

  20. Do patient and practice characteristics confound age-group differences in preferences for general practice care? A quantitative study

    PubMed Central

    2013-01-01

    Background Previous research showed inconsistent results regarding the relationship between the age of patients and preference statements regarding GP care. This study investigates whether elderly patients have different preference scores and ranking orders concerning 58 preference statements for GP care than younger patients. Moreover, this study examines whether patient characteristics and practice location may confound the relationship between age and the categorisation of a preference score as very important. Methods Data of the Consumer Quality Index GP Care were used, which were collected in 32 general practices in the Netherlands. The rank order and preference score were calculated for 58 preference statements for four age groups (0–30, 31–50, 51–74, 75 years and older). Using chi-square tests and logistic regression analyses, it was investigated whether a significant relationship between age and preference score was confounded by patient characteristics and practice location. Results Elderly patients did not have a significant different ranking order for the preference statements than the other three age groups (r = 0.0193; p = 0.41). However, in 53% of the statements significant differences were found in preference score between the four age groups. Elderly patients categorized significantly less preference statements as ‘very important’. In most cases, the significant relationships were not confounded by gender, education, perceived health, the number of GP contacts and location of the GP practice. Conclusion The preferences of elderly patients for GP care concern the same items as younger patients. However, their preferences are less strong, which cannot be ascribed to gender, education, perceived health, the number of GP contacts and practice location. PMID:23800156

  1. Beyond total treatment effects in randomised controlled trials: Baseline measurement of intermediate outcomes needed to reduce confounding in mediation investigations.

    PubMed

    Landau, Sabine; Emsley, Richard; Dunn, Graham

    2018-06-01

    the three processes involving baseline measures of intermediate or clinical outcomes is operating. Necessary assumptions for the change score approach (B) to provide unbiased estimates under either process include the independence of baseline measures and change scores of the intermediate variable. Finally, estimates provided by the analysis of covariance approach (C) were found to be unbiased under all the three processes considered here. When applied to the example, there was evidence of mediation under all methods but the estimate of the indirect effect depended on the approach used with the proportion mediated varying from 57% to 86%. Trialists planning mediation analyses should measure baseline values of putative mediators as well as of continuous clinical outcomes. An analysis of covariance approach is recommended to avoid potential biases due to confounding processes involving baseline measures of intermediate or clinical outcomes, and not simply for increased precision.

  2. Biasogram: Visualization of Confounding Technical Bias in Gene Expression Data

    PubMed Central

    Krzystanek, Marcin; Szallasi, Zoltan; Eklund, Aron C.

    2013-01-01

    Gene expression profiles of clinical cohorts can be used to identify genes that are correlated with a clinical variable of interest such as patient outcome or response to a particular drug. However, expression measurements are susceptible to technical bias caused by variation in extraneous factors such as RNA quality and array hybridization conditions. If such technical bias is correlated with the clinical variable of interest, the likelihood of identifying false positive genes is increased. Here we describe a method to visualize an expression matrix as a projection of all genes onto a plane defined by a clinical variable and a technical nuisance variable. The resulting plot indicates the extent to which each gene is correlated with the clinical variable or the technical variable. We demonstrate this method by applying it to three clinical trial microarray data sets, one of which identified genes that may have been driven by a confounding technical variable. This approach can be used as a quality control step to identify data sets that are likely to yield false positive results. PMID:23613961

  3. Do digestive contents confound body mass as a measure of relative condition in nestling songbirds?

    USGS Publications Warehouse

    Streby, Henry M.; Peterson, Sean M.; Lehman, Justin A.; Kramer, Gunnar R.; Vernasco, Ben J.; Andersen, David E.

    2014-01-01

    Relative nestling condition, typically measured as nestling mass or as an index including nestling mass, is commonly purported to correlate with fledgling songbird survival. However, most studies directly investigating fledgling survival have found no such relationship. We weighed feces and stomach contents of nestling golden-winged warblers (Vermivora chrysoptera) to investigate the potential contribution of variation in digestive contents to differences in nestling mass. We estimated that the mass of a seventh-day (near fledging) nestling golden-winged warbler varies by 0.65 g (approx. 9% of mean nestling mass) depending on the contents of the nestling's digestive system at the time of weighing, and that digestive contents are dissimilar among nestlings at any moment the brood is removed from the nest for weighing. Our conservative estimate of within-individual variation in digestive contents equals 72% and 24% of the mean within-brood and population-wide range in nestling mass, respectively. Based on our results, a substantive but typically unknown amount of the variation in body mass among nestlings is confounded by differences in digestive contents. We conclude that short-term variation in digestive contents likely precludes the use of body mass, and therefore any mass-dependent index, as a measure of relative nestling condition or as a predictor of survival in golden-winged warblers and likely in many other songbirds of similar size.

  4. Meta-analysis of lung cancer in asphalt roofing and paving workers with external adjustment for confounding by coal tar

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fayerweather, W.E.

    2007-07-01

    The study's objectives were to update Partanen's and Boffetta's 1994 meta-analysis of lung cancer among roofing and paving asphalt workers and explore the role of coal tar in explaining the statistical heterogeneity among these studies. Information retrieval strategies and eligibility criteria were defined for identifying the epidemiologic studies to be included in the analysis. The relative risk ratio (RR) for lung cancer was selected as the effect measure of interest. Coal tar bias factors were developed and used to externally adjust each eligible study's published RR for confounding by coal tar. The meta-Relative Risk (meta-RR) and its variance were estimatedmore » by general variance-based methods. Heterogeneity of the RRs was assessed by heterogeneity chi-square and I{sup 2} tests. The results from this update were similar to those in Partanen's and Boffetta's original meta-analysis. Although the meta-RRs for the roofers and the pavers were no longer statistically significantly different from one another, significant heterogeneity remained within each of the coal tar-adjusted sectors. Meta-analysis of non-experimental epidemiologic studies is subject to significant uncertainties as is externally correcting studies for confounding. Given these uncertainties, the specific quantitative estimates in this (or any similar) analysis must be viewed with caution. Nevertheless, this analysis provides support for the hypothesis proposed by several major reviewers that confounding by coal tar-related PAH exposures may explain most or all of the lung cancer risks found in the epidemiologic literature on asphalt roofing and paving workers.« less

  5. Fresh fruit intake and asthma symptoms in young British adults: confounding or effect modification by smoking?

    PubMed

    Butland, B K; Strachan, D P; Anderson, H R

    1999-04-01

    Antioxidant vitamins have been postulated as a protective factor in asthma. The associations between the frequency of fresh fruit consumption in summer, and the prevalence of self-reported asthma symptoms were investigated. The analysis was based on 5,582 males and 5,770 females, born in England, Wales and Scotland between March 3-9, 1958 and aged 33 yrs at the time of survey. The 12-month period prevalence of wheeze and frequent wheeze were inversely associated with frequent intakes of fresh fruit and salad/raw vegetables and positively associated with smoking and lower social class. After adjustment for mutual confounding and sex, associations with smoking persisted, but those with social class and salad/raw vegetable consumption lost significance. The frequency of fresh fruit intake was no longer associated with wheeze after adjustment, but was inversely associated with frequent wheeze and speech-limiting attacks. The association with frequent wheeze differed significantly between smoking groups (never, former, current) and appeared to be confined to exsmokers and current smokers. These findings support postulated associations between infrequent fresh fruit consumption and the prevalence of frequent or severe asthma symptoms in adults. Associations appeared to be restricted to smokers, with effect modification as a more likely explanation of this pattern than residual confounding by smoking.

  6. Corticospinal activation confounds cerebellar effects of posterior fossa stimuli.

    PubMed

    Fisher, Karen M; Lai, H Ming; Baker, Mark R; Baker, Stuart N

    2009-12-01

    To investigate the efficacy of magnetic stimulation over the posterior fossa (PF) as a non-invasive assessment of cerebellar function in man. We replicated a previously reported conditioning-test paradigm in 11 healthy subjects. Transcranial magnetic stimulation (TMS) at varying intensities was applied to the PF and motor cortex with a 3, 5 or 7 ms interstimulus interval (ISI), chosen randomly for each trial. Surface electromyogram (EMG) activity was recorded from two intrinsic hand muscles and two forearm muscles. Responses were averaged and rectified, and MEP amplitudes were compared to assess whether suppression of the motor output occurred as a result of the PF conditioning pulse. Cortical MEPs were suppressed following conditioning-test ISIs of 5 or 7 ms. No suppression occurred with an ISI of 3 ms. PF stimuli alone also produced EMG responses, suggesting direct activation of the corticospinal tract (CST). CST collaterals are known to contact cortical inhibitory interneurones; antidromic CST activation could therefore contribute to the observed suppression of cortical MEPs. PF stimulation probably activates multiple pathways; even at low intensities it should not be regarded as a selective assessment of cerebellar function unless stringent controls can confirm the absence of confounding activity in other pathways.

  7. Implications of NCLB Accountability for Comprehensive School Reform

    ERIC Educational Resources Information Center

    Le Floch, Kerstin Carlson; Taylor, James E.; Thomsen, Kerri

    2006-01-01

    No Child Left Behind (NCLB) accountability mechanisms have the potential to derail comprehensive school reform (CSR) implementation. For those pursuing CSR, the question is how to reconcile the implementation of NCLB accountability mandates with ongoing CSR efforts. Drawing from longitudinal data from a national study of CSR, this article explores…

  8. Interpretational Confounding Is Due to Misspecification, Not to Type of Indicator: Comment on Howell, Breivik, and Wilcox (2007)

    ERIC Educational Resources Information Center

    Bollen, Kenneth A.

    2007-01-01

    R. D. Howell, E. Breivik, and J. B. Wilcox (2007) have argued that causal (formative) indicators are inherently subject to interpretational confounding. That is, they have argued that using causal (formative) indicators leads the empirical meaning of a latent variable to be other than that assigned to it by a researcher. Their critique of causal…

  9. Correlations between cannabis use and IQ change in the Dunedin cohort are consistent with confounding from socioeconomic status

    PubMed Central

    Rogeberg, Ole

    2013-01-01

    Does cannabis use have substantial and permanent effects on neuropsychological functioning? Renewed and intense attention to the issue has followed recent research on the Dunedin cohort, which found a positive association between, on the one hand, adolescent-onset cannabis use and dependence and, on the other hand, a decline in IQ from childhood to adulthood [Meier et al. (2012) Proc Natl Acad Sci USA 109(40):E2657–E2664]. The association is given a causal interpretation by the authors, but existing research suggests an alternative confounding model based on time-varying effects of socioeconomic status on IQ. A simulation of the confounding model reproduces the reported associations from the Dunedin cohort, suggesting that the causal effects estimated in Meier et al. are likely to be overestimates, and that the true effect could be zero. Further analyses of the Dunedin cohort are proposed to distinguish between the competing interpretations. Although it would be too strong to say that the results have been discredited, the methodology is flawed and the causal inference drawn from the results premature. PMID:23319626

  10. Holding Accountability Models Accountable

    ERIC Educational Resources Information Center

    Pyatte, Jeff A.

    1974-01-01

    This article provides an accurate account of the history of the Texarkana Project, the first attempt to demonstrate accountability in education by using the engineering model. Using the average per pupil expenditure as a basis for comparison, the cost of engineering in Texarkana is shown to be very high. (Author)

  11. Trade-based carbon sequestration accounting.

    PubMed

    King, Dennis M

    2004-04-01

    This article describes and illustrates an accounting method to assess and compare "early" carbon sequestration investments and trades on the basis of the number of standardized CO2 emission offset credits they will provide. The "gold standard" for such credits is assumed to be a relatively riskless credit based on a CO2 emission reduction that provides offsets against CO2 emissions on a one-for-one basis. The number of credits associated with carbon sequestration needs to account for time, risk, durability, permanence, additionality, and other factors that future trade regulators will most certainly use to assign "official" credits to sequestration projects. The method that is presented here uses established principles of natural resource accounting and conventional rules of asset valuation to "score" projects. A review of 20 "early" voluntary United States based CO2 offset trades that involve carbon sequestration reveals that the assumptions that buyers, sellers, brokers, and traders are using to characterize the economic potential of their investments and trades vary enormously. The article develops a "universal carbon sequestration credit scoring equation" and uses two of these trades to illustrate the sensitivity of trade outcomes to various assumptions about how future trade auditors are likely to "score" carbon sequestration projects in terms of their "equivalency" with CO2 emission reductions. The article emphasizes the importance of using a standard credit scoring method that accounts for time and risk to assess and compare even unofficial prototype carbon sequestration trades. The scoring method illustrated in this article is a tool that can protect the integrity of carbon sequestration credit trading and can assist buyers and sellers in evaluating the real economic potential of prospective trades.

  12. Teaching Elementary Accounting to Non-Accounting Majors

    ERIC Educational Resources Information Center

    Lloyd, Cynthia B.; Abbey, Augustus

    2009-01-01

    A central recurring theme in business education is the optimal strategy for improving introductory accounting, the gateway subject of business education. For many students, especially non-accounting majors, who are required to take introductory accounting as a requirement of the curriculum, introductory accounting has become a major obstacle for…

  13. Estimating influenza vaccine effectiveness: Evolution of methods to better understand effects of confounding in older adults.

    PubMed

    McElhaney, Janet E; Andrew, Melissa K; McNeil, Shelly A

    2017-11-01

    Older adults are at high risk for serious complications of influenza illness and loss of vaccine-mediated protection. It is increasingly recognized that in addition to age, multiple chronic conditions and associated frailty contribute to the decline in vaccine effectiveness in this population. However, observational studies have been fraught with issues of confounding related to the degree of frailty and functional decline, measures of which are not included in standard administrative health care databases that are used to calculate vaccine effectiveness. This issue has led to the identification of confounding by indication or from "healthy vaccinee" bias, which respectively lead to underestimates or overestimates of influenza vaccine effectiveness. In addition, the sensitivity and specificity of the criteria used to define influenza-like illness declines with increasing age due to atypical presentations of illness and the inability to distinguish between influenza and other respiratory viruses. The test-negative case:control design has emerged as a method to estimate influenza vaccine effectiveness by comparing vaccination rates in those with laboratory-confirmed influenza to those with other acute viral respiratory illnesses. This review provides a perspective on how test-negative case:control study designs and new insights into mechanisms of protection have considerably strengthened influenza vaccination policy decisions for older adults that have historically been undermined by the conclusions of observational studies. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Accounting for GC-content bias reduces systematic errors and batch effects in ChIP-seq data.

    PubMed

    Teng, Mingxiang; Irizarry, Rafael A

    2017-11-01

    The main application of ChIP-seq technology is the detection of genomic regions that bind to a protein of interest. A large part of functional genomics' public catalogs is based on ChIP-seq data. These catalogs rely on peak calling algorithms that infer protein-binding sites by detecting genomic regions associated with more mapped reads (coverage) than expected by chance, as a result of the experimental protocol's lack of perfect specificity. We find that GC-content bias accounts for substantial variability in the observed coverage for ChIP-seq experiments and that this variability leads to false-positive peak calls. More concerning is that the GC effect varies across experiments, with the effect strong enough to result in a substantial number of peaks called differently when different laboratories perform experiments on the same cell line. However, accounting for GC content bias in ChIP-seq is challenging because the binding sites of interest tend to be more common in high GC-content regions, which confounds real biological signals with unwanted variability. To account for this challenge, we introduce a statistical approach that accounts for GC effects on both nonspecific noise and signal induced by the binding site. The method can be used to account for this bias in binding quantification as well to improve existing peak calling algorithms. We use this approach to show a reduction in false-positive peaks as well as improved consistency across laboratories. © 2017 Teng and Irizarry; Published by Cold Spring Harbor Laboratory Press.

  15. Can jurors recognize missing control groups, confounds, and experimenter bias in psychological science?

    PubMed

    McAuliff, Bradley D; Kovera, Margaret Bull; Nunez, Gabriel

    2009-06-01

    This study examined the ability of jury-eligible community members (N = 248) to detect internal validity threats in psychological science presented during a trial. Participants read a case summary in which an expert testified about a study that varied in internal validity (valid, missing control group, confound, and experimenter bias) and ecological validity (high, low). Ratings of expert evidence quality and expert credibility were higher for the valid versus missing control group versions only. Internal validity did not influence verdict or ratings of plaintiff credibility and no differences emerged as a function of ecological validity. Expert evidence quality, expert credibility, and plaintiff credibility were positively correlated with verdict. Implications for the scientific reasoning literature and for trials containing psychological science are discussed.

  16. Accounting Fundamentals for Non-Accountants

    EPA Pesticide Factsheets

    The purpose of this module is to provide an introduction and overview of accounting fundamentals for non-accountants. The module also covers important topics such as communication, internal controls, documentation and recordkeeping.

  17. Does environmental confounding mask pleiotropic effects of a multiple sclerosis susceptibility variant on vitamin D in psychosis?

    PubMed

    Iyegbe, Conrad O; Acharya, Anita; Lally, John; Gardner-Sood, Poonam; Smith, Louise S; Smith, Shubulade; Murray, Robin; Howes, Oliver; Gaughran, Fiona

    2015-01-01

    This work addresses the existing and emerging evidence of overlap within the environmental and genetic profiles of multiple sclerosis (MS) and schizophrenia. To investigate whether a genetic risk factor for MS (rs703842), whose variation is indicative of vitamin D status in the disorder, could also be a determinant of vitamin D status in chronic psychosis patients. A cohort of 224 chronic psychosis cases was phenotyped and biologically profiled. The relationship between rs703842 and physiological vitamin D status in the blood plasma was assessed by logistic regression. Deficiency was defined as a blood plasma concentration below 10 ng/µl. Potential environmental confounders of the vitamin D status were considered as part of the analysis. We report suggestive evidence of an association with vitamin D status in established psychosis (ß standardized=0.51, P=0.04). The logistic model fit significantly benefited from controlling for body mass index, depression and ethnicity (χ (2)=91.7; 2 degrees of freedom (df); P=1.2×10(20)). The results suggest that, in addition to lifestyle changes that accompany the onset of illness, vitamin D dysregulation in psychosis has a genetic component that links into MS. Further, comprehensive studies are needed to evaluate this prospect.

  18. Effects of Process and Outcome Accountability on Idea Generation.

    PubMed

    Häusser, Jan Alexander; Frisch, Johanna Ute; Wanzel, Stella; Schulz-Hardt, Stefan

    2017-07-01

    Previous research on the effects of outcome and process accountability on decision making has neglected the preceding phase of idea generation. We conducted a 2 (outcome accountability: yes vs. no) × 2 (process accountability: yes vs. no) experiment (N = 147) to test the effects of accountability on quantity and quality of generated ideas in a product design task. Furthermore, we examined potential negative side effects of accountability (i.e., stress and lengthened decision making). We found that (a) outcome accountability had a negative effect on quantity of ideas and (b) process accountability extended the idea generation process. Furthermore, any type of accountability (c) had a negative effect on uniqueness of ideas, (d) did not affect the quality of the idea that was selected, and (e) increased stress. Moreover, the negative effect of accountability on uniqueness of ideas was mediated by stress.

  19. Moral Emotion Attributions and Personality Traits as Long-Term Predictors of Antisocial Conduct in Early Adulthood: Findings from a 20-Year Longitudinal Study

    ERIC Educational Resources Information Center

    Krettenauer, Tobias; Asendorpf, Jens B.; Nunner-Winkler, Gertrud

    2013-01-01

    The study investigated long-term relations between moral emotion attributions in childhood and adolescence and antisocial conduct in early adulthood while taking into account potentially confounding personality factors. Specifically, onset of prediction, unique and indirect effects of moral emotion attributions were examined. In a longitudinal…

  20. Accounting for social accountability: developing critiques of social accountability within medical education.

    PubMed

    Ritz, Stacey A; Beatty, Kathleen; Ellaway, Rachel H

    2014-01-01

    The concept of the social accountability of medical schools has garnered many followers, in response to a broad desire for greater social justice in health care. As its use has spread, the term 'social accountability' has become a meta-narrative for social justice and an inevitable and unquestionable good, while at the same time becoming increasingly ambiguous in its meaning and intent. In this article, we use the lenses of postmodernism and critical reflexivity to unpack the multiple meanings of social accountability. In our view, subjecting the concept of 'social accountability' to critique will enhance the ability to appraise the ways in which it is understood and enacted. We contend that critical reflexivity is necessary for social accountability to achieve its aspirations, and hence we must be prepared to become accountable not only for our actions, but also for the ideologies and discourses underlying them.

  1. The Impact of Individual Learning Accounts: A Study of the Early and Potential Impact of Individual Learning Accounts on Learning Providers and Learning. Research Report.

    ERIC Educational Resources Information Center

    Gray, Michael; Peters, Jane; Fletcher, Mick; Kirk, Gordon

    The impact of individual learning accounts (ILAs) on the success of learners in post-16 education sector in the United Kingdom was explored through an examination of available research on ILAs. The following were among the study's 12 messages for providers, the Department for Education and Skills, and the Individual Learning Account Centre: (1)…

  2. 77 FR 43542 - Cost Accounting Standards: Cost Accounting Standards 412 and 413-Cost Accounting Standards...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-25

    ... rule that revised Cost Accounting Standard (CAS) 412, ``Composition and Measurement of Pension Cost... Accounting Standards: Cost Accounting Standards 412 and 413--Cost Accounting Standards Pension Harmonization Rule AGENCY: Cost Accounting Standards Board, Office of Federal Procurement Policy, Office of...

  3. Estimating the monetary value of willingness to pay for E-book reader's attributes using partially confounded factorial conjoint choice experiment

    NASA Astrophysics Data System (ADS)

    Yong, Chin-Khian

    2013-09-01

    A partially confounded factorial conjoint choice experiments design was used to examine the monetary value of the willingness to pay for E-book Reader's attributes. Conjoint analysis is an efficient, cost-effective, and most widely used quantitative method in marketing research to understand consumer preferences and value trade-off. Value can be interpreted by customer or consumer as the received of multiple benefits from a price that was paid. The monetary value of willingness to pay for battery life, internal memory, external memory, screen size, text to Speech, touch screen, and converting handwriting to digital text of E-book reader were estimated in this study. Due to the significant interaction effect of the attributes with the price, the monetary values for the seven attributes were found to be different at different values of odds of purchasing versus not purchasing. The significant interactions effects were one of the main contribution of the partially confounded factorial conjoint choice experiment.

  4. Confounding environmental colour and distribution shape leads to underestimation of population extinction risk.

    PubMed

    Fowler, Mike S; Ruokolainen, Lasse

    2013-01-01

    The colour of environmental variability influences the size of population fluctuations when filtered through density dependent dynamics, driving extinction risk through dynamical resonance. Slow fluctuations (low frequencies) dominate in red environments, rapid fluctuations (high frequencies) in blue environments and white environments are purely random (no frequencies dominate). Two methods are commonly employed to generate the coloured spatial and/or temporal stochastic (environmental) series used in combination with population (dynamical feedback) models: autoregressive [AR(1)] and sinusoidal (1/f) models. We show that changing environmental colour from white to red with 1/f models, and from white to red or blue with AR(1) models, generates coloured environmental series that are not normally distributed at finite time-scales, potentially confounding comparison with normally distributed white noise models. Increasing variability of sample Skewness and Kurtosis and decreasing mean Kurtosis of these series alter the frequency distribution shape of the realised values of the coloured stochastic processes. These changes in distribution shape alter patterns in the probability of single and series of extreme conditions. We show that the reduced extinction risk for undercompensating (slow growing) populations in red environments previously predicted with traditional 1/f methods is an artefact of changes in the distribution shapes of the environmental series. This is demonstrated by comparison with coloured series controlled to be normally distributed using spectral mimicry. Changes in the distribution shape that arise using traditional methods lead to underestimation of extinction risk in normally distributed, red 1/f environments. AR(1) methods also underestimate extinction risks in traditionally generated red environments. This work synthesises previous results and provides further insight into the processes driving extinction risk in model populations. We must let

  5. PERMANOVA-S: association test for microbial community composition that accommodates confounders and multiple distances.

    PubMed

    Tang, Zheng-Zheng; Chen, Guanhua; Alekseyenko, Alexander V

    2016-09-01

    Recent advances in sequencing technology have made it possible to obtain high-throughput data on the composition of microbial communities and to study the effects of dysbiosis on the human host. Analysis of pairwise intersample distances quantifies the association between the microbiome diversity and covariates of interest (e.g. environmental factors, clinical outcomes, treatment groups). In the design of these analyses, multiple choices for distance metrics are available. Most distance-based methods, however, use a single distance and are underpowered if the distance is poorly chosen. In addition, distance-based tests cannot flexibly handle confounding variables, which can result in excessive false-positive findings. We derive presence-weighted UniFrac to complement the existing UniFrac distances for more powerful detection of the variation in species richness. We develop PERMANOVA-S, a new distance-based method that tests the association of microbiome composition with any covariates of interest. PERMANOVA-S improves the commonly-used Permutation Multivariate Analysis of Variance (PERMANOVA) test by allowing flexible confounder adjustments and ensembling multiple distances. We conducted extensive simulation studies to evaluate the performance of different distances under various patterns of association. Our simulation studies demonstrate that the power of the test relies on how well the selected distance captures the nature of the association. The PERMANOVA-S unified test combines multiple distances and achieves good power regardless of the patterns of the underlying association. We demonstrate the usefulness of our approach by reanalyzing several real microbiome datasets. miProfile software is freely available at https://medschool.vanderbilt.edu/tang-lab/software/miProfile z.tang@vanderbilt.edu or g.chen@vanderbilt.edu Supplementary data are available at Bioinformatics online. © The Author 2016. Published by Oxford University Press.

  6. PERMANOVA-S: association test for microbial community composition that accommodates confounders and multiple distances

    PubMed Central

    Tang, Zheng-Zheng; Chen, Guanhua; Alekseyenko, Alexander V.

    2016-01-01

    Motivation: Recent advances in sequencing technology have made it possible to obtain high-throughput data on the composition of microbial communities and to study the effects of dysbiosis on the human host. Analysis of pairwise intersample distances quantifies the association between the microbiome diversity and covariates of interest (e.g. environmental factors, clinical outcomes, treatment groups). In the design of these analyses, multiple choices for distance metrics are available. Most distance-based methods, however, use a single distance and are underpowered if the distance is poorly chosen. In addition, distance-based tests cannot flexibly handle confounding variables, which can result in excessive false-positive findings. Results: We derive presence-weighted UniFrac to complement the existing UniFrac distances for more powerful detection of the variation in species richness. We develop PERMANOVA-S, a new distance-based method that tests the association of microbiome composition with any covariates of interest. PERMANOVA-S improves the commonly-used Permutation Multivariate Analysis of Variance (PERMANOVA) test by allowing flexible confounder adjustments and ensembling multiple distances. We conducted extensive simulation studies to evaluate the performance of different distances under various patterns of association. Our simulation studies demonstrate that the power of the test relies on how well the selected distance captures the nature of the association. The PERMANOVA-S unified test combines multiple distances and achieves good power regardless of the patterns of the underlying association. We demonstrate the usefulness of our approach by reanalyzing several real microbiome datasets. Availability and Implementation: miProfile software is freely available at https://medschool.vanderbilt.edu/tang-lab/software/miProfile. Contact: z.tang@vanderbilt.edu or g.chen@vanderbilt.edu Supplementary information: Supplementary data are available at Bioinformatics

  7. Government Accounting

    DTIC Science & Technology

    1999-06-22

    Commercial Industry • Financial Standards Accounting Board (GAAP) • Internal Revenue Service - Tax Accounting • DoD - Cost Accounting Standards...internal management control systems, managers shall focus on results, not process” Government Accounting • Intent EVM Accounting Criteria : – Record costs ...consistent with established budgets – Insure control of indirect costs – Insure disciplined accumulation of cost – Insure proper material accounting and

  8. Data-driven confounder selection via Markov and Bayesian networks.

    PubMed

    Häggström, Jenny

    2018-06-01

    To unbiasedly estimate a causal effect on an outcome unconfoundedness is often assumed. If there is sufficient knowledge on the underlying causal structure then existing confounder selection criteria can be used to select subsets of the observed pretreatment covariates, X, sufficient for unconfoundedness, if such subsets exist. Here, estimation of these target subsets is considered when the underlying causal structure is unknown. The proposed method is to model the causal structure by a probabilistic graphical model, for example, a Markov or Bayesian network, estimate this graph from observed data and select the target subsets given the estimated graph. The approach is evaluated by simulation both in a high-dimensional setting where unconfoundedness holds given X and in a setting where unconfoundedness only holds given subsets of X. Several common target subsets are investigated and the selected subsets are compared with respect to accuracy in estimating the average causal effect. The proposed method is implemented with existing software that can easily handle high-dimensional data, in terms of large samples and large number of covariates. The results from the simulation study show that, if unconfoundedness holds given X, this approach is very successful in selecting the target subsets, outperforming alternative approaches based on random forests and LASSO, and that the subset estimating the target subset containing all causes of outcome yields smallest MSE in the average causal effect estimation. © 2017, The International Biometric Society.

  9. Serotonin-1A receptors in major depression quantified using PET: controversies, confounds, and recommendations.

    PubMed

    Shrestha, Saurav; Hirvonen, Jussi; Hines, Christina S; Henter, Ioline D; Svenningsson, Per; Pike, Victor W; Innis, Robert B

    2012-02-15

    The serotonin-1A (5-HT(1A)) receptor is of particular interest in human positron emission tomography (PET) studies of major depressive disorder (MDD). Of the eight studies investigating this issue in the brains of patients with MDD, four reported decreased 5-HT(1A) receptor density, two reported no change, and two reported increased 5-HT(1A) receptor density. While clinical heterogeneity may have contributed to these differing results, methodological factors by themselves could also explain the discrepancies. This review highlights several of these factors, including the use of the cerebellum as a reference region and the imprecision of measuring the concentration of parent radioligand in arterial plasma, the method otherwise considered to be the 'gold standard'. Other potential confounds also exist that could restrict or unexpectedly affect the interpretation of results. For example, the radioligand may be a substrate for an efflux transporter - like P-gp - at the blood-brain barrier; furthermore, the binding of the radioligand to the receptor in various stages of cellular trafficking is unknown. Efflux transport and cellular trafficking may also be differentially expressed in patients compared to healthy subjects. We believe that, taken together, the existing disparate findings do not reliably answer the question of whether 5-HT(1A) receptors are altered in MDD or in subgroups of patients with MDD. In addition, useful meta-analysis is precluded because only one of the imaging centers acquired all the data necessary to address these methodological concerns. We recommend that in the future, individual centers acquire more thorough data capable of addressing methodological concerns, and that multiple centers collaborate to meaningfully pool their data for meta-analysis. Published by Elsevier Inc.

  10. Serotonin-1A receptors in major depression quantified using PET: controversies, confounds, and recommendations

    PubMed Central

    Shrestha, Saurav; Hirvonen, Jussi; Hines, Christina S.; Henter, Ioline; Svenningsson, Per; Pike, Victor W.; Innis, Robert B.

    2011-01-01

    The serotonin-1A (5-HT1A) receptor is of particular interest in human positron emission tomography (PET) studies of major depressive disorder (MDD). Of the eight studies investigating this issue in the brains of patients with MDD, four reported decreased 5-HT1A receptor density, two reported no change, and two reported increased 5-HT1A receptor density. While clinical heterogeneity may have contributed to these differing results, methodological factors by themselves could also explain the discrepancies. This review highlights several of these factors, including the use of the cerebellum as a reference region and the imprecision of measuring the concentration of parent radioligand in arterial plasma, the method otherwise considered to be the `gold standard'. Other potential confounds also exist that could restrict or unexpectedly affect the interpretation of results. For example, the radioligand may be a substrate for an efflux transporter—like P-gp—at the blood-brain barrier; furthermore, the binding of the radioligand to the receptor in various stages of cellular trafficking is unknown. Efflux transport and cellular trafficking may also be differentially expressed in patients compared to healthy subjects. We believe that, taken together, the existing disparate findings do not reliably answer the question of whether 5-HT1A receptors are altered in MDD or in subgroups of patients with MDD. In addition, useful meta-analysis is precluded because only one of the imaging centers acquired all the data necessary to address these methodological concerns. We recommend that in the future, individual centers acquire more thorough data capable of addressing methodological concerns, and that multiple centers collaborate to meaningfully pool their data for meta-analysis. PMID:22155042

  11. An Association Mapping Framework To Account for Potential Sex Difference in Genetic Architectures.

    PubMed

    Kang, Eun Yong; Lee, Cue Hyunkyu; Furlotte, Nicholas A; Joo, Jong Wha J; Kostem, Emrah; Zaitlen, Noah; Eskin, Eleazar; Han, Buhm

    2018-05-11

    Over the past few years, genome-wide association studies have identified many trait-associated loci that have different effects on females and males, which increased attention to the genetic architecture differences between the sexes. The between-sex differences in genetic architectures can cause a variety of phenomena such as differences in the effect sizes at trait-associated loci, differences in the magnitudes of polygenic background effects, and differences in the phenotypic variances. However, current association testing approaches for dealing with sex, such as including sex as a covariate, cannot fully account for these phenomena and can be suboptimal in statistical power. We present a novel association mapping framework, MetaSex, that can comprehensively account for the genetic architecture differences between the sexes. Through simulations and applications to real data, we show that our framework has superior performance than previous approaches in association mapping. Copyright © 2018, Genetics.

  12. 18 CFR 367.1420 - Account 142, Customer accounts receivable.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 18 Conservation of Power and Water Resources 1 2010-04-01 2010-04-01 false Account 142, Customer... GAS ACT Balance Sheet Chart of Accounts Current and Accrued Assets § 367.1420 Account 142, Customer accounts receivable. (a) This account must include amounts due from customers for service, and for...

  13. Psychiatrists' accounts of insight.

    PubMed

    Galasinski, Dariusz; Opalinski, Konrad

    2012-11-01

    Our main aim was to examine how insight into schizophrenia is discursively represented in psychiatrists' accounts, how these accounts relate to the current psychiatric literature on insight, and their potential clinical consequences. The article is anchored in the constructionist view of discourse and is based on nine semistructured interviews with specialist psychiatrists. We discuss three dimensions of insight into schizophrenia in the data we collected: a sense of illness, criticism, and readiness to receive treatment. We argue that they are embodiments of the dominant medical perspective in the relations between patients and physicians. Whereas in the former two it is possessing and accepting psychiatric knowledge which constitutes having insight, in the latter it is unquestioning acceptance and trust in whatever treatment the doctor deems fit to administer. We conclude with a discussion of medicalization of experience of mental illness, which appears to be the preferred mode of patient narrative for psychiatrists.

  14. Survey material choices in haematology EQA: a confounding factor in automated counting performance assessment.

    PubMed

    De la Salle, Barbara

    2017-02-15

    The complete blood count (CBC) is one of the most frequently requested tests in laboratory medicine, performed in a range of healthcare situations. The provision of an ideal assay material for external quality assessment is confounded by the fragility of the cellular components of blood, the lack of commutability of stabilised whole blood material and the lack of certified reference materials and methods to which CBC results can be traced. The choice of assay material between fresh blood, extended life assay material and fully stabilised, commercially prepared, whole blood material depends upon the scope and objectives of the EQA scheme. The introduction of new technologies in blood counting and the wider clinical application of parameters from the extended CBC will bring additional challenges for the EQA provider.

  15. Greenhouse gas accounting and waste management.

    PubMed

    Gentil, Emmanuel; Christensen, Thomas H; Aoustin, Emmanuelle

    2009-11-01

    Accounting of emissions of greenhouse gas (GHG) is a major focus within waste management. This paper analyses and compares the four main types of GHG accounting in waste management including their special features and approaches: the national accounting, with reference to the Intergovernmental Panel on Climate Change (IPCC), the corporate level, as part of the annual reporting on environmental issues and social responsibility, life-cycle assessment (LCA), as an environmental basis for assessing waste management systems and technologies, and finally, the carbon trading methodology, and more specifically, the clean development mechanism (CDM) methodology, introduced to support cost-effective reduction in GHG emissions. These types of GHG accounting, in principle, have a common starting point in technical data on GHG emissions from specific waste technologies and plants, but the limited availability of data and, moreover, the different scopes of the accounting lead to many ways of quantifying emissions and producing the accounts. The importance of transparency in GHG accounting is emphasised regarding waste type, waste composition, time period considered, GHGs included, global warming potential (GWP) assigned to the GHGs, counting of biogenic carbon dioxide, choice of system boundaries, interactions with the energy system, and generic emissions factors. In order to enhance transparency and consistency, a format called the upstream-operating-downstream framework (UOD) is proposed for reporting basic technology-related data regarding GHG issues including a clear distinction between direct emissions from waste management technologies, indirect upstream (use of energy and materials) and indirect downstream (production of energy, delivery of secondary materials) activities.

  16. Excel in the Accounting Curriculum: Perceptions from Accounting Professors

    ERIC Educational Resources Information Center

    Ramachandran Rackliffe, Usha; Ragland, Linda

    2016-01-01

    Public accounting firms emphasize the importance of accounting graduates being proficient in Excel. Since many accounting graduates often aspire to work in public accounting, a question arises as to whether there should be an emphasis on Excel in accounting education. The purpose of this paper is to specifically look at this issue by examining…

  17. A focus group study to understand biases and confounders in a cluster randomized controlled trial on low back pain in primary care in Norway.

    PubMed

    Werner, Erik L; Løchting, Ida; Storheim, Kjersti; Grotle, Margreth

    2018-05-22

    Cluster randomized controlled trials are often used in research in primary care but creates challenges regarding biases and confounders. We recently presented a study on low back pain from primary care in Norway with equal effects in the intervention and the control group. In order to understand the specific mechanisms that may produce biases in a cluster randomized trial we conducted a focus group study among the participating health care providers. The aim of this study was to understand how the participating providers themselves influenced on the study and thereby possibly on the results of the cluster randomized controlled trial. The providers were invited to share their experiences from their participation in the COPE study, from recruitment of patients to accomplishment of either the intervention or control consultations. Six clinicians from the intervention group and four from the control group took part in the focus group interviews. The group discussions focused on feasibility of the study in primary care and particularly on identifying potential biases and confounders in the study. The audio-recorded interviews were transcribed verbatim and analyzed according to a systematic text condensation. The themes for the analysis emerged from the group discussions. A personal interest for back pain, logistic factors at the clinics and an assessment of the patients' capacity to accomplish the study prior to their recruitment was reported. The providers were allowed to provide additional therapy to the intervention and it turned out that some of these could be regarded as opposed to the messages of the intervention. The providers seemed to select different items from the educational package according to personal beliefs and their perception of the patients' acceptance. The study disclosed several potential biases to the COPE study which may have impacted on the study results. Awareness of these is highly important when planning and conducting a cluster randomized

  18. Shared processing in multiple object tracking and visual working memory in the absence of response order and task order confounds

    PubMed Central

    Howe, Piers D. L.

    2017-01-01

    To understand how the visual system represents multiple moving objects and how those representations contribute to tracking, it is essential that we understand how the processes of attention and working memory interact. In the work described here we present an investigation of that interaction via a series of tracking and working memory dual-task experiments. Previously, it has been argued that tracking is resistant to disruption by a concurrent working memory task and that any apparent disruption is in fact due to observers making a response to the working memory task, rather than due to competition for shared resources. Contrary to this, in our experiments we find that when task order and response order confounds are avoided, all participants show a similar decrease in both tracking and working memory performance. However, if task and response order confounds are not adequately controlled for we find substantial individual differences, which could explain the previous conflicting reports on this topic. Our results provide clear evidence that tracking and working memory tasks share processing resources. PMID:28410383

  19. Shared processing in multiple object tracking and visual working memory in the absence of response order and task order confounds.

    PubMed

    Lapierre, Mark D; Cropper, Simon J; Howe, Piers D L

    2017-01-01

    To understand how the visual system represents multiple moving objects and how those representations contribute to tracking, it is essential that we understand how the processes of attention and working memory interact. In the work described here we present an investigation of that interaction via a series of tracking and working memory dual-task experiments. Previously, it has been argued that tracking is resistant to disruption by a concurrent working memory task and that any apparent disruption is in fact due to observers making a response to the working memory task, rather than due to competition for shared resources. Contrary to this, in our experiments we find that when task order and response order confounds are avoided, all participants show a similar decrease in both tracking and working memory performance. However, if task and response order confounds are not adequately controlled for we find substantial individual differences, which could explain the previous conflicting reports on this topic. Our results provide clear evidence that tracking and working memory tasks share processing resources.

  20. Later Start, Longer Sleep: Implications of Middle School Start Times

    ERIC Educational Resources Information Center

    Temkin, Deborah A.; Princiotta, Daniel; Ryberg, Renee; Lewin, Daniel S.

    2018-01-01

    Background: Although adolescents generally get less than the recommended 9 hours of sleep per night, research and effort to delay school start times have generally focused on high schools. This study assesses the relation between school start times and sleep in middle school students while accounting for potentially confounding demographic…

  1. Combating QR-Code-Based Compromised Accounts in Mobile Social Networks.

    PubMed

    Guo, Dong; Cao, Jian; Wang, Xiaoqi; Fu, Qiang; Li, Qiang

    2016-09-20

    Cyber Physical Social Sensing makes mobile social networks (MSNs) popular with users. However, such attacks are rampant as malicious URLs are spread covertly through quick response (QR) codes to control compromised accounts in MSNs to propagate malicious messages. Currently, there are generally two types of methods to identify compromised accounts in MSNs: one type is to analyze the potential threats on wireless access points and the potential threats on handheld devices' operation systems so as to stop compromised accounts from spreading malicious messages; the other type is to apply the method of detecting compromised accounts in online social networks to MSNs. The above types of methods above focus neither on the problems of MSNs themselves nor on the interaction of sensors' messages, which leads to the restrictiveness of platforms and the simplification of methods. In order to stop the spreading of compromised accounts in MSNs effectively, the attacks have to be traced to their sources first. Through sensors, users exchange information in MSNs and acquire information by scanning QR codes. Therefore, analyzing the traces of sensor-related information helps to identify the compromised accounts in MSNs. This paper analyzes the diversity of information sending modes of compromised accounts and normal accounts, analyzes the regularity of GPS (Global Positioning System)-based location information, and introduces the concepts of entropy and conditional entropy so as to construct an entropy-based model based on machine learning strategies. To achieve the goal, about 500,000 accounts of Sina Weibo and about 100 million corresponding messages are collected. Through the validation, the accuracy rate of the model is proved to be as high as 87.6%, and the false positive rate is only 3.7%. Meanwhile, the comparative experiments of the feature sets prove that sensor-based location information can be applied to detect the compromised accounts in MSNs.

  2. Combating QR-Code-Based Compromised Accounts in Mobile Social Networks

    PubMed Central

    Guo, Dong; Cao, Jian; Wang, Xiaoqi; Fu, Qiang; Li, Qiang

    2016-01-01

    Cyber Physical Social Sensing makes mobile social networks (MSNs) popular with users. However, such attacks are rampant as malicious URLs are spread covertly through quick response (QR) codes to control compromised accounts in MSNs to propagate malicious messages. Currently, there are generally two types of methods to identify compromised accounts in MSNs: one type is to analyze the potential threats on wireless access points and the potential threats on handheld devices’ operation systems so as to stop compromised accounts from spreading malicious messages; the other type is to apply the method of detecting compromised accounts in online social networks to MSNs. The above types of methods above focus neither on the problems of MSNs themselves nor on the interaction of sensors’ messages, which leads to the restrictiveness of platforms and the simplification of methods. In order to stop the spreading of compromised accounts in MSNs effectively, the attacks have to be traced to their sources first. Through sensors, users exchange information in MSNs and acquire information by scanning QR codes. Therefore, analyzing the traces of sensor-related information helps to identify the compromised accounts in MSNs. This paper analyzes the diversity of information sending modes of compromised accounts and normal accounts, analyzes the regularity of GPS (Global Positioning System)-based location information, and introduces the concepts of entropy and conditional entropy so as to construct an entropy-based model based on machine learning strategies. To achieve the goal, about 500,000 accounts of Sina Weibo and about 100 million corresponding messages are collected. Through the validation, the accuracy rate of the model is proved to be as high as 87.6%, and the false positive rate is only 3.7%. Meanwhile, the comparative experiments of the feature sets prove that sensor-based location information can be applied to detect the compromised accounts in MSNs. PMID:27657071

  3. Batch Effect Confounding Leads to Strong Bias in Performance Estimates Obtained by Cross-Validation

    PubMed Central

    Delorenzi, Mauro

    2014-01-01

    Background With the large amount of biological data that is currently publicly available, many investigators combine multiple data sets to increase the sample size and potentially also the power of their analyses. However, technical differences (“batch effects”) as well as differences in sample composition between the data sets may significantly affect the ability to draw generalizable conclusions from such studies. Focus The current study focuses on the construction of classifiers, and the use of cross-validation to estimate their performance. In particular, we investigate the impact of batch effects and differences in sample composition between batches on the accuracy of the classification performance estimate obtained via cross-validation. The focus on estimation bias is a main difference compared to previous studies, which have mostly focused on the predictive performance and how it relates to the presence of batch effects. Data We work on simulated data sets. To have realistic intensity distributions, we use real gene expression data as the basis for our simulation. Random samples from this expression matrix are selected and assigned to group 1 (e.g., ‘control’) or group 2 (e.g., ‘treated’). We introduce batch effects and select some features to be differentially expressed between the two groups. We consider several scenarios for our study, most importantly different levels of confounding between groups and batch effects. Methods We focus on well-known classifiers: logistic regression, Support Vector Machines (SVM), k-nearest neighbors (kNN) and Random Forests (RF). Feature selection is performed with the Wilcoxon test or the lasso. Parameter tuning and feature selection, as well as the estimation of the prediction performance of each classifier, is performed within a nested cross-validation scheme. The estimated classification performance is then compared to what is obtained when applying the classifier to independent data. PMID:24967636

  4. Translational Rodent Models for Research on Parasitic Protozoa—A Review of Confounders and Possibilities

    PubMed Central

    Ehret, Totta; Torelli, Francesca; Klotz, Christian; Pedersen, Amy B.; Seeber, Frank

    2017-01-01

    Rodents, in particular Mus musculus, have a long and invaluable history as models for human diseases in biomedical research, although their translational value has been challenged in a number of cases. We provide some examples in which rodents have been suboptimal as models for human biology and discuss confounders which influence experiments and may explain some of the misleading results. Infections of rodents with protozoan parasites are no exception in requiring close consideration upon model choice. We focus on the significant differences between inbred, outbred and wild animals, and the importance of factors such as microbiota, which are gaining attention as crucial variables in infection experiments. Frequently, mouse or rat models are chosen for convenience, e.g., availability in the institution rather than on an unbiased evaluation of whether they provide the answer to a given question. Apart from a general discussion on translational success or failure, we provide examples where infections with single-celled parasites in a chosen lab rodent gave contradictory or misleading results, and when possible discuss the reason for this. We present emerging alternatives to traditional rodent models, such as humanized mice and organoid primary cell cultures. So-called recombinant inbred strains such as the Collaborative Cross collection are also a potential solution for certain challenges. In addition, we emphasize the advantages of using wild rodents for certain immunological, ecological, and/or behavioral questions. The experimental challenges (e.g., availability of species-specific reagents) that come with the use of such non-model systems are also discussed. Our intention is to foster critical judgment of both traditional and newly available translational rodent models for research on parasitic protozoa that can complement the existing mouse and rat models. PMID:28638807

  5. Translational Rodent Models for Research on Parasitic Protozoa-A Review of Confounders and Possibilities.

    PubMed

    Ehret, Totta; Torelli, Francesca; Klotz, Christian; Pedersen, Amy B; Seeber, Frank

    2017-01-01

    Rodents, in particular Mus musculus , have a long and invaluable history as models for human diseases in biomedical research, although their translational value has been challenged in a number of cases. We provide some examples in which rodents have been suboptimal as models for human biology and discuss confounders which influence experiments and may explain some of the misleading results. Infections of rodents with protozoan parasites are no exception in requiring close consideration upon model choice. We focus on the significant differences between inbred, outbred and wild animals, and the importance of factors such as microbiota, which are gaining attention as crucial variables in infection experiments. Frequently, mouse or rat models are chosen for convenience, e.g., availability in the institution rather than on an unbiased evaluation of whether they provide the answer to a given question. Apart from a general discussion on translational success or failure, we provide examples where infections with single-celled parasites in a chosen lab rodent gave contradictory or misleading results, and when possible discuss the reason for this. We present emerging alternatives to traditional rodent models, such as humanized mice and organoid primary cell cultures. So-called recombinant inbred strains such as the Collaborative Cross collection are also a potential solution for certain challenges. In addition, we emphasize the advantages of using wild rodents for certain immunological, ecological, and/or behavioral questions. The experimental challenges (e.g., availability of species-specific reagents) that come with the use of such non-model systems are also discussed. Our intention is to foster critical judgment of both traditional and newly available translational rodent models for research on parasitic protozoa that can complement the existing mouse and rat models.

  6. International Accounting and the Accounting Educator.

    ERIC Educational Resources Information Center

    Laribee, Stephen F.

    The American Assembly of Collegiate Schools of Business (AACSB) has been instrumental in internationalizing the accounting curriculum by means of accreditation requirements and standards. Colleges and universities have met the AACSB requirements either by providing separate international accounting courses or by integrating international topics…

  7. 17 CFR 17.01 - Identification of special accounts, volume threshold accounts, and omnibus accounts.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 17 Commodity and Securities Exchanges 1 2014-04-01 2014-04-01 false Identification of special accounts, volume threshold accounts, and omnibus accounts. 17.01 Section 17.01 Commodity and Securities Exchanges COMMODITY FUTURES TRADING COMMISSION REPORTS BY REPORTING MARKETS, FUTURES COMMISSION MERCHANTS, CLEARING MEMBERS, AND FOREIGN BROKERS §...

  8. Depreciation Accounting in the Uniform Chart of Accounts.

    DTIC Science & Technology

    1982-12-01

    footage of building occupied. Reason( s ) for Compute full cost of Rate setting, cash accounting for patient care flow generation and fund- depreciation ing... Horngren , Charles T., Cost Accounting ; A Managerial Emphasis, Prentice-Hall Inc., 1972. 32. Sawyer, Lawrence B., The Practice of Modern Internal Auditing...Awd ubtlft) S . TYPE or RE PORT a PE*IoO CovIERWO Master’s Thesis; Depreciation Accounting in the Uniform Dembr18 Chart of Accounts .PSOiwON.EORlumm

  9. Accountability studies of air pollution and health effects: lessons learned and recommendations for future natural experiment opportunities.

    PubMed

    Rich, David Q

    2017-03-01

    To address limitations of observational epidemiology studies of air pollution and health effects, including residual confounding by temporal and spatial factors, several studies have taken advantage of 'natural experiments', where an environmental policy or air quality intervention has resulted in reductions in ambient air pollution concentrations. Researchers have examined whether the population impacted by these air quality improvements, also experienced improvements in various health indices (e.g. reduced morbidity/mortality). In this paper, I review key accountability studies done previously and new studies done over the past several years in Beijing, Atlanta, London, Ireland, and other locations, describing study design and analysis strengths and limitations of each. As new 'natural experiment' opportunities arise, several lessons learned from these studies should be applied when planning a new accountability study. Comparison of health outcomes during the intervention to both before and after the intervention in the population of interest, as well as use of a control population to assess whether any temporal changes in the population of interest were also seen in populations not impacted by air quality improvements, should aid in minimizing residual confounding by these long term time trends. Use of either detailed health records for a population, or prospectively collected data on relevant mechanistic biomarkers coupled with such morbidity/mortality data may provide a more thorough assessment of if the intervention beneficially impacted the health of the community, and if so by what mechanism(s). Further, prospective measurement of a large suite of air pollutants may allow a more thorough understanding of what pollutant source(s) is/are responsible for any health benefit observed. The importance of using multiple statistical analysis methods in each paper and the difference in how the timing of the air pollution/outcome association may impact which of these

  10. Accountability studies of air pollution and health effects: lessons learned and recommendations for future natural experiment opportunities

    PubMed Central

    Rich, David Q.

    2017-01-01

    To address limitations of observational epidemiology studies of air pollution and health effects, including residual confounding by temporal and spatial factors, several studies have taken advantage of ‘natural experiments’, where an environmental policy or air quality intervention has resulted in reductions in ambient air pollution concentrations. Researchers have examined whether the population impacted by these air quality improvements, also experienced improvements in various health indices (e.g. reduced morbidity/mortality). In this paper, I review key accountability studies done previously and new studies done over the past several years in Beijing, Atlanta, London, Ireland, and other locations, describing study design and analysis strengths and limitations of each. As new ‘natural experiment’ opportunities arise, several lessons learned from these studies should be applied when planning a new accountability study. Comparison of health outcomes during the intervention to both before and after the intervention in the population of interest, as well as use of a control population to assess whether any temporal changes in the population of interest were also seen in populations not impacted by air quality improvements, should aid in minimizing residual confounding by these long term time trends. Use of either detailed health records for a population, or prospectively collected data on relevant mechanistic biomarkers coupled with such morbidity/mortality data may provide a more thorough assessment of if the intervention beneficially impacted the health of the community, and if so by what mechanism(s). Further, prospective measurement of a large suite of air pollutants may allow a more thorough understanding of what pollutant source(s) is/are responsible for any health benefit observed. The importance of using multiple statistical analysis methods in each paper and the difference in how the timing of the air pollution/outcome association may impact which

  11. Accounting Employers' Expectations--The Ideal Accounting Graduates

    ERIC Educational Resources Information Center

    Low, Mary; Botes, Vida; Rue, David Dela; Allen, Jackie

    2016-01-01

    This research examined what accounting employers are seeking in their "ideal" accounting graduate and sought to provide clarification on the "expectation gap" between what accounting employers require in their graduates, and the skills these graduates are exhibiting. Adopting a qualitative research method, this research paper…

  12. Labour and Individual Learning Accounts: Let's Keep Talking.

    ERIC Educational Resources Information Center

    Thomson, Alastair

    1996-01-01

    Reviews British political party proposals for individual learning accounts, designed to give adults purchasing power for further education and training. Raises concerns about effects on existing employee development programs and other potential problems. (SK)

  13. New Frontiers: Training Forensic Accountants within the Accounting Program

    ERIC Educational Resources Information Center

    Ramaswamy, Vinita

    2007-01-01

    Accountants have recently been subject to very unpleasant publicity following the collapse of Enron and other major companies. There has been a plethora of accounting failures and accounting restatements of falsified earnings, with litigations and prosecutions taking place every day. As the FASB struggles to tighten the loopholes in accounting,…

  14. 76 FR 53378 - Cost Accounting Standards: Accounting for Insurance Costs

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-26

    ... Accounting Standards: Accounting for Insurance Costs AGENCY: Cost Accounting Standards Board (Board), Office... Discontinuation of Rulemaking. SUMMARY: The Office of Federal Procurement Policy (OFPP), Cost Accounting Standards... development of an amendment to Cost Accounting Standard (CAS) 416 regarding the use of the term ``catastrophic...

  15. Accountable care organizations and prostate cancer care.

    PubMed

    Hollenbeck, Brent K; Kaufman, Samuel R; Borza, Tudor; Yan, Phyllis; Herrel, Lindsey A; Miller, David C; Luckenbaugh, Amy N; Skolarus, Ted A; Shahinian, Vahakn B

    2017-11-01

    Accountable care organizations have the potential to increase the value of healthcare by improving population health and enhanced financial stewardship. How practice context modifies effects on a specialty-focused disease, such as prostate cancer care, has implications for their success. We performed a retrospective cohort study of newly diagnosed men with prostate cancer between 2012 and 2013 using national Medicare data. Practice affiliation (small single-specialty, large single-specialty, multispecialty groups) and accountable care organization alignment were measured at the patient level. Generalized linear multivariable models were fitted to derive adjusted rates of treatment and spending for the 12-month period after diagnosis according to accountable care organization alignment and practice affiliation. Of 15,640 patients with newly diagnosed prostate cancer, 1,100 (7.0%) were aligned with accountable care organizations. Patients in these organizations had similar use of curative treatment to those not in accountable care organizations (71.4% vs. 70.0%, respectively; p=0.33), which did not vary with practice affiliation (p=0.39). Adjusted spending was higher among patients in accountable care organizations ($20,916 vs. $19,773, p=0.03); however, this relationship was independent of the practice affiliation (p=0.90). Higher accountable care organization penetration within a practice was associated with increased spending (p<0.05) but not with treatment (p=0.87). Prostate cancer patients aligned with accountable care organizations had similar rates of treatment, but increased spending, in the year following diagnosis. These findings were similar across practice affiliations. Better specialist engagement by accountable care organizations may be necessary for them to alter practice patterns for specialty care.

  16. 18 CFR 367.1840 - Account 184, Clearing accounts.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 18 Conservation of Power and Water Resources 1 2010-04-01 2010-04-01 false Account 184, Clearing accounts. 367.1840 Section 367.1840 Conservation of Power and Water Resources FEDERAL ENERGY REGULATORY... POWER ACT AND NATURAL GAS ACT UNIFORM SYSTEM OF ACCOUNTS FOR CENTRALIZED SERVICE COMPANIES SUBJECT TO...

  17. 18 CFR 367.2320 - Account 232, Accounts payable.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 18 Conservation of Power and Water Resources 1 2010-04-01 2010-04-01 false Account 232, Accounts payable. 367.2320 Section 367.2320 Conservation of Power and Water Resources FEDERAL ENERGY REGULATORY... POWER ACT AND NATURAL GAS ACT UNIFORM SYSTEM OF ACCOUNTS FOR CENTRALIZED SERVICE COMPANIES SUBJECT TO...

  18. Accounting Education for the Non-Accountant.

    ERIC Educational Resources Information Center

    Spiceland, J. David

    1983-01-01

    The nondegree Certified Public Accountant (CPA) preparation program at Memphis State University is an accelerated series of eight credit courses in accounting designed for those who have earned a nonaccounting degree and need the technical training and required courses to enable them to take the CPA examination in Tennessee. (JOW)

  19. Accountability, California Style: Counting or Accounting?

    ERIC Educational Resources Information Center

    Russell, Michael; Higgins, Jennifer; Raczek, Anastasia

    2004-01-01

    Across the nation and at nearly all levels of our educational system, efforts to hold schools accountable for student learning dominate strategies for improving the quality of education. At both the national and state level, student testing stands at the center of educational accountability programs, such that schools are effectively held…

  20. Patient accounting systems: needs and capabilities.

    PubMed

    Kennedy, O G; Collignon, S

    1987-09-01

    In the first article of this series, it was stated that most finance executives are not very satisfied with the performance of their current patient accounting systems. What steps can a patient accounting system planner take to help ensure the system selected will garner high ratings from managers and users? Two primarily steps need to be taken. First, the planner needs to perform a thorough evaluation of both near- and long-term patient accounting requirements. He should determine which features and functions are most critical and ensure they are incorporated as selection criteria. The planner should also incorporate institutional planning into that process, such as planned expansion of facilities or services, to ensure that the system selected has the growth potential, interfacing capabilities, and flexibility to respond to the changing environment. Then, once system needs are fully charted, the planner should educate himself about the range of patient accounting system solutions available. The data show that most financial managers lack knowledge about most of the major patient accounting system vendors in the marketplace. Once vendors that offer systems that seemingly could meet needs are identified, the wise system planner will also want to obtain information from users about those vendors, to determine whether the systems perform as described and whether the vendor has been responsive to the needs of its customers. This step is a particularly important part of the planning process, because the data also show that users of some systems are significantly more satisfied than users of other patient accounting systems.

  1. Accounting for biases in riboprofiling data indicates a major role for proline in stalling translation.

    PubMed

    Artieri, Carlo G; Fraser, Hunter B

    2014-12-01

    The recent advent of ribosome profiling-sequencing of short ribosome-bound fragments of mRNA-has offered an unprecedented opportunity to interrogate the sequence features responsible for modulating translational rates. Nevertheless, numerous analyses of the first riboprofiling data set have produced equivocal and often incompatible results. Here we analyze three independent yeast riboprofiling data sets, including two with much higher coverage than previously available, and find that all three show substantial technical sequence biases that confound interpretations of ribosomal occupancy. After accounting for these biases, we find no effect of previously implicated factors on ribosomal pausing. Rather, we find that incorporation of proline, whose unique side-chain stalls peptide synthesis in vitro, also slows the ribosome in vivo. We also reanalyze a method that implicated positively charged amino acids as the major determinant of ribosomal stalling and demonstrate that it produces false signals of stalling in low-coverage data. Our results suggest that any analysis of riboprofiling data should account for sequencing biases and sparse coverage. To this end, we establish a robust methodology that enables analysis of ribosome profiling data without prior assumptions regarding which positions spanned by the ribosome cause stalling. © 2014 Artieri and Fraser; Published by Cold Spring Harbor Laboratory Press.

  2. 76 FR 81295 - Cost Accounting Standards: Cost Accounting Standards 412 and 413-Cost Accounting Standards...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-27

    ... accounting standards governing measurement, assignment, and allocation of costs to contracts with the United... contracting parties; Measurement of pension costs must be objectively verifiable; Accounting rules must keep... cost accounting that preclude their use for the appropriate measurement, assignment and allocation of...

  3. A procedural, pragmatist account of ethical objectivity.

    PubMed

    Roth, Amanda

    2013-06-01

    This article offers a procedural, pragmatist account of objectivity in the domain of the good that is inspired by pragmatic and feminist critiques of objectivity in philosophy of science and epistemology. I begin by asking first what we want to capture--or ought to want to capture--with a notion of ethical objectivity and in answer to this question I identify four "points" to ethical objectivity: undergirding the possibility of mistakenness, making genuine disagreement possible, making sense of our appreciation of the ethical perspectives of others, and making possible a sense of ethical improvement or learning. I then lay out a process-based account of objectivity in ethics that makes good on the four points I have identified. Finally, I consider worries related to convergence, bias, and ontology and defend the procedural, pragmatist account in light of those potential objections.

  4. Oral Health Care Delivery Within the Accountable Care Organization.

    PubMed

    Blue, Christine; Riggs, Sheila

    2016-06-01

    The accountable care organization (ACO) provides an opportunity to strategically design a comprehensive health system in which oral health works within primary care. A dental hygienist/therapist within the ACO represents value-based health care in action. Inspired by health care reform efforts in Minnesota, a vision of an accountable care organization that integrates oral health into primary health care was developed. Dental hygienists and dental therapists can help accelerate the integration of oral health into primary care, particularly in light of the compelling evidence confirming the cost-effectiveness of care delivered by an allied workforce. A dental insurance Chief Operating Officer and a dental hygiene educator used their unique perspectives and experience to describe the potential of an interdisciplinary team-based approach to individual and population health, including oral health, via an accountable care community. The principles of the patient-centered medical home and the vision for accountable care communities present a paradigm shift from a curative system of care to a prevention-based system that encompasses the behavioral, social, nutritional, economic, and environmental factors that impact health and well-being. Oral health measures embedded in the spectrum of general health care have the potential to ensure a truly comprehensive healthcare system. Published by Elsevier Inc.

  5. Mental health and retirement savings: Confounding issues with compounding interest.

    PubMed

    Bogan, Vicki L; Fertig, Angela R

    2018-02-01

    The questionable ability of the U.S. pension system to provide for the growing elderly population combined with the rising number of people affected by depression and other mental health issues magnifies the need to understand how these household characteristics affect retirement. Mental health problems have a large and significant negative effect on retirement savings. Specifically, psychological distress is associated with decreasing the probability of holding retirement accounts by as much as 24 percentage points and decreasing retirement savings as a share of financial assets by as much as 67 percentage points. The magnitude of these effects underscores the importance of employer management policy and government regulation of these accounts to help ensure households have adequate retirement savings. Copyright © 2017 John Wiley & Sons, Ltd.

  6. 18 CFR 367.9050 - Account 905, Miscellaneous customer accounts expenses.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 18 Conservation of Power and Water Resources 1 2010-04-01 2010-04-01 false Account 905, Miscellaneous customer accounts expenses. 367.9050 Section 367.9050 Conservation of Power and Water Resources..., Miscellaneous customer accounts expenses. (a) This account must include the cost of labor, materials used and...

  7. Accountability.

    ERIC Educational Resources Information Center

    Lashway, Larry

    1999-01-01

    This issue reviews publications that provide a starting point for principals looking for a way through the accountability maze. Each publication views accountability differently, but collectively these readings argue that even in an era of state-mandated assessment, principals can pursue proactive strategies that serve students' needs. James A.…

  8. The Sander parallelogram illusion dissociates action and perception despite control for the litany of past confounds.

    PubMed

    Whitwell, Robert L; Goodale, Melvyn A; Merritt, Kate E; Enns, James T

    2018-01-01

    The two visual systems hypothesis proposes that human vision is supported by an occipito-temporal network for the conscious visual perception of the world and a fronto-parietal network for visually-guided, object-directed actions. Two specific claims about the fronto-parietal network's role in sensorimotor control have generated much data and controversy: (1) the network relies primarily on the absolute metrics of target objects, which it rapidly transforms into effector-specific frames of reference to guide the fingers, hands, and limbs, and (2) the network is largely unaffected by scene-based information extracted by the occipito-temporal network for those same targets. These two claims lead to the counter-intuitive prediction that in-flight anticipatory configuration of the fingers during object-directed grasping will resist the influence of pictorial illusions. The research confirming this prediction has been criticized for confounding the difference between grasping and explicit estimates of object size with differences in attention, sensory feedback, obstacle avoidance, metric sensitivity, and priming. Here, we address and eliminate each of these confounds. We asked participants to reach out and pick up 3D target bars resting on a picture of the Sander Parallelogram illusion and to make explicit estimates of the length of those bars. Participants performed their grasps without visual feedback, and were permitted to grasp the targets after making their size-estimates to afford them an opportunity to reduce illusory error with haptic feedback. The results show unequivocally that the effect of the illusion is stronger on perceptual judgments than on grasping. Our findings from the normally-sighted population provide strong support for the proposal that human vision is comprised of functionally and anatomically dissociable systems. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Cost Accounting and Accountability for Early Education Programs for Handicapped Children.

    ERIC Educational Resources Information Center

    Gingold, William

    The paper offers some basic information for making decisions about allocating and accounting for resources provided to young handicapped children. Sections address the following topics: reasons for costing, audiences for cost accounting and accountability information, and a process for cost accounting and accountability (defining cost categories,…

  10. Identity and Epistemic Emotions during Knowledge Revision: A Potential Account for the Backfire Effect

    ERIC Educational Resources Information Center

    Trevors, Gregory J.; Muis, Krista R.; Pekrun, Reinhard; Sinatra, Gale M.; Winne, Philip H.

    2016-01-01

    Recent research has shown that for some topics, messages to refute and revise misconceptions may backfire. The current research offers one possible account for this backfire effect (i.e., the ironic strengthening of belief in erroneous information after an attempted refutation) from an educational psychology perspective and examines whether…

  11. Confounding factors and genetic polymorphism in the evaluation of individual steroid profiling

    PubMed Central

    Kuuranne, Tiia; Saugy, Martial; Baume, Norbert

    2014-01-01

    In the fight against doping, steroid profiling is a powerful tool to detect drug misuse with endogenous anabolic androgenic steroids. To establish sensitive and reliable models, the factors influencing profiling should be recognised. We performed an extensive literature review of the multiple factors that could influence the quantitative levels and ratios of endogenous steroids in urine matrix. For a comprehensive and scientific evaluation of the urinary steroid profile, it is necessary to define the target analytes as well as testosterone metabolism. The two main confounding factors, that is, endogenous and exogenous factors, are detailed to show the complex process of quantifying the steroid profile within WADA-accredited laboratories. Technical aspects are also discussed as they could have a significant impact on the steroid profile, and thus the steroid module of the athlete biological passport (ABP). The different factors impacting the major components of the steroid profile must be understood to ensure scientifically sound interpretation through the Bayesian model of the ABP. Not only should the statistical data be considered but also the experts in the field must be consulted for successful implementation of the steroidal module. PMID:24764553

  12. Computerised Accounting Software; A Curriculum That Enhances an Accounting Programme

    ERIC Educational Resources Information Center

    Machera, Robert P.; Machera, Precious C.

    2017-01-01

    There has been an outcry in commerce and industry about students who fail to perform in the accounting department due to lack of "practical accounting skills". It is from this background that the researchers were motivated to investigate the impact of a Computerised Accounting Software Curriculum that enhances an Accounting Programme. At…

  13. Counting, accounting, and accountability: Helen Verran's relational empiricism.

    PubMed

    Kenney, Martha

    2015-10-01

    Helen Verran uses the term 'relational empiricism' to describe situated empirical inquiry that is attentive to the relations that constitute its objects of study, including the investigator's own practices. Relational empiricism draws on and reconfigures Science and Technology Studies' traditional concerns with reflexivity and relationality, casting empirical inquiry as an important and non-innocent world-making practice. Through a reading of Verran's postcolonial projects in Nigeria and Australia, this article develops a concept of empirical and political 'accountability' to complement her relational empiricism. In Science and an African Logic, Verran provides accounts of the relations that materialize her empirical objects. These accounts work to decompose her original objects, generating new objects that are more promising for the specific postcolonial contexts of her work. The process of decomposition is part of remaining accountable for her research methods and accountable to the worlds she is working in and writing about. This is a practice of narrating relations and learning to tell better technoscientific stories. What counts as better, however, is not given, but is always contextual and at stake. In this way, Verran acts not as participant-observer, but as participant-storyteller, telling stories to facilitate epistemic flourishing within and as part of a historically located community of practice. The understanding of accountability that emerges from this discussion is designed as a contribution, both practical and evocative, to the theoretical toolkit of Science and Technology Studies scholars who are interested in thinking concretely about how we can be more accountable to the worlds we study.

  14. Desire thinking as a confounder in the relationship between mindfulness and craving: Evidence from a cross-cultural validation of the Desire Thinking Questionnaire.

    PubMed

    Chakroun-Baggioni, Nadia; Corman, Maya; Spada, Marcantonio M; Caselli, Gabriele; Gierski, Fabien

    2017-10-01

    Desire thinking and mindfulness have been associated with craving. The aim of the present study was to validate the French version of the Desire Thinking Questionnaire (DTQ) and to investigate the relationship between mindfulness, desire thinking and craving among a sample of university students. Four hundred and ninety six university students completed the DTQ and measures of mindfulness, craving and alcohol use. Results from confirmatory factor analyses showed that the two-factor structure proposed in the original DTQ exhibited suitable goodness-of-fit statistics. The DTQ also demonstrated good internal reliability, temporal stability and predictive validity. A set of linear regressions revealed that desire thinking had a confounding effect in the relationship between mindfulness and craving. The confounding role of desire thinking in the relationship between mindfulness and craving suggests that interrupting desire thinking may be a viable clinical option aimed at reducing craving. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. School Accountability.

    ERIC Educational Resources Information Center

    Evers, Williamson M., Ed.; Walberg, Herbert J., Ed.

    This book presents the perspectives of experts from the fields of history, economics, political science, and psychology on what is known about accountability, what still needs to be learned, what should be done right now, and what should be avoided in devising accountability systems. The common myths about accountability are dispelled and how it…

  16. Accounting Issues: An Essay Series. Part II--Accounts Receivable

    ERIC Educational Resources Information Center

    Laux, Judith A.

    2007-01-01

    This is the second in a series of articles designed to help academics refocus the introductory accounting course on the theoretical underpinnings of accounting. Intended as a supplement for the principles course, this article connects the asset Accounts Receivable to the essential theoretical constructs, discusses the inherent tradeoffs and…

  17. Solving Accounting Problems: Differences between Accounting Experts and Novices.

    ERIC Educational Resources Information Center

    Marshall, P. Douglas

    2002-01-01

    Performance of 90 accounting experts (faculty and practitioners) and 60 novices (senior accounting majors) was compared. Experts applied more accounting principles to solving problems. There were no differences in types of principles applied and no correlation between (1) principles applied and number of breadth comments or (2) importance placed…

  18. LIFE CLIMATREE project: A novel approach for accounting and monitoring carbon sequestration of tree crops and their potential as carbon sink areas

    NASA Astrophysics Data System (ADS)

    Stergiou, John; Tagaris, Efthimios; -Eleni Sotiropoulou, Rafaella

    2016-04-01

    Climate Change Mitigation is one of the most important objectives of the Kyoto Convention, and is mostly oriented towards reducing GHG emissions. However, carbon sink is retained only in the calculation of the forests capacity since agricultural land and farmers practices for securing carbon stored in soils have not been recognized in GHG accounting, possibly resulting in incorrect estimations of the carbon dioxide balance in the atmosphere. The agricultural sector, which is a key sector in the EU, presents a consistent strategic framework since 1954, in the form of Common Agricultural Policy (CAP). In its latest reform of 2013 (reg. (EU) 1305/13) CAP recognized the significance of Agriculture as a key player in Climate Change policy. In order to fill this gap the "LIFE ClimaTree" project has recently founded by the European Commission aiming to provide a novel method for including tree crop cultivations in the LULUCF's accounting rules for GHG emissions and removal. In the framework of "LIFE ClimaTree" project estimation of carbon sink within EU through the inclusion of the calculated tree crop capacity will be assessed for both current and future climatic conditions by 2050s using the GISS-WRF modeling system in a very fine scale (i.e., 9km x 9km) using RCP8.5 and RCP4.5 climate scenarios. Acknowledgement: LIFE CLIMATREE project "A novel approach for accounting and monitoring carbon sequestration of tree crops and their potential as carbon sink areas" (LIFE14 CCM/GR/000635).

  19. Colorful Accounting

    ERIC Educational Resources Information Center

    Warrick, C. Shane

    2006-01-01

    As instructors of accounting, we should take an abstract topic (at least to most students) and connect it to content known by students to help increase the effectiveness of our instruction. In a recent semester, ordinary items such as colors, a basketball, and baseball were used to relate the subject of accounting. The accounting topics of account…

  20. Randomly Accountable

    ERIC Educational Resources Information Center

    Kane, Thomas J.; Staiger, Douglas O.; Geppert, Jeffrey

    2002-01-01

    The accountability debate tends to devolve into a battle between the pro-testing and anti-testing crowds. When it comes to the design of a school accountability system, the devil is truly in the details. A well-designed accountability plan may go a long way toward giving school personnel the kinds of signals they need to improve performance.…

  1. An Improved Framework for Confound Regression and Filtering for Control of Motion Artifact in the Preprocessing of Resting-State Functional Connectivity Data

    PubMed Central

    Satterthwaite, Theodore D.; Elliott, Mark A.; Gerraty, Raphael T.; Ruparel, Kosha; Loughead, James; Calkins, Monica E.; Eickhoff, Simon B.; Hakonarson, Hakon; Gur, Ruben C.; Gur, Raquel E.; Wolf, Daniel H.

    2013-01-01

    Several recent reports in large, independent samples have demonstrated the influence of motion artifact on resting-state functional connectivity MRI (rsfc-MRI). Standard rsfc-MRI preprocessing typically includes regression of confounding signals and band-pass filtering. However, substantial heterogeneity exists in how these techniques are implemented across studies, and no prior study has examined the effect of differing approaches for the control of motion-induced artifacts. To better understand how in-scanner head motion affects rsfc-MRI data, we describe the spatial, temporal, and spectral characteristics of motion artifacts in a sample of 348 adolescents. Analyses utilize a novel approach for describing head motion on a voxelwise basis. Next, we systematically evaluate the efficacy of a range of confound regression and filtering techniques for the control of motion-induced artifacts. Results reveal that the effectiveness of preprocessing procedures on the control of motion is heterogeneous, and that improved preprocessing provides a substantial benefit beyond typical procedures. These results demonstrate that the effect of motion on rsfc-MRI can be substantially attenuated through improved preprocessing procedures, but not completely removed. PMID:22926292

  2. Getting tough with home health accounts receivable.

    PubMed

    Cantone, L; Bullock, A

    2000-04-01

    Home health organizations seeking to improve the performance of their accounts receivable should concentrate first on establishing practices that promote the greatest percentage of clean claims and reviewing payments received to be sure rates paid are optimal. They also may find it worthwhile to survey their business office operations for potential improvements to key areas.

  3. Measurement error, time lag, unmeasured confounding: Considerations for longitudinal estimation of the effect of a mediator in randomised clinical trials.

    PubMed

    Goldsmith, K A; Chalder, T; White, P D; Sharpe, M; Pickles, A

    2018-06-01

    Clinical trials are expensive and time-consuming and so should also be used to study how treatments work, allowing for the evaluation of theoretical treatment models and refinement and improvement of treatments. These treatment processes can be studied using mediation analysis. Randomised treatment makes some of the assumptions of mediation models plausible, but the mediator-outcome relationship could remain subject to bias. In addition, mediation is assumed to be a temporally ordered longitudinal process, but estimation in most mediation studies to date has been cross-sectional and unable to explore this assumption. This study used longitudinal structural equation modelling of mediator and outcome measurements from the PACE trial of rehabilitative treatments for chronic fatigue syndrome (ISRCTN 54285094) to address these issues. In particular, autoregressive and simplex models were used to study measurement error in the mediator, different time lags in the mediator-outcome relationship, unmeasured confounding of the mediator and outcome, and the assumption of a constant mediator-outcome relationship over time. Results showed that allowing for measurement error and unmeasured confounding were important. Contemporaneous rather than lagged mediator-outcome effects were more consistent with the data, possibly due to the wide spacing of measurements. Assuming a constant mediator-outcome relationship over time increased precision.

  4. Measurement error, time lag, unmeasured confounding: Considerations for longitudinal estimation of the effect of a mediator in randomised clinical trials

    PubMed Central

    Goldsmith, KA; Chalder, T; White, PD; Sharpe, M; Pickles, A

    2016-01-01

    Clinical trials are expensive and time-consuming and so should also be used to study how treatments work, allowing for the evaluation of theoretical treatment models and refinement and improvement of treatments. These treatment processes can be studied using mediation analysis. Randomised treatment makes some of the assumptions of mediation models plausible, but the mediator–outcome relationship could remain subject to bias. In addition, mediation is assumed to be a temporally ordered longitudinal process, but estimation in most mediation studies to date has been cross-sectional and unable to explore this assumption. This study used longitudinal structural equation modelling of mediator and outcome measurements from the PACE trial of rehabilitative treatments for chronic fatigue syndrome (ISRCTN 54285094) to address these issues. In particular, autoregressive and simplex models were used to study measurement error in the mediator, different time lags in the mediator–outcome relationship, unmeasured confounding of the mediator and outcome, and the assumption of a constant mediator–outcome relationship over time. Results showed that allowing for measurement error and unmeasured confounding were important. Contemporaneous rather than lagged mediator–outcome effects were more consistent with the data, possibly due to the wide spacing of measurements. Assuming a constant mediator–outcome relationship over time increased precision. PMID:27647810

  5. Cross-sectional analysis of food choice frequency, sleep confounding beverages, and psychological distress predictors of sleep quality.

    PubMed

    Knowlden, Adam P; Burns, Maranda; Harcrow, Andy; Shewmake, Meghan E

    2016-03-16

    Poor sleep quality is a significant public health problem. The role of nutrition in predicting sleep quality is a relatively unexplored area of inquiry. The purpose of this study was to evaluate the capacity of 10 food choice categories, sleep confounding beverages, and psychological distress to predict the sleep quality of college students. A logistic regression model comprising 10 food choice variables (healthy proteins, unhealthy proteins, healthy dairy, unhealthy dairy, healthy grains, unhealthy grains, healthy fruits and vegetables, unhealthy empty calories, healthy beverages, unhealthy beverages), sleep confounding beverages (caffeinated/alcoholic beverages), as well as psychological distress (low, moderate, serious distress) was computed to determine the capacity of the variables to predict sleep quality (good/poor). The odds of poor sleep quality were 32.4% lower for each unit of increased frequency of healthy proteins consumed (p<0.001; OR=0.676), 14.1% lower for each unit of increased frequency of healthy dairy food choices consumed (p=0.024; OR=0.859), 13.1% higher for each unit of increased frequency of empty calorie food choices consumed (p=0.003; OR=1.131), and 107.3% higher for those classified in the moderate psychological distress (p=0.016; OR=2.073). Collectively, healthy proteins, healthy dairy, unhealthy empty calories, and moderate psychological distress were moderately predictive of sleep quality in the sample (Nagelkerke R2=23.8%). Results of the study suggested higher frequency of consumption of healthy protein and healthy dairy food choices reduced the odds of poor sleep quality, while higher consumption of empty calories and moderate psychological distress increased the odds of poor sleep quality.

  6. Sampling depth confounds soil acidification outcomes

    USDA-ARS?s Scientific Manuscript database

    In the northern Great Plains (NGP) of North America, surface sampling depths of 0-15 or 0-20 cm are suggested for testing soil characteristics such as pH. However, acidification is often most pronounced near the soil surface. Thus, sampling deeper can potentially dilute (increase) pH measurements an...

  7. Why revisit your cost-accounting strategy.

    PubMed

    Arredondo, Ricky

    2014-07-01

    Healthcare entities seeking to develop effective cost-accounting systems should take six steps to avoid potential pitfalls: Secure broad executive-level support for the effort. Ensure systems are in place to analyze the disparate data. Define measurable objectives to ensure that implementation achieves desired results. Give due consideration to implementation planning. Train support staff sufficiently to avoid underutilization. Develop a sufficiently broad base of staff support for the system.

  8. Influence of GSTM1 and GSTT1 genotypes and confounding factors on the frequency of sister chromatid exchange and micronucleus among road construction workers.

    PubMed

    Kumar, Anil; Yadav, Anita; Giri, Shiv Kumar; Dev, Kapil; Gautam, Sanjeev Kumar; Gupta, Ranjan; Aggarwal, Neeraj

    2011-07-01

    In the present study, we have investigated the influence of polymorphism of GSTM1 and GSTT1 genes and confounding factors such as age, sex, exposure duration and consumption habits on cytogenetic biomarkers. Frequency of sister chromatid exchanges (SCEs), high frequency cell (HFC) and cytokinesis blocked micronuclei (CBMN) were evaluated in peripheral blood lymphocytes of 115 occupationally exposed road construction workers and 105 unexposed individuals. The distribution of null and positive genotypes of glutathione-S transferase gene was evaluated by multiplex PCR among control and exposed subjects. An increased frequency of CBMN (7.03±2.08); SCE (6.95±1.76) and HFC (6.28±1.69) were found in exposed subjects when compared to referent (CBMN - 3.35±1.10; SCE - 4.13±1.30 and HFC - 3.98±1.56). These results were found statistically significant at p<0.05. When the effect of confounding factors on the frequency of studied biomarkers was evaluated, a strong positive interaction was found. The individuals having GSTM1 and GSTT1 null genotypes had higher frequency of CBMN, SCE and HFC. The association between GSTM1 and GSTT1 genotypes and studied biomarkers was found statistically significant at p<0.05. Our findings suggest that individuals having null type of GST are more susceptible to cytogenetic damage by occupational exposure regardless of confounding factors. There is a significant effect of polymorphism of these genes on cytogenetic biomarkers which are considered as early effects of genotoxic carcinogens. Copyright © 2011 Elsevier Ltd. All rights reserved.

  9. Confounding factors in using upward feedback to assess the quality of medical training: a systematic review.

    PubMed

    Zhou, Anli Yue; Baker, Paul

    2014-01-01

    Upward feedback is becoming more widely used in medical training as a means of quality control. Multiple biases exist, thus the accuracy of upward feedback is debatable. This study aims to identify factors that could influence upward feedback, especially in medical training. A systematic review using a structured search strategy was performed. Thirty-five databases were searched. Results were reviewed and relevant abstracts were shortlisted. All studies in English, both medical and non-medical literature, were included. A simple pro-forma was used initially to identify the pertinent areas of upward feedback, so that a focused pro-forma could be designed for data extraction. A total of 204 articles were reviewed. Most studies on upward feedback bias were evaluative studies and only covered Kirkpatrick level 1-reaction. Most studies evaluated trainers or training, were used for formative purposes and presented quantitative data. Accountability and confidentiality were the most common overt biases, whereas method of feedback was the most commonly implied bias within articles. Although different types of bias do exist, upward feedback does have a role in evaluating medical training. Accountability and confidentiality were the most common biases. Further research is required to evaluate which types of bias are associated with specific survey characteristics and which are potentially modifiable.

  10. The use of the transition cost accounting system in health services research

    PubMed Central

    Azoulay, Arik; Doris, Nadine M; Filion, Kristian B; Caron, Joanna; Pilote, Louise; Eisenberg, Mark J

    2007-01-01

    The Transition cost accounting system integrates clinical, resource utilization, and financial information and is currently being used by several hospitals in Canada and the United States to calculate the costs of patient care. Our objectives were to review the use of hospital-based cost accounting systems to measure costs of treatment and discuss potential use of the Transition cost accounting system in health services research. Such systems provide internal reports to administrators for formulating major policies and strategic plans for future activities. Our review suggests that the Transition cost accounting information system may useful for estimating in-hospital costs of treatment. PMID:17686148

  11. The use of the transition cost accounting system in health services research.

    PubMed

    Azoulay, Arik; Doris, Nadine M; Filion, Kristian B; Caron, Joanna; Pilote, Louise; Eisenberg, Mark J

    2007-08-08

    The Transition cost accounting system integrates clinical, resource utilization, and financial information and is currently being used by several hospitals in Canada and the United States to calculate the costs of patient care. Our objectives were to review the use of hospital-based cost accounting systems to measure costs of treatment and discuss potential use of the Transition cost accounting system in health services research. Such systems provide internal reports to administrators for formulating major policies and strategic plans for future activities. Our review suggests that the Transition cost accounting information system may useful for estimating in-hospital costs of treatment.

  12. SENSE OF CONTROL AND SELF-REPORTED HEALTH IN A POPULATION-BASED SAMPLE OF OLDER AMERICANS: ASSESSMENT OF POTENTIAL CONFOUNDING BY AFFECT, PERSONALITY, AND SOCIAL SUPPORT

    PubMed Central

    Ward, Michael M.

    2012-01-01

    Background Sense of control has been linked to improved health outcomes, but it is unclear if this association is independent of other psychosocial factors. Purpose To test the strength of association between sense of control and self-reported health after adjustment for positive and negative affect, “Big 5” personality factors, and social support. Method Data on sense of control (measured by personal mastery, perceived constraints, and a health-specific rating of control), affect, personality, social support, and two measures of self-reported health (global rating of fair or poor health, and presence of functional limitations) were obtained on 6891 participants in the Health and Retirement Study, a population-based survey of older Americans. The cross-sectional association between sense of control measures and each measure of self-reported health was tested in hierarchical logistic regression models, before and after adjustment for affect, personality, and social support. Results Participants with higher personal mastery were less likely to report fair/poor health (odds ratio 0.76 per 1-point increase) while those with higher perceived constraints were more likely to report fair/poor health (odds ratio 1.37 per 1-point increase). Associations remained after adjustment for affect, but adjustment for affect attenuated the association of personal mastery by 37% and of perceived constraints by 67%. Further adjustment for personality and social support did not alter the strength of association. Findings were similar for the health-specific rating of control, and for associations with functional limitations. Conclusions Sense of control is associated with self-reported health in older Americans, but this association is partly confounded by affect. PMID:22282403

  13. 48 CFR 9904.406 - Cost accounting standard-cost accounting period.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 7 2010-10-01 2010-10-01 false Cost accounting standard-cost accounting period. 9904.406 Section 9904.406 Federal Acquisition Regulations System COST ACCOUNTING STANDARDS BOARD, OFFICE OF FEDERAL PROCUREMENT POLICY, OFFICE OF MANAGEMENT AND BUDGET PROCUREMENT...

  14. Assessment of the Accounting and Joint Accounting/Computer Information Systems Programs.

    ERIC Educational Resources Information Center

    Appiah, John; Cernigliaro, James; Davis, Jeffrey; Gordon, Millicent; Richards, Yves; Santamaria, Fernando; Siegel, Annette; Lytle, Namy; Wharton, Patrick

    This document presents City University of New York LaGuardia Community College's Department of Accounting and Managerial Studies assessment of its accounting and joint accounting/computer information systems programs report, and includes the following items: (1) description of the mission and goals of the Department of Accounting and Managerial…

  15. Trends in Accounting Education: Decreasing Accounting Anxiety and Promoting New Methods

    ERIC Educational Resources Information Center

    Buckhaults, Jessica; Fisher, Diane

    2011-01-01

    In this paper, authors (a) identified accounting anxiety for the educator and the student as a possible explanation for the decline in accounting education and (b) investigated new methods for teaching accounting at the secondary and postsecondary levels that will increase interest in accounting education as well as decrease educator and student…

  16. Disease risk score as a confounder summary method: systematic review and recommendations.

    PubMed

    Tadrous, Mina; Gagne, Joshua J; Stürmer, Til; Cadarette, Suzanne M

    2013-02-01

    To systematically examine trends and applications of the disease risk score (DRS) as a confounder summary method. We completed a systematic search of MEDLINE and Web of Science® to identify all English language articles that applied DRS methods. We tabulated the number of publications by year and type (empirical application, methodological contribution, or review paper) and summarized methods used in empirical applications overall and by publication year (<2000, ≥2000). Of 714 unique articles identified, 97 examined DRS methods and 86 were empirical applications. We observed a bimodal distribution in the number of publications over time, with a peak 1979-1980, and resurgence since 2000. The majority of applications with methodological detail derived DRS using logistic regression (47%), used DRS as a categorical variable in regression (93%), and applied DRS in a non-experimental cohort (47%) or case-control (42%) study. Few studies examined effect modification by outcome risk (23%). Use of DRS methods has increased yet remains low. Comparative effectiveness research may benefit from more DRS applications, particularly to examine effect modification by outcome risk. Standardized terminology may facilitate identification, application, and comprehension of DRS methods. More research is needed to support the application of DRS methods, particularly in case-control studies. Copyright © 2012 John Wiley & Sons, Ltd.

  17. The potential impact of accountable care organizations with respect to cost and quality with special attention to imaging.

    PubMed

    Mukherji, Suresh K

    2014-04-01

    An accountable care organization is a form of a managed care organization in which a group of networked health care providers, which may include hospitals, group practices, networks of practices, hospital-provider partnerships, or joint ventures, are accountable for the health care of a defined group of patients. Initial results of the institutions participating in CMS's Physician Group Demonstration Project did not demonstrate a substantial reduction in imaging that could be directly attributed to the accountable care organization model. However, the initial results suggest that incentive-based methodology appears to be successful for increasing compliance for measuring quality metrics. Copyright © 2014 American College of Radiology. Published by Elsevier Inc. All rights reserved.

  18. Excess Mortality in Hyperthyroidism: The Influence of Preexisting Comorbidity and Genetic Confounding: A Danish Nationwide Register-Based Cohort Study of Twins and Singletons

    PubMed Central

    Brandt, Frans; Almind, Dorthe; Christensen, Kaare; Green, Anders; Brix, Thomas Heiberg

    2012-01-01

    Context: Hyperthyroidism is associated with severe comorbidity, such as stroke, and seems to confer increased mortality. However, it is unknown whether this increased mortality is explained by hyperthyroidism per se, comorbidity, and/or genetic confounding. Objective: The objective of the study was to investigate whether hyperthyroidism is associated with an increased mortality and, if so, whether the association is influenced by comorbidity and/or genetic confounding. Methods: This was an observational cohort study using record-linkage data from nationwide Danish health registers. We identified 4850 singletons and 926 twins from same-sex pairs diagnosed with hyperthyroidism. Each case was matched with four controls for age and gender. The Charlson score was calculated from discharge diagnoses on an individual level to measure comorbidity. Cases and controls were followed up for a mean of 10 yr (range 0–31 yr), and the hazard ratio (HR) for mortality was calculated using Cox regression analyses. Results: In singletons there was a significantly higher mortality in individuals diagnosed with hyperthyroidism than in controls [HR 1.37; 95% confidence interval (CI) 1.30–1.46]. This persisted after adjustment for preexisting comorbidity (HR 1,28; 95% CI 1.21–1.36). In twin pairs discordant for hyperthyroidism (625 pairs), the twin with hyperthyroidism had an increased mortality compared with the corresponding cotwin (HR 1.43; 95% CI 1.09–1.88). However, this was found only in dizygotic pairs (HR 1.80; 95% CI 1.27–2.55) but not in monozygotic pairs (HR 0.95; 95% CI 0.60–1.50). Conclusions: Hyperthyroidism is associated with an increased mortality independent of preexisting comorbidity. The study of twin pairs discordant for hyperthyroidism suggests that genetic confounding influences the association between hyperthyroidism and mortality. PMID:22930783

  19. 77 FR 202 - Federal Acquisition Regulation; Updated Financial Accounting Standards Board Accounting References

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-03

    ... 9000-AM00 Federal Acquisition Regulation; Updated Financial Accounting Standards Board Accounting... accounting standards owing to the Financial Accounting Standards Board's Accounting Standards Codification of Generally Accepted Accounting Principles. DATES: Effective Date: February 2, 2012. FOR FURTHER INFORMATION...

  20. Physical work load and psychological stress of daily activities as predictors of disability pension due to musculoskeletal disorders.

    PubMed

    Ropponen, Annina; Svedberg, Pia; Koskenvuo, Markku; Silventoinen, Karri; Kaprio, Jaakko

    2014-06-01

    Physical work loading and psychological stress commonly co-occur in working life, hence potentially having an interrelationship that may affect work incapacity. This prospective cohort study aimed to investigate the effect of stability and change in physical work loading and stress on the risk of disability pension (DP) due to musculoskeletal diagnoses (MSD), while accounting for familial confounding in these associations. Data on 12,455 twins born before 1958 were surveyed of their physical work loading and psychological stress of daily activities in 1975 and 1981. The follow-up data was collected from pension registers until 2004. Cox proportional hazards regression models were used. During the follow up, 893 participants were granted DP due to MSD. Stable high (hazard ratio, HR, 2.21), but also increased physical work loading (HR 2.05) and high psychological stress (HR 2.22) were associated with increased risk for DP, and had significant interaction (p=0.032). The associations were confirmed when accounting for several confounding factors. Stable high but also increased physical work loading and psychological stress of daily activities between two timepoints with 6 years apart confirms their predictive role for an increased risk of DP. Both physical work loading and psychological stress seem to be independent from various confounding factors hence suggesting direct effect on risk for DP providing potential for occupational health care to early identification of persons at risk. © 2014 the Nordic Societies of Public Health.

  1. Occupational exposure and ovarian cancer risk.

    PubMed

    Le, Nhu D; Leung, Andy; Brooks-Wilson, Angela; Gallagher, Richard P; Swenerton, Kenneth D; Demers, Paul A; Cook, Linda S

    2014-07-01

    Relatively little work has been done concerning occupational risk factors in ovarian cancer. Although studies conducted in occupational settings have reported positive associations, their usefulness is generally limited by the lack of information on important confounders. In a population-based case-control study, we assessed risk for developing epithelial ovarian cancer (EOC) associated with occupational exposure while accounting for important confounders. Participants were identified through provincial population-based registries. Lifetime occupational history and information on potential confounding factors were obtained through a self-administered questionnaire. Unconditional logistic regression and the likelihood ratio test were used to assess EOC risk with each occupation (or industry), relative to all other occupations (or industries), adjusting for potential confounders including body mass index, oral contraceptive use, menopausal hormone therapy, parity, age at first childbirth, age at menarche, age at menopause, family history of breast and ovarian cancer in mother and sister(s), tubal ligation, partial oophorectomy, and hysterectomy. Occupations and industries were coded according to the Canadian Standard Occupational Classification (SOC) and Standard Industrial Classification (SIC). Significant excess risk was observed for several groups of teaching occupations, including SOC 27, teaching and related (adjusted OR 1.77, 95% CI 1.15-2.81) and SOC 279, other teaching and related (adjusted OR 3.11, 95% CI 1.35-8.49). Significant excess was also seen for a four-digit occupational group SOC 4131, bookkeepers and accounting clerks (adjusted OR 2.80, 95% CI 1.30-6.80). Industrial sub-groups showing significant excess risk included SIC 65, other retail stores (adjusted OR 2.19, 95 % CI 1.16-4.38); SIC 85, educational service (adjusted OR 1.45, 95% CI 1.00-2.13); and SIC 863, non-institutional health services (adjusted OR 2.54, 95% CI 1.13-6.52). Our study found

  2. Analysis of emergency physicians' Twitter accounts.

    PubMed

    Lulic, Ileana; Kovic, Ivor

    2013-05-01

    Twitter is one of the fastest growing social media networks for communication between users via short messages. Technology proficient physicians have demonstrated enthusiasm in adopting social media for their work. To identify and create the largest directory of emergency physicians on Twitter, analyse their user accounts and reveal details behind their connections. Several web search tools were used to identify emergency physicians on Twitter with biographies completely or partially written in English. NodeXL software was used to calculate emergency physicians' Twitter network metrics and create visualisation graphs. The authors found 672 Twitter accounts of self-identified emergency physicians. Protected accounts were excluded from the study, leaving 632 for further analysis. Most emergency physicians were located in USA (55.4%), had created their accounts in 2009 (43.4%), used their full personal name (77.5%) and provided a custom profile picture (92.2%). Based on at least one published tweet in the last 15 days, there were 345 (54.6%) active users on 31 December 2011. Active users mostly used mobile devices based on the Apple operating system to publish tweets (69.2%). Visualisation of emergency physicians' Twitter network revealed many users with no connections with their colleagues, and a small group of most influential users who were highly interconnected. Only a small proportion of registered emergency physicians use Twitter. Among them exists a smaller inner network of emergency physicians with strong social bonds that is using Twitter's full potentials for professional development.

  3. Soil acidification as a confounding factor on metal phytotoxicity in soils spiked with copper-rich mine wastes.

    PubMed

    Ginocchio, Rosanna; De la Fuente, Luz María; Sánchez, Pablo; Bustamante, Elena; Silva, Yasna; Urrestarazu, Paola; Rodríguez, Patricio H

    2009-10-01

    Pollution of soil with mine wastes results in both Cu enrichment and soil acidification. This confounding effect may be very important in terms of phytotoxicity, because pH is a key parameter influencing Cu solubility in soil solution. Laboratory toxicity tests were used to assess the effect of acidification by acidic mine wastes on Cu solubility and on root elongation of barley (Hordeum vulgare L.). Three contrasting substrates (two soils and a commercial sand) and two acidic, Cu-rich mine wastes (oxidized tailings [OxT] and smelter dust [SmD]) were selected as experimental materials. Substrates were spiked with a fixed amount of either SmD or OxT, and the pH of experimental mixtures was then modified in the range of 4.0 to 6.0 and 7.0 using PIPES (piperazine-1,4-bis(2-ethanesulfonic acid)), MES (2-(N-morpholino)ethanesulfonic acid), and MOPS (3-(N-Morpholino)-propanesulfonic acid) buffers. Chemical (pore-water Cu and pH) and toxicological (root length of barley plants) parameters were determined for experimental mixtures. Addition of SmD and OxT to substrates resulted in acidification (0.11-1.16 pH units) and high levels of soluble Cu and Zn. Neutralization of experimental mixtures with MES (pH 6.0) and MOPS (pH 7.0) buffers resulted in a marked decrease in soluble Cu and Zn, but the intensity of the effect was substrate-dependent. Adjustment of soil pH above the range normally considered to be toxic to plants (pH in water extract, > 5.5) significantly reduced metal toxicity in barley, but phytotoxicity was not completely eliminated. The present results stress the importance of considering confounding effects on derivation of toxicity thresholds to plants when using laboratory phytotoxicity tests.

  4. Neuroticism explains unwanted variance in Implicit Association Tests of personality: possible evidence for an affective valence confound.

    PubMed

    Fleischhauer, Monika; Enge, Sören; Miller, Robert; Strobel, Alexander; Strobel, Anja

    2013-01-01

    Meta-analytic data highlight the value of the Implicit Association Test (IAT) as an indirect measure of personality. Based on evidence suggesting that confounding factors such as cognitive abilities contribute to the IAT effect, this study provides a first investigation of whether basic personality traits explain unwanted variance in the IAT. In a gender-balanced sample of 204 volunteers, the Big-Five dimensions were assessed via self-report, peer-report, and IAT. By means of structural equation modeling (SEM), latent Big-Five personality factors (based on self- and peer-report) were estimated and their predictive value for unwanted variance in the IAT was examined. In a first analysis, unwanted variance was defined in the sense of method-specific variance which may result from differences in task demands between the two IAT block conditions and which can be mirrored by the absolute size of the IAT effects. In a second analysis, unwanted variance was examined in a broader sense defined as those systematic variance components in the raw IAT scores that are not explained by the latent implicit personality factors. In contrast to the absolute IAT scores, this also considers biases associated with the direction of IAT effects (i.e., whether they are positive or negative in sign), biases that might result, for example, from the IAT's stimulus or category features. None of the explicit Big-Five factors was predictive for method-specific variance in the IATs (first analysis). However, when considering unwanted variance that goes beyond pure method-specific variance (second analysis), a substantial effect of neuroticism occurred that may have been driven by the affective valence of IAT attribute categories and the facilitated processing of negative stimuli, typically associated with neuroticism. The findings thus point to the necessity of using attribute category labels and stimuli of similar affective valence in personality IATs to avoid confounding due to recoding.

  5. The confounding recent behaviour of the Quasi-Biennial Oscillation

    NASA Astrophysics Data System (ADS)

    Osprey, Scott; Butchart, Neal; Knight, Jeff; Scaife, Adam; Hamilton, Kevin; Anstey, James; Schenzinger, Verena; Zhang, Chunxi

    2017-04-01

    High above the equator winds slowly change from blowing eastward to westward and back again roughly every 28 months in a natural climate rhythm known as the quasibiennial oscillation (QBO). These regular winds have been recorded since the 1950s and emerge from natural processes within the tropics e.g. clouds, convection, rainfall and the wave disturbances arising from these. The latter break down high up in the stratosphere, analogous to waves on a beach. Although a little tricky to capture in climate models, our understanding of the basic processes underpinning this climate rhythm was thought to be relatively complete. However, early in 2016 the stratospheric heart skipped a beat, confounding our present understanding of it. The disruption was seen as a thin and rapidly growing westward wind jet at 25km within a deep background of eastward winds. The position of the thin jet could not be explained by waves percolating up through underlying winds from the turbulent lower atmosphere. Rather clues to the origin of the disruption pointed to agents outside the tropics - large scale waves usually found at mid-latitudes made their way to the tropics, causing the disruption. Clear links are found between the winds occurring in the tropical stratosphere and the sorts of seasonal weather experienced in the tropics (e.g. MJO) and Northern/Southern Europe. Because these tropical stratosphere winds are predictable out to years, weather centres are keen to exploit them for seasonal forecasting. The 2016 disruption was not anticipated by weather centres and this has clear implications for the limiting skill of future seasonal forecasts. The results from this study raise many questions. How will the disrupted QBO impact future seasonal forecasting? Will similar events recur more often in the future, and if so what role did anthropogenic climate change play in the 2016 event? Finally, what conditions ultimately resulted in the disruption? Osprey, S. M. et al. An unexpected

  6. Determining confounding sensitivities in eddy current thin film measurements

    NASA Astrophysics Data System (ADS)

    Gros, Ethan; Udpa, Lalita; Smith, James A.; Wachs, Katelyn

    2017-02-01

    Eddy current (EC) techniques are widely used in industry to measure the thickness of non-conductive films on a metal substrate. This is done by using a system whereby a coil carrying a high-frequency alternating current is used to create an alternating magnetic field at the surface of the instrument's probe. When the probe is brought near a conductive surface, the alternating magnetic field will induce ECs in the conductor. The substrate characteristics and the distance of the probe from the substrate (the coating thickness) affect the magnitude of the ECs. The induced currents load the probe coil affecting the terminal impedance of the coil. The measured probe impedance is related to the lift off between coil and conductor as well as conductivity of the test sample. For a known conductivity sample, the probe impedance can be converted into an equivalent film thickness value. The EC measurement can be confounded by a number of measurement parameters. It was the goal of this research to determine which physical properties of the measurement set-up and sample can adversely affect the thickness measurement. The eddy-current testing was performed using a commercially available, hand-held eddy-current probe (ETA3.3H spring-loaded eddy probe running at 8 MHz) that comes with a stand to hold the probe. The stand holds the probe and adjusts the probe on the z-axis to help position the probe in the correct area as well as make precise measurements. The signal from the probe was sent to a hand-held readout, where the results are recorded directly in terms of liftoff or film thickness. Understanding the effect of certain factors on the measurements of film thickness, will help to evaluate how accurate the ETA3.3H spring-loaded eddy probe was at measuring film thickness under varying experimental conditions. This research studied the effects of a number of factors such as i) conductivity, ii) edge effect, iii) surface finish of base material and iv) cable condition.

  7. FASB (Financial Accounting Standards Board) proposal changes retiree healthcare benefit accounting.

    PubMed

    Grimaldi, P L; Bertko, J M

    1989-07-01

    The Financial Accounting Standards Board (FASB) recently issued an exposure draft (ED) of a standard that would change the way organizations account for their employees' post-retirement healthcare benefits. According to the ED, organizations would have to switch from cash accounting to accrual accounting for post-retirement benefits as well as record their retiree healthcare liabilities on their balance sheets by 1992.

  8. Human Resource Accounting.

    DTIC Science & Technology

    1984-12-01

    costs . The goal of this thesis is to help the Portuguese Navy in formulating a formal and coherent approach to its human resource accounting , and in so...ABSTRACT Human Resource Accounting means accounting for people as an organizational asset. It is the measurement of the cost and value of people to the...29 II.HUMAN RESOURCE COSTS . . . . . . . . . . . 30 A. CONCEPTS OF COST AND MEASUREMENT METHODS . . . 30 1. Accounting Concepts of Costs

  9. Electrical conduction along endothelial cell tubes from mouse feed arteries: confounding actions of glycyrrhetinic acid derivatives

    PubMed Central

    Behringer, Erik J; Socha, Matthew J; Polo-Parada, Luis; Segal, Steven S

    2012-01-01

    BACKGROUND AND PURPOSE Electrical conduction along endothelium of resistance vessels has not been determined independently of the influence of smooth muscle, surrounding tissue or blood. Two interrelated hypotheses were tested: (i) Intercellular conduction of electrical signals is manifest in endothelial cell (EC) tubes; and (ii) Inhibitors of gap junction channels (GJCs) have confounding actions on EC electrical and Ca2+ signalling. EXPERIMENTAL APPROACH Intact EC tubes were isolated from abdominal muscle feed (superior epigastric) arteries of C57BL/6 mice. Hyperpolarization was initiated with indirect (ACh) and direct (NS309) stimulation of intermediate- and small-conductance Ca2+-activated K+ channels (IKCa/SKCa). Remote membrane potential (Vm) responses to intracellular current injection defined the length constant (λ) for electrical conduction. Dye coupling was evaluated following intracellular microinjection of propidium iodide. Intracellular Ca2+ dynamics were determined using Fura-2 photometry. Carbenoxolone (CBX) or β-glycyrrhetinic acid (βGA) was used to investigate the role of GJCs. KEY RESULTS Steady-state Vm of ECs was −25 mV. ACh and NS309 hyperpolarized ECs by −40 and −60 mV respectively. Electrical conduction decayed monoexponentially with distance (λ∼1.4 mm). Propidium iodide injected into one EC spread into surrounding ECs. CBX or βGA inhibited dye transfer, electrical conduction and EC hyperpolarization reversibly. Both agents elevated resting Ca2+ while βGA inhibited responses to ACh. CONCLUSIONS AND IMPLICATIONS Individual cells were effectively coupled to each other within EC tubes. Inhibiting GJCs with glycyrrhetinic acid derivatives blocked hyperpolarization mediated by IKCa/SKCa channels, regardless of Ca2+ signalling, obviating use of these agents in distinguishing key determinants of electrical conduction along the endothelium. PMID:22168386

  10. Multimedia and Management Accounting: Adding Creativity to Accounting.

    ERIC Educational Resources Information Center

    Heisz, Mary A.; Blake, Catherine M.; Andrusyszyn, Mary-Anne

    2000-01-01

    Describes the development of an interactive multimedia accounting module for management accounting at the University of Western Ontario. Discusses results of a study of graduate students that investigated the influence of the module on learning and retention compared to traditional instruction as well as students' perceptions of the module.…

  11. Implantation and Recording of Wireless Electroretinogram and Visual Evoked Potential in Conscious Rats.

    PubMed

    Charng, Jason; He, Zheng; Bui, Bang; Vingrys, Algis; Ivarsson, Magnus; Fish, Rebecca; Gurrell, Rachel; Nguyen, Christine

    2016-06-29

    The full-field electroretinogram (ERG) and visual evoked potential (VEP) are useful tools to assess retinal and visual pathway integrity in both laboratory and clinical settings. Currently, preclinical ERG and VEP measurements are performed with anesthesia to ensure stable electrode placements. However, the very presence of anesthesia has been shown to contaminate normal physiological responses. To overcome these anesthesia confounds, we develop a novel platform to assay ERG and VEP in conscious rats. Electrodes are surgically implanted sub-conjunctivally on the eye to assay the ERG and epidurally over the visual cortex to measure the VEP. A range of amplitude and sensitivity/timing parameters are assayed for both the ERG and VEP at increasing luminous energies. The ERG and VEP signals are shown to be stable and repeatable for at least 4 weeks post surgical implantation. This ability to record ERG and VEP signals without anesthesia confounds in the preclinical setting should provide superior translation to clinical data.

  12. Public health departments and accountable care organizations: finding common ground in population health.

    PubMed

    Ingram, Richard; Scutchfield, F Douglas; Costich, Julia F

    2015-05-01

    We examined areas of potential collaboration between accountable care organizations and public health agencies, as well as perceived barriers and facilitators. We interviewed 9 key informants on 4 topics: advantages of public health agency involvement in accountable care organizations; services public health agencies could provide; practical, cultural, and legal barriers to accountable care organization-public health agency involvement; and business models that facilitate accountable care organization-public health agency collaboration. Public health agencies could help accountable care organizations partner with community organizations and reach vulnerable patients, provide population-based services and surveillance data, and promote policies that improve member health. Barriers include accountable care organizations' need for short-term financial yield, limited public health agency technical and financial capacity, and the absence of a financial model.

  13. 18 CFR 367.5000 - Accounts 500-598, Electric operation and maintenance accounts.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 18 Conservation of Power and Water Resources 1 2012-04-01 2012-04-01 false Accounts 500-598... Accounts 500-598, Electric operation and maintenance accounts. Service companies must use accounts 500 through 598 in part 101 of this chapter. ...

  14. 18 CFR 367.5000 - Accounts 500-598, Electric operation and maintenance accounts.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 18 Conservation of Power and Water Resources 1 2013-04-01 2013-04-01 false Accounts 500-598... Accounts 500-598, Electric operation and maintenance accounts. Service companies must use accounts 500 through 598 in part 101 of this chapter. ...

  15. 18 CFR 367.5000 - Accounts 500-598, Electric operation and maintenance accounts.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 18 Conservation of Power and Water Resources 1 2010-04-01 2010-04-01 false Accounts 500-598... Accounts 500-598, Electric operation and maintenance accounts. Service companies must use accounts 500 through 598 in part 101 of this chapter. ...

  16. 18 CFR 367.5000 - Accounts 500-598, Electric operation and maintenance accounts.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 18 Conservation of Power and Water Resources 1 2014-04-01 2014-04-01 false Accounts 500-598... Accounts 500-598, Electric operation and maintenance accounts. Service companies must use accounts 500 through 598 in part 101 of this chapter. ...

  17. 18 CFR 367.5000 - Accounts 500-598, Electric operation and maintenance accounts.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 18 Conservation of Power and Water Resources 1 2011-04-01 2011-04-01 false Accounts 500-598... Accounts 500-598, Electric operation and maintenance accounts. Service companies must use accounts 500 through 598 in part 101 of this chapter. ...

  18. Association between Exposure to Endocrine Disruptors in Drinking Water and Preterm Birth, Taking Neighborhood Deprivation into Account: A Historic Cohort Study.

    PubMed

    Albouy-Llaty, Marion; Limousi, Frédérike; Carles, Camille; Dupuis, Antoine; Rabouan, Sylvie; Migeot, Virginie

    2016-08-09

    The relationship between preterm birth (PTB) and endocrine disruptor exposure in drinking-water has only occasionally been studied. The objective of this work was to investigate the relation between exposure to atrazine metabolites, or atrazine/nitrate mixtures, in drinking-water during pregnancy and prevalence of PTB neonates, while taking neighborhood deprivation into account. A historic cohort study in Deux-Sèvres, France, between 2005 and 2010 with a multiple imputation model for data of exposure to atrazine metabolites and a logistic regression were carried out. We included 13,654 mother/neonate pairs living in 279 different census districts. The prevalence of PTB was 4%. Average atrazine metabolite concentration was 0.019 ± 0.009 (0.014-0.080) µg/L and 39% of mothers lived in less deprived areas. The individual data were associated with risk of PTB. The risk of PTB when exposed to highest concentration of atrazine metabolite adjusted for confounders, was ORa 1.625 95% CI [0.975; 2.710]. Taking, or not, neighborhood deprivation into account did not change the result. Exposure to atrazine/nitrate mixtures remained non-significant. Even if we took neighborhood deprivation into account, we could not show a significant relationship between exposure to atrazine metabolites, or mixtures, in drinking-water during the second trimester of pregnancy and PTB.

  19. Association between Exposure to Endocrine Disruptors in Drinking Water and Preterm Birth, Taking Neighborhood Deprivation into Account: A Historic Cohort Study

    PubMed Central

    Albouy-Llaty, Marion; Limousi, Frédérike; Carles, Camille; Dupuis, Antoine; Rabouan, Sylvie; Migeot, Virginie

    2016-01-01

    Background: The relationship between preterm birth (PTB) and endocrine disruptor exposure in drinking-water has only occasionally been studied. The objective of this work was to investigate the relation between exposure to atrazine metabolites, or atrazine/nitrate mixtures, in drinking-water during pregnancy and prevalence of PTB neonates, while taking neighborhood deprivation into account. Method: A historic cohort study in Deux-Sèvres, France, between 2005 and 2010 with a multiple imputation model for data of exposure to atrazine metabolites and a logistic regression were carried out. Results: We included 13,654 mother/neonate pairs living in 279 different census districts. The prevalence of PTB was 4%. Average atrazine metabolite concentration was 0.019 ± 0.009 (0.014–0.080) µg/L and 39% of mothers lived in less deprived areas. The individual data were associated with risk of PTB. The risk of PTB when exposed to highest concentration of atrazine metabolite adjusted for confounders, was ORa 1.625 95% CI [0.975; 2.710]. Taking, or not, neighborhood deprivation into account did not change the result. Exposure to atrazine/nitrate mixtures remained non-significant. Conclusions: Even if we took neighborhood deprivation into account, we could not show a significant relationship between exposure to atrazine metabolites, or mixtures, in drinking-water during the second trimester of pregnancy and PTB. PMID:27517943

  20. Absolute and proportional measures of potential markers of rehearsal, and their implications for accounts of its development

    PubMed Central

    Jarrold, Christopher; Danielsson, Henrik; Wang, Xiaoli

    2015-01-01

    Previous studies of the development of phonological similarity and word length effects in children have shown that these effects are small or absent in young children, particularly when measured using visual presentation of the memoranda. This has often been taken as support for the view that young children do not rehearse. The current paper builds on recent evidence that instead suggests that absent phonological similarity and word length effects in young children reflects the same proportional cost of these effects in children of all ages. Our aims are to explore the conditions under which this proportional scaling account can reproduce existing developmental data, and in turn suggest ways that future studies might measure and model phonological similarity and word length effects in children. To that end, we first fit a single mathematical function through previously reported data that simultaneously captures absent and negative proportional effects of phonological similarity in young children plus constant proportional similarity effects in older children. This developmental function therefore provides the benchmark that we seek to re-produce in a series of subsequent simulations that test the proportional scaling account. These simulations reproduce the developmental function well, provided that they take into account the influence of floor effects and of measurement error. Our simulations suggest that future empirical studies examining these effects in the context of the development of rehearsal need to take into account proportional scaling. They also provide a demonstration of how proportional costs can be explored, and of the possible developmental functions associated with such an analysis. PMID:25852615

  1. Moving toward implementation: the potential for accountable care organizations and private-public partnerships to advance active neighborhood design.

    PubMed

    Zusman, Edie E; Carr, Sara Jensen; Robinson, Judy; Kasirye, Olivia; Zell, Bonnie; Miller, William Jahmal; Duarte, Teri; Engel, Adrian B; Hernandez, Monica; Horton, Mark B; Williams, Frank

    2014-12-01

    The 2010 Affordable Care Act's (ACA) aims of lowering costs and improving quality of care will renew focus on preventive health strategies. This coincides with a trend in medicine to reconsider population health approaches as part of the standard curriculum. This intersection of new policy and educational climates presents a unique opportunity to reconsider traditional healthcare structures. This paper introduces and advances an alignment that few have considered. We propose that accountable care organizations (ACOs), which are expected to proliferate under the ACA, present the best opportunity to establish partnerships between healthcare, public health, and community-based organizations to achieve the legislation's goals. One example is encouraging daily physical activity via built environment interventions and programs, which is recommended by numerous groups. We highlight how nonprofit organizations in Sacramento, California have been able to leverage influence, capital, and policy to encourage design for active living, and how their work is coordinating with public health and healthcare initiatives. In conclusion, we critically examine potential barriers to the success of partnerships between ACOs and community organizations and encourage further exploration and evaluation. Copyright © 2014 Elsevier Inc. All rights reserved.

  2. The Accounting Principles Instructor's Influence on Students' Decision To Major in Accounting.

    ERIC Educational Resources Information Center

    Mauldin, Shawn; Crain, John L.; Mounce, Patricia H.

    2000-01-01

    A survey of 81 accounting majors, 60 business majors, 12 nonbusiness majors, and 13 undecided students in accounting principles courses found that accounting principles instructors play the most significant role in the decision to major in accounting. Many students decide to major during their first principles course. (SK)

  3. Updating the Duplex Design for Test-Based Accountability in the Twenty-First Century

    ERIC Educational Resources Information Center

    Bejar, Isaac I.; Graf, E. Aurora

    2010-01-01

    The duplex design by Bock and Mislevy for school-based testing is revisited and evaluated as a potential platform in test-based accountability assessments today. We conclude that the model could be useful in meeting the many competing demands of today's test-based accountability assessments, although many research questions will need to be…

  4. Radiology applications of financial accounting.

    PubMed

    Leibenhaut, Mark H

    2005-03-01

    A basic knowledge of financial accounting can help radiologists analyze business opportunities and examine the potential impacts of new technology or predict the adverse consequences of new competitors entering their service area. The income statement, balance sheet, and cash flow statement are the three basic financial statements that document the current financial position of the radiology practice and allow managers to monitor the ongoing financial operations of the enterprise. Pro forma, or hypothetical, financial statements can be generated to predict the financial impact of specific business decisions or investments on the profitability of the practice. Sensitivity analysis, or what-if scenarios, can be performed to determine the potential impact of changing key revenue, investment, operating cost or financial assumptions. By viewing radiology as both a profession and a business, radiologists can optimize their use of scarce economic resources and maximize the return on their financial investments.

  5. Accounting for quality: on the relationship between accounting and quality improvement in healthcare.

    PubMed

    Pflueger, Dane

    2015-04-23

    Accounting-that is, standardized measurement, public reporting, performance evaluation and managerial control-is commonly seen to provide the core infrastructure for quality improvement in healthcare. Yet, accounting successfully for quality has been a problematic endeavor, often producing dysfunctional effects. This has raised questions about the appropriate role for accounting in achieving quality improvement. This paper contributes to this debate by contrasting the specific way in which accounting is understood and operationalized for quality improvement in the UK National Health Service (NHS) with findings from the broadly defined 'social studies of accounting' literature and illustrative examples. This paper highlights three significant differences between the way that accounting is understood to operate in the dominant health policy discourse and recent healthcare reforms, and in the social studies of accounting literature. It shows that accounting does not just find things out, but makes them up. It shows that accounting is not simply a matter of substance, but of style. And it shows that accounting does not just facilitate, but displaces, control. The illumination of these differences in the way that accounting is conceptualized helps to diagnose why accounting interventions often fail to produce the quality improvements that were envisioned. This paper concludes that accounting is not necessarily incompatible with the ambition of quality improvement, but that it would need to be understood and operationalized in new ways in order to contribute to this end. Proposals for this new way of advancing accounting are discussed. They include the cultivation of overlapping and even conflicting measures of quality, the evaluation of accounting regimes in terms of what they do to practice, and the development of distinctively skeptical calculative cultures.

  6. Improving observational study estimates of treatment effects using joint modeling of selection effects and outcomes: the case of AAA repair.

    PubMed

    O'Malley, A James; Cotterill, Philip; Schermerhorn, Marc L; Landon, Bruce E

    2011-12-01

    When 2 treatment approaches are available, there are likely to be unmeasured confounders that influence choice of procedure, which complicates estimation of the causal effect of treatment on outcomes using observational data. To estimate the effect of endovascular (endo) versus open surgical (open) repair, including possible modification by institutional volume, on survival after treatment for abdominal aortic aneurysm, accounting for observed and unobserved confounding variables. Observational study of data from the Medicare program using a joint model of treatment selection and survival given treatment to estimate the effects of type of surgery and institutional volume on survival. We studied 61,414 eligible repairs of intact abdominal aortic aneurysms during 2001 to 2004. The outcome, perioperative death, is defined as in-hospital death or death within 30 days of operation. The key predictors are use of endo, transformed endo and open volume, and endo-volume interactions. There is strong evidence of nonrandom selection of treatment with potential confounding variables including institutional volume and procedure date, variables not typically adjusted for in clinical trials. The best fitting model included heterogeneous transformations of endo volume for endo cases and open volume for open cases as predictors. Consistent with our hypothesis, accounting for unmeasured selection reduced the mortality benefit of endo. The effect of endo versus open surgery varies nonlinearly with endo and open volume. Accounting for institutional experience and unmeasured selection enables better decision-making by physicians making treatment referrals, investigators evaluating treatments, and policy makers.

  7. Public Health Departments and Accountable Care Organizations: Finding Common Ground in Population Health

    PubMed Central

    Ingram, Richard; Scutchfield, F. Douglas

    2015-01-01

    We examined areas of potential collaboration between accountable care organizations and public health agencies, as well as perceived barriers and facilitators. We interviewed 9 key informants on 4 topics: advantages of public health agency involvement in accountable care organizations; services public health agencies could provide; practical, cultural, and legal barriers to accountable care organization–public health agency involvement; and business models that facilitate accountable care organization–public health agency collaboration. Public health agencies could help accountable care organizations partner with community organizations and reach vulnerable patients, provide population-based services and surveillance data, and promote policies that improve member health. Barriers include accountable care organizations’ need for short-term financial yield, limited public health agency technical and financial capacity, and the absence of a financial model. PMID:25790392

  8. Accounting History in Undergraduate Introductory Financial Accounting Courses: An Exploratory Study.

    ERIC Educational Resources Information Center

    Williams, Satina V.; Schwartz, Bill N.

    2002-01-01

    Accounting faculty surveyed (n=45) did not overwhelmingly support incorporating accounting history into introductory courses, despite Accounting Education Change Commission recommendations. They did not support a separate course or believe history would attract more students. Attitudes of those already including history did not differ greatly from…

  9. The obesity paradox in stable chronic heart failure does not persist after matching for indicators of disease severity and confounders.

    PubMed

    Frankenstein, Lutz; Zugck, Christian; Nelles, Manfred; Schellberg, Dieter; Katus, Hugo A; Remppis, B Andrew

    2009-12-01

    To verify whether controlling for indicators of disease severity and confounders represents a solution to the obesity paradox in chronic heart failure (CHF). From a cohort of 1790 patients, we formed 230 nested matched triplets by individually matching patients with body mass index (BMI) > 30 kg/m(2) (Group 3), BMI 20-24.9 k/m(2) (Group 1) and BMI 25-29.9 kg/m(2) (Group 2), according to NT-proBNP, age, sex, and NYHA class (triplet = one matched patient from each group). Although in the pre-matching cohort, BMI group was a significant univariable prognostic indicator, it did not retain significance [heart rate (HR): 0.91, 95% CI: 0.78-1.05, chi(2): 1.67] when controlled for group propensities as covariates. Furthermore, in the matched cohort, 1-year mortality and 3-year mortality did not differ significantly. Here, BMI again failed to reach statistical significance for prognosis, either as a continuous or categorical variable, whether crude or adjusted. This result was confirmed in the patients not selected for matching. NT-proBNP, however, remained statistically significant (log(NT-proBNP): HR: 1.49, 95% CI: 1.13-1.97, chi(2): 7.82) after multivariable adjustment. The obesity paradox does not appear to persist in a matched setting with respect to indicators of disease severity and other confounders. NT-proBNP remains an independent prognostic indicator of adverse outcome irrespective of obesity status.

  10. Sample size calculations for case-control studies

    Cancer.gov

    This R package can be used to calculate the required samples size for unconditional multivariate analyses of unmatched case-control studies. The sample sizes are for a scalar exposure effect, such as binary, ordinal or continuous exposures. The sample sizes can also be computed for scalar interaction effects. The analyses account for the effects of potential confounder variables that are also included in the multivariate logistic model.

  11. Inverse probability weighting to control confounding in an illness-death model for interval-censored data.

    PubMed

    Gillaizeau, Florence; Sénage, Thomas; Le Borgne, Florent; Le Tourneau, Thierry; Roussel, Jean-Christian; Leffondrè, Karen; Porcher, Raphaël; Giraudeau, Bruno; Dantan, Etienne; Foucher, Yohann

    2018-04-15

    Multistate models with interval-censored data, such as the illness-death model, are still not used to any considerable extent in medical research regardless of the significant literature demonstrating their advantages compared to usual survival models. Possible explanations are their uncommon availability in classical statistical software or, when they are available, by the limitations related to multivariable modelling to take confounding into consideration. In this paper, we propose a strategy based on propensity scores that allows population causal effects to be estimated: the inverse probability weighting in the illness semi-Markov model with interval-censored data. Using simulated data, we validated the performances of the proposed approach. We also illustrated the usefulness of the method by an application aiming to evaluate the relationship between the inadequate size of an aortic bioprosthesis and its degeneration or/and patient death. We have updated the R package multistate to facilitate the future use of this method. Copyright © 2017 John Wiley & Sons, Ltd.

  12. Missing variables: how exclusion of human resources policy information confounds research connecting health and business outcomes.

    PubMed

    Lynch, Wendy D; Sherman, Bruce W

    2014-01-01

    When corporate health researchers examine the effects of health on business outcomes or the effect of health interventions on health and business outcomes, results will necessarily be confounded by the corporate environment(s) in which they are studied. In this research setting, most studies control for factors traditionally identified in public health, such as demographics and health status. Nevertheless, often overlooked is the extent to which company policies can also independently impact health care cost, work attendance, and productivity outcomes. With changes in employment and benefits practices resulting from health care reform, including incentives and plan design options, consideration of these largely neglected variables in research design has become increasingly important. This commentary summarizes existing knowledge regarding the implications of policy variations in research outcomes and provides a framework for incorporating them into future employer-based research.

  13. A Comparative Study of the Perceptions of Accounting Educators and Accountants on Skills Required of Accounting Education Graduates in Automated Offices

    ERIC Educational Resources Information Center

    Nwokike, Felicia Ogonnia; Eya, Gloria Mgboyibo

    2015-01-01

    The study dealt with perception of accounting educators and senior accountants on skills required of accounting education graduates for effective job performance in automated offices. The study adopted a descriptive research design.The population consisted of 149 respondents, made up of 80 accounting educators in public tertiary institutions and…

  14. Is social isolation/alienation confounded with, and non-independent of, emotional distress in its association with early onset of coronary artery disease?

    PubMed

    Ketterer, Mark; Rose, Benjamin; Knysz, Walter; Farha, Amjad; Deveshwar, Sangita; Schairer, John; Keteyian, Steven J

    2011-03-01

    Both emotional distress (ED) and social isolation/alienation (SI/A) have been found to prospectively predict adverse cardiac events, but few studies have tested the confounding/redundancy of these measures as correlates/predictors of outcomes. In this study, 163 patients with documented coronary artery disease (CAD) were interviewed for multiple indices of SI/A and administered the Symptom Checklist 90 - Revised (SCL90R). A spouse or friend provided an independent rating of ED using the spouse/friend version of the Ketterer Stress Symptom Frequency Checklist (KSSFC). The measures of ED and SI/A covaried. All three scales from the KSSFC (depression, anxiety, and "AIAI" - aggravation, irritation, anger, and impatience), and three scales from the SCL90R (anxiety, depression, and psychoticism), were associated with early Age at Initial Diagnosis (AAID) of CAD. Neither three scales derived from the SCL90R (shyness, feeling abused, and feeling lonely) nor the interview indices of SI/A (married, living alone, having a confidant, self description as a lone wolf, and self-description as lonely) were associated with early AAID. Thus, it is concluded that the present results indicate that ED and SI/A are confounded and that, even when tested head-to-head in a multivariate analysis, only ED is associated with AAID.

  15. 18 CFR 367.1460 - Account 146, Accounts receivable from associate companies.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... POWER ACT AND NATURAL GAS ACT Balance Sheet Chart of Accounts Current and Accrued Assets § 367.1460... 18 Conservation of Power and Water Resources 1 2010-04-01 2010-04-01 false Account 146, Accounts receivable from associate companies. 367.1460 Section 367.1460 Conservation of Power and Water Resources...

  16. 18 CFR 367.2340 - Account 234, Accounts payable to associate companies.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... POWER ACT AND NATURAL GAS ACT Balance Sheet Chart of Accounts Current and Accrued Liabilities § 367.2340... 18 Conservation of Power and Water Resources 1 2010-04-01 2010-04-01 false Account 234, Accounts payable to associate companies. 367.2340 Section 367.2340 Conservation of Power and Water Resources...

  17. Potential sources of bias in the use of Escherichia coli to measure waterborne diarrhoea risk in low-income settings.

    PubMed

    Ercumen, Ayse; Arnold, Benjamin F; Naser, Abu Mohd; Unicomb, Leanne; Colford, John M; Luby, Stephen P

    2017-01-01

    Escherichia coli is the standard water quality indicator for diarrhoea risk. Yet, the association between E. coli and diarrhoea is inconsistent across studies without a systematic assessment of methodological differences behind this variation. Most studies measure water quality cross-sectionally with diarrhoea, risking exposure misclassification and reverse causation. Studies use different recall windows for self-reported diarrhoea; longer periods increase potential outcome misclassification through misrecall. Control of confounding is inconsistent across studies. Additionally, diarrhoea measured in unblinded intervention trials can present courtesy bias. We utilised measurements from a randomised trial of water interventions in Bangladesh to assess how these factors affect the E. coli-diarrhoea association. We compared cross-sectional versus prospective measurements of water quality and diarrhoea, 2-versus 7-day symptom recall periods, estimates with and without controlling for confounding and using measurements from control versus intervention arms of the trial. In the control arm, 2-day diarrhoea prevalence, measured prospectively 1 month after water quality, significantly increased with log 10 E. coli (PR = 1.50, 1.02-2.20). This association weakened when we used 7-day recall (PR = 1.18, 0.88-1.57), cross-sectional measurements of E. coli and diarrhoea (PR = 1.11, 0.79-1.56) or did not control for confounding (PR = 1.20, 0.88-1.62). Including data from intervention arms led to less interpretable associations, potentially due to courtesy bias, effect modification and/or reverse causation. By systematically addressing potential sources of bias, our analysis demonstrates a clear relationship between E. coli in drinking water and diarrhoea, suggesting that the continued use of E. coli as an indicator of waterborne diarrhoea risk is justified. © 2016 John Wiley & Sons Ltd.

  18. 76 FR 8989 - Federal Acquisition Regulation; Updated Financial Accounting Standards Board Accounting References

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-16

    ... Acquisition Regulation; Updated Financial Accounting Standards Board Accounting References AGENCIES... Acquisition Regulation (FAR) to update references to authoritative accounting standards owing to the Financial... Accounting Principles (GAAP) (``Codification of GAAP''). DATES: Interested parties should submit written...

  19. High SNR Acquisitions Improve the Repeatability of Liver Fat Quantification Using Confounder-corrected Chemical Shift-encoded MR Imaging

    PubMed Central

    Motosugi, Utaroh; Hernando, Diego; Wiens, Curtis; Bannas, Peter; Reeder, Scott. B

    2017-01-01

    Purpose: To determine whether high signal-to-noise ratio (SNR) acquisitions improve the repeatability of liver proton density fat fraction (PDFF) measurements using confounder-corrected chemical shift-encoded magnetic resonance (MR) imaging (CSE-MRI). Materials and Methods: Eleven fat-water phantoms were scanned with 8 different protocols with varying SNR. After repositioning the phantoms, the same scans were repeated to evaluate the test-retest repeatability. Next, an in vivo study was performed with 20 volunteers and 28 patients scheduled for liver magnetic resonance imaging (MRI). Two CSE-MRI protocols with standard- and high-SNR were repeated to assess test-retest repeatability. MR spectroscopy (MRS)-based PDFF was acquired as a standard of reference. The standard deviation (SD) of the difference (Δ) of PDFF measured in the two repeated scans was defined to ascertain repeatability. The correlation between PDFF of CSE-MRI and MRS was calculated to assess accuracy. The SD of Δ and correlation coefficients of the two protocols (standard- and high-SNR) were compared using F-test and t-test, respectively. Two reconstruction algorithms (complex-based and magnitude-based) were used for both the phantom and in vivo experiments. Results: The phantom study demonstrated that higher SNR improved the repeatability for both complex- and magnitude-based reconstruction. Similarly, the in vivo study demonstrated that the repeatability of the high-SNR protocol (SD of Δ = 0.53 for complex- and = 0.85 for magnitude-based fit) was significantly higher than using the standard-SNR protocol (0.77 for complex, P < 0.001; and 0.94 for magnitude-based fit, P = 0.003). No significant difference was observed in the accuracy between standard- and high-SNR protocols. Conclusion: Higher SNR improves the repeatability of fat quantification using confounder-corrected CSE-MRI. PMID:28190853

  20. Accounting for unprotected sex: stories of agency and acceptability.

    PubMed

    Rhodes, Tim; Cusick, Linda

    2002-07-01

    Based on the idea that risks are knowable, calculable and preventable, dominant social scientific and health promotion discourses foster an image of individual risk control and responsibility. The presentation of the self is a moral enterprise. Accounts of unprotected sex by HIV positive people who have the potential to transmit HIV to their sexual partners can be particularly morally charged. Drawing on 73 depth qualitative interviews with HIV positive people and their sexual partners, this paper explores how the interview accounts of unprotected sex can illuminate the way in which the self is presented within the context of situated norms of risk acceptability and moral responsibility. We identify two forms of account: stories of agency; and stories of acceptability. Stories of agency tend to deny agency and abdicate individual responsibility given the circumstances, and were also a key feature of accounts in which the sexual partners of HIV positive people were placed at risk of HIV transmission. Categories of appeal included the denial of agency as a consequence of: risk calculus and condom accidents; alcohol and drug effects; powerlessness and coercion; and forces of nature. By contrast, stories of acceptability tend to justify unprotected sex as acceptable. Categories of appeal included: HIV positive concordance; and commitment in relationships. Other forms of justification included: alter responsibility; and intentional HIV transmission. We conclude that accounts of risk management are risk managed. We call for greater attention by social scientists to the way in which accounts are constructed, and in particular, to 'anti-rational' forms of explanation within accounts.

  1. Women Accountants in Practicing Accounting Firms: Their Status, Investments and Returns

    ERIC Educational Resources Information Center

    Okpechi, Simeon O.; Belmasrour, Rachid

    2011-01-01

    In the past twenty years, the number of qualified women accountants in the U.S. has outstripped that of men according to American Institute of Certified Public Accountants; yet these women occupy few strategic positions in accounting firms. Retention has been a major issue. This study explores how the perception of their status, investments and…

  2. Research Assessments and Rankings: Accounting for Accountability in "Higher Education Ltd"

    ERIC Educational Resources Information Center

    Singh, Geeta

    2008-01-01

    Over the past two decades, higher education in advanced capitalist societies has undergone a process of radical "reform". A key element of this reform has been the introduction of a number of accounting-based techniques in the pursuit of improved accountability and transparency. While the "old" accounting was to do with stewardship, the "new"…

  3. Measures of Cognitive Limitations and Their Relation to Perceived Work Limitations in Breast Cancer Survivors

    DTIC Science & Technology

    2009-03-06

    impact work limitations in BCS and a Non-Cancer Comparison Group (NCCG) and to investigate the relationship between perceived and observed measures of...NCCG), and to investigate the relationship between perceived and observed measures of cognitive limitations, accounting for possible confounders in...accounting for proposed confounders; 3) replicate previous work indicating a stronger relationship between physical fatigue and work limitations in

  4. Commentary: How can family-based quasi-experimental designs and national registers be used to address confounding in risk factor studies of psychopathology? A reflection on Obel et al. (2016).

    PubMed

    Larsson, Henrik

    2016-04-01

    Standard observational studies have reported a robust correlation between maternal smoking during pregnancy and risk of ADHD in offspring. In the accompanying article, Obel et al. used sibling-comparisons to explore the extent to which unmeasured familial confounding explains this association. This commentary highlights three important implications of the study. At a general level, Obel et al. illustrates how (1) family-based quasi-experimental designs and (2) national registers can be used to address confounding in risk factor studies of psychopathology. At a more specific level, the study suggests that maternal smoking during pregnancy is probably not a causal risk factor for ADHD. © 2016 Association for Child and Adolescent Mental Health.

  5. A cognitive account of belief: a tentative road map

    PubMed Central

    Connors, Michael H.; Halligan, Peter W.

    2015-01-01

    Over the past decades, delusions have become the subject of growing and productive research spanning clinical and cognitive neurosciences. Despite this, the nature of belief, which underpins the construct of delusions, has received little formal investigation. No account of delusions, however, would be complete without a cognitive level analysis of belief per se. One reason for this neglect is the assumption that, unlike more established and accessible modular psychological process (e.g., vision, audition, face-recognition, language-processing, and motor-control systems), beliefs comprise more distributed and therefore less accessible central cognitive processes. In this paper, we suggest some defining characteristics and functions of beliefs. Working back from cognitive accounts of delusions, we consider potential candidate cognitive processes that may be involved in normal belief formation. Finally, we advance a multistage account of the belief process that could provide the basis for a more comprehensive model of belief. PMID:25741291

  6. Disease Risk Score (DRS) as a Confounder Summary Method: Systematic Review and Recommendations

    PubMed Central

    Tadrous, Mina; Gagne, Joshua J.; Stürmer, Til; Cadarette, Suzanne M.

    2013-01-01

    Purpose To systematically examine trends and applications of the disease risk score (DRS) as a confounder summary method. Methods We completed a systematic search of MEDLINE and Web of Science® to identify all English language articles that applied DRS methods. We tabulated the number of publications by year and type (empirical application, methodological contribution, or review paper) and summarized methods used in empirical applications overall and by publication year (<2000, ≥2000). Results Of 714 unique articles identified, 97 examined DRS methods and 86 were empirical applications. We observed a bimodal distribution in the number of publications over time, with a peak 1979-1980, and resurgence since 2000. The majority of applications with methodological detail derived DRS using logistic regression (47%), used DRS as a categorical variable in regression (93%), and applied DRS in a non-experimental cohort (47%) or case-control (42%) study. Few studies examined effect modification by outcome risk (23%). Conclusion Use of DRS methods has increased yet remains low. Comparative effectiveness research may benefit from more DRS applications, particularly to examine effect modification by outcome risk. Standardized terminology may facilitate identification, application, and comprehension of DRS methods. More research is needed to support the application of DRS methods, particularly in case-control studies. PMID:23172692

  7. Adjusting for the Confounding Effects of Treatment Switching-The BREAK-3 Trial: Dabrafenib Versus Dacarbazine.

    PubMed

    Latimer, Nicholas R; Abrams, Keith R; Amonkar, Mayur M; Stapelkamp, Ceilidh; Swann, R Suzanne

    2015-07-01

    Patients with previously untreated BRAF V600E mutation-positive melanoma in BREAK-3 showed a median overall survival (OS) of 18.2 months for dabrafenib versus 15.6 months for dacarbazine (hazard ratio [HR], 0.76; 95% confidence interval, 0.48-1.21). Because patients receiving dacarbazine were allowed to switch to dabrafenib at disease progression, we attempted to adjust for the confounding effects on OS. Rank preserving structural failure time models (RPSFTMs) and the iterative parameter estimation (IPE) algorithm were used. Two analyses, "treatment group" (assumes treatment effect could continue until death) and "on-treatment observed" (assumes treatment effect disappears with discontinuation), were used to test the assumptions around the durability of the treatment effect. A total of 36 of 63 patients (57%) receiving dacarbazine switched to dabrafenib. The adjusted OS HRs ranged from 0.50 to 0.55, depending on the analysis. The RPSFTM and IPE "treatment group" and "on-treatment observed" analyses performed similarly well. RPSFTM and IPE analyses resulted in point estimates for the OS HR that indicate a substantial increase in the treatment effect compared with the unadjusted OS HR of 0.76. The results are uncertain because of the assumptions associated with the adjustment methods. The confidence intervals continued to cross 1.00; thus, the adjusted estimates did not provide statistically significant evidence of a treatment benefit on survival. However, it is clear that a standard intention-to-treat analysis will be confounded in the presence of treatment switching-a reliance on unadjusted analyses could lead to inappropriate practice. Adjustment analyses provide useful additional information on the estimated treatment effects to inform decision making. Treatment switching is common in oncology trials, and the implications of this for the interpretation of the clinical effectiveness and cost-effectiveness of the novel treatment are important to consider. If

  8. Adjusting for the Confounding Effects of Treatment Switching—The BREAK-3 Trial: Dabrafenib Versus Dacarbazine

    PubMed Central

    Abrams, Keith R.; Amonkar, Mayur M.; Stapelkamp, Ceilidh; Swann, R. Suzanne

    2015-01-01

    Background. Patients with previously untreated BRAF V600E mutation-positive melanoma in BREAK-3 showed a median overall survival (OS) of 18.2 months for dabrafenib versus 15.6 months for dacarbazine (hazard ratio [HR], 0.76; 95% confidence interval, 0.48–1.21). Because patients receiving dacarbazine were allowed to switch to dabrafenib at disease progression, we attempted to adjust for the confounding effects on OS. Materials and Methods. Rank preserving structural failure time models (RPSFTMs) and the iterative parameter estimation (IPE) algorithm were used. Two analyses, “treatment group” (assumes treatment effect could continue until death) and “on-treatment observed” (assumes treatment effect disappears with discontinuation), were used to test the assumptions around the durability of the treatment effect. Results. A total of 36 of 63 patients (57%) receiving dacarbazine switched to dabrafenib. The adjusted OS HRs ranged from 0.50 to 0.55, depending on the analysis. The RPSFTM and IPE “treatment group” and “on-treatment observed” analyses performed similarly well. Conclusion. RPSFTM and IPE analyses resulted in point estimates for the OS HR that indicate a substantial increase in the treatment effect compared with the unadjusted OS HR of 0.76. The results are uncertain because of the assumptions associated with the adjustment methods. The confidence intervals continued to cross 1.00; thus, the adjusted estimates did not provide statistically significant evidence of a treatment benefit on survival. However, it is clear that a standard intention-to-treat analysis will be confounded in the presence of treatment switching—a reliance on unadjusted analyses could lead to inappropriate practice. Adjustment analyses provide useful additional information on the estimated treatment effects to inform decision making. Implications for Practice: Treatment switching is common in oncology trials, and the implications of this for the interpretation of the

  9. Correlation between serum 25(OH)D values and lupus disease activity: an original article and a systematic review with meta-analysis focusing on serum VitD confounders.

    PubMed

    Sahebari, M; Nabavi, N; Salehi, M

    2014-10-01

    Notwithstanding that several original studies and some systematic reviews have been undertaken on the subject "correlation between serum values of vitamin D (VitD) and lupus disease activity," there is still no consensus on the importance of sectional measurement of serum VitD in the prediction of disease activity and important confounders in estimation of serum VitD. Medline, Web of Knowledge, and Scopus databases were searched from 1995 to 2013. The following medical subject heading (MeSH) terms and/or text words were used: "Vitamin D" OR "25OHD" OR "25(OH)D" combined with "systemic lupus erythematosus" OR "lupus" OR "SLE." References cited in the identified articles were also manually searched. Human studies in any language were included. Original research on this topic was also carried out on 82 lupus patients, considering important VitD confounders according to our systematic review and we included them in the meta-analysis. A total of 35 studies were registered for this study. Only 11 of these pointed to this correlation by Pearson test. The pooled Pearson correlation (r) of associations between disease activity and VitD was -0.365 (95% CI: -0.536, -0.165) with significant heterogeneity (p = 0.001 I (2 )= 93%). Sensitivity analysis resulted in no significant differences. The most important adjustable confounders considered by researchers were drugs, especially hydroxychloroquine, prednisolone and supplementary VitD, body mass index (BMI) and proteinuria or renal function. Only proteinuria was reported to influence VitD concentration strongly. BMI was another probable influencing factor. Our original research presented no correlation between VitD and SLEDAI (p = 0.68, r s = 0.003). This meta-analysis demonstrated that most of the studies on the relationship between VitD and lupus disease activity that found no correlation did not present the details of the statistics. However, analyzing 11 studies, most of which found a reverse correlation and

  10. Toward Reflective Accountability: Using NSSE for Accountability and Transparency

    ERIC Educational Resources Information Center

    McCormick, Alexander C.

    2009-01-01

    Accountability pressures in higher education are not new; they are part of an enduring public policy discourse about the costs and benefits, both individual and social, of higher education. What is relatively new, however, is the prominent place that issues of accountability now occupy on the nation's higher education agenda. There is an important…

  11. Accountable care organizations and radiology: threat or opportunity?

    PubMed

    Abramson, Richard G; Berger, Paul E; Brant-Zawadzki, Michael N

    2012-12-01

    Although the anticipated rise of accountable care organizations brings certain potential threats to radiologists, including direct threats to revenue and indirect systemic changes jeopardizing the bargaining leverage of radiology groups, accountable care organizations, and other integrated health care delivery models may provide radiology with an important opportunity to reassert its leadership and assume a more central role within health care systems. Capitalizing on this potential opportunity, however, will require radiology groups to abandon the traditional "film reader" mentality and engage actively in the design and implementation of nontraditional systems service lines aimed at adding differentiated value to larger health care organizations. Important interlinked and mutually reinforcing components of systems service lines, derived from radiology's core competencies, may include utilization management and decision support, IT leadership, quality and safety assurance, and operational enhancements to meet organizational goals. Such systems-oriented service products, tailored to the needs of individual integrated care entities and supported by objective performance metrics, may provide market differentiation to shield radiology from commoditization and could become an important source of new nonclinical revenue. Copyright © 2012 American College of Radiology. Published by Elsevier Inc. All rights reserved.

  12. The Organizational Account of Function is an Etiological Account of Function.

    PubMed

    Artiga, Marc; Martínez, Manolo

    2016-06-01

    The debate on the notion of function has been historically dominated by dispositional and etiological accounts, but recently a third contender has gained prominence: the organizational account. This original theory of function is intended to offer an alternative account based on the notion of self-maintaining system. However, there is a set of cases where organizational accounts seem to generate counterintuitive results. These cases involve cross-generational traits, that is, traits that do not contribute in any relevant way to the self-maintenance of the organism carrying them, but instead have very important effects on organisms that belong to the next generation. We argue that any plausible solution to the problem of cross-generational traits shows that the organizational account just is a version of the etiological theory and, furthermore, that it does not provide any substantive advantage over standard etiological theories of function.

  13. Health savings accounts and health reimbursement arrangements: assets, account balances, and rollovers, 2006-2011.

    PubMed

    Fronstin, Paul

    2012-01-01

    ASSET LEVELS GROWING: In 2011, there was $12.4 billion in health savings accounts (HSAs) and health reimbursement arrangements (HRAs), spread across 8.4 million accounts, according to data from the 2011 EBRI/MGA Consumer Engagement in Health Care Survey, sponsored by EBRI and Matthew Greenwald & Associates. This is up from 2006, when there were 1.3 million accounts with $873.4 million in assets, and 2010, when 5.4 million accounts held $7.3 billion in assets. AFTER LEVELING OFF, AVERAGE ACCOUNT BALANCES INCREASED: After average account balances leveled off in 2008 and 2009, and fell slightly in 2010, they increased in 2011. In 2006, account balances averaged $696. They increased to $1,320 in 2007, a 90 percent increase. Account balances averaged $1,356 in 2008 and $1,419 in 2009, 3 percent and 5 percent increases, respectively. In 2010, average account balances fell to $1,355, down 4.5 percent from the previous year. In 2011, average account balances increased to $1,470, a 9 percent increase from 2010. TOTAL AND AVERAGE ROLLOVERS INCREASE: After declining to $1,029 in 2010, average rollover amounts increased to $1,208 in 2011. Total assets being rolled over increased as well: $6.7 billion was rolled over in 2011, up from $3.7 billion in 2010. The percentage of individuals without a rollover remained at 13 percent in 2011. HEALTHY BEHAVIOR DOES NOT MEAN HIGHER ACCOUNT BALANCES AND HIGHER ROLLOVERS: Individuals who smoke have more money in their accounts than those who do not smoke. In contrast, obese individuals have less money in their account than the nonobese. There is very little difference in account balances by level of exercise. Very small differences were found in account balances and rollover amounts between individuals who used cost or quality information, compared with those who did not use such information. However, next to no relationship was found between either account balance or rollover amounts and various cost-conscious behaviors. When a difference

  14. A Commentary on "Contextualizing the Intermediate Financial Accounting Courses in the Financial Global Crisis"

    ERIC Educational Resources Information Center

    Woods, Margaret

    2011-01-01

    The breadth of issues raised by the ongoing global financial crisis (GFC) has made accounting education potentially very exciting of late, particularly in the fields of financial reporting and auditing. Students can find it difficult to engage with the conceptual principles that underpin accounting regulation and it can be challenging for the…

  15. Identifying Effective Signals to Predict Deleted and Suspended Accounts on Twitter across Languages

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Volkova, Svitlana; Bell, Eric B.

    Social networks have an ephemerality to them where accounts and messages are constantly being edited, deleted, or marked as private. This continuous change comes from concerns around privacy, a potential desire for deception, and spam-like behavior. In this study we analyze multiple large datasets of thousands of active and deleted Twitter accounts to produce a series of predictive features for the removal or shutdown of an account. We have selected these accounts from speakers of three languages -- Russian, Spanish, and English to evaluate if speakers of various languages behave differently with regards to deleting accounts. We find that unlikemore » previously used profile and network features, the discourse of deleted vs. active accounts forms the basis for highly accurate account deletion prediction. More precisely, we observed that the presence of a certain set of terms in user tweets leads to a higher likelihood for that user's account deletion. We show that the predictive power of profile, language, affect, and network features is not consistent across speakers of the three evaluated languages.« less

  16. Accounting Issues: An Essay Series Part I--Introduction to Accounting Theory and Cash

    ERIC Educational Resources Information Center

    Laux, Judy

    2007-01-01

    Recent accounting scandals challenge academics to refocus the educational process on the theoretical underpinnings of accounting. This is the first in a series of articles designed to facilitate this realignment. Intended as a supplement for the introductory accounting course, the essay series connects each of the primary accounting elements to…

  17. Responses of Schools to Accountability Systems Using Multiple Measures: The Case of New York City Elementary Schools

    ERIC Educational Resources Information Center

    Ehren, M. C. M.; Hatch, T.

    2013-01-01

    Many studies point to potential unintended consequences of accountability systems such as when schools narrow their teaching to fixate on tested subjects. As a result, some states and districts in the USA have complemented the federal test-based accountability system with additional measures of educational practices to hold schools accountable on…

  18. A sequential Cox approach for estimating the causal effect of treatment in the presence of time-dependent confounding applied to data from the Swiss HIV Cohort Study.

    PubMed

    Gran, Jon Michael; Røysland, Kjetil; Wolbers, Marcel; Didelez, Vanessa; Sterne, Jonathan A C; Ledergerber, Bruno; Furrer, Hansjakob; von Wyl, Viktor; Aalen, Odd O

    2010-11-20

    When estimating the effect of treatment on HIV using data from observational studies, standard methods may produce biased estimates due to the presence of time-dependent confounders. Such confounding can be present when a covariate, affected by past exposure, is both a predictor of the future exposure and the outcome. One example is the CD4 cell count, being a marker for disease progression for HIV patients, but also a marker for treatment initiation and influenced by treatment. Fitting a marginal structural model (MSM) using inverse probability weights is one way to give appropriate adjustment for this type of confounding. In this paper we study a simple and intuitive approach to estimate similar treatment effects, using observational data to mimic several randomized controlled trials. Each 'trial' is constructed based on individuals starting treatment in a certain time interval. An overall effect estimate for all such trials is found using composite likelihood inference. The method offers an alternative to the use of inverse probability of treatment weights, which is unstable in certain situations. The estimated parameter is not identical to the one of an MSM, it is conditioned on covariate values at the start of each mimicked trial. This allows the study of questions that are not that easily addressed fitting an MSM. The analysis can be performed as a stratified weighted Cox analysis on the joint data set of all the constructed trials, where each trial is one stratum. The model is applied to data from the Swiss HIV cohort study. Copyright © 2010 John Wiley & Sons, Ltd.

  19. Consistency endangered by FASB-GASB (Financial Accounting Standards Board, Government Accounting Standards Board ) dispute.

    PubMed

    Garner, M; Grossman, W

    1991-02-01

    The Financial Accounting Foundation's (FAF's) November 1989 decision to uphold the 1984 jurisdictional arrangement between the Financial Accounting Standards Board (FASB) and the Government Accounting Standards Board (GASB) leaves little doubt that the healthcare industry will now be subject to two sets of accounting standards. The FAF's decision created a distinction between the accounting practices of government-owned hospitals and non-hospital governmental entities and their adherence to standards set by FASB, GASB, and the American Institute of Certified Public Accountants. A governmental healthcare organization should carefully determine which accounting rules it follows and remain attentive to further GASB developments.

  20. 12 CFR 513.8 - Removal, suspension, or debarment of independent public accountants and accounting firms...

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... independent public accountants and accounting firms performing audit services. 513.8 Section 513.8 Banks and... Removal, suspension, or debarment of independent public accountants and accounting firms performing audit... of independent public accountants and their accounting firms from performing independent audit and...

  1. 12 CFR 513.8 - Removal, suspension, or debarment of independent public accountants and accounting firms...

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... public accountants and accounting firms performing audit services. 513.8 Section 513.8 Banks and Banking..., suspension, or debarment of independent public accountants and accounting firms performing audit services. (a... independent public accountants and their accounting firms from performing independent audit and attestation...

  2. 12 CFR 513.8 - Removal, suspension, or debarment of independent public accountants and accounting firms...

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... public accountants and accounting firms performing audit services. 513.8 Section 513.8 Banks and Banking..., suspension, or debarment of independent public accountants and accounting firms performing audit services. (a... independent public accountants and their accounting firms from performing independent audit and attestation...

  3. 12 CFR 513.8 - Removal, suspension, or debarment of independent public accountants and accounting firms...

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... independent public accountants and accounting firms performing audit services. 513.8 Section 513.8 Banks and... Removal, suspension, or debarment of independent public accountants and accounting firms performing audit... of independent public accountants and their accounting firms from performing independent audit and...

  4. Effect of Coulomb interaction on chemical potential of metal film

    NASA Astrophysics Data System (ADS)

    Kostrobij, P. P.; Markovych, B. M.

    2018-07-01

    The chemical potential of a metal film within the jellium model taking into account the Coulomb interaction between electrons is calculated. The surface potential is modelled as the infinite rectangular potential well. The behaviour of the chemical potential as a function of the film thickness is studied, the quantum size effect for this quantity is analysed. It is shown that taking into account the Coulomb interaction leads to a significant decrease of the chemical potential and to an enhancement of the quantum size effect.

  5. 12 CFR 390.97 - Removal, suspension, or debarment of independent public accountants and accounting firms...

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... independent public accountants and accounting firms performing audit services. 390.97 Section 390.97 Banks and... debarment of independent public accountants and accounting firms performing audit services. (a) Scope. This... accountants and their accounting firms from performing independent audit and attestation services required by...

  6. 12 CFR 390.97 - Removal, suspension, or debarment of independent public accountants and accounting firms...

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... independent public accountants and accounting firms performing audit services. 390.97 Section 390.97 Banks and... debarment of independent public accountants and accounting firms performing audit services. (a) Scope. This... accountants and their accounting firms from performing independent audit and attestation services required by...

  7. 12 CFR 390.97 - Removal, suspension, or debarment of independent public accountants and accounting firms...

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... independent public accountants and accounting firms performing audit services. 390.97 Section 390.97 Banks and... debarment of independent public accountants and accounting firms performing audit services. (a) Scope. This... accountants and their accounting firms from performing independent audit and attestation services required by...

  8. Developing a cost accounting system for a physician group practice.

    PubMed

    Mays, J; Gordon, G

    1996-10-01

    Physicians in group practices must gain a competitive edge to survive in a healthcare environment in which cost efficiency has become critical to success. One tool that can help them is a cost accounting system that yields reliable, detailed data on the costs of delivering care. Such a system not only can enable physicians and group administrators to manage their operations more cost-effectively, but also can help them accurately assess the potential profitability of prospective managed care plans. An otolaryngology practice located in Mississippi provides a model for developing a cost accounting system that can be applied to physician group practices.

  9. Childhood trauma is not a confounder of the overlap between autistic and schizotypal traits: A study in a non-clinical adult sample.

    PubMed

    Gong, Jing-Bo; Wang, Ya; Lui, Simon S Y; Cheung, Eric F C; Chan, Raymond C K

    2017-11-01

    Childhood trauma has been shown to be a robust risk factor for mental disorders, and may exacerbate schizotypal traits or contribute to autistic trait severity. However, little is known whether childhood trauma confounds the overlap between schizotypal traits and autistic traits. This study examined whether childhood trauma acts as a confounding variable in the overlap between autistic and schizotypal traits in a large non-clinical adult sample. A total of 2469 participants completed the Autism Spectrum Quotient (AQ), the Schizotypal Personality Questionnaire (SPQ), and the Childhood Trauma Questionnaire-Short Form. Correlation analysis showed that the majority of associations between AQ variables and SPQ variables were significant (p < 0.05). In the multiple regression models predicting scores on the AQ total, scores on the three SPQ subscales were significant predictors(Ps < 0.05). Scores on the Positive schizotypy and Negative schizotypy subscales were significant predictors in the multiple regression model predicting scores on the AQ Social Skill, AQ Attention Switching, AQ Attention to Detail, AQ Communication, and AQ Imagination subscales. The association between autistic and schizotypal traits could not be explained by shared variance in terms of exposure to childhood trauma. The findings point to important overlaps in the conceptualization of ASD and SSD, independent of childhood trauma. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. High frequency bone conduction auditory evoked potentials in the guinea pig: Assessing cochlear injury after ossicular chain manipulation.

    PubMed

    Bergin, M J; Bird, P A; Vlajkovic, S M; Thorne, P R

    2015-12-01

    Permanent high frequency (>4 kHz) sensorineural hearing loss following middle ear surgery occurs in up to 25% of patients. The aetiology of this loss is poorly understood and may involve transmission of supra-physiological forces down the ossicular chain to the cochlea. Investigating the mechanisms of this injury using animal models is challenging, as evaluating cochlear function with evoked potentials is confounded when ossicular manipulation disrupts the normal air conduction (AC) pathway. Bone conduction (BC) using clinical bone vibrators in small animals is limited by poor transducer output at high frequencies sensitive to trauma. The objectives of the present study were firstly to evaluate a novel high frequency bone conduction transducer with evoked auditory potentials in a guinea pig model, and secondly to use this model to investigate the impact of middle ear surgical manipulation on cochlear function. We modified a magnetostrictive device as a high frequency BC transducer and evaluated its performance by comparison with a calibrated AC transducer at frequencies up to 32 kHz using the auditory brainstem response (ABR), compound action potential (CAP) and summating potential (SP). To mimic a middle ear traumatising stimulus, a rotating bur was brought in to contact with the incudomalleal complex and the effect on evoked cochlear potentials was observed. BC-evoked potentials followed the same input-output function pattern as AC potentials for all ABR frequencies. Deterioration in CAP and SP thresholds was observed after ossicular manipulation. It is possible to use high frequency BC to evoke responses from the injury sensitive basal region of the cochlea and so not rely on AC with the potential confounder of conductive hearing loss. Ongoing research explores how these findings evolve over time, and ways in which injury may be reduced and the cochlea protected during middle ear surgery. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Highway proximity associated with cardiovascular disease risk: the influence of individual-level confounders and exposure misclassification

    PubMed Central

    2013-01-01

    Background Elevated cardiovascular disease risk has been reported with proximity to highways or busy roadways, but proximity measures can be challenging to interpret given potential confounders and exposure error. Methods We conducted a cross sectional analysis of plasma levels of C-Reactive Protein (hsCRP), Interleukin-6 (IL-6), Tumor Necrosis Factor alpha receptor II (TNF-RII) and fibrinogen with distance of residence to a highway in and around Boston, Massachusetts. Distance was assigned using ortho-photo corrected parcel matching, as well as less precise approaches such as simple parcel matching and geocoding addresses to street networks. We used a combined random and convenience sample of 260 adults >40 years old. We screened a large number of individual-level variables including some infrequently collected for assessment of highway proximity, and included a subset in our final regression models. We monitored ultrafine particle (UFP) levels in the study areas to help interpret proximity measures. Results Using the orthophoto corrected geocoding, in a fully adjusted model, hsCRP and IL-6 differed by distance category relative to urban background: 43% (-16%,141%) and 49% (6%,110%) increase for 0-50 m; 7% (-39%,45%) and 41% (6%,86%) for 50-150 m; 54% (-2%,142%) and 18% (-11%,57%) for 150-250 m, and 49% (-4%, 131%) and 42% (6%, 89%) for 250-450 m. There was little evidence for association for TNF-RII or fibrinogen. Ortho-photo corrected geocoding resulted in stronger associations than traditional methods which introduced differential misclassification. Restricted analysis found the effect of proximity on biomarkers was mostly downwind from the highway or upwind where there was considerable local street traffic, consistent with patterns of monitored UFP levels. Conclusion We found associations between highway proximity and both hsCRP and IL-6, with non-monotonic patterns explained partly by individual-level factors and differences between proximity and UFP

  12. Highway proximity associated with cardiovascular disease risk: the influence of individual-level confounders and exposure misclassification.

    PubMed

    Brugge, Doug; Lane, Kevin; Padró-Martínez, Luz T; Stewart, Andrea; Hoesterey, Kyle; Weiss, David; Wang, Ding Ding; Levy, Jonathan I; Patton, Allison P; Zamore, Wig; Mwamburi, Mkaya

    2013-10-03

    Elevated cardiovascular disease risk has been reported with proximity to highways or busy roadways, but proximity measures can be challenging to interpret given potential confounders and exposure error. We conducted a cross sectional analysis of plasma levels of C-Reactive Protein (hsCRP), Interleukin-6 (IL-6), Tumor Necrosis Factor alpha receptor II (TNF-RII) and fibrinogen with distance of residence to a highway in and around Boston, Massachusetts. Distance was assigned using ortho-photo corrected parcel matching, as well as less precise approaches such as simple parcel matching and geocoding addresses to street networks. We used a combined random and convenience sample of 260 adults >40 years old. We screened a large number of individual-level variables including some infrequently collected for assessment of highway proximity, and included a subset in our final regression models. We monitored ultrafine particle (UFP) levels in the study areas to help interpret proximity measures. Using the orthophoto corrected geocoding, in a fully adjusted model, hsCRP and IL-6 differed by distance category relative to urban background: 43% (-16%,141%) and 49% (6%,110%) increase for 0-50 m; 7% (-39%,45%) and 41% (6%,86%) for 50-150 m; 54% (-2%,142%) and 18% (-11%,57%) for 150-250 m, and 49% (-4%, 131%) and 42% (6%, 89%) for 250-450 m. There was little evidence for association for TNF-RII or fibrinogen. Ortho-photo corrected geocoding resulted in stronger associations than traditional methods which introduced differential misclassification. Restricted analysis found the effect of proximity on biomarkers was mostly downwind from the highway or upwind where there was considerable local street traffic, consistent with patterns of monitored UFP levels. We found associations between highway proximity and both hsCRP and IL-6, with non-monotonic patterns explained partly by individual-level factors and differences between proximity and UFP concentrations. Our analyses emphasize

  13. Accounting and accountability: observations on the AHERF settlements.

    PubMed

    Maco, P S; Weinstein, S J

    2000-10-01

    Recent enforcement proceedings involving health care and accounting--relating primarily to the Allegheny Health, Education and Research Foundation (AHERF)--have sparked renewed interest in the activities of the U.S. Securities and Exchange Commission in the municipal securities market. Officials and accountants who are working for public-sector issuers in the healthcare industry have responsibilities under the Federal securities laws. Other issues of relevance include disclosure in the secondary market as well as upon initial issuance, and the significance of antifraud actions in other areas.

  14. Automating Base Fuels Accounting.

    DTIC Science & Technology

    1986-03-01

    base fuels accounting system as a means to decrease operating cost and increase capability. Author reviews the present accounting system, then proposes...g .:..: . . ; ,N :’- .’ :+-" : :*- . ’++ : :,:- :1:.-’ ."-..: :.:.:’’ AIR WAR COLLEGE No. AU-AWC86-0 9 0 00a AUTOMATING BASE FUELS ACCOUNTING ... ACCOUNTING by Victor E. Hardin Lieutenant Colonel, USAF A RESEARCH REPORT SUBMITTED TO THE FACULTY IN FULFILLMENT OF THE RESEARCH REQUI REMENT

  15. Health savings accounts and health reimbursement arrangements: assets, account balances, and rollovers, 2006-2010.

    PubMed

    Fronstin, Paul

    2011-01-01

    ASSET LEVELS GROWING: In 2010, there was $7.7 billion in health savings accounts (HSAs) and health reimbursement arrangements (HRAs), spread across 5.7 million accounts. This is up from 2006, when there were 1.2 million accounts with $835.4 million in assets, and 2009, when 5 million accounts held $7.1 billion in assets. AFTER LEVELING OFF, AVERAGE ACCOUNT BALANCE DROPS SLIGHTLY: Increases in average account balances leveled off in 2008 and 2009, and fell slightly in 2010. In 2006, account balances averaged $696. They increased to $1,320 in 2007, a 90 percent increase. Account balances averaged $1,356 in 2008 and $1,419 in 2009, 3 percent and 5 percent increases, respectively. In 2010, average account balances fell to $1,355, down 4.5 percent from the previous year. AVERAGE ROLLOVER DECLINES, WHILE TOTAL ROLLOVERS INCREASE: Despite a decline in the average rollover amount in 2010, total assets being rolled over have been increasing. $4.2 billion was rolled over in 2010, up from $4 billion in 2009. The average rollover increased from $592 in 2006 to $1,295 in 2009, and fell to $1,029 in 2010. The percentage of individuals without a rollover decreased from 23 percent in 2006 to 10 percent in 2009 and increased slightly to 13 percent in 2010. HEALTHY BEHAVIOR MEANS HIGHER ACCOUNT BALANCES AND HIGHER ROLLOVERS: Individuals who exercised, those who did not smoke, and those who were not obese had higher account balances and higher rollovers than those with less healthy behaviors. It was also found that individuals who used cost or quality information had higher account balances and higher rollovers compared with those who did not use such information. However, no relationship was found between either account balance or rollover amounts and various cost-conscious behaviors such as checking pricing before getting services or asking for generic drugs instead of brand names, among other things. DIFFERENCES IN ACCOUNT BALANCES: Men have higher account balances than women

  16. A managerial accounting analysis of hospital costs.

    PubMed

    Frank, W G

    1976-01-01

    Variance analysis, an accounting technique, is applied to an eight-component model of hospital costs to determine the contribution each component makes to cost increases. The method is illustrated by application to data on total costs from 1950 to 1973 for all U.S. nongovernmental not-for-profit short-term general hospitals. The costs of a single hospital are analyzed and compared to the group costs. The potential uses and limitations of the method as a planning and research tool are discussed.

  17. Twitter accounts followed by Congressional health staff.

    PubMed

    Grande, David; Meisel, Zachary F; Merchant, Raina M; Seymour, Jane; Gollust, Sarah E

    2017-07-01

    Although health policy research should inform policy making, the communication gap between researchers and policy makers limits successful translation. Social media represents a new opportunity to connect researchers and policy makers. Our objective was to assess who Congressional health policy staff follow on a major social media platform. Cross-sectional study. Our study measured Congressional health policy staff's use of Twitter and the types of individuals and organizations they follow. To focus on more influential Twitter accounts, we restricted our sample to those followed by at least 3 individual Congressional staff members. Of the 30,843 accounts followed by the 115 Congressional health policy staff, 1273 were potentially policy-related and followed by 3 or more staff. Of these, few were academically affiliated (2.4%) or explicitly health-related (5.6%) sites; many were general news media sources (50.9%) and political and governmental sources (36.4%). Health-focused accounts were frequently connected to the news media or government rather than academia. Top accounts followed (ie, highest quintile) were most likely to be national news organizations (odds ratio [OR], 5.88; 95% confidence interval [CI], 1.75-19.7) and elected officials (OR, 8.22; 95% CI, 1.75-38.6) compared with advocacy and interest groups. Health-related and academic sources are largely absent from the Twitter conversations with US Congressional health policy staff. Even within social media, traditional and political news media are important information intermediaries that researchers and journals should target to disseminate health policy evidence.

  18. Accounting Issues: An Essay Series Part VI--Investments in Securities

    ERIC Educational Resources Information Center

    Laux, Judy

    2008-01-01

    The sixth in a series of theory-based essays, this article presents accounting for investments in debt and equity securities along with some related conceptual and measurement issues. Additional coverage is devoted to potential ethical dilemmas and both theoretical and empirical literature related to this asset. (Contains 1 footnote.)

  19. Mechanisms of Accountability for the Realization of the Right to Health in China

    PubMed Central

    2017-01-01

    Abstract China ratified the International Covenant on Economic, Social and Cultural Rights in 2001. It thus bears obligations under Article 12 of the covenant to take appropriate measures at the domestic level to realize the right to health in China. Accountability is an important component of the right to health. This article examines whether the Western concept of accountability, recently imported into China, has the potential to improve the protection of the right to health within China’s existing political, legal, and cultural framework. In so doing, it reviews current Chinese institutional mechanisms and considers the use of less formal mechanisms by which duty-bearers might be held accountable in China. More specifically, this article provides an overview of a range of health-related accountability mechanisms, including judicial, political, administrative, professional, and social accountability arrangements. It concludes that although there is the basis of an accountability framework for the right to health in China, the effective operation of accountability mechanisms is hindered by longstanding cultural and political barriers. PMID:28630560

  20. Accountable Care Organizations: The National Landscape.

    PubMed

    Shortell, Stephen M; Colla, Carrie H; Lewis, Valerie A; Fisher, Elliott; Kessell, Eric; Ramsay, Patricia

    2015-08-01

    There are now more than seven hundred accountable care organizations (ACOs) in the United States. This article describes some of their most salient characteristics including the number and types of contracts involved, organizational structures, the scope of services offered, care management capabilities, and the development of a three-category taxonomy that can be used to target technical assistance efforts and to examine performance. The current evidence on the performance of ACOs is reviewed. Since California has the largest number of ACOs (N=67) and a history of providing care under risk-bearing contracts, some additional assessments of quality and patient experience are made between California ACOs and non-ACO provider organizations. Six key issues likely to affect future ACO growth and development are discussed, and some potential "diagnostic" indicators for assessing the likelihood of potential antitrust violations are presented. Copyright © 2015 by Duke University Press.

  1. The Accounting Capstone Problem

    ERIC Educational Resources Information Center

    Elrod, Henry; Norris, J. T.

    2012-01-01

    Capstone courses in accounting programs bring students experiences integrating across the curriculum (University of Washington, 2005) and offer unique (Sanyal, 2003) and transformative experiences (Sill, Harward, & Cooper, 2009). Students take many accounting courses without preparing complete sets of financial statements. Accountants not only…

  2. The “Insight Paradox” in Schizophrenia: Magnitude, Moderators and Mediators of the Association Between Insight and Depression

    PubMed Central

    Belvederi Murri, Martino; Amore, Mario; Calcagno, Pietro; Respino, Matteo; Marozzi, Valentina; Masotti, Mattia; Bugliani, Michele; Innamorati, Marco; Pompili, Maurizio; Galderisi, Silvana; Maj, Mario

    2016-01-01

    The so-called “insight paradox” posits that among patients with schizophrenia higher levels of insight are associated with increased levels of depression. Although different studies examined this issue, only few took in account potential confounders or factors that could influence this association. In a sample of clinically stable patients with schizophrenia, insight and depression were evaluated using the Scale to assess Unawareness of Mental Disorder and the Calgary Depression Scale for Schizophrenia. Other rating scales were used to assess the severity of psychotic symptoms, extrapyramidal symptoms, hopelessness, internalized stigma, self-esteem, and service engagement. Regression models were used to estimate the magnitude of the association between insight and depression while accounting for the role of confounders. Putative psychological and sociodemographic factors that could act as mediators and moderators were examined using the PROCESS macro. By accounting for the role of confounding factors, the strength of the association between insight into symptoms and depression increased from 13% to 25% explained covariance. Patients with lower socioeconomic status (F = 8.5, P = .04), more severe illness (F = 4.8, P = .03) and lower levels of service engagement (F = 4.7, P = .03) displayed the strongest association between insight and depression. Lastly, hopelessness, internalized stigma and perceived discrimination acted as significant mediators. The relationship between insight and depression should be considered a well established phenomenon among patients with schizophrenia: it seems stronger than previously reported especially among patients with lower socioeconomic status, severe illness and poor engagement with services. These findings may have relevant implications for the promotion of insight among patients with schizophrenia. PMID:27069064

  3. Ecosystem accounts define explicit and spatial trade-offs for managing natural resources.

    PubMed

    Keith, Heather; Vardon, Michael; Stein, John A; Stein, Janet L; Lindenmayer, David

    2017-11-01

    Decisions about natural resource management are frequently complex and vexed, often leading to public policy compromises. Discord between environmental and economic metrics creates problems in assessing trade-offs between different current or potential resource uses. Ecosystem accounts, which quantify ecosystems and their benefits for human well-being consistent with national economic accounts, provide exciting opportunities to contribute significantly to the policy process. We advanced the application of ecosystem accounts in a regional case study by explicitly and spatially linking impacts of human and natural activities on ecosystem assets and services to their associated industries. This demonstrated contributions of ecosystems beyond the traditional national accounts. Our results revealed that native forests would provide greater benefits from their ecosystem services of carbon sequestration, water yield, habitat provisioning and recreational amenity if harvesting for timber production ceased, thus allowing forests to continue growing to older ages.

  4. Iowa Community Colleges Accounting Manual.

    ERIC Educational Resources Information Center

    Iowa State Dept. of Education, Des Moines. Div. of Community Colleges and Workforce Preparation.

    This document describes account classifications and definitions for the accounting system of the Iowa community colleges. In view of the objectives of the accounting system, it is necessary to segregate the assets of the community college according to its source and intended use. Additionally, the accounting system should provide for accounting by…

  5. Effectiveness of inactivated influenza vaccines in preventing influenza-associated deaths and hospitalizations among Ontario residents aged ≥ 65 years: estimates with generalized linear models accounting for healthy vaccinee effects.

    PubMed

    Ridenhour, Benjamin J; Campitelli, Michael A; Kwong, Jeffrey C; Rosella, Laura C; Armstrong, Ben G; Mangtani, Punam; Calzavara, Andrew J; Shay, David K

    2013-01-01

    Estimates of the effectiveness of influenza vaccines in older adults may be biased because of difficulties identifying and adjusting for confounders of the vaccine-outcome association. We estimated vaccine effectiveness for prevention of serious influenza complications among older persons by using methods to account for underlying differences in risk for these complications. We conducted a retrospective cohort study among Ontario residents aged ≥ 65 years from September 1993 through September 2008. We linked weekly vaccination, hospitalization, and death records for 1.4 million community-dwelling persons aged ≥ 65 years. Vaccine effectiveness was estimated by comparing ratios of outcome rates during weeks of high versus low influenza activity (defined by viral surveillance data) among vaccinated and unvaccinated subjects by using log-linear regression models that accounted for temperature and time trends with natural spline functions. Effectiveness was estimated for three influenza-associated outcomes: all-cause deaths, deaths occurring within 30 days of pneumonia/influenza hospitalizations, and pneumonia/influenza hospitalizations. During weeks when 5% of respiratory specimens tested positive for influenza A, vaccine effectiveness among persons aged ≥ 65 years was 22% (95% confidence interval [CI], -6%-42%) for all influenza-associated deaths, 25% (95% CI, 13%-37%) for deaths occurring within 30 days after an influenza-associated pneumonia/influenza hospitalization, and 19% (95% CI, 4%-31%) for influenza-associated pneumonia/influenza hospitalizations. Because small proportions of deaths, deaths after pneumonia/influenza hospitalizations, and pneumonia/influenza hospitalizations were associated with influenza virus circulation, we estimated that vaccination prevented 1.6%, 4.8%, and 4.1% of these outcomes, respectively. By using confounding-reducing techniques with 15 years of provincial-level data including vaccination and health outcomes, we estimated that

  6. "Accounting Education at a Crossroad in 2010" and "Challenges Facing Accounting Education in Australia"

    ERIC Educational Resources Information Center

    de Lange, Paul; Watty, Kim

    2011-01-01

    Of the various reports released in 2010, two purport to examine the state of accounting education in Australia. These are "Accounting Education at a Crossroad in 2010" and "Challenges Facing Accounting Education in Australia". Both were released as collaborations of the leading academic organisation, the Accounting and Finance…

  7. He Asked Me What!?--Using Shared Online Accounts as Training Tools for Distance Learning Librarians

    ERIC Educational Resources Information Center

    Robinson, Kelly; Casey, Anne Marie; Citro, Kathleen

    2017-01-01

    This study explores the idea of creating a knowledge base from shared online accounts to use in training librarians who perform distance reference services. Through a survey, follow-up interviews and a case study, the investigators explored current and potential use of shared online accounts as training tools. This study revealed that the…

  8. Endotoxemia and mortality prediction in ICU and other settings: underlying risk and co-detection of gram negative bacteremia are confounders

    PubMed Central

    2012-01-01

    Introduction The interdependence between endotoxemia, gram negative (GN) bacteremia and mortality has been extensively studied. Underlying patient risk and GN bacteremia types are possible confounders of the relationship. Methods Published studies with ≥10 patients in either ICU or non-ICU settings, endotoxemia detection by limulus assay, reporting mortality proportions and ≥1 GN bacteremia were included. Summary odds ratios (OR) for mortality were derived across all studies by meta-analysis for the following contrasts: sub-groups with either endotoxemia (group three), GN bacteremia (group two) or both (group one) each versus the group with neither detected (group four; reference group). The mortality proportion for group four is the proxy measure of study level risk within L'Abbé plots. Results Thirty-five studies were found. Among nine studies in an ICU setting, the OR for mortality was borderline (OR <2) or non-significantly increased for groups two (GN bacteremia alone) and three (endotoxemia alone) and patient group one (GN bacteremia and endotoxemia co-detected) each versus patient group four (neither endotoxemia nor GN bacteremia detected). The ORs were markedly higher for group one versus group four (OR 6.9; 95% confidence interval (CI), 4.4 -to 11.0 when derived from non-ICU studies. The distributions of Pseudomonas aeruginosa and Escherichia coli bacteremias among groups one versus two are significantly unequal. Conclusions The co-detection of GN bacteremia and endotoxemia is predictive of increased mortality risk versus the detection of neither but only in studies undertaken in a non-ICU setting. Variation in GN bacteremia species types and underlying risk are likely unrecognized confounders in the individual studies. PMID:22871090

  9. PHOSPHATE BINDER USE AND MORTALITY AMONG HEMODIALYSIS PATIENTS IN THE DOPPS: EVALUATION OF POSSIBLE CONFOUNDING BY NUTRITIONAL STATUS

    PubMed Central

    Lopes, Antonio Alberto; Tong, Lin; Thumma, Jyothi; Li, Yun; Fuller, Douglas S.; Morgenstern, Hal; Bommer, Jürgen; Kerr, Peter G; Tentori, Francesca; Akiba, Takashi; Gillespie, Brenda; Robinson, Bruce M.; Port, Friedrich K; Pisoni, Ronald L.

    2014-01-01

    residual confounding. Conclusions Longer survival and better nutritional status were observed for MHD patients prescribed PBs and in facilities with greater percentage PB prescription. Understanding the mechanisms for explaining this effect and ruling out possible residual confounding require additional research. PMID:22385781

  10. Accounting & Computing Curriculum Guide.

    ERIC Educational Resources Information Center

    Avani, Nathan T.; And Others

    This curriculum guide consists of materials for use in teaching a competency-based accounting and computing course that is designed to prepare students for employability in the following occupational areas: inventory control clerk, invoice clerk, payroll clerk, traffic clerk, general ledger bookkeeper, accounting clerk, account information clerk,…

  11. Hospital cost accounting: implementing the system successfully.

    PubMed

    Burik, D; Duvall, T J

    1985-05-01

    To successfully implement a cost accounting system, certain key steps should be undertaken. These steps include developing and installing software; developing cost center budgets and inter-cost center allocations; developing service item standard costs; generating cost center level and patient level standard cost reports and reconciling these costs to actual costs; generating product line profitability reports and reconciling these reports to the financial statements; and providing ad hoc reporting capabilities. By following these steps, potential problems in the implementation process can be anticipated and avoided.

  12. A managerial accounting analysis of hospital costs.

    PubMed Central

    Frank, W G

    1976-01-01

    Variance analysis, an accounting technique, is applied to an eight-component model of hospital costs to determine the contribution each component makes to cost increases. The method is illustrated by application to data on total costs from 1950 to 1973 for all U.S. nongovernmental not-for-profit short-term general hospitals. The costs of a single hospital are analyzed and compared to the group costs. The potential uses and limitations of the method as a planning and research tool are discussed. PMID:965233

  13. 48 CFR 9904.411 - Cost accounting standard-accounting for acquisition costs of material.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 7 2010-10-01 2010-10-01 false Cost accounting standard-accounting for acquisition costs of material. 9904.411 Section 9904.411 Federal Acquisition Regulations System COST ACCOUNTING STANDARDS BOARD, OFFICE OF FEDERAL PROCUREMENT POLICY, OFFICE OF MANAGEMENT AND...

  14. Accounting and Accountability for Distributed and Grid Systems

    NASA Technical Reports Server (NTRS)

    Thigpen, William; McGinnis, Laura F.; Hacker, Thomas J.

    2001-01-01

    While the advent of distributed and grid computing systems will open new opportunities for scientific exploration, the reality of such implementations could prove to be a system administrator's nightmare. A lot of effort is being spent on identifying and resolving the obvious problems of security, scheduling, authentication and authorization. Lurking in the background, though, are the largely unaddressed issues of accountability and usage accounting: (1) mapping resource usage to resource users; (2) defining usage economies or methods for resource exchange; (3) describing implementation standards that minimize and compartmentalize the tasks required for a site to participate in a grid.

  15. Maternal obesity and childhood wheezing and asthma.

    PubMed

    Rusconi, Franca; Popovic, Maja

    2017-03-01

    Obesity represents one of the major public health problems worldwide, with an increased prevalence also among women of reproductive age. Maternal pre-pregnancy overweight and obesity are important risk factors for a number of maternal and foetal/neonatal complications. The objective of this review is to provide an overview of the most recent evidence regarding the associations between pre-pregnancy overweight/obesity and wheezing and asthma in childhood. Potential mechanisms, mediators and confounding factors involved in these associations are also discussed. Despite the relatively large body of studies examining these associations and taking into account main confounders and potential mediators, the causal relationship between maternal obesity and wheezing and asthma in childhood is still uncertain. This uncertainty is not trivial, as any prevention strategy aimed at reducing the burden of these conditions would necessarily imply better understanding of the factors that are in the causal chain. Copyright © 2016. Published by Elsevier Ltd.

  16. Managerial Accounting. Study Guide.

    ERIC Educational Resources Information Center

    Plachta, Leonard E.

    This self-instructional study guide is part of the materials for a college-level programmed course in managerial accounting. The study guide is intended for use by students in conjuction with a separate textbook, Horngren's "Accounting for Management Control: An Introduction," and a workbook, Curry's "Student Guide to Accounting for Management…

  17. Intelligent Accountability in Education

    ERIC Educational Resources Information Center

    O'Neill, Onora

    2013-01-01

    Systems of accountability are "second order" ways of using evidence of the standard to which "first order" tasks are carried out for a great variety of purposes. However, more accountability is not always better, and processes of holding to account can impose high costs without securing substantial benefits. At their worst,…

  18. Ranking Accounting Authors and Departments in Accounting Education: Different Methodologies--Significantly Different Results

    ERIC Educational Resources Information Center

    Bernardi, Richard A.; Zamojcin, Kimberly A.; Delande, Taylor L.

    2016-01-01

    This research tests whether Holderness Jr., D. K., Myers, N., Summers, S. L., & Wood, D. A. [(2014). "Accounting education research: Ranking institutions and individual scholars." "Issues in Accounting Education," 29(1), 87-115] accounting-education rankings are sensitive to a change in the set of journals used. It provides…

  19. Accounting Academics' Perceptions of the Effect of Accreditation on UK Accounting Degrees

    ERIC Educational Resources Information Center

    Ellington, Peter; Williams, Amanda

    2017-01-01

    Students graduating from undergraduate accounting degree programmes in the UK are eligible for and attracted by accreditation available from professional accountancy body (PAB) examinations. The study reviews factual information available from PAB websites to confirm that virtually all accounting degrees in the UK have accreditation, and many are…

  20. The use of aquatic bioconcentration factors in ecological risk assessments: Confounding issues, laboratory v/s modeled results

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Brandt, C.; Blanton, M.L.; Dirkes, R.

    1995-12-31

    Bioconcentration in aquatic systems is generally taken to refer to contaminant uptake through non-ingestion pathways (i.e., dermal and respiration uptake). Ecological risk assessments performed on aquatic systems often rely on published data on bioconcentration factors to calibrate models of exposure. However, many published BCFs, especially those from in situ studies, are confounded by uptake from ingestion of prey. As part of exposure assessment and risk analysis of the Columbia River`s Hanford Reach, the authors tested a methodology to estimate radionuclide BCFs for several aquatic species in the Hanford Reach of the Columbia River. The iterative methodology solves for BCFs frommore » known body burdens and environmental media concentrations. This paper provides BCF methodology description comparisons of BCF from literature and modeled values and how they were used in the exposure assessment and risk analysis of the Columbia River`s Hanford Reach.« less

  1. Revamping High School Accounting Courses.

    ERIC Educational Resources Information Center

    Bittner, Joseph

    2002-01-01

    Provides ideas for updating accounting courses: convert to semester length; focus on financial reporting/analysis, financial statements, the accounting cycle; turn textbook exercises into practice sets for the accounting cycle; teach about corporate accounting; and address individual line items on financial statements. (SK)

  2. Integer programming applications: Bond trading, mortgage backed security financing, and FASB 115 accounting

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nauss, R.

    1994-12-31

    In this review we describe three integer programming applications involving fixed income securities. A bond trading model is presented that features a number of possible different objectives and collections of constraints including future interest rate scenarios. A mortgage backed security (MBS) financing model that accounts for potential defaults in the MBS is also presented. Finally we describe an approach to allocate collections of bank securities into three categories: hold to maturity, available for sale, or trading. Placement of securities in these categories affects the capital, net income, and liquidity of a bank according to new accounting rules promulgated by themore » Financial Accounting Standards Board.« less

  3. Public Accountancy Handbook.

    ERIC Educational Resources Information Center

    New York State Education Dept., Albany. Office of the Professions.

    A reference guide to laws, rules, and regulations that govern public accountancy practice in New York State is presented. In addition to identifying licensing requirements/procedures for certified public accountants, general provisions of Title VIII of the Education Law are covered, along with state management, professional misconduct, and…

  4. Energy Storage Sizing Taking Into Account Forecast Uncertainties and Receding Horizon Operation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Baker, Kyri; Hug, Gabriela; Li, Xin

    Energy storage systems (ESS) have the potential to be very beneficial for applications such as reducing the ramping of generators, peak shaving, and balancing not only the variability introduced by renewable energy sources, but also the uncertainty introduced by errors in their forecasts. Optimal usage of storage may result in reduced generation costs and an increased use of renewable energy. However, optimally sizing these devices is a challenging problem. This paper aims to provide the tools to optimally size an ESS under the assumption that it will be operated under a model predictive control scheme and that the forecast ofmore » the renewable energy resources include prediction errors. A two-stage stochastic model predictive control is formulated and solved, where the optimal usage of the storage is simultaneously determined along with the optimal generation outputs and size of the storage. Wind forecast errors are taken into account in the optimization problem via probabilistic constraints for which an analytical form is derived. This allows for the stochastic optimization problem to be solved directly, without using sampling-based approaches, and sizing the storage to account not only for a wide range of potential scenarios, but also for a wide range of potential forecast errors. In the proposed formulation, we account for the fact that errors in the forecast affect how the device is operated later in the horizon and that a receding horizon scheme is used in operation to optimally use the available storage.« less

  5. Media accounts of unintentional child injury deaths in New Zealand: a teachable moment?

    PubMed

    John, Savesh; Kool, Bridget

    2017-09-01

    To review media accounts of fatal child unintentional injury events reported in leading New Zealand newspapers for their completeness and potential to deliver evidence-based injury prevention messages. Media accounts of fatal unintentional child (0-14 years) injury events in New Zealand's four largest newspapers between 2011 and 2015 were reviewed. Variables of interest included: date, mechanism of injury and victim details. The article prominence, presence of prevention messages and case ascertainment for the two leading causes of death (2011 to 2013 only) were evaluated. Two hundred and forty-two media accounts detailing 122 fatal child injury events (133 deaths) were located for the five-year period. The most common causes of injury were transport-related (56%) and drownings (21%). Only 20% (n=49) of accounts included clear prevention messages. Just over 33% of accounts included images and 66% were located within the first three pages. Case ascertainment in the media accounts was complete for all transport deaths and all but one drowning. The low frequency of prevention messages in the media accounts reviewed highlights a missed opportunity for the dissemination of prevention messages to the New Zealand public. The findings confirm the utility of these accounts as a timely source of fatal child injury information.

  6. 31 CFR 561.504 - Transactions related to closing a correspondent account or payable-through account.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... accounts or payable-through accounts for the foreign financial institution are authorized to: (1) Process... TREASURY IRANIAN FINANCIAL SANCTIONS REGULATIONS Licenses, Authorizations, and Statements of Licensing... opening or maintaining of a correspondent account or a payable-through account for a foreign financial...

  7. 75 FR 81684 - Order Approving Public Company Accounting Oversight Board Budget and Annual Accounting Support...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-28

    ... Accounting Oversight Board Budget and Annual Accounting Support Fee for Calendar Year 2011 The Sarbanes-Oxley Act of 2002, as amended (the ``Sarbanes-Oxley Act''), established the Public Company Accounting... through registration of public accounting firms and standard setting, inspection, and disciplinary...

  8. 78 FR 11915 - Order Approving Public Company Accounting Oversight Board Budget and Annual Accounting Support...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-20

    ... Accounting Oversight Board Budget and Annual Accounting Support Fee for Calendar Year 2013 The Sarbanes-Oxley Act of 2002, as amended (the ``Sarbanes-Oxley Act''),\\1\\ established the Public Company Accounting... through registration of public accounting firms and standard setting, inspection, and disciplinary...

  9. 76 FR 49365 - Cost Accounting Standards: Elimination of the Exemption From Cost Accounting Standards for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-10

    ... Accounting Standards: Elimination of the Exemption From Cost Accounting Standards for Contracts and...: Office of Management and Budget (OMB), Office of Federal Procurement Policy (OFPP), Cost Accounting... Accounting Standards (CAS) Board, is publishing a final rule to eliminate the exemption from regulations...

  10. 77 FR 2576 - Order Approving Public Company Accounting Oversight Board Budget and Annual Accounting Support...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-18

    ... Accounting Oversight Board Budget and Annual Accounting Support Fee for Calendar Year 2012 The Sarbanes-Oxley Act of 2002, as amended (the ``Sarbanes-Oxley Act''),\\1\\ established the Public Company Accounting... through registration of public accounting firms and standard setting, inspection, and disciplinary...

  11. Accountability and the New Essentials.

    ERIC Educational Resources Information Center

    Dowd, Steven B.

    The current emphasis in education on accountability is tending toward "push-button accountability." The challenge is to evaluate access and retention as well as other educationally relevant goals to define "quality" or "accountability." In higher education, accountability should be proven through assessment and should consist of proof that what…

  12. Financial accounting for radiology executives.

    PubMed

    Seidmann, Abraham; Mehta, Tushar

    2005-03-01

    The authors review the role of financial accounting information from the perspective of a radiology executive. They begin by introducing the role of pro forma statements. They discuss the fundamental concepts of accounting, including the matching principle and accrual accounting. The authors then explore the use of financial accounting information in making investment decisions in diagnostic medical imaging. The paper focuses on critically evaluating the benefits and limitations of financial accounting for decision making in a radiology practice.

  13. 13 CFR 120.463 - Regulatory accounting-What are SBA's regulatory accounting requirements for SBA Supervised Lenders?

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... basis in accordance with Generally Accepted Accounting Principles (GAAP) as promulgated by the Financial Accounting Standards Board (FASB), supplemented by Regulatory Accounting Principles (RAP) as identified by... set forth in FASB Statement of Financial Accounting Standards No. 15, Accounting by Debtors and...

  14. 75 FR 20363 - Notice of Issuance of Statement of Federal Financial Accounting Standard 38, Accounting for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-19

    ... FEDERAL ACCOUNTING STANDARDS ADVISORY BOARD Notice of Issuance of Statement of Federal Financial Accounting Standard 38, Accounting for Federal Oil and Gas Resources AGENCY: Federal Accounting Standards... is hereby given that the Federal Accounting Standards Advisory Board (FASAB) has issued Statement of...

  15. Implementing Replacement Cost Accounting

    DTIC Science & Technology

    1976-12-01

    cost accounting Clickener, John Ross Monterey, California. Naval Postgraduate School http://hdl.handle.net/10945/17810 Downloaded from NPS Archive...Calhoun IMPLEMENTING REPLACEMENT COST ACCOUNTING John Ross CHckener NAVAL POSTGRADUATE SCHOOL Monterey, California THESIS IMPLEMENTING REPLACEMENT COST ...Implementing Replacement Cost Accounting 7. AUTHORS John Ross Clickener READ INSTRUCTIONS BEFORE COMPLETING FORM 3. RECIPIENT’S CATALOG NUMBER 9. TYRE OF

  16. Accounting Education in Crisis

    ERIC Educational Resources Information Center

    Turner, Karen F.; Reed, Ronald O.; Greiman, Janel

    2011-01-01

    Almost on a daily basis new accounting rules and laws are put into use, creating information that must be known and learned by the accounting faculty and then introduced to and understood by the accounting student. Even with the 150 hours of education now required for CPA licensure, it is impossible to teach and learn all there is to learn. Over…

  17. Combined effect of short-term dehydration and sublethal acute oral dicrotophos exposure confounds the diagnosis of anticholinesterase exposure in common quail (Coturnix coturnix) using plasma cholinesterase activity.

    PubMed

    Heffernan, James; Mineau, Pierre; Falk, Ramona; Wickstrom, Mark

    2012-07-01

    Common Quail (Coturnix coturnix) were subjected to controlled and replicated experiments in the summer of 2008 to investigate the effects of short-term dehydration on cholinesterase activity in brain and plasma and the interaction between dehydration and exposure to the organophosphorus pesticide dicrotophos in these same tissues. Our objective was to determine if dehydration could confound the diagnosis of anticholinesterase exposure using inhibition of cholinesterase activity in quail tissues. The effect of dehydration was quantified using measures of plasma osmolality and hematocrit. Dicrotophos exposure caused significant inhibition of cholinesterase activity in brain, while the effects of dehydration and interaction were not significant. Dehydration caused significant duration-dependent increases in plasma osmolality and hematocrit. Dehydration also caused a significant increase in plasma cholinesterase activity. Variation in the change in plasma cholinesterase activity in response to dehydration was significantly and positively correlated with dehydration-induced variation in both the change in plasma osmolality and the change in hematocrit. These correlations suggest that plasma cholinesterase activity in quail is not limited to plasma but occupies some larger pool of the extracellular fluid volume, and we suggest lymph is part of that pool. The effects of dehydration on plasma cholinesterase activity masked the inhibitory effects of dicrotophos. Here, the combination of dehydration and dicrotophos exposure produced plasma cholinesterase activity that was not significantly different from reference and pre-exposure values, confounding the diagnosis of anticholinesterase exposure in dehydrated, dicrotophos-exposed quail. A method to adjust plasma cholinesterase activities for the confounding effects of dehydration and enable the diagnosis of anticholinesterase exposure in dehydrated, dicrotophos-exposed quail was developed. Clinicians and practitioners

  18. Where Are the Accounting Professors?

    ERIC Educational Resources Information Center

    Chang, Jui-Chin; Sun, Huey-Lian

    2008-01-01

    Accounting education is facing a crisis of shortage of accounting faculty. This study discusses the reasons behind the shortage and offers suggestions to increase the supply of accounting faculty. Our suggestions are as followings. First, educators should begin promoting accounting academia as one of the career choices to undergraduate and…

  19. Accountability: A Bibliography.

    ERIC Educational Resources Information Center

    Hanson, Gordon; Gold, James

    This bibliography, the 6th in a series of reports dealing with accountability, is designed to provide those interested in assessment and accountability with a ready reference for identifying articles relevant to their individual needs. The citations are listed under a general section, the ERIC files section, and the CAP section. Entries within…

  20. Public Accountancy Handbook.

    ERIC Educational Resources Information Center

    New York State Education Dept., Albany. Office of the Professions.

    The laws, rules and regulations of the State Education Department governing public accountancy practice in New York State are provided in this handbook. Licensure requirements are also described, and the forms for obtaining a license and first registration as a certified public accountant are provided. The booklet is divided into the following…

  1. User Accounts | High-Performance Computing | NREL

    Science.gov Websites

    see information on user account policies. ACCOUNT PASSWORDS Logging in for the first time? Forgot your Accounts User Accounts Learn how to request an NREL HPC user account. Request an HPC Account To request an HPC account, please complete our request form. This form is provided using DocuSign. REQUEST

  2. Combined Pulmonary Fibrosis and Emphysema in Scleroderma-Related Lung Disease Has a Major Confounding Effect on Lung Physiology and Screening for Pulmonary Hypertension.

    PubMed

    Antoniou, K M; Margaritopoulos, G A; Goh, N S; Karagiannis, K; Desai, S R; Nicholson, A G; Siafakas, N M; Coghlan, J G; Denton, C P; Hansell, D M; Wells, A U

    2016-04-01

    To assess the prevalence of combined pulmonary fibrosis and emphysema (CPFE) in systemic sclerosis (SSc) patients with interstitial lung disease (ILD) and the effect of CPFE on the pulmonary function tests used to evaluate the severity of SSc-related ILD and the likelihood of pulmonary hypertension (PH). High-resolution computed tomography (HRCT) scans were obtained in 333 patients with SSc-related ILD and were evaluated for the presence of emphysema and the extent of ILD. The effects of emphysema on the associations between pulmonary function variables and the extent of SSc-related ILD as visualized on HRCT and echocardiographic evidence of PH were quantified. Emphysema was present in 41 (12.3%) of the 333 patients with SSc-related ILD, in 26 (19.7%) of 132 smokers, and in 15 (7.5%) of 201 lifelong nonsmokers. When the extent of fibrosis was taken into account, emphysema was associated with significant additional differences from the expected values for diffusing capacity for carbon monoxide (DLco) (average reduction of 24.1%; P < 0.0005), and the forced vital capacity (FVC)/DLco ratio (average increase of 34.8%; P < 0.0005) but not FVC. These effects were identical in smokers and nonsmokers. Multivariate analysis showed that the presence of emphysema had a greater effect than echocardiographically determined PH on the FVC/DLco ratio, regardless of whether it was analyzed as a continuous variable or using a threshold value of 1.6 or 2.0. Among patients with SSc-related ILD, emphysema is sporadically present in nonsmokers and is associated with a low pack-year history in smokers. The confounding effect of CPFE on measures of gas exchange has major implications for the construction of screening algorithms for PH in patients with SSc-related ILD. © 2016, American College of Rheumatology.

  3. Accountability in action?: the case of a database purchasing decision.

    PubMed

    Neyland, Daniel; Woolgar, Steve

    2002-06-01

    The increasing prevalence of audit in university settings has raised concerns about the potentially adverse effects of invasive measures of performance upon the conduct of research and generation of knowledge. What sustains the current commitment to audit? It is argued that in order to address this question we need to understand how and to what extent notions of accountability are played out in practice. This is illustrated through the analysis of materials from an ethnographic study of 'good management practice' in the deployment of technologies in university settings. The paper examines the ways in which ideas of accountability - involving considerations such as 'value for money' - inform the practical processes of deciding about the purchase of a new database technology.

  4. Accountability and Primary Healthcare

    PubMed Central

    Mukhi, Shaheena; Barnsley, Jan; Deber, Raisa B.

    2014-01-01

    This paper examines the accountability structures within primary healthcare (PHC) in Ontario; in particular, who is accountable for what and to whom, and the policy tools being used. Ontario has implemented a series of incremental reforms, using expenditure policy instruments, enforced through contractual agreements to provide a defined set of publicly financed services that are privately delivered, most often by family physicians. The findings indicate that reporting, funding, evaluation and governance accountability requirements vary across service provider models. Accountability to the funder and patients is most common. Agreements, incentives and compensation tools have been used but may be insufficient to ensure parties are being held responsible for their activities related to stated goals. Clear definitions of various governance structures, a cohesive approach to monitoring critical performance indicators and associated improvement strategies are important elements in operationalizing accountability and determining whether goals are being met. PMID:25305392

  5. Ideas for the Accounting Classroom.

    ERIC Educational Resources Information Center

    Kerby, Debra; Romine, Jeff

    2003-01-01

    Innovative ideas for accounting education include having students study accounting across historical periods, using businesses for student research, exploring nontraditional accounting careers, and collaborating with professional associations. (SK)

  6. Accounting for misclassification error in retrospective smoking data.

    PubMed

    Kenkel, Donald S; Lillard, Dean R; Mathios, Alan D

    2004-10-01

    Recent waves of major longitudinal surveys in the US and other countries include retrospective questions about the timing of smoking initiation and cessation, creating a potentially important but under-utilized source of information on smoking behavior over the life course. In this paper, we explore the extent of, consequences of, and possible solutions to misclassification errors in models of smoking participation that use data generated from retrospective reports. In our empirical work, we exploit the fact that the National Longitudinal Survey of Youth 1979 provides both contemporaneous and retrospective information about smoking status in certain years. We compare the results from four sets of models of smoking participation. The first set of results are from baseline probit models of smoking participation from contemporaneously reported information. The second set of results are from models that are identical except that the dependent variable is based on retrospective information. The last two sets of results are from models that take a parametric approach to account for a simple form of misclassification error. Our preliminary results suggest that accounting for misclassification error is important. However, the adjusted maximum likelihood estimation approach to account for misclassification does not always perform as expected. Copyright 2004 John Wiley & Sons, Ltd.

  7. 17 CFR 247.723 - Exemptions for special accounts, transferred accounts, foreign branches and a de minimis number...

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... accounts, transferred accounts, foreign branches and a de minimis number of accounts. 247.723 Section 247... Exemptions for special accounts, transferred accounts, foreign branches and a de minimis number of accounts... dealer. (e) De minimis exclusion. A bank may, in determining its compliance with the chiefly compensated...

  8. 17 CFR 247.723 - Exemptions for special accounts, transferred accounts, foreign branches and a de minimis number...

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... accounts, transferred accounts, foreign branches and a de minimis number of accounts. 247.723 Section 247... Exemptions for special accounts, transferred accounts, foreign branches and a de minimis number of accounts... dealer. (e) De minimis exclusion. A bank may, in determining its compliance with the chiefly compensated...

  9. Smokers' increased risk for disability pension: social confounding or health-mediated effects? Gender-specific analyses of the Hordaland Health Study cohort.

    PubMed

    Haukenes, Inger; Riise, Trond; Haug, Kjell; Farbu, Erlend; Maeland, John Gunnar

    2013-09-01

    Studies indicate that cigarette smokers have an increased risk for disability pension, presumably mediated by adverse health effects. However, smoking is also related to socioeconomic status. The current study examined the association between smoking and subsequent disability pension, and whether the association is explained by social confounding and/or health-related mediation. A subsample of 7934 men and 8488 women, aged 40-46, from the Hordaland Health Study, Norway (1997-1999), provided baseline information on smoking status, self-reported health measures and socioeconomic status. Outcome was register-based disability pension from 12 months after baseline to end of 2004. Gender stratified Cox regression analyses were used adjusted for socioeconomic status, physical activity, self-reported health and musculoskeletal pain sites. A total of 155 (2%) men and 333 (3.9%) women were granted disability pension during follow-up. The unadjusted disability risk associated with heavy smoking versus non-smoking was 1.88 (95% CI 1.23 to 2.89) among men and 3.06 (95% CI 2.23 to 4.20) among women. In multivariate analyses, adjusting for socioeconomic status, HRs were 1.33 (95% CI 0.84 to 2.11) among men and 2.22 (95% CI 1.58 to 3.13) among women. Final adjustment for physical activity, self-reported health and musculoskeletal pain further reduced the effect of heavy smoking in women (HR=1.53, 95% CI 1.09 to 2.16). Socioeconomic status confounded the smoking-related risk for disability pension; for female heavy smokers, however, a significant increased risk persisted after adjustment. Women may be particularly vulnerable to heavy smoking and to its sociomedical consequences, such as disability pension.

  10. Cost Accounting and Accountability: One Approach.

    ERIC Educational Resources Information Center

    Gingold, William

    This paper outlines an approach designed to provide an accurate and efficient cost accounting system for use in schools and other social service organizations. In his discussion, the author presents a detailed step-by-step description of how to establish, plan, and operate the system. The basic element of the system is the Daily Event Record…

  11. Metabolic syndrome and shift work: a systematic review.

    PubMed

    Canuto, Raquel; Garcez, Anderson S; Olinto, Maria T A

    2013-12-01

    The aim of this systematic review was to examine the association between shift work and metabolic syndrome (MetS) as well as the potential confounders investigated. A systematic search was conducted with the aim of finding original articles on the association between shift work and MetS. The included articles were chosen based on established inclusion criteria; their methodological quality was assessed using a validated quality checklist. A total of 10 articles were included in this review. The majority of the studies were classified as having a low risk of bias. The definitions of MetS and shift work varied between studies. Among the ten studies, eight found a positive association between shift work and MetS after controlling for socio-demographic and behavioral factors. Only three studies included sleep duration as a confounder, and these studies presented discordant results. We conclude that there was insufficient evidence regarding the association between shift work and prevalent MetS when the confounders are taken into account. Copyright © 2012 Elsevier Ltd. All rights reserved.

  12. Quality, and not just quantity, of education accounts for differences in psychometric performance between african americans and white non-hispanics with Alzheimer's disease.

    PubMed

    Chin, Alexander L; Negash, Selam; Xie, Sharon; Arnold, Steven E; Hamilton, Roy

    2012-03-01

    The effect of race on cognitive test performance in the evaluation of Alzheimer's disease (AD) remains controversial. One factor that may contribute substantially to differences in cognitive test performance in diverse populations is education. The current study examined the extent to which quality of education, even after controlling for formal years of education, accounts for differences in cognitive performance between African Americans and White Non-Hispanics (WNHs). The retrospective cohort included 244 patients diagnosed with AD who self-identified as African Americans (n = 51) or WNHs (n = 193). The Wechsler Test of Adult Reading (WTAR) was used as an estimate of quality of education. In an analysis that controlled for traditional demographics, including age, sex, and years of formal education, African Americans scored significantly lower than WNHs on the Mini-Mental State Examination, as well as on neuropsychological tests of memory, attention, and language. However, after also adjusting for reading level, all previously observed differences were significantly attenuated. The attenuating effect remained even after controlling for disease severity, indicating that reading scores are not confounded by severity of dementia. These findings suggest that quality, and not just quantity, of education needs to be taken into account when assessing cognitive performance in African Americans with AD.

  13. Accountability

    ERIC Educational Resources Information Center

    Fielding, Michael; Inglis, Fred

    2017-01-01

    This contribution republishes extracts from two important articles published around 2000 concerning the punitive accountability system suffered by English primary and secondary schools. The first concerns the inspection agency Ofsted, and the second managerialism. Though they do not directly address assessment, they are highly relevant to this…

  14. Quantification of the impact of a confounding variable on functional connectivity confirms anti-correlated networks in the resting-state.

    PubMed

    Carbonell, F; Bellec, P; Shmuel, A

    2014-02-01

    The effect of regressing out the global average signal (GAS) in resting state fMRI data has become a concern for interpreting functional connectivity analyses. It is not clear whether the reported anti-correlations between the Default Mode and the Dorsal Attention Networks are intrinsic to the brain, or are artificially created by regressing out the GAS. Here we introduce a concept, Impact of the Global Average on Functional Connectivity (IGAFC), for quantifying the sensitivity of seed-based correlation analyses to the regression of the GAS. This voxel-wise IGAFC index is defined as the product of two correlation coefficients: the correlation between the GAS and the fMRI time course of a voxel, times the correlation between the GAS and the seed time course. This definition enables the calculation of a threshold at which the impact of regressing-out the GAS would be large enough to introduce spurious negative correlations. It also yields a post-hoc impact correction procedure via thresholding, which eliminates spurious correlations introduced by regressing out the GAS. In addition, we introduce an Artificial Negative Correlation Index (ANCI), defined as the absolute difference between the IGAFC index and the impact threshold. The ANCI allows a graded confidence scale for ranking voxels according to their likelihood of showing artificial correlations. By applying this method, we observed regions in the Default Mode and Dorsal Attention Networks that were anti-correlated. These findings confirm that the previously reported negative correlations between the Dorsal Attention and Default Mode Networks are intrinsic to the brain and not the result of statistical manipulations. Our proposed quantification of the impact that a confound may have on functional connectivity can be generalized to global effect estimators other than the GAS. It can be readily applied to other confounds, such as systemic physiological or head movement interferences, in order to quantify their

  15. Effect of confounding variables on hemodynamic response function estimation using averaging and deconvolution analysis: An event-related NIRS study.

    PubMed

    Aarabi, Ardalan; Osharina, Victoria; Wallois, Fabrice

    2017-07-15

    Slow and rapid event-related designs are used in fMRI and functional near-infrared spectroscopy (fNIRS) experiments to temporally characterize the brain hemodynamic response to discrete events. Conventional averaging (CA) and the deconvolution method (DM) are the two techniques commonly used to estimate the Hemodynamic Response Function (HRF) profile in event-related designs. In this study, we conducted a series of simulations using synthetic and real NIRS data to examine the effect of the main confounding factors, including event sequence timing parameters, different types of noise, signal-to-noise ratio (SNR), temporal autocorrelation and temporal filtering on the performance of these techniques in slow and rapid event-related designs. We also compared systematic errors in the estimates of the fitted HRF amplitude, latency and duration for both techniques. We further compared the performance of deconvolution methods based on Finite Impulse Response (FIR) basis functions and gamma basis sets. Our results demonstrate that DM was much less sensitive to confounding factors than CA. Event timing was the main parameter largely affecting the accuracy of CA. In slow event-related designs, deconvolution methods provided similar results to those obtained by CA. In rapid event-related designs, our results showed that DM outperformed CA for all SNR, especially above -5 dB regardless of the event sequence timing and the dynamics of background NIRS activity. Our results also show that periodic low-frequency systemic hemodynamic fluctuations as well as phase-locked noise can markedly obscure hemodynamic evoked responses. Temporal autocorrelation also affected the performance of both techniques by inducing distortions in the time profile of the estimated hemodynamic response with inflated t-statistics, especially at low SNRs. We also found that high-pass temporal filtering could substantially affect the performance of both techniques by removing the low-frequency components of

  16. Towards a balanced account of autism etiology

    PubMed Central

    Hall, Genae A.

    2004-01-01

    Drash and Tudor describe six sets of reinforcement contingencies which may be present in the environments of some children eventually diagnosed with autism and suggest that these contingencies account for the etiology of “autistic” behaviors. Nevertheless, merely observing such contingencies in the environments of these children is insufficient to establish a positive correlation between the contingencies and “autistic” behaviors, let alone a causal relationship. To demonstrate a positive correlation, it is necessary to present evidence that the relevant contingencies are present more often in the environments of children exhibiting these behaviors than in the environments of children not exhibiting these behaviors. This condition has not been met, since no evidence to the effect that such contingencies are absent in the environments of typical children or children with disabilities other than autism has been presented. In fact, the opposite appears to be true, as is argued in the present commentary. It appears that Drash and Tudor's account of autism etiology is incomplete in that it neglects the role of unlearned differences between children and their possible interactions with the social environment in shaping “autistic” behaviors. Despite the misconception held by some that behavior analysis is a radically environmental approach, unlearned differences may be discussed within a behavioral framework. A “completely behavioral” account may discuss such differences in terms of susceptibility to reinforcement or punishment, speed of conditioning, or other unlearned characteristics which are potentially testable. PMID:22477286

  17. The OPTN Deceased Donor Potential Study: Implications for Policy and Practice.

    PubMed

    Klassen, D K; Edwards, L B; Stewart, D E; Glazier, A K; Orlowski, J P; Berg, C L

    2016-06-01

    The Organ Procurement and Transplantation Network (OPTN) Deceased Donor Potential Study, funded by the Health Resources and Services Administration, characterized the current pool of potential deceased donors and estimated changes through 2020. The goal was to inform policy development and suggest practice changes designed to increase the number of donors and organ transplants. Donor estimates used filtering methodologies applied to datasets from the OPTN, the National Center for Health Statistics, and the Agency for Healthcare Research and Quality and used these estimates with the number of actual donors to estimate the potential donor pool through 2020. Projected growth of the donor pool was 0.5% per year through 2020. Potential donor estimates suggested unrealized donor potential across all demographic groups, with the most significant unrealized potential (70%) in the 50-75-year-old age group and potential Donation after Circulatory Death (DCD) donors. Actual transplants that may be realized from potential donors in these categories are constrained by confounding medical comorbidities not identified in administrative databases and by limiting utilization practices for organs from DCD donors. Policy, regulatory, and practice changes encouraging organ procurement and transplantation of a broader population of potential donors may be required to increase transplant numbers in the United States. © Copyright 2016 The American Society of Transplantation and the American Society of Transplant Surgeons.

  18. 7 CFR 1770.13 - Accounting requirements.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 12 2010-01-01 2010-01-01 false Accounting requirements. 1770.13 Section 1770.13... AGRICULTURE (CONTINUED) ACCOUNTING REQUIREMENTS FOR RUS TELECOMMUNICATIONS BORROWERS Uniform System of Accounts § 1770.13 Accounting requirements. (a) Each borrower shall maintain its books of accounts on the...

  19. The Impact of the Principles of Accounting Experience on Student Preparation for Intermediate Accounting

    ERIC Educational Resources Information Center

    Carrington, Linda G.

    2012-01-01

    Both students and instructors alike will generally agree that intermediate accounting courses are among the most difficult and demanding in an accounting or finance curriculum, and perhaps even on the college campus. Intermediate accounting contains subject matter which requires a higher level of thinking and a greater ability to process prior…

  20. Residual Associations of Inflammatory Markers with eGFR after Accounting for Measured GFR in a Community-Based Cohort without CKD.

    PubMed

    Schei, Jørgen; Stefansson, Vidar T N; Mathisen, Ulla Dorte; Eriksen, Bjørn O; Solbu, Marit D; Jenssen, Trond G; Melsom, Toralf

    2016-02-05

    eGFR on the basis of creatinine (eGFRcre) associates differently with cardiovascular disease and mortality than eGFR on the basis of cystatin C (eGFRcys). This may be related to risk factors affecting the level of creatinine and cystatin C along non-GFR pathways, which may confound the association between eGFR and outcome. Nontraditional risk factors are usually not measured in epidemiologic studies of eGFR and cannot be adjusted for to reduce confounding. We examined whether the inflammatory markers soluble TNF receptor type 2 (sTNFR2), C-reactive protein (CRP), and fibrinogen associated differently with eGFR than with measured GFR (mGFR). GFR was measured by iohexol clearance in 1627 middle-aged participants without kidney disease, diabetes, or cardiovascular disease enrolled in the Renal Iohexol Clearance Survey Study from the Sixth Tromsø Study between 2007 and 2009. Generalized estimating equations were used to assess the residual associations between eGFR (eGFRcre, eGFRcys, and eGFR on the basis of creatinine and cystatin C) and the inflammatory markers relative to mGFR. sTNFR2, CRP, and fibrinogen were associated with a higher eGFRcre after accounting for mGFR in multivariable-adjusted models (2.63 ml/min per 1.73 m(2); 95% confidence interval [95% CI], 2.1 to 3.2 per SD increase in sTNFR2, 0.93 ml/min per 1.73 m(2); 95% CI, 0.3 to 1.5 per SD increase in log CRP, and 1.19 ml/min per 1.73 m(2); 95% CI, 0.6 to 1.8 per SD increase in fibrinogen). sTNFR2 and CRP were inversely associated with eGFRcys (-1.4 ml/min per 1.73 m(2); 95% CI, -2.1 to -0.6 per SD increase in sTNFR2, and -0.76 ml/min per 1.73 m(2); 95% CI, -1.4 to -0.1 per SD increase in log CRP). eGFRcre and eGFRcys are associated with inflammatory factors after accounting for mGFR but in opposite directions. These non-GFR-related associations may bias risk estimates by eGFR and, in part, explain the different risks predicted by eGFRcre and eGFRcys in longitudinal studies. Copyright © 2016 by the