Risk Implications of the New CKD Epidemiology Collaboration (CKD-EPI) Equation as Compared With the MDRD Study Equation for Estimated GFR: The Atherosclerosis Risk in Communities (ARIC) Study

PubMed Central

Matsushita, Kunihiro; Selvin, Elizabeth; Bash, Lori D.; Astor, Brad C.; Coresh, Josef

2010-01-01

Background The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) recently published an equation for estimated glomerular filtration rate (eGFR) using the same variables (serum creatinine, age, gender and race) as the Modification of Diet in Renal Disease Study (MDRD) equation. Although the CKD-EPI equation estimates GFR more precisely as compared with the MDRD equation, whether this equation improves risk prediction is unknown. Study Design Prospective cohort study, the Atherosclerosis Risk in Communities (ARIC) Study. Setting & Participants 13,905 middle-aged participants without a history of cardiovascular disease with median follow-up of 16.9 years. Predictor eGFR Outcomes & Measurements We compared the association of eGFR in categories (≥120, 90–119, 60–89, 30–59, <30 ml/min/1.73m2) by the CKD-EPI and MDRD equations with risk of incident end-stage renal disease (ESRD), all-cause mortality, coronary heart disease (CHD), and stroke. Results Median of eGFRCKD-EPI was higher than that of eGFRMDRD (97.6 vs. 88.8 ml/min/1.73m2, P<0.001). The CKD-EPI equation reclassified 44.9% (n=3,079) and 43.5% (n=151) of participants with eGFRMDRD 60–89 and 30–59, respectively, upward to a higher eGFR category but no one with eGFRMDRD 90–119 or <30, lowering the prevalence of CKD stage 3–5 from 2.7% to 1.6%. Participants with eGFRMDRD 30–59 who were reclassified upward had lower risk as compared to those who were not reclassified (ESRD incidence rate ratio, 0.10 [95% CI, 0.03–0.33], all-cause mortality, 0.30 [0.19–0.48], CHD, 0.36 [0.21–0.61], stroke, 0.50 [0.24–1.01]). Similar results were observed for participants with eGFRMDRD 60–89. More frequent reclassification of younger, female, and white participants explained some of these trends. Net reclassification improvement among participants with eGFR <120 was positive for all outcomes (P<0.001). Limitations Limited number of cases with eGFR <60 and no measurement of albuminuria. Conclusions The CKD-EPI equation more appropriately categorized individuals with respect to long-term clinical risk as compared to the MDRD equation, suggesting improved clinical usefulness in this middle-aged population. PMID:20189275

[Diagnostic ability of Chronic Kidney Disease Epidemiology Collaboration and Modification of Diet in Renal Disease-4 equations to estimate glomerular filtration rate in with multimorbidity patients].

PubMed

Cabrerizo-García, José Luis; Díez-Manglano, Jesús; García-Arilla, Ernesto; Revillo-Pinilla, Paz; Ramón-Puertas, José; Sebastián-Royo, Mariano

2015-01-06

The Modification of Diet in Renal Disease (MDRD) equation is recommended by most scientific societies to calculate the estimated glomerular filtration rate (GFR). Recently the group Chronic Kidney Disease Epidemiology Collaboration (CKP-EPI) has published a new, more precise and accurate equation. We have analyzed its behavior in a group of polypathological patients (PP) and compared it with the classic MDRD-4.version Multicenter, observational, descriptive and transversal study. We calculated GFR by MDRD-4 and CKD-EPI in 425 PP. Each stage was assigned according to the GFR: 1:>90; 2: 60-89; 3: 30-59; 4: 15-29; and 5 < 15 ml/min/1.73m(2). We analyzed the correlation between both and the patients reclassified by CKD-EPI. Mean age was (mean [SD]) 81.7 (7.9) years. 55.3% were women. The mean estimated GFR was 58.6 (26.3) ml/min/1,73m(2) by MDRD-4 and 52.7 (23.0) ml/min/1.73m(2) by CKD-EPI (P<.001; Spearman's Rho correlation and Lin concordance coefficients: 0.993 and 0.948). The Bland-Altman plots reflected lower values for GFR for CKD-EPI equation. In the stage 2, 21.2% were reclassified by CKD-EPI to the stage 3, with women older than 83 years being the more disadvantaged subgroup with 27.3% or reclassification. CKD-EPI equation applied to PP worsens the results of MDRD-4. In general, it originates low values of GFR and increases the degree of renal insufficiency, especially in older women. Copyright © 2013 Elsevier España, S.L.U. All rights reserved.

[Prevalence of chronic kidney disease in hypertensive persons attended in primary care from Spain determined by application of estimating equations].

PubMed

Gómez Navarro, Rafael

2009-01-01

To study the renal function (FR) of the hypertensive patients by means of estimating equations and serum creatinine (Crp). To calculate the percentage of patients with chronic kidney disease (ERC) that present normal values of Crp. To analyze which factors collaborate in the deterioration of the FR. Descriptive cross-sectional study of patients with HTA. Crp and arterial tension (TA) were determined. The glomerular filtration rate was calculated by means of Cockroft-Gault and MDRD's formula. The years of evolution of the HTA were registered. A descriptive study of the variables and the possible dependence among them was completed, using several times linear multiple regression. 52 patients were studied (57,7% women). Average age 72,4 +/- 10,8. 32,6% (Cockcroft-Gault) or 21,5% (MDRD) were fulfilling ERC criterion. The ERC was mainly diagnosed in females. 21,4% (Cockcroft-Gault) and 9,5 % patients (MDRD) with ERC had normal Crp values. We do not find linear dependence between the numbers of TA and the FR. The TA check-up objectives do not suppose less development of ERC. In males we find linear dependence within the FR (MDRD) and the years of evolution of the HTA. The ERC is a frequent pathology in the hypertense persons. The systematical utilization of estimating equations facilitates the detection of hidden ERC in patients with normal Crp.

Estimating equations for glomerular filtration rate in the era of creatinine standardization: a systematic review.

PubMed

Earley, Amy; Miskulin, Dana; Lamb, Edmund J; Levey, Andrew S; Uhlig, Katrin

2012-06-05

Clinical laboratories are increasingly reporting estimated glomerular filtration rate (GFR) by using serum creatinine assays traceable to a standard reference material. To review the performance of GFR estimating equations to inform the selection of a single equation by laboratories and the interpretation of estimated GFR by clinicians. A systematic search of MEDLINE, without language restriction, between 1999 and 21 October 2011. Cross-sectional studies in adults that compared the performance of 2 or more creatinine-based GFR estimating equations with a reference GFR measurement. Eligible equations were derived or reexpressed and validated by using creatinine measurements traceable to the standard reference material. Reviewers extracted data on study population characteristics, measured GFR, creatinine assay, and equation performance. Eligible studies compared the MDRD (Modification of Diet in Renal Disease) Study and CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equations or modifications thereof. In 12 studies in North America, Europe, and Australia, the CKD-EPI equation performed better at higher GFRs (approximately >60 mL/min per 1.73 m(2)) and the MDRD Study equation performed better at lower GFRs. In 5 of 8 studies in Asia and Africa, the equations were modified to improve their performance by adding a coefficient derived in the local population or removing a coefficient. Methods of GFR measurement and study populations were heterogeneous. Neither the CKD-EPI nor the MDRD Study equation is optimal for all populations and GFR ranges. Using a single equation for reporting requires a tradeoff to optimize performance at either higher or lower GFR ranges. A general practice and public health perspective favors the CKD-EPI equation. Kidney Disease: Improving Global Outcomes.

Comparison of the Chronic Kidney Disease Epidemiology Collaboration, the Modification of Diet in Renal Disease study and the Cockcroft-Gault equation in patients with heart failure.

PubMed

Szummer, Karolina; Evans, Marie; Carrero, Juan Jesus; Alehagen, Urban; Dahlström, Ulf; Benson, Lina; Lund, Lars H

2017-01-01

It is unknown how the creatinine-based renal function estimations differ for dose adjustment cut-offs and risk prediction in patients with heart failure. The renal function was similar with the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) (median 59 mL/min/1.73 m 2 , IQR 42 to 77) and Modification of Diet in Renal Disease Study (MDRD) (59 mL/min/1.73 m 2 , IQR 43 to 75) and slightly lower with the Cockcroft-Gault (CG) equation (57 mL/min, IQR 39 to 82). Across the commonly used renal function stages, the CKD-EPI and the MDRD classified patients into the same stage in 87.2% (kappa coefficient 0.83, p<0.001); the CKD-EPI and the CG equation agreed in 52.3% (kappa coefficient 0.39, p<0.001). Hence, a differing number of patients will receive dose adjustment depending on which formula is used as cut-off. The CG equation predicted worse prognosis better (c-statistics 0.740, 95% CI 0.734 to 0.746) than CKD-EPI (0.697, 95% CI 0.690 to 0.703, p<0.001) and MDRD (0.680, 95% CI 0.734 to 0.746). Using net reclassification improvement (NRI), the CG identified 12.8% more patients at higher risk of death as compared with the CKD-EPI equation. Patients registered in the Swedish Heart Failure Registry (n= 40 736) with standardised creatinine values between 2000 and 2012 had their renal function estimated with the CKD-EPI, the MDRD and the CG. Agreement between the formulas was compared for categories. Prediction of death was assessed with c-statistics and with NRI. The choice of renal function estimation formula has clinical implications and differing results at various cut-off levels. For prognosis, the CG predicts mortality better than the CKD-EPI and MDRD.

Comparison of the Chronic Kidney Disease Epidemiology Collaboration, the Modification of Diet in Renal Disease study and the Cockcroft-Gault equation in patients with heart failure

PubMed Central

Szummer, Karolina; Evans, Marie; Carrero, Juan Jesus; Alehagen, Urban; Dahlström, Ulf; Benson, Lina; Lund, Lars H

2017-01-01

Background It is unknown how the creatinine-based renal function estimations differ for dose adjustment cut-offs and risk prediction in patients with heart failure. Method and results The renal function was similar with the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) (median 59 mL/min/1.73 m2, IQR 42 to 77) and Modification of Diet in Renal Disease Study (MDRD) (59 mL/min/1.73 m2, IQR 43 to 75) and slightly lower with the Cockcroft-Gault (CG) equation (57 mL/min, IQR 39 to 82). Across the commonly used renal function stages, the CKD-EPI and the MDRD classified patients into the same stage in 87.2% (kappa coefficient 0.83, p<0.001); the CKD-EPI and the CG equation agreed in 52.3% (kappa coefficient 0.39, p<0.001). Hence, a differing number of patients will receive dose adjustment depending on which formula is used as cut-off. The CG equation predicted worse prognosis better (c-statistics 0.740, 95% CI 0.734 to 0.746) than CKD-EPI (0.697, 95% CI 0.690 to 0.703, p<0.001) and MDRD (0.680, 95% CI 0.734 to 0.746). Using net reclassification improvement (NRI), the CG identified 12.8% more patients at higher risk of death as compared with the CKD-EPI equation. Patients registered in the Swedish Heart Failure Registry (n= 40 736) with standardised creatinine values between 2000 and 2012 had their renal function estimated with the CKD-EPI, the MDRD and the CG. Agreement between the formulas was compared for categories. Prediction of death was assessed with c-statistics and with NRI. Conclusion The choice of renal function estimation formula has clinical implications and differing results at various cut-off levels. For prognosis, the CG predicts mortality better than the CKD-EPI and MDRD. PMID:28761677

Creatinine-based equations for the adjustment of drug dosage in an obese population.

PubMed

Bouquegneau, Antoine; Vidal-Petiot, Emmanuelle; Moranne, Olivier; Mariat, Christophe; Boffa, Jean-Jacques; Vrtovsnik, François; Scheen, André-Jean; Krzesinski, Jean-Marie; Flamant, Martin; Delanaye, Pierre

2016-02-01

For drug dosing adaptation, the Kidney Disease: Improving Global Outcomes (KDIGO) guidelines recommend using estimated glomerular filtration rate (eGFR) by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation, after 'de-indexation' by body surface area (BSA). In pharmacology, the Cockcroft-Gault (CG) equation is still recommended to adapt drug dosage. In the context of obesity, adjusted ideal body weight (AIBW) is sometimes preferred to actual body weight (ABW) for the CG equation. The aim of the present study was to compare the performance of the different GFR-estimating equations, non-indexed or de-indexed by BSA for the purpose of drug-dosage adaptation in obese patients. We analysed data from patients with a body mass index (BMI) higher than 30 kg m(-2) who underwent a GFR measurement. eGFR was calculated using the CKD-EPI and Modification of Diet in Renal Disease (MDRD) equations, de-indexed by BSA, and the CG equation, using either ABW, AIBW or lean body weight (LBW) for the weight variable and compared with measured GFR, expressed in ml min(-1). In our population of obese patients, use of the AIBW instead of the ABW in the CG equation, markedly improved the overall accuracy of this equation [57% for CGABW and 79% for CGAIBW (P < 0.05)]. For high BMI (over 40 kg m(-2)), the accuracy of the CG equations is no different when using LBW than when using AIBW. The MDRD and CKD-EPI equations de-indexed by the BSA also performed well, with an overall higher accuracy for the MDRD de-indexed equation [(80% and 76%, respectively (P < 0.05)]. The de-indexed MDRD equation appeared to be the most suitable for estimating the non-indexed GFR for the purpose of drug dosage adaptation in obese patients. © 2015 The British Pharmacological Society.

Discrepancies between the use of MDRD-4 IDMS and CKD-EPI equations, instead of the Cockcroft-Gault equation, in the determination of the dosage of direct oral anticoagulants in patients with non-valvular atrial fibrillation.

PubMed

Pérez Cabeza, Alejandro Isidoro; Chinchurreta Capote, Pedro Antonio; González Correa, Jose Antonio; Ruiz Mateas, Francisco; Rosas Cervantes, Gabriel; Rivas Ruiz, Francisco; Valle Alberca, Almudena; Bravo Marqués, Rafael

2018-02-09

Direct oral anticoagulants (DOACs) require dose adjustment according to estimated clearance creatinine (eClCr) using the Cockcroft-Gault (CG) equation. There are discrepancies with the equations that estimate glomerular filtration rate (eGFR). We analyse how the use of the CKD-EPI and MDRD-4 IDMS equations affect the recommended dosage for ACODs. Retrospective study of patients with non-valvular atrial fibrillation seen at a cardiology clinic between November 2012 and August 2014. Patients were reclassified according to the recommended dosage for dabigatran, rivaroxaban, apixaban and edoxaban, based on the eGFR equation used. Other clinical factors are taken into account, according to the product label. We analysed the percentage of discordance. Four hundred and fifty-four patients, 53.3% men, with a mean age of 68.7±13.8 years were studied. The mean intra-individual differences recorded for the CG equation were 3.9ml/min/1.73m 2 with MDRD-4 IDMS (95% CI 1.4-6.4, P=.003) and 11.3ml/min/1.73m 2 with CKD-EPI (95% CI 8.9-13.7, P<.001). A gradient is observed in the discordance of the posology (apixaban 1.1%, dabigatran 3.5%, edoxaban 5.7%, rivaroxaban 8.4% with MDRD-4 IDMS). Differences were limited to patients with eClCr<60ml/min and were more evident in≥75 years in which the eGFR equations overestimate renal function. In patients with non-valvular atrial fibrillation, especially with renal failure and in the elderly, eGFR equations tend to overestimate renal function relative to CG and therefore suggest an overdose of DOACs. Copyright © 2017 Elsevier España, S.L.U. All rights reserved.

Comparison of CKD-EPI and MDRD to estimate baseline renal function in HIV-positive patients.

PubMed

Ibrahim, Fowzia; Hamzah, Lisa; Jones, Rachael; Nitsch, Dorothea; Sabin, Caroline; Post, Frank A

2012-06-01

Renal dysfunction is common in HIV-positive patients, and guidelines suggest regular monitoring of renal function with estimated glomerular filtration rate (eGFR) and urinalysis. It is unknown whether Chronic Kidney Disease Epidemiological Collaboration (CKD-EPI) or Modification of Diet in Renal Disease (MDRD) provide better estimates of glomerular filtration rate (GFR) in this population. We compared the CKD-EPI and MDRD equations to estimate GFR at baseline in 20,132 HIV-positive individuals in the UK CHIC cohort. Kappa statistics and Bland-Altman plots were used to assess agreement between the two estimates and Kaplan-Meier plots and Cox regression analysis to describe mortality patterns. At baseline, median eGFR was 100 (87, 112) (CKD-EPI) and 94 (83, 108) (MDRD) (mL/min/1.73 m(2)). Good overall agreement between CKD-EPI- and MDRD-defined eGFR bands was observed (Kappa = 0.71, 95% confidence interval: 0.70-0.72). Of the 367 patients with eGFR MDRD 30-59, 57 (15.5%) were categorized as eGFR 60-89 by CKD-EPI. After adjustment for covariates, eGFR <60 (CKD-EPI), eGFR <30 (MDRD) and eGFR ≥105 (both formulae) were significantly associated with an increased risk of death. Mortality in patients classified as having eGFR 60-89 by CKD-EPI and eGFR 30-59 by MDRD more closely resembled mortality of patients who had eGFR 60-89 by both formulae. MDRD and CKD-EPI equations showed a high degree of agreement in stratifying patients by baseline eGFR. CKD-EPI estimates of GFR <60 at baseline are more strongly associated with mortality than MDRD estimates of GFR <60, supporting the concept that MDRD may have overestimated the severity of renal impairment in these patients. Our findings support the use of CKD-EPI in HIV-positive individuals.

Performance of three glomerular filtration rate estimation equations in a population of sub-Saharan Africans with Type 2 diabetes.

PubMed

Agoons, D D; Balti, E V; Kaze, F F; Azabji-Kenfack, M; Ashuntantang, G; Kengne, A P; Sobngwi, E; Mbanya, J C

2016-09-01

We evaluated the performance of the Modification of Diet in Renal Disease (MDRD), Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and Cockcroft-Gault (CG) equations against creatinine clearance (CrCl) to estimate glomerular filtration rate (GFR) in 51 patients with Type 2 diabetes. The CrCl value was obtained from the average of two consecutive 24-h urine samples. Results were adjusted for body surface area using the Dubois formula. Serum creatinine was measured using the kinetic Jaffe method and was calibrated to standardized levels. Bland-Altman analysis and kappa statistic were used to examine agreement between measured and estimated GFR. Estimates of GFR from the CrCl, MDRD, CKD-EPI and CG equations were similar (overall P = 0.298), and MDRD (r = 0.58; 95% CI: 0.36-0.74), CKD-EPI (r = 0.55; 95% CI: 0.33-0.72) and CG (r = 0.61; 95% CI: 0.39-0.75) showed modest correlation with CrCl (all P < 0.001). Bias was -0.3 for MDRD, 1.7 for CKD-EPI and -5.4 for CG. All three equations showed fair-to-moderate agreement with CrCl (kappa: 0.38-0.51). The c-statistic for all three equations ranged between 0.75 and 0.77 with no significant difference (P = 0.639 for c-statistic comparison). The MDRD equation seems to have a modest advantage over CKD-EPI and CG in estimating GFR and detecting impaired renal function in sub-Saharan African patients with Type 2 diabetes. The overall relatively modest correlation with CrCl, however, suggests the need for context-specific estimators of GFR or context adaptation of existing estimators. © 2015 Diabetes UK.

Estimating Renal Function in the Elderly Malaysian Patients Attending Medical Outpatient Clinic: A Comparison between Creatinine Based and Cystatin-C Based Equations.

PubMed

Jalalonmuhali, Maisarah; Elagel, Salma Mohamed Abouzriba; Tan, Maw Pin; Lim, Soo Kun; Ng, Kok Peng

2018-01-01

To assess the performance of different GFR estimating equations, test the diagnostic value of serum cystatin-C, and compare the applicability of cystatin-C based equation with serum creatinine based equation for estimating GFR (eGFR) in comparison with measured GFR in the elderly Malaysian patients. A cross-sectional study recruiting volunteered patients 65 years and older attending medical outpatient clinic. 51 chromium EDTA ( 51 Cr-EDTA) was used as measured GFR. The predictive capabilities of Cockcroft-Gault equation corrected for body surface area (CGBSA), four-variable Modification of Diet in Renal Disease (4-MDRD), and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations using serum creatinine (CKD-EPIcr) as well as serum cystatin-C (CKD-EPIcys) were calculated. A total of 40 patients, 77.5% male, with mean measured GFR 41.2 ± 18.9 ml/min/1.73 m 2 were enrolled. Mean bias was the smallest for 4-MDRD; meanwhile, CKD-EPIcr had the highest precision and accuracy with lower limit of agreement among other equations. CKD-EPIcys equation did not show any improvement in GFR estimation in comparison to CKD-EPIcr and MDRD. The CKD-EPIcr formula appears to be more accurate and correlates better with measured GFR in this cohort of elderly patients.

Mortality Prediction in the Oldest Old with Five Different Equations to Estimate Glomerular Filtration Rate: The Health and Anemia Population-based Study

PubMed Central

Mandelli, Sara; Riva, Emma; Tettamanti, Mauro; Detoma, Paolo; Giacomin, Adriano; Lucca, Ugo

2015-01-01

Background Kidney function declines considerably with age, but little is known about its clinical significance in the oldest-old. Objectives To study the association between reduced glomerular filtration rate (GFR) estimated according to five equations with mortality in the oldest-old. Design Prospective population-based study. Setting Municipality of Biella, Piedmont, Italy. Participants 700 subjects aged 85 and older participating in the “Health and Anemia” Study in 2007–2008. Measurements GFR was estimated using five creatinine-based equations: the Cockcroft-Gault (C-G), Modification of Diet in Renal Disease (MDRD), MAYO Clinic, Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and Berlin Initiative Study-1 (BIS-1). Survival analysis was used to study mortality in subjects with reduced eGFR (<60 mL/min/1.73m2) compared to subjects with eGFR ≥60 mL/min/1.73m2. Results Prevalence of reduced GFR was 90.7% with the C-G, 48.1% with MDRD, 23.3% with MAYO, 53.6% with CKD-EPI and 84.4% with BIS-1. After adjustment for confounders, two-year mortality was significantly increased in subjects with reduced eGFR using BIS-1 and C-G equations (adjusted HRs: 2.88 and 3.30, respectively). Five-year mortality was significantly increased in subjects with eGFR <60 mL/min/1.73m2 using MAYO, CKD-EPI and, in a graduated fashion in reduced eGFR categories, MDRD. After 5 years, oldest old with an eGFR <30 mL/min/1.73m2 showed a significantly higher risk of death whichever equation was used (adjusted HRs between 2.04 and 2.70). Conclusion In the oldest old, prevalence of reduced eGFR varies noticeably depending on the equation used. In this population, risk of mortality was significantly higher for reduced GFR estimated with the BIS-1 and C-G equations over the short term. Though after five years the MDRD appeared on the whole a more consistent predictor, differences in mortality prediction among equations over the long term were less apparent. Noteworthy, subjects with a severely reduced GFR were consistently at higher risk of death regardless of the equation used to estimate GFR. PMID:26317988

Mortality Prediction in the Oldest Old with Five Different Equations to Estimate Glomerular Filtration Rate: The Health and Anemia Population-based Study.

PubMed

Mandelli, Sara; Riva, Emma; Tettamanti, Mauro; Detoma, Paolo; Giacomin, Adriano; Lucca, Ugo

2015-01-01

Kidney function declines considerably with age, but little is known about its clinical significance in the oldest-old. To study the association between reduced glomerular filtration rate (GFR) estimated according to five equations with mortality in the oldest-old. Prospective population-based study. Municipality of Biella, Piedmont, Italy. 700 subjects aged 85 and older participating in the "Health and Anemia" Study in 2007-2008. GFR was estimated using five creatinine-based equations: the Cockcroft-Gault (C-G), Modification of Diet in Renal Disease (MDRD), MAYO Clinic, Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and Berlin Initiative Study-1 (BIS-1). Survival analysis was used to study mortality in subjects with reduced eGFR (<60 mL/min/1.73 m(2)) compared to subjects with eGFR ≥ 60 mL/min/1.73 m(2). Prevalence of reduced GFR was 90.7% with the C-G, 48.1% with MDRD, 23.3% with MAYO, 53.6% with CKD-EPI and 84.4% with BIS-1. After adjustment for confounders, two-year mortality was significantly increased in subjects with reduced eGFR using BIS-1 and C-G equations (adjusted HRs: 2.88 and 3.30, respectively). Five-year mortality was significantly increased in subjects with eGFR <60 mL/min/1.73 m(2) using MAYO, CKD-EPI and, in a graduated fashion in reduced eGFR categories, MDRD. After 5 years, oldest old with an eGFR <30 mL/min/1.73 m(2) showed a significantly higher risk of death whichever equation was used (adjusted HRs between 2.04 and 2.70). In the oldest old, prevalence of reduced eGFR varies noticeably depending on the equation used. In this population, risk of mortality was significantly higher for reduced GFR estimated with the BIS-1 and C-G equations over the short term. Though after five years the MDRD appeared on the whole a more consistent predictor, differences in mortality prediction among equations over the long term were less apparent. Noteworthy, subjects with a severely reduced GFR were consistently at higher risk of death regardless of the equation used to estimate GFR.

Comparison of creatinine clearance estimates in subgroups based on Body Mass Index and albumin.

PubMed

Grapsa, Eirini; Pipili, Chrysoula; Angelopoulos, Epameinondas; Pantelias, Kostantinos; Kapetanaki, Antigoni; Deda, Edmond; Kiousi, Eva; Tzanatos, Helen

2016-02-01

The establishment of accurate equations for glomerular filtration rate (GFR) estimations is still far from the realization. Factors such as age, diabetes, stage of CKD, pregnancy, muscle mass and ethic nation are associated with less reliance upon commonly utilized estimation equations. We aimed to compare the routine use of 24-hour creatinine clearance (CrCl) and GFR estimates calculated by Crockoft-Gault (CG) and modification of diet in renal disease (MDRD) formulas in patients with different levels of renal dysfunction in subgroups, based on Body Mass Index (BMI) and serum albumin (Alb) levels. Two hundred and seventy-nine non diabetic patients (172 men and 107 women), aged 54±23 years, with BMI 27.3±4.4 were enrolled in the study. All patients presented creatinine 1.8±1.2 (mg/dL) and Alb 3.5±1.3g/dL. The comparison of CrCl versus CG had bias 3.1 while the comparison of CrCl versus MDRD had a bias of 6.6. Univariate analysis showed that age, sex and BMI were not significant biases related to the CG, MDRD and CrCl. Indeed, the bias related to the CG was significantly lower than that related to MDRD in patients with either low or high serum albumin. Interestingly, the bias associated with CG was 1.3 in non-diabetic patients with Alb ≤3.5 mg /dL suggesting that CG equation could be used interchangeable to CrCl in these patients. CG gave a better prediction of measured CrCl than MDRD in Mediterranean, non-diabetic, non-hospitalized patients although misclassification of patients with regard to renal impairment stage was not present.

Cystatin C enhances GFR estimating Equations in Kidney Transplant Recipients

PubMed Central

Kukla, Aleksandra; Issa, Naim; Jackson, Scott; Spong, Richard; Foster, Meredith C.; Matas, Arthur J.; Mauer, Michael S.; Eckfeldt, John H.; Ibrahim, Hassan N.

2014-01-01

Background The glomerular filtration rate (GFR) estimating equation incorporating both cystatin C and creatinine perform better than those using creatinine or cystatin C alone in patients with reduced GFR. Whether this equation performs well in kidney transplant recipients cross-sectionally, and more importantly, over time has not been addressed. Methods We analyzed four GFR estimating equations in participants of the Angiotensin II Blockade for Chronic Allograft Nephropathy Trial (NCT 00067990): Chronic Kidney Disease Epidemiology Collaboration equations based on serum cystatin C and creatinine (eGFR (CKD-EPI-Creat+CysC)), cystatin C alone (eGFR (CKD-EPI-CysC)), creatinine alone (eGFR (CKD-EPI-Creat)) and the Modification of Diet in Renal Disease study equation (eGFR(MDRD)). Iothalamate GFR served as a standard (mGFR). Results mGFR, serum creatinine, and cystatin C shortly after transplant were 56.1 ± 17.0 mL/min/1.73 m2, 1.2 ± 0.4 mg/dL, and 1.2 ± 0.3 mg/L respectively. eGFR (CKD-EPI-Creat+CysC) was most precise (R2=0.50) but slightly more biased than eGFR (MDRD); 9.0 ± 12.7 ml/min/1.73m2 vs. 6.4 ± 15.8 ml/min/1.73m2, respectively. This improved precision was most evident in recipients with mGFR >60 ml/min/1.73m2. For relative accuracy, eGFR (MDRD) and eGFR (CKD-EPI-Creat+CysC) had the highest percentage of estimates falling within 30% of mGFR; 75.8% and 68.9%, respectively. Longitudinally, equations incorporating cystatin C most closely paralleled the change in mGFR. Conclusion eGFR (CKD-EPI-Creat+CysC) is more precise and reflects GFR change over time reasonably well. eGFR (MDRD) had superior performance in recipients with mGFR between 30–60 ml/min/1.73m2. PMID:24457184

Effect of picric acid and enzymatic creatinine on the efficiency of the glomerular filtration rate predicator formula.

PubMed

Qiu, Ling; Guo, Xiuzhi; Zhu, Yan; Shou, Weilin; Gong, Mengchun; Zhang, Lin; Han, Huijuan; Quan, Guoqiang; Xu, Tao; Li, Hang; Li, Xuewang

2013-01-01

To investigate the impact of serum creatinine measurement on the applicability of glomerular filtration rate (GFR) evaluation equations. 99mTc-DTPA plasma clearance rate was used as GFR reference (rGFR) in patients with chronic kidney disease (CKD). Serum creatinine was measureded using enzymatic or picric acid creatinine reagent. The GFR of the patients were estimated using the Cockcroft-Gault equation corrected for body surface area, simplified Modification of Diet in Renal Disease (MDRD) equation, simplified MDRD equation corrected to isotopes dilution mass spectrometry, the CKD epidemiology collaborative research equation, and two Chinese simplified MDRD equations. Significant differences in the eGFR results estimated through enzymatic and picric acid methods were observed for the same evaluation equation. The intraclass correlation coefficient (ICC) of eGFR when the creatinine was measured by the picric acid method was significantly lower than that of the enzymatic method. The assessment accuracy of every equation using the enzymatic method to measure creatinine was significantly higher than that measured by the picric acid method when rGFR was > or = 60 mL/min/1.73m2. A significant difference was demonstrated in the same GFR evaluation equation using the picric acid and enzymatic methods. The enzymatic creatinine method was better than the picric acid method.

CKD-EPI equation: A suitable Glomerular Filtration Rate estimate for drug dosing in HIV-infected patients.

PubMed

Gagneux-Brunon, A; Botelho-Nevers, E; Delanaye, P; Lucht, F; Frésard, A; Cazorla, C; Guglielminotti, C; Fafin, C; Mariat, C; Moranne, O

2017-06-01

To evaluate concordance between glomerular filtration rate (GFR) estimates (Cockcroft and Gault, modification of diet in renal diseases, chronic kidney disease epidemiology study group equations) for drug dosing in HIV-infected patients. We performed a monocentric study. GFR was measured using the gold standard method (plasma clearance of iohexol) in 230 HIV-infected patients. Concordance rate was evaluated between measured GFR (mGFR) and estimated GFR (eGFR) for different GFR categories (GFR>90 mL/min, GFR<90 mL/min, GFR>70 mL/min, and GFR<70 mL/min). MDRD and CKD-EPI were used with and without indexation to body surface area (BSA). Mean age was 48±10 years, mean mGFR was 101±26 mL/min. Concordance between mGFR and eGFR estimated with CG, CKD-EPI (indexed and not indexed to BSA), or MDRD equations (not indexed to BSA) was similar (73%, 73%, 74%, and 73% respectively) for a breakpoint value of 90 mL/min for GFR. At this value, the concordance rate between mGFR and MDRD indexed to BSA was significantly lower (65%, P<0.05). Using 70 mL/min of GFR as the breakpoint value, all equations had similar concordance rates with mGFR (with or without indexation to BSA). CKD-EPI equation has the same concordance with GFR and with CG when used for drug dosing. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Performance of the Cockcroft-Gault, MDRD, and New CKD-EPI Formulas in Relation to GFR, Age, and Body Size

PubMed Central

Grootendorst, Diana Carina; Verduijn, Marion; Elliott, Elise Grace; Dekker, Friedo Wilhelm; Krediet, Raymond Theodorus

2010-01-01

Background and objectives: We compared the estimations of Cockcroft-Gault, Modification of Diet in Renal Disease (MDRD), and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations to a gold standard GFR measurement using 125I-iothalamate, within strata of GFR, gender, age, body weight, and body mass index (BMI). Design, setting, participants, & measurements: For people who previously underwent a GFR measurement, bias, precision, and accuracies between measured and estimated kidney functions were calculated within strata of the variables. The relation between the absolute bias and the variables was tested with linear regression analysis. Results: Overall (n = 271, 44% male, mean measured GFR 72.6 ml/min per 1.73 m2 [SD 30.4 ml/min per 1.73 m2]), mean bias was smallest for MDRD (P < 0.01). CKD-EPI had highest accuracy (P < 0.01 compared with Cockcroft-Gault), which did not differ from MDRD (P = 0.14). The absolute bias of all formulas was related to age. For MDRD and CKD-EPI, absolute bias was also related to the GFR; for Cockcroft-Gault, it was related to body weight and BMI as well. In all extreme subgroups, MDRD and CKD-EPI provided highest accuracies. Conclusions: The absolute bias of all formulas is influenced by age; CKD-EPI and MDRD are also influenced by GFR. Cockcroft-Gault is additionally influenced by body weight and BMI. In general, CKD-EPI gives the best estimation of GFR, although its accuracy is close to that of the MDRD. PMID:20299365

KDIGO 2012 Clinical Practice Guideline CKD classification rules out creatinine clearance 24 hour urine collection?

PubMed

Ognibene, A; Grandi, G; Lorubbio, M; Rapi, S; Salvadori, B; Terreni, A; Veroni, F

2016-01-01

The recent guideline for the evaluation and management of Chronic Kidney Disease recommends assessing GFR employing equations based on serum creatinine; despite this, creatinine clearance 24-hour urine collection is used routinely in many settings. In this study we compared the classification assessed from CrCl (creatinine clearance 24h urine collection) and e-GFR calculated with CKD-EPI or MDRD formulas. In this retrospective study we analyze consecutive laboratory data: creatinine clearance 24h urine collection, serum creatinine and demographic data such as sex and age from 15,777 patients >18 years of age collected from 2011 to 2013 in our laboratory at Careggi Hospital. The results were then compared to the estimated GFR calculated with the equations according to the recent treatment guidelines. Consecutive and retrospective laboratory data (creatinine clearance 24h urine collection, serum creatinine and, demographic data such as sex and age) from 15,777 patients >18 years of age seen at Careggi Hospital were collected. Comparison between e-GFR calculated with CKD-EPI or MDRD formulas and GFR according CrCl determinations and bias [95% CI] were 11.34 [-47,4/70.1] and 11.4 [-50.2/73] respectively. The concordance for 18/65 years aged group when compared with e-GFR classification between MDRD vs CKDEPI, MDRD vs CrCl and CKD-EPI vs CrCl were 0.78, 0.34, and 0.41 respectively, while in the 65/110years aged group the concordance Kappas were 0.84, 0.38, and 0.36 respectively. The use of CrCl provides a different classification than the estimation of GFR using a prediction equation. The CrCl is unreliable when it is necessary to identify CKD subjects with decrease of GFR of 5ml/min/1.73m(2)/year. Copyright © 2015 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.

Optimal equation for estimation of glomerular filtration rate in autosomal dominant polycystic kidney disease: influence of tolvaptan.

PubMed

Yamaguchi, Tsuyoshi; Higashihara, Eiji; Okegawa, Takatsugu; Miyazaki, Isao; Nutahara, Kikuo

2018-05-22

The reliability of various equations for estimating the GFR in ADPKD patients and the influence of tolvaptan on the resulting estimates have not been examined when GFR is calculated on the basis of inulin clearance. We obtained baseline and on-tolvaptan measured GFRs (mGFRs), calculated on the basis of inulin clearance, in 114 ADPKD, and these mGFRs were compared with eGFRs calculated according to four basic equations: the MDRD, CKD-EPI, and JSN-CKDI equations and the Cockcroft-Gault formula, as well as the influence of tolvaptan and of inclusion of cystatin C on accuracy of the results. Accuracy of each of the seven total equations was evaluated on the basis of the percentage of eGFR values within mGFR ± 30% (P 30 ). mGFRs were distributed throughout CKD stages 1-5. Regardless of the CKD stage, P 30 s of the MDRD, CKD-EPI, and JSN-CKDI equations did not differ significantly between baseline values and on-tolvaptan values. In CKD 1-2 patients, P 30 of the CKD-EPI equation was 100.0%, whether or not the patient was on-tolvaptan. In CKD 3-5 patients, P 30 s of the MDRD, CKD-EPI, and JSN-CKDI equations were similar. For all four equations, regression coefficients and intercepts did not differ significantly between baseline and on-tolvaptan values, but accuracy of the Cockcroft-Gault formula was inferior to that of the other three equations. Incorporation of serum cystatin C reduced accuracy. The CKD-EPI equation is most reliable, regardless of the severity of CKD. Tolvaptain intake has minimal influence and cystatin C incorporation does not improve accuracy.

Determination of the best method to estimate glomerular filtration rate from serum creatinine in adult patients with sickle cell disease: a prospective observational cohort study.

PubMed

Arlet, Jean-Benoît; Ribeil, Jean-Antoine; Chatellier, Gilles; Eladari, Dominique; De Seigneux, Sophie; Souberbielle, Jean-Claude; Friedlander, Gérard; de Montalembert, Marianne; Pouchot, Jacques; Prié, Dominique; Courbebaisse, Marie

2012-08-06

Sickle cell disease (SCD) leads to tissue hypoxia resulting in chronic organ dysfunction including SCD associated nephropathy. The goal of our study was to determine the best equation to estimate glomerular filtration rate (GFR) in SCD adult patients. We conducted a prospective observational cohort study. Since 2007, all adult SCD patients in steady state, followed in two medical departments, have had their GFR measured using iohexol plasma clearance (gold standard). The Cockcroft-Gault, MDRD-v4, CKP-EPI and finally, MDRD and CKD-EPI equations without adjustment for ethnicity were tested to estimate GFR from serum creatinine. Estimated GFRs were compared to measured GFRs according to the graphical Bland and Altman method. Sixty-four SCD patients (16 men, median age 27.5 years [range 18.0-67.5], 41 with SS-genotype were studied. They were Sub-Saharan Africa and French West Indies natives and predominantly lean (median body mass index: 22 kg/m2 [16-33]). Hyperfiltration (defined as measured GFR >110 mL/min/1.73 m2) was detected in 53.1% of patients. Urinary albumin/creatinine ratio was higher in patients with hyperfiltration than in patients with normal GFR (4.05 mg/mmol [0.14-60] versus 0.4 mg/mmol [0.7-81], p = 0.01). The CKD-EPI equation without adjustment for ethnicity had both the lowest bias and the greatest precision. Differences between estimated GFRs using the CKP-EPI equation and measured GFRs decreased with increasing GFR values, whereas it increased with the Cockcroft-Gault and MDRD-v4 equations. We confirm that SCD patients have a high rate of glomerular hyperfiltration, which is frequently associated with microalbuminuria or macroalbuminuria. In non-Afro-American SCD patients, the best method for estimating GFR from serum creatinine is the CKD-EPI equation without adjustment for ethnicity. This equation is particularly accurate to estimate high GFR values, including glomerular hyperfiltration, and thus should be recommended to screen SCD adult patients at high risk for SCD nephropathy.

Identification and characterization of kidney transplants with good glomerular filtration rate at 1 year but subsequent progressive loss of renal function.

PubMed

Park, Walter D; Larson, Timothy S; Griffin, Matthew D; Stegall, Mark D

2012-11-15

After the first year after kidney transplantation, 3% to 5% of grafts fail each year but detailed studies of how grafts progress to failure are lacking. This study aimed to analyze the functional stability of kidney transplants between 1 and 5 years after transplantation and to identify initially well-functioning grafts with progressive decline in allograft function. The study included 788 adult conventional kidney transplants performed at the Mayo Clinic Rochester between January 2000 and December 2005 with a minimum graft survival and follow-up of 2.6 years. The modification of diet in renal disease equation for estimating glomerular filtration rate (eGFR(MDRD)) was used to calculate the slope of renal function over time using all available serum creatinine values between 1 and 5 years after transplantation. Most transplants demonstrated good function (eGFR(MDRD) ≥40 mL/min) at 1 year with positive eGFR(MDRD) slope between 1 and 5 years after transplantation. However, a subset of grafts with 1-year eGFR(MDRD) ≥40 mL/min exhibited strongly negative eGFR(MDRD) slope between 1 and 5 years suggestive of progressive loss of graft function. Forty-one percent of this subset reached graft failure during follow-up, accounting for 69% of allograft failures occurring after 2.5 years after transplantation. This pattern of progressive decline in estimated glomerular filtration rate despite good early function was associated with but not fully attributable to factors suggestive of enhanced antidonor immunity. Longitudinal analysis of serial estimated glomerular filtration ratemeasurements identifies initially well-functioning kidney transplants at high risk for subsequent graft loss. For this subset, further studies are needed to identify modifiable causes of functional decline.

Performance of Creatinine and Cystatin C GFR Estimating Equations in an HIV-positive population on Antiretrovirals

PubMed Central

INKER, Lesley A; WYATT, Christina; CREAMER, Rebecca; HELLINGER, James; HOTTA, Matthew; LEPPO, Maia; LEVEY, Andrew S; OKPARAVERO, Aghogho; GRAHAM, Hiba; SAVAGE, Karen; SCHMID, Christopher H; TIGHIOUART, Hocine; WALLACH, Fran; KRISHNASAMI, Zipporah

2013-01-01

Objective To evaluate the performance of CKD-EPI creatinine, cystatin C and creatinine-cystatin C estimating equations in HIV-positive patients. Methods We evaluated the performance of the MDRD Study and CKD-EPI creatinine 2009, CKD-EPI cystatin C 2012 and CKD-EPI creatinine-cystatin C 2012 glomerular filtration rate (GFR) estimating equations compared to GFR measured using plasma clearance of iohexol in 200 HIV-positive patients on stable antiretroviral therapy. Creatinine and cystatin C assays were standardized to certified reference materials. Results Of the 200 participants, median (IQR) CD4 count was 536 (421) and 61% had an undetectable HIV-viral load. Mean (SD) measured GFR (mGFR) was 87 (26) ml/min/1.73m2. All CKD-EPI equations performed better than the MDRD Study equation. All three CKD-EPI equations had similar bias and precision. The cystatin C equation was not more accurate than the creatinine equation. The creatinine-cystatin C equation was significantly more accurate than the cystatin C equation and there was a trend toward greater accuracy than the creatinine equation. Accuracy was equal or better in most subgroups with the combined equation compared to either alone. Conclusions The CKD-EPI cystatin C equation does not appear to be more accurate than the CKD-EPI creatinine equation in patients who are HIV-positive, supporting the use of the CKD-EPI creatinine equation for routine clinical care for use in North American populations with HIV. The use of both filtration markers together as a confirmatory test for decreased estimated GFR based on creatinine in individuals who are HIV-positive requires further study. PMID:22842844

Using Mathematical Algorithms to Modify Glomerular Filtration Rate Estimation Equations

PubMed Central

Zhu, Bei; Wu, Jianqing; Zhu, Jin; Zhao, Weihong

2013-01-01

Background The equations provide a rapid and low-cost method of evaluating glomerular filtration rate (GFR). Previous studies indicated that the Modification of Diet in Renal Disease (MDRD), Chronic Kidney Disease-Epidemiology (CKD-EPI) and MacIsaac equations need further modification for application in Chinese population. Thus, this study was designed to modify the three equations, and compare the diagnostic accuracy of the equations modified before and after. Methodology With the use of 99 mTc-DTPA renal dynamic imaging as the reference GFR (rGFR), the MDRD, CKD-EPI and MacIsaac equations were modified by two mathematical algorithms: the hill-climbing and the simulated-annealing algorithms. Results A total of 703 Chinese subjects were recruited, with the average rGFR 77.14±25.93 ml/min. The entire modification process was based on a random sample of 80% of subjects in each GFR level as a training sample set, the rest of 20% of subjects as a validation sample set. After modification, the three equations performed significant improvement in slop, intercept, correlated coefficient, root mean square error (RMSE), total deviation index (TDI), and the proportion of estimated GFR (eGFR) within 10% and 30% deviation of rGFR (P10 and P30). Of the three modified equations, the modified CKD-EPI equation showed the best accuracy. Conclusions Mathematical algorithms could be a considerable tool to modify the GFR equations. Accuracy of all the three modified equations was significantly improved in which the modified CKD-EPI equation could be the optimal one. PMID:23472113

GFR Estimation: From Physiology to Public Health

PubMed Central

Levey, Andrew S.; Inker, Lesley A.; Coresh, Josef

2014-01-01

Estimating glomerular filtration rate (GFR) is essential for clinical practice, research, and public health. Appropriate interpretation of estimated GFR (eGFR) requires understanding the principles of physiology, laboratory medicine, epidemiology and biostatistics used in the development and validation of GFR estimating equations. Equations developed in diverse populations are less biased at higher GFR than equations developed in CKD populations and are more appropriate for general use. Equations that include multiple endogenous filtration markers are more precise than equations including a single filtration marker. The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations are the most accurate GFR estimating equations that have been evaluated in large, diverse populations and are applicable for general clinical use. The 2009 CKD-EPI creatinine equation is more accurate in estimating GFR and prognosis than the 2006 Modification of Diet in Renal Disease (MDRD) Study equation and provides lower estimates of prevalence of decreased eGFR. It is useful as a “first” test for decreased eGFR and should replace the MDRD Study equation for routine reporting of serum creatinine–based eGFR by clinical laboratories. The 2012 CKD-EPI cystatin C equation is as accurate as the 2009 CKD-EPI creatinine equation in estimating eGFR, does not require specification of race, and may be more accurate in patients with decreased muscle mass. The 2012 CKD-EPI creatinine–cystatin C equation is more accurate than the 2009 CKD-EPI creatinine and 2012 CKD-EPI cystatin C equations and is useful as a confirmatory test for decreased eGFR as determined by an equation based on serum creatinine. Further improvement in GFR estimating equations will require development in more broadly representative populations, including diverse racial and ethnic groups, use of multiple filtration markers, and evaluation using statistical techniques to compare eGFR to “true GFR”. PMID:24485147

eGFRs from Asian-modified CKD-EPI and Chinese-modified CKD-EPI equations were associated better with hypertensive target organ damage in the community-dwelling elderly Chinese: the Northern Shanghai Study.

PubMed

Ji, Hongwei; Zhang, Han; Xiong, Jing; Yu, Shikai; Chi, Chen; Bai, Bin; Li, Jue; Blacher, Jacques; Zhang, Yi; Xu, Yawei

2017-01-01

With increasing age, estimated glomerular filtration rate (eGFR) decline is a frequent manifestation and is strongly associated with other preclinical target organ damage (TOD). In literature, many equations exist in assessing patients' eGFR. However, these equations were mainly derived and validated in the population from Western countries, which equation should be used for risk stratification in the Chinese population remains unclear, as well as their comparison. Considering that TOD is a good marker for risk stratification in the elderly, in this analysis, we aimed to investigate whether the recent eGFR equations derived from Asian and Chinese are better associated with preclinical TOD than the other equations in elderly Chinese. A total of 1,599 community-dwelling elderly participants (age >65 years) in northern Shanghai were prospectively recruited from June 2014 to August 2015. Conventional cardiovascular risk factors were assessed, and hypertensive TOD including left ventricular mass index (LVMI), carotid-femoral pulse wave velocity (cf-PWV), carotid intima-media thickness (IMT), ankle-brachial index (ABI) and urine albumin to creatinine ratio (UACR) was evaluated for each participant. Participant's eGFR was calculated from the Modification of Diet in Renal Disease (MDRD), Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI), Chinese-abbreviated MDRD (c-aMDRD), Asian-modified CKD-EPI (aCKD-EPI) equation and Chinese-modified CKD-EPI (cCKD-EPI) equation. In multivariate regression analysis, only eGFRs from aCKD-EPI were significantly and inversely associated with carotid IMT ( P =0.005). In multivariate logistic models, decreased eGFR from all the equations were significantly associated with lower ABI ( P <0.001), microalbuminuria ( P =0.02 to P <0.001) and increased cf-PWV ( P <0.001). Only decreased eGFRs from aCKD-EPI and cCKD-EPI equations were significantly associated with increased IMT (both crude P <0.05). In the receiver operator characteristic (ROC) analysis, only aCKD-EPI and cCKD-EPI equations presented significant associations with all the listed preclinical TODs ( P -value from <0.05 to <0.001). In community-dwelling elderly Chinese, eGFRs from aCKD-EPI and cCKD-EPI equations are better associated with preclinical TOD. aCKD-EPI and cCKD-EPI equations should be preferred when making risk assessment.

Correlation of Glomerular Filtration Rate Between Renal Scan and Estimation Equation for Patients With Scleroderma.

PubMed

Suebmee, Patcharawan; Foocharoen, Chingching; Mahakkanukrauh, Ajanee; Suwannaroj, Siraphop; Theerakulpisut, Daris; Nanagara, Ratanavadee

2016-08-01

Renal involvement in scleroderma is life-threatening. Early detection of a deterioration of the glomerular filtration rate (GFR) is needed to preserve kidney function. To (A) determine the correlation between (1) estimated GFR (eGFR) using 4 different formulae and (2) measured GFR (mGFR) using isotopic renal scan in Thai patients with scleroderma with normal serum creatinine and (B) to define the factors influencing eGFR. A cross-sectional study was performed in adult Thai patients with scleroderma at Srinagarind Hospital, Khon Kaen University, between December 2013 and April 2015. GFR was measured using the gold standard Tc-99m DTPA (Tc-99m diethylenetriaminepentaacetic acid) renal scan. We compared the latter with the eGFR, calculated using the Cockroft-Gault formula, Modification of Diet in Renal Disease (MDRD), Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation and creatinine clearance equation. A total of 76 patients with scleroderma (50 women and 26 men) with median age 54.8 years (interquartile range: 47.4 to 58.9) were enrolled. Mean disease duration was 5.6 ± 4.5 years. Median value of mGFR was 100.1 ± 27.6mL/minute/1.73m². There was a correlation between mGFR from the Tc-99m DTPA renal scan and the eGFR using the Cockroft-Gault formula, MDRD and CKD-EPI equation (P = 0.01, <0.001 and <0.001, respectively), but no correlation with eGFR using the creatinine clearance equation (P = 0.27). Body weight, prednisolone use and systolic blood pressure (SBP) had a negative association with mGFR (P = 0.01, 0.01 and 0.007, respectively). After multivariate analysis, SBP was the only clinical parameter that influenced mGFR (P = 0.03). The Cockroft-Gault formula, MDRD study equation and CKD-EPI were useful formulae for assessing GFR in Thai patients with scleroderma. Higher SBP was associated with a lower GFR. Copyright © 2016 Southern Society for Clinical Investigation. Published by Elsevier Inc. All rights reserved.

Associations of blood lead with estimated glomerular filtration rate using MDRD, CKD-EPI and serum cystatin C-based equations

PubMed Central

Spector, June T.; Navas-Acien, Ana; Fadrowski, Jeffrey; Guallar, Eliseo; Jaar, Bernard

2011-01-01

Background. Low-level lead exposure is widespread and has been implicated as a chronic kidney disease (CKD) risk factor. However, studies evaluating associations of lead dose with newer, potentially more accurate, estimates of kidney function, in participants with a wide range of glomerular filtration rates (GFRs), are scarce. Methods. We compared associations of blood lead and estimated glomerular filtration rate (eGFR) using the Modification of Diet in Renal Disease (MDRD), Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and cystatin C single variable, multivariable and combined creatinine/cystatin C equations in 3941 adults who participated in the 1999–2002 National Health and Nutrition Examination Survey cystatin C subsample. Results. Geometric mean blood lead was 1.7 μg/dL. After multivariable adjustment, differences [95% confidence interval (CI)] in mean eGFR for a doubling of blood lead were −1.9 (−3.2, −0.7), −1.7 (−3.0, −0.5) and −1.4 (−2.3, −0.5) mL/min/1.73 m2, using the cystatin C single variable, multivariable and combined creatinine/cystatin C equations, respectively, reflecting lower eGFR with increased blood lead. The corresponding differences (95% CI) were −0.9 (−1.9, 0.02) and −0.9 (−1.8, 0.01) using the creatinine-based MDRD and CKD-EPI equations, respectively. In participants aged ≥60 years, differences in mean eGFR ranged from −3.0 to −4.5 mL/min/1.73 m2, and odds of reduced eGFR (<60 mL/min/1.73 m2) were increased for all estimates of GFR. Conclusions. These results support the inclusion of cystatin C-based eGFR in future lead research and provide additional evidence for environmental lead exposure as a CKD risk factor. PMID:21248295

Marker of lipid peroxidation related to diabetic nephropathy in Indonesian type 2 diabetes mellitus patients.

PubMed

Sauriasari, R; Andrajati, R; Azizahwati; Dharmeizar; Saputri, D A; Muris, R U; Manfaatun, A; Amanda, O F; Setiawan, H; Sakano, N; Wang, D H; Ogino, K

2015-04-01

Even though diabetes patients exhibit an increased oxidative stress, its correlation with diabetic nephropathy is not fully understood. The purpose of this study was to determine whether lipid peroxidation marker correlates well with eGFR and UACR in type 2 diabetes mellitus patients. We collected urine and serum samples of Indonesian type 2 diabetes mellitus outpatients with normo- and microalbuminuria at a Local Government Clinic (from ages: 39-74 years). Urinary 8-iso-PGF2α was measured by ELISA, the serum malondialdehyde by TBARS assay, and urinary albumin by BCG albumin assay. eGFR was calculated using the corrected-Cockcroft-Gault (CG), MDRD, and CKD-EPI equation. Other necessary data were obtained through questionnaires. The results showed that the increasing level of malondialdehyde was mildly correlated with the decline in eGFR (MDRD). In contrary, there was a significant positive correlation between 8-iso-PGF2α concentration and eGFR based on the corrected-CG, MDRD study, and CKD-EPI equation (r=0.457, p<0.001; r=0.424, p<0.001; r=0.443, p<0.001). This relationship still persisted in the normoalbuminuric subjects (n=43) (r=0.491, p=0.001; r=0.461, p=0.002; r=0.455, p=0.002). The multivariate analysis showed that 8-iso-PGF2α together with fasting plasma glucose was the most predictive factor for the high 2-quantile eGFR (adjusted OR 1.001, (95% CI, 1.000-1.001)). However, there was no significant correlation between UACR with malondialdehyde (r=0.268, p=0.050) and 8-iso-PGF2α(r=-0.030, p=0.808). UACR itself was inversely correlated with eGFR based on the corrected-CG, the MDRD, and CKD-EPI (r=-0.232, p<0.05; r=-0.228, p<0.05; r=-0.232, p<0.05). Increased 8-iso-PGF2α and malondialdehyde in type 2 diabetes mellitus patients may play a role in the pathophysiologic significance of diabetic nephropathy, even while considering the effect of potential confounders. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Prognostic value of chronic kidney disease in patients with coronary heart disease: role of estimating equations.

PubMed

Zhang, Qiu-Li; Brenner, Hermann; Koenig, Wolfgang; Rothenbacher, Dietrich

2010-07-01

Chronic kidney disease (CKD) increases risk of coronary heart disease (CHD), but the impact of using different equations for estimating kidney function on CHD is not clear yet. This study described the prognostic value of CKD as defined by various creatinine- (Cr-eGFR) and cystatin C-based estimating (Cys-eGFR) equations and their combinations on subsequent cardiovascular disease (CVD) events in patients with CHD. Cohort study. Patients with coronary heart disease in in-patient rehabilitation and long-term follow-up (mean 63.4 months). 1050 patients with coronary heart disease aged 30-70 years at baseline. CKD was defined as eGFR<60 mL/min/1.73 m2 (CKD stages 3-5) estimated by three Cr-eGFR equations (Cockroft-Gault equation adjusted for body surface area (CG/BSA), Modification of Diet in Renal Disease Study (MDRD) equation, CKD-EPIcrea) and by two Cys-eGFR equations (Arnal-Dade equation, CKD-EPIcys) and a combination. The primary endpoint of our study was subsequent CVD events. During follow-up 118 patients (11.2%) experienced the outcome of our study. CKD assessed by the CG/BSA, MDRD, and CKD-EPIcrea equations showed no statistically significant association with subsequent CVD events after adjustment for multiple covariates (hazard ratio (HR) 1.45 [95% CI, 0.81-2.59], HR 1.47 [95% CI, 0.84-2.60], and HR 1.31 [95% CI, 0.72-2.83], respectively). By contrast, the Cys-eGFR equations were much stronger associated with subsequent CVD endpoints (Arnal-Dade: HR, 2.01 [95% CI, 1.34-3.04]; CKD-EPIcys HR, 2.22 [95% CI, 1.46-3.37]). The CKD-EPIcys also provided the highest area under the curve value. Our study shows that prevalent CKD is an independent risk factor for subsequent CVD in patients with prevalent CHD and implies that Cys-eGFR equations show a better clinical utility compared to the Cr-eGFR equations. Copyright (c) 2010 Elsevier Ireland Ltd. All rights reserved.

Kidney function estimating equations in patients with chronic kidney disease.

PubMed

Hojs, R; Bevc, S; Ekart, R; Gorenjak, M; Puklavec, L

2011-04-01

The current guidelines emphasise the need to assess kidney function using predictive equations rather than just serum creatinine. The present study compares serum cystatin C-based equations and serum creatinine-based equations in patients with chronic kidney disease (CKD). Seven hundred and sixty-four adult patients with CKD were enrolled. In each patient serum creatinine and serum cystatin C were determined. Their glomerular filtration rate (GFR) was estimated using three serum creatinine-based equations [Cockcroft-Gault (C&G), modification of diet in renal disease (MDRD) and the Chronic Kidney Disease Epidemiology Collaboration equation (CKD-EPI)] and two serum cystatin C-based equations [our own cystatin C formula (GFR=90.63 × cystatin C(-1.192) ) and simple cystatin C formula (GFR=100/cystatin C)]. The GFR was measured using (51) CrEDTA clearance. Statistically significant correlation between (51) CrEDTA clearance with serum creatinine, serum cystatin C and all observed formulas was found. The receiver operating characteristic curve analysis (cut-off for GFR 60 ml/min/1.73m(2)) showed that serum cystatin C and both cystatin C formulas had a higher diagnostic accuracy than C&G formula. Bland and Altman analysis for the same cut-off value showed that all formulas except simple cystatin C formula underestimated measured GFR. The accuracy within 30% of estimated (51) CrEDTA clearance values differs according to stages of CKD. Analysis of ability to correctly predict patient's GFR below or above 60 ml/min/1.73m(2) showed statistically significant higher ability for both cystatin C formulas compared to MDRD formula. Our results indicate that serum cystatin C-based equations are reliable markers of GFR comparable with creatinine-based formulas. © 2011 Blackwell Publishing Ltd.

28 CFR 79.57 - Proof of chronic renal disease.

Code of Federal Regulations, 2014 CFR

2014-07-01

... filtration rate (by either measured creatinine or iothalamate clearance or calculated by MDRD equation); and... discharge summary report; (6) Hospital admitting report; or (7) Death certificate, provided that it is signed by a physician at the time of death. ...

28 CFR 79.57 - Proof of chronic renal disease.

Code of Federal Regulations, 2012 CFR

2012-07-01

... filtration rate (by either measured creatinine or iothalamate clearance or calculated by MDRD equation); and... discharge summary report; (6) Hospital admitting report; or (7) Death certificate, provided that it is signed by a physician at the time of death. ...

28 CFR 79.57 - Proof of chronic renal disease.

Code of Federal Regulations, 2013 CFR

2013-07-01

... filtration rate (by either measured creatinine or iothalamate clearance or calculated by MDRD equation); and... discharge summary report; (6) Hospital admitting report; or (7) Death certificate, provided that it is signed by a physician at the time of death. ...

A new modified CKD-EPI equation for Chinese patients with type 2 diabetes.

PubMed

Liu, Xun; Gan, Xiaoliang; Chen, Jinxia; Lv, Linsheng; Li, Ming; Lou, Tanqi

2014-01-01

To improve the performance of glomerular filtration rate (GFR) estimating equation in Chinese type 2 diabetic patients by modification of the CKD-EPI equation. A total of 1196 subjects were enrolled. Measured GFR was calibrated to the dual plasma sample 99mTc-DTPA-GFR. GFRs estimated by the re-expressed 4-variable MDRD equation, the CKD-EPI equation and the Asian modified CKD-EPI equation were compared in 351 diabetic/non-diabetic pairs. And a new modified CKD-EPI equation was reconstructed in a total of 589 type 2 diabetic patients. In terms of both precision and accuracy, GFR estimating equations all achieved better results in the non-diabetic cohort comparing with those in the type 2 diabetic cohort (30% accuracy, P≤0.01 for all comparisons). In the validation data set, the new modified equation showed less bias (median difference, 2.3 ml/min/1.73 m2 for the new modified equation vs. ranged from -3.8 to -7.9 ml/min/1.73 m2 for the other 3 equations [P<0.001 for all comparisons]), as was precision (IQR of the difference, 24.5 ml/min/1.73 m2 vs. ranged from 27.3 to 30.7 ml/min/1.73 m2), leading to a greater accuracy (30% accuracy, 71.4% vs. 55.2% for the re-expressed 4 variable MDRD equation and 61.0% for the Asian modified CKD-EPI equation [P = 0.001 and P = 0.02]). A new modified CKD-EPI equation for type 2 diabetic patients was developed and validated. The new modified equation improves the performance of GFR estimation.

Estimating glomerular filtration rate in diabetes: a comparison of cystatin-C- and creatinine-based methods.

PubMed

Macisaac, R J; Tsalamandris, C; Thomas, M C; Premaratne, E; Panagiotopoulos, S; Smith, T J; Poon, A; Jenkins, M A; Ratnaike, S I; Power, D A; Jerums, G

2006-07-01

We compared the predictive performance of a GFR based on serum cystatin C levels with commonly used creatinine-based methods in subjects with diabetes. In a cross-sectional study of 251 consecutive clinic patients, the mean reference (plasma clearance of (99m)Tc-diethylene-triamine-penta-acetic acid) GFR (iGFR) was 88+/-2 ml min(-1) 1.73 m(-2). A regression equation describing the relationship between iGFR and 1/cystatin C levels was derived from a test population (n=125) to allow for the estimation of GFR by cystatin C (eGFR-cystatin C). The predictive performance of eGFR-cystatin C, the Modification of Diet in Renal Disease 4 variable formula (MDRD-4) and Cockcroft-Gault (C-G) formulas were then compared in a validation population (n=126). There was no difference in renal function (ml min(-1) 1.73 m(-2)) as measured by iGFR (89.2+/-3.0), eGFR-cystatin C (86.8+/-2.5), MDRD-4 (87.0+/-2.8) or C-G (92.3+/-3.5). All three estimates of renal function had similar precision and accuracy. Estimates of GFR based solely on serum cystatin C levels had the same predictive potential when compared with the MDRD-4 and C-G formulas.

Renal Function, Bisphenol A, and Alkylphenols: Results from the National Health and Nutrition Examination Survey (NHANES 2003–2006)

PubMed Central

You, Li; Zhu, Xiangzhu; Shrubsole, Martha J.; Fan, Hong; Chen, Jing; Dong, Jie; Hao, Chuan-Ming; Dai, Qi

2011-01-01

Background Urinary excretion of bisphenol A (BPA) and alkylphenols (APs) was used as a biomarker in most previous studies, but no study has investigated whether urinary excretion of these environmental phenols differed by renal function. Objective We estimated the association between renal function and urinary excretion of BPA and APs. Methods Analyses were conducted using data from the National Health and Nutrition Examination Survey (NHANES) 2003–2006. Renal function was measured as estimated glomerular filtration rate (eGFR) calculated by the Modification of Diet in Renal Disease (MDRD) Study equation and by the newly developed Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation. Regression models were used to calculate geometric means of urinary BPA and APs excretion by eGFR category (≥ 90, 60–90, < 60 mL/min/m2) after adjusting for potential confounding factors. Results When we used the MDRD Study equation, participants without known renal disease (n = 2,573), 58.2% (n = 1,499) had mildly decreased renal function or undiagnosed chronic kidney disease. The adjusted geometric means for urinary BPA excretion decreased with decreasing levels of eGFR (p for trend = 0.04). The associations appeared primarily in females (p for trend = 0.03). Urinary triclosan excretion decreased with decreasing levels of eGFR (p for trend < 0.01) for both males and females, and the association primarily appeared in participants < 65 years of age. The association between BPA and eGFR was nonsignificant when we used the CKD-EPI equation. Conclusions Urinary excretion of triclosan, and possibly BPA, decreased with decreasing renal function. The associations might differ by age or sex. Further studies are necessary to replicate our results and understand the mechanism. PMID:21147601

Combining Cystatin C and Creatinine Yields a Reliable Glomerular Filtration Rate Estimation in Older Adults in Contrast to β-Trace Protein and β2-Microglobulin.

PubMed

Werner, Karin; Pihlsgård, Mats; Elmståhl, Sölve; Legrand, Helen; Nyman, Ulf; Christensson, Anders

2017-01-01

The glomerular filtration rate (GFR) is the most important measure of kidney function and chronic kidney disease (CKD). This study aims to validate commonly used equations for estimated GFR (eGFR) based on creatinine (cr), cystatin C (cys), β-trace protein (BTP), and β2-microglobulin (B2M) in older adults. We conducted a validation study with 126 participants aged between 72 and 98 with a mean measured GFR (mGFR) by iohexol clearance of 54 mL/min/1.73 m2. The eGFR equations (CKD-Epidemiology collaboration [CKD-EPI], Berlin Initiative Study [BIS], Full Age Spectrum [FAS], Modification of Diet in Renal Disease [MDRD]cr, Caucasian-Asian-Pediatric-Adult [CAPA]cys, Lund-Malmö Revised [LM-REV]cr, and MEAN-LM-CAPAcr-cys), were assessed in terms of bias (median difference: eGFR-mGFR), precision (interquartile range of the differences), and accuracy (P30: percentage of estimates ±30% of mGFR). The equations were compared to a benchmark equation: CKD-EPIcr-cys. All cystatin C-based equations underestimated the GFR compared to mGFR, whereas bias was mixed for the equations based only on creatinine. Accuracy was the highest for CKD-EPIcr-cys (98%) and lowest for MDRD (82%). Below mGFR 45 mL/min/1.73 m2 only equations incorporating cystatin C reached P30 accuracy >90%. CKD-EPIcr-cys was not significantly more accurate than the other cystatin C-based equations. In contrast, CKD-EPIcr-cys was significantly more accurate than all creatinine-based equations except LM-REVcr. This study confirms that it is reasonable to use equations incorporating cystatin C and creatinine in older patients across a wide spectrum of GFR. However, the results call into question the use of creatinine alone below mGFR 45 mL/min/1.73 m2. B2M and BTP do not demonstrate additional value in eGFR determination in older adults. © 2017 S. Karger AG, Basel.

Estimation of GFR in South Asians: A Study From the General Population in Pakistan

PubMed Central

Jessani, Saleem; Levey, Andrew S.; Bux, Rasool; Inker, Lesley A.; Islam, Muhammad; Chaturvedi, Nish; Mariat, Christophe; Schmid, Christopher H.; Jafar, Tazeen H.

2015-01-01

Background South Asians are at high risk for chronic kidney disease. However, unlike those in the United States and United Kingdom, laboratories in South Asian countries do not routinely report estimated glomerular filtration rate (eGFR) when serum creatinine is measured. The objectives of the study were to: (1) evaluate the performance of existing GFR estimating equations in South Asians, and (2) modify the existing equations or develop a new equation for use in this population. Study Design Cross-sectional population-based study. Setting & Participants 581 participants 40 years or older were enrolled from 10 randomly selected communities and renal clinics in Karachi. Predictors eGFR, age, sex, serum creatinine level. Outcomes Bias (the median difference between measured GFR [mGFR] and eGFR), precision (the IQR of the difference), accuracy (P30; percentage of participants with eGFR within 30% of mGFR), and the root mean squared error reported as cross-validated estimates along with bootstrapped 95% CIs based on 1,000 replications. Results The CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) creatinine equation performed better than the MDRD (Modification of Diet in Renal Disease) Study equation in terms of greater accuracy at P30 (76.1% [95% CI, 72.7%–79.5%] vs 68.0% [95% CI, 64.3%–71.7%]; P <0.001) and improved precision (IQR, 22.6 [95% CI, 19.9–25.3] vs 28.6 [95% CI, 25.8–31.5] mL/min/1.73 m2; P < 0.001). However, both equations overestimated mGFR. Applying modification factors for slope and intercept to the CKD-EPI equation to create a CKD-EPI Pakistan equation (such that eGFRCKD-EPI(PK) = 0.686 × eGFRCKD-EPI1.059) in order to eliminate bias improved accuracy (P30, 81.6% [95% CI, 78.4%–84.8%]; P < 0.001) comparably to new estimating equations developed using creatinine level and additional variables. Limitations Lack of external validation data set and few participants with low GFR. Conclusions The CKD-EPI creatinine equation is more accurate and precise than the MDRD Study equation in estimating GFR in a South Asian population in Karachi. The CKD-EPI Pakistan equation further improves the performance of the CKD-EPI equation in South Asians and could be used for eGFR reporting. PMID:24074822

Effect of renal impairment on the pharmacokinetics, pharmacodynamics, and safety of apixaban.

PubMed

Chang, Ming; Yu, Zhigang; Shenker, Andrew; Wang, Jessie; Pursley, Janice; Byon, Wonkyung; Boyd, Rebecca A; LaCreta, Frank; Frost, Charles E

2016-05-01

This open-label study evaluated apixaban pharmacokinetics, pharmacodynamics, and safety in subjects with mild, moderate, or severe renal impairment and in healthy subjects following a single 10-mg oral dose. The primary analysis determined the relationship between apixaban AUC∞ and 24-hour creatinine clearance (CLcr ) as a measure of renal function. The relationships between 24-hour CLcr and iohexol clearance, estimated CLcr (Cockcroft-Gault equation), and estimated glomerular filtration rate (modification of diet in renal disease [MDRD] equation) were also assessed. Secondary objectives included assessment of safety and tolerability as well as international normalized ratio (INR) and anti-factor Xa activity as pharmacodynamic endpoints. The regression analysis showed that decreasing renal function resulted in modestly increased apixaban exposure (AUC∞ increased by 44% in severe impairment with a 24-hour CLcr of 15 mL/min, compared with subjects with normal renal function), but it did not affect Cmax or the direct relationship between apixaban plasma concentration and anti-factor Xa activity or INR. The assessment of renal function measured by iohexol clearance, Cockcroft-Gault, and MDRD was consistent with that determined by 24-hour CLcr . Apixaban was well tolerated in this study. These results suggest that dose adjustment of apixaban is not required on the basis of renal function alone. © 2015, The American College of Clinical Pharmacology.

Early Acute Kidney Injury in Military Casualties

DTIC Science & Technology

2015-05-01

days, because of the high rates of amputations in this patient popu- lation, which may lower creatinine independent of renal func- tion.26 Data on...combat support hospi- tal in Afghanistan. Levels of serum creatinine were collected for up to 14 days and were available in both Afghanistan and...patient did not have a baseline creatinine , then a baseline creatinine was derived using theModification of Diet in Renal Disease (MDRD) study equation

Assessment of the Renal Function in Potential Donors of Living Kidney Transplants: Expanded Study.

PubMed

Macías, L B; Poblet, M S; Pérez, N N; Jerez, R I; Gonzalez Roncero, F M; Blanco, G B; Valdivia, M A P; Benjumea, A S; Gentil Govantes, M A

2015-11-01

It is very important to determine as accurately as possible the renal function in potential living renal transplant donors, especially those with limited renal function (CrCl <90 mL/m/1.73 m(2)), age older than 50 years, and cardiovascular risk factors that might favor the development of long-term kidney diseases. The objective of this study was to compare the direct measurement of glomerular filtration rate (GFR) using EDTA-Cr51 and the estimations based on creatinine (eGFR): Cr clearance (CCr) with 24-hour urine and estimated using Cockroft-Gault (adjusted by using body surface area-Mosteller formula-SC), MDRD-4, MDRD-6, and CKD-EPI to determine the usefulness of different methods from EDTA-Cr51to evaluate the kidney function. The kidney function evaluation has been made to 105 potential kidney donors using the EDTA-Cr51 method. The GFR obtained through the EDTA-Cr51 is compared with the CCr values in 24-hour urine and eGFR based on creatinine (Cockcroft-Gault, MDRD4, MDRD6, and CKD-EPI). Using the Bland Altman graphic we have observed that the most dispersed results are obtained with the eGFR using CCr in 24-hour urine and CKD-EPI. By means of Pasing & Bablock, we realized that MDRD-4 and MDRD-6 show the highest approximation to the reference method proposed to be substituted, whereas CCr shows a high dispersion. eGFR using MDRD-4 and MDRD-6 formulas reveal the best adjustment to the measure by EDTA-Cr51. This might represent the best option if a direct eGFR measure is not available. Copyright © 2015 Elsevier Inc. All rights reserved.

Implications of method specific creatinine adjustments on General Medical Services chronic kidney disease classification

PubMed Central

Reynolds, Timothy M; Twomey, Patrick J

2007-01-01

Aims To evaluate the impact of different equations for calculation of estimated glomerular filtration rate (eGFR) on general practitioner (GP) workload. Methods Retrospective evaluation of routine workload data from a district general hospital chemical pathology laboratory serving a GP patient population of approximately 250 000. The most recent serum creatinine result from 80 583 patients was identified and used for the evaluation. eGFR was calculated using one of three different variants of the four‐parameter Modification of Diet in Renal Disease (MDRD) equation. Results The original MDRD equation (eGFR186) and the modified equation with assay‐specific data (eGFR175corrected) both identified similar numbers of patients with stage 4 and stage 5 chronic kidney disease (ChKD), but the modified equation without assay specific data (eGFR175) resulted in a significant increase in stage 4 ChKD. For stage 3 ChKD the eGFR175 identified 28.69% of the population, the eGFR186 identified 21.35% of the population and the eGFR175corrected identified 13.6% of the population. Conclusions Depending on the choice of equation there can be very large changes in the proportions of patients identified with the different stages of ChKD. Given that according to the General Medical Services Quality Framework, all patients with ChKD stages 3–5 should be included on a practice renal registry, and receive relevant drug therapy, this could have significant impacts on practice workload and drug budgets. It is essential that practices work with their local laboratories. PMID:17761741

Current use of equations for estimating glomerular filtration rate in Spanish laboratories.

PubMed

Gràcia-Garcia, Sílvia; Montañés-Bermúdez, Rosario; Morales-García, Luis J; Díez-de Los Ríos, M José; Jiménez-García, Juan Á; Macías-Blanco, Carlos; Martínez-López, Rosalina; Ruiz-Altarejos, Joaquín; Ruiz-Martín, Guadalupe; Sanz-Hernández, Sonia; Ventura-Pedret, Salvador

2012-07-17

In 2006 the Spanish Society of Clinical Biochemistry and Molecular Pathology (SEQC) and the Spanish Society of Nephrology (S.E.N.) developed a consensus document in order to facilitate the diagnosis and monitoring of chronic kidney disease with the incorporation of equations for estimating glomerular filtration rate (eGFR) into laboratory reports. The current national prevalence of eGFR reporting and the degree of adherence to these recommendations among clinical laboratories is unknown. We administered a national survey in 2010-11 to Spanish clinical laboratories. The survey was through e-mail or telephone to laboratories that participated in the SEQC’s Programme for External Quality Assurance, included in the National Hospitals Catalogue 2010, including both primary care and private laboratories. A total of 281 laboratories answered to the survey. Of these, 88.2% reported on the eGFR, with 61.9% reporting on the MDRD equation and 31.6% using the MDRD-IDMS equation. A total of 42.5% of laboratories always reported serum creatinine values, and other variables only when specifically requested. Regarding the way results were presented, 46.2% of laboratories reported the exact numerical value only when the filtration rate was below 60mL/min/1.73m2, while 50.6% reported all values regardless. In 56.3% of the cases reporting eGFR, an interpretive commentary of it was enclosed. Although a high percentage of Spanish laboratories have added eGFR in their reports, this metric is not universally used. Moreover, some aspects, such as the equation used and the correct expression of eGFR results, should be improved.

Potential influence of tubular dysfunction on the difference between estimated and measured glomerular filtration rate after kidney transplantation.

PubMed

Lezaic, V; Mirkovic, D; Ristic, S; Radivojevic, D; Dajak, M; Naumovic, R; Marinkovic, J; Djukanovic, L J

2013-05-01

Because no consensus exists regarding the most accurate calculation to estimate glomerular filtration rate (GFR) based on serum creatinine concentrations (sCr) after kidney transplantation, this study sought to assess the potential role of tubular dysfunction on GFR estimates using various equations as well as the effect of pharmacologic blockades on tubular secretion of creatinine on creatinine clearance (ClCr). Iohexol GFR (mGFR) was performed in 17 stable kidney transplant recipients(R) at >24 months post-transplantation. Their mean age was 48.3 ± 11.3 years. All R were treated with a calcineurin inhibitor (CNI). At the time of study we measured sCr, 24 hour-ClCr, cystatin C, 24-hour proteinuria, microalbuminuria, FE Na, alfa1-microglobulinuria (alfa1-MG), and CNI concentrations. To block tubular secretion of Cr, recipients were prescribed cimetidine (2400 mg) 2 days before the sCr measurement. Additionally, to exclude dietary influences on sCr, R did not eat meat for 2 days before testing. GFR was estimated using the Modification of Diet in Renal Disease (MDRD), Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI), Cockroft-Gault (C&G), and Cystatin C (Cyst C) GFR equations. Mean kidney graft function over the previous 6 months was used as the control. Pearson correlation was determined between the differences between mGFR and estimatedGFR: Iohexol minus MDRD, EPI, Cyst C or C&G GFR for paired estimates. The diagnostic accuracy of the eGFRs to detect an mGFR of 60 mL/min/1.73 m(2) was examined by receiver operating characteristic curves. Mean mGFR was 75.2 ± 35.8 mL/min/1.73 m(2). The sCr increased but the 24-hour ClCr, MDRD, EPI, and C&G decreased after vs before cimetidine. The difference was significant for sCr (F = 12.933; P = .002) and MDRD GFR (F = 15.750; P = .001). mGFR was not significantly higher than all pair values of eGFRs, and not significantly lower than 24-hour ClCr before and after cimetidine. However, in comparison to all eGFRs, ClCr after cimetidine most approached mGFR. A significant positive correlation was observed between alfa1-MG and the difference between mGFR and MDRD (before, r = .543 [P = .045]; after cimetidine, 0.568 [P = .034]), EPI (before, r = 0.516 [P = .050]; after cimetidine, r = 0.562 [P = .036]), and ClCr (r = 0.633; P = .016), C&G (P = .581; P = .029) before cimetidine. Accuracy of eGFRs to detect mGFR of 60 mL/min/1.73 m(2) showed EPI GFR before cimetidine to show diagnostic accuracy for patients with GFR >60 mL/min/1.73 m(2) with a sensitivity of 81.8% and a specificity of 71.4%. Because mGFR is unavailable in many transplant centers, determination of ClCr after cimetidine may help to achieve a more accurate diagnosis of CKD among transplant patients. Copyright © 2013 Elsevier Inc. All rights reserved.

Changes in estimated glomerular filtration rate over time in South African HIV-1-infected patients receiving tenofovir: a retrospective cohort study

PubMed Central

De Waal, Reneé; Cohen, Karen; Fox, Matthew P; Stinson, Kathryn; Maartens, Gary; Boulle, Andrew; Igumbor, Ehimario U; Davies, Mary-Ann

2017-01-01

Abstract Introduction: Tenofovir has been associated with decline in kidney function, but in patients with low baseline kidney function, improvements over time have been reported. Additionally, the magnitude and trajectory of estimated glomerular filtration rate (eGFR) changes may differ according to how eGFR is calculated. We described changes in eGFR over time, and the incidence of, and risk factors for, kidney toxicity, in a South African cohort. Methods: We included antiretroviral-naïve patients ≥16 years old who started tenofovir-containing antiretroviral therapy (ART) between 2002 and 2013. We calculated eGFR using the Modification of Diet in Renal Disease (MDRD), Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI), and Cockcroft-Gault equations. We described changes in eGFR from ART initiation using linear mixed effects regression. We described the incidence of eGFR <30 mL/min on treatment, and identified associations with low eGFR using Cox regression. Results: We included 15156 patients with median age of 35.4 years (IQR 29.9–42.0), median CD4 cell count of 168 cells/µL (IQR 83–243), and median eGFR (MDRD) of 98.6 mL/min (IQR 84.4–115.6). Median duration of follow up on tenofovir was 12.9 months (IQR 5.1–23.3). Amongst those with a baseline and subsequent eGFR  available, mean eGFR change from baseline at 12 months was −4.4 mL/min (95% CI −4.9 to −4.0), −2.3 (−2.5 to −2.1), and 0.6 (0.04 to 1.2) in those with baseline eGFR ≥90 mL/min; and 11.9 mL/min (11.0 to 12.7), 14.6 (13.5 to 15.7), and 11.0 (10.3 to 11.7) in those with baseline eGFR <90 mL/min, according to the MDRD, CKD-EPI (n = 11 112), and Cockcroft-Gault (n = 9 283) equations, respectively. Overall, 292 (1.9%) patients developed eGFR <30 mL/min. Significant associations with low eGFR included older age, baseline eGFR <60 mL/min, CD4 count <200 cells/µL, body weight <60 kg, and concomitant protease inhibitor use. Conclusions: Patients on tenofovir with baseline eGFR ≥90 mL/min experienced small but significant declines in eGFR over time when eGFR was estimated using the MDRD or CKD-EPI equations. However, eGFR increased in patients with eGFR <90 mL/min, regardless of which estimating equation was used. Decreases to below 30 mL/min were uncommon. In settings with limited access to laboratory testing, monitoring guidelines should consider focusing on higher risk patients. PMID:28406595

The Modification of Diet in Renal Disease 4-calculated glomerular filtration rate is a better prognostic factor of cardiovascular events than classical cardiovascular risk factors in patients with peripheral arterial disease.

PubMed

Romero, Jose-María; Bover, Jordi; Fite, Joan; Bellmunt, Sergi; Dilmé, Jaime-Félix; Camacho, Mercedes; Vila, Luis; Escudero, Jose-Román

2012-11-01

Risk prediction is important in medical management, especially to optimize patient management before surgical intervention. No quantitative risk scores or predictors are available for patients with peripheral arterial disease (PAD). Surgical risk and prognosis are usually based on anesthetic scores or clinical evaluation. We suggest that renal function is a better predictor of risk than other cardiovascular parameters. This study used the four-variable Modification of Diet in Renal Disease (MDRD-4)-calculated glomerular filtration rate (GFR) to compare classical cardiovascular risk factors with prognosis and cardiovascular events of hospitalized PAD patients. The study evaluated 204 patients who were admitted for vascular intervention and diagnosed with grade IIb, III, or IV PAD or with carotid or renal stenosis. Those with carotid or renal stenosis were excluded, leaving 188 patients who were randomized from 2004 to 2005 and monitored until 2010. We performed a life-table analysis with a 6-year follow-up period and one final checkpoint. The following risk factors were evaluated: age, sex, ischemic heart disease, ictus (as a manifestation of cerebrovascular disease related to systemic arterial disease), diabetes, arterial hypertension, dyslipidemia, smoking, chronic obstructive pulmonary disease, type of vascular intervention, and urea and creatinine plasma levels. The GFR was calculated using the MDRD-4 equation. Death, major cardiovascular events, and reintervention for arterial disease were recorded during the follow-up. Patients (73% men) were a mean age of 71.38 ± 11.43 (standard deviation) years. PAD grade IIb was diagnosed in 41 (20%) and grade III-IV in 147 (72%). Forty-two minor amputations (20.6%), 21 major amputations (10.3%), and 102 revascularizations (50%) were performed. A major cardiovascular event occurred in 60 patients (29.4%), and 71 (34.8%) died. Multivariate logistic regression analysis showed that the MDRD-4 GFR, age, and male sex were independent variables related to death and that the MDRD-4 GFR and chronic obstructive pulmonary disease were related to major cardiovascular events. A statistically significant relationship was also found between serum creatinine levels and reintervention rates. The MDRD-4 GFR was a better predictor of risk of death or infarction than classical cardiovascular risk factors in patients with PAD. This suggests that its routine use in the initial evaluation in patients with PAD is beneficial. Copyright © 2012 Society for Vascular Surgery. Published by Mosby, Inc. All rights reserved.

Individualizing Pharmacotherapy in Patients with Renal Impairment: The Validity of the Modification of Diet in Renal Disease Formula in Specific Patient Populations with a Glomerular Filtration Rate below 60 Ml/Min. A Systematic Review

PubMed Central

Kramers, Cornelis; Derijks, Hieronymus J.; Wensing, Michel; Wetzels, Jack F. M.

2015-01-01

Background The Modification of Diet in Renal Disease (MDRD) formula is widely used in clinical practice to assess the correct drug dose. This formula is based on serum creatinine levels which might be influenced by chronic diseases itself or the effects of the chronic diseases. We conducted a systematic review to determine the validity of the MDRD formula in specific patient populations with renal impairment: elderly, hospitalized and obese patients, patients with cardiovascular disease, cancer, chronic respiratory diseases, diabetes mellitus, liver cirrhosis and human immunodeficiency virus. Methods and Findings We searched for articles in Pubmed published from January 1999 through January 2014. Selection criteria were (1) patients with a glomerular filtration rate (GFR) < 60 ml/min (/1.73m2), (2) MDRD formula compared with a gold standard and (3) statistical analysis focused on bias, precision and/or accuracy. Data extraction was done by the first author and checked by a second author. A bias of 20% or less, a precision of 30% or less and an accuracy expressed as P30% of 80% or higher were indicators of the validity of the MDRD formula. In total we included 27 studies. The number of patients included ranged from 8 to 1831. The gold standard and measurement method used varied across the studies. For none of the specific patient populations the studies provided sufficient evidence of validity of the MDRD formula regarding the three parameters. For patients with diabetes mellitus and liver cirrhosis, hospitalized patients and elderly with moderate to severe renal impairment we concluded that the MDRD formula is not valid. Limitations of the review are the lack of considering the method of measuring serum creatinine levels and the type of gold standard used. Conclusion In several specific patient populations with renal impairment the use of the MDRD formula is not valid or has uncertain validity. PMID:25741695

Estimating the glomerular filtration rate in the Spanish working population: chronic kidney disease prevalence and its association with risk factors.

PubMed

Sánchez-Chaparro, Miguel-Angel; Calvo-Bonacho, Eva; González-Quintela, Arturo; Cabrera, Martha; Quevedo-Aguado, Luis; Fernández-Labandera, Carlos; Ruiz-Moraga, Montserrat; Sainz-Gutiérrez, Juan Carlos; Gómez-Martínez, Pablo; Román-García, Javier; Felices, Pedro Valdivielso; Ruilope, Luis-Miguel; Zanchetti, Alberto

2014-10-01

This study aims to investigate the influence of estimated glomerular filtration rate (eGFR) with two equations (and by one or two separate measurements), on the prevalence of chronic kidney disease (CKD) and its association with blood pressure, and cardiovascular and metabolic risk factors. Between January 2010 and October 2011, the Ibermutuamur CArdiovascular RIsk Assessment project included 128 588 workers (77.2% men, mean age 39.3 years, range 16-75), who underwent two consecutive yearly medical check-ups and had information for eGFR according to the MDRD-IDMS and CKD-EPI equations (serum creatinine was measured by a isotope-dilution mass spectrometry traceable method in a single central laboratory). CKD was defined by an eGFR less than 60 ml/min per 1.73 m. Subclinical (occult) renal disease was defined as an eGFR less than 60 ml/min per 1.73 m in patients with serum creatinine below 1.3 mg/dl and below 1.2 mg/dl in men and women, respectively. In this working population, prevalence of CKD was very low, but two to six times lower when two separate eGFRs below 60 ml/min per 1.73 m were used. The prevalence of CKD was significantly lower with the CKD-EPI compared to the MDRD-IDMS equation. The same applies to occult CKD. In male workers, occult CKD was practically nonexistent.Multivariate analyses show that blood pressure, total serum cholesterol, and serum glucose (positively), and high-density lipoprotein and low-density lipoprotein (negatively) were associated with CKD, with both equations. Another metabolic factor (waist circumference) was only associated (positively) with CKD defined by the CKD-EPI equation, which appears to be associated with most components of the metabolic syndrome. The CKD-EPI formula, calculated on the basis of two reported blood samples, may provide the most specific definition of CKD.

Tubular secretion of creatinine in autosomal dominant polycystic kidney disease: consequences for cross-sectional and longitudinal performance of kidney function estimating equations.

PubMed

Spithoven, Edwin M; Meijer, Esther; Boertien, Wendy E; Sinkeler, Steef J; Tent, Hilde; de Jong, Paul E; Navis, Gerjan; Gansevoort, Ron T

2013-09-01

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by renal tubular cell proliferation and dedifferentiation, which may influence tubular secretion of creatinine (CCr[TS]). Diagnostic test study. We therefore investigated CCr(TS) in patients with ADPKD and controls and studied consequences for the performance of glomerular filtration rate (GFR) estimating equations. In patients with ADPKD and healthy controls, we measured GFR as (125)I-iothalamate clearance while simultaneously determining creatinine clearance. 24-hour urinary albumin excretion. In 121 patients with ADPKD (56% men; mean age, 40 ± 11 [SD] years) and 215 controls (48% men; mean age, 53 ± 10 years), measured GFR (mGFR) was 78 ± 30 and 98 ± 17 mL/min/1.73 m(2), respectively, and CCr(TS) was 15.9 ± 10.8 and 10.9 ± 10.6 mL/min/1.73 m(2), respectively (P < 0.001). The higher CCr(TS) in patients with ADPKD remained significant after adjustment for covariates and appeared to be dependent on mGFR. Correlation and accuracy between mGFR and CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) estimated GFR (eGFR) were 0.95 and 99%, respectively; between mGFR and MDRD (Modification of Diet in Renal Disease) Study eGFR, they were 0.93 and 97%, respectively. Values for bias, precision, and accuracy were similar or slightly better than in controls. In addition, change in mGFR during 3 years of follow-up in 45 patients with ADPKD correlated well with change in eGFR. Cross-sectional, single center. CCr(TS) in patients with ADPKD is higher than that in controls, but this effect is limited and observed at only high-normal mGFR. Consequently, the CKD-EPI and MDRD Study equations perform relatively well in estimating GFR and change in GFR in patients with ADPKD. Copyright © 2013 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

Simplifying contrast-induced acute kidney injury prediction after primary percutaneous coronary intervention: the age, creatinine and ejection fraction score.

PubMed

Araujo, Gustavo N; Pivatto Junior, Fernando; Fuhr, Bruno; Cassol, Elvis P; Machado, Guilherme P; Valle, Felipe H; Bergoli, Luiz C; Wainstein, Rodrigo V; Polanczyk, Carisi A; Wainstein, Marco V

2017-05-24

Contrast-induced acute kidney injury (CI-AKI) is a common event after percutaneous coronary intervention (PCI). Presently, the main strategy to avoid CI-AKI lies in saline hydration, since to date none pharmacologic prophylaxis proved beneficial. Our aim was to determine if a low complexity mortality risk model is able to predict CI-AKI in patients undergoing PCI after ST elevation myocardial infarction (STEMI). We have included patients with STEMI submitted to primary PCI in a tertiary hospital. The definition of CI-AKI was a raise of 0.3 mg/dL or 50% in post procedure (24-72 h) serum creatinine compared to baseline. Age, glomerular filtration and ejection fraction were used to calculate ACEF-MDRD score. We have included 347 patients with mean age of 60 years. In univariate analysis, age, diabetes, previous ASA use, Killip 3 or 4 at admission, ACEF-MDRD and Mehran scores were predictors of CI-AKI. After multivariate adjustment, only ACEF-MDRD score and diabetes remained CI-AKI predictors. Areas under the ROC curve of ACEF-MDRD and Mehran scores were 0.733 (0.68-0.78) and 0.649 (0.59-0.70), respectively. When we compared both scores with DeLong test ACEF-MDRDs AUC was greater than Mehran's (P = 0.03). An ACEF-MDRD score of 2.33 or lower has a negative predictive value of 92.6% for development of CI-AKI. ACEF-MDRD score is a user-friendly tool that has an excellent CI-AKI predictive accuracy in patients undergoing primary percutaneous coronary intervention. Moreover, a low ACEF-MDRD score has a very good negative predictive value for CI-AKI, which makes this complication unlikely in patients with an ACEF-MDRD score of <2.33.

Creatinine Versus Cystatin C: Differing Estimates of Renal Function in Hospitalized Veterans Receiving Anticoagulants.

PubMed

Wang, Christina Hao; Rubinsky, Anna D; Minichiello, Tracy; Shlipak, Michael G; Price, Erika Leemann

2018-05-31

Current practice in anticoagulation dosing relies on kidney function estimated by serum creatinine using the Cockcroft-Gault equation. However, creatinine can be unreliable in patients with low or high muscle mass. Cystatin C provides an alternative estimation of glomerular filtration rate (eGFR) that is independent of muscle. We compared cystatin C-based eGFR (eGFR cys ) with multiple creatinine-based estimates of kidney function in hospitalized patients receiving anticoagulants, to assess for discordant results that could impact medication dosing. Retrospective chart review of hospitalized patients over 1 year who received non-vitamin K antagonist anticoagulation, and who had same-day measurements of cystatin C and creatinine. Seventy-five inpatient veterans (median age 68) at the San Francisco VA Medical Center (SFVAMC). We compared the median difference between eGFR by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) study equation using cystatin C (eGFR cys ) and eGFRs using three creatinine-based equations: CKD-EPI (eGFR EPI ), Modified Diet in Renal Disease (eGFR MDRD ), and Cockcroft-Gault (eGFR CG ). We categorized patients into standard KDIGO kidney stages and into drug-dosing categories based on each creatinine equation and calculated proportions of patients reclassified across these categories based on cystatin C. Cystatin C predicted overall lower eGFR compared to creatinine-based equations, with a median difference of - 7.1 (IQR - 17.2, 2.6) mL/min/1.73 m 2 versus eGFR EPI , - 21.2 (IQR - 43.7, - 8.1) mL/min/1.73 m 2 versus eGFR MDRD , and - 25.9 (IQR - 46.8, - 8.7) mL/min/1.73 m 2 versus eGFR CG . Thirty-one to 52% of patients were reclassified into lower drug-dosing categories using cystatin C compared to creatinine-based estimates. We found substantial discordance in eGFR comparing cystatin C with creatinine in this group of anticoagulated inpatients. Our sample size was limited and included few women. Further investigation is needed to confirm these findings and evaluate implications for bleeding and other clinical outcomes. Not applicable.

Comparison of Cockcroft-Gault and modification of diet in renal disease formulas as predictors of cardiovascular outcomes in patients with myocardial infarction treated with primary percutaneous coronary intervention.

PubMed

Ekmekci, Ahmet; Uluganyan, Mahmut; Gungor, Baris; Tufan, Fatih; Cekirdekci, Elif Iclal; Ozcan, Kazim Serhan; Erer, Hatice Betul; Orhan, Ahmet; Osmanov, Damir; Bozbay, Mehmet; Cicek, Gokhan; Sayar, Nurten; Eren, Mehmet

2014-10-01

We prospectively assessed the value of estimated glomerular filtration rate (eGFR) by the Modification of Diet in Renal Disease (MDRD) and Cockcroft-Gault (C-G) equations in predicting inhospital adverse outcomes after primary coronary intervention for acute ST-segment elevation myocardial infarction. We classified 647 patients into 3 categories according to eGFR, <60, 60 to 90, and >90 mL/min/1.73 m(2). The eGFRC-G classified 17 patients in the >90 mL/min/1.73 m(2) subgroup and 6 and 11 patients in the 60 to 90 and <60 mL/min/1.73 m(2) subgroups, respectively. In multivariate analysis, patients with eGFRC-G < 60 mL/min/1.73 m(2) had 19.5-fold (95% confidence interval [CI] 1.55-178) higher mortality risk and 5.48-fold (95% CI 1.75-24.21) higher major adverse cardiac events risk compared to patients with eGFRC-G >90 mL/min/1.73 m(2) (P = .01 and P = .01, respectively); the eGFRMDRD was not predictive. Although the MDRD equation more accurately estimates GFR in certain populations, the CG formula may be a better predictor of adverse events. © The Author(s) 2013.

Serum Cystatin C as an Early Diagnostic Biomarker of Diabetic Kidney Disease in Type 2 Diabetic Patients.

PubMed

Qamar, Ayesha; Hayat, Asma; Ahmad, Tariq Mahmood; Khan, Alamgir; Hasnat, Mohammad Najam Ul; Tahir, Sufyan

2018-04-01

To determine the diagnostic accuracy and cut-off values of serum cystatin C as early diagnostic biomarker of diabetic kidney disease. Cross-sectional analytical study. Department of Pathology, Army Medical College, Rawalpindi in collaboration with Endocrinology Department, Military Hospital (MH), Rawalpindi from November 2015 to November 2016. One hundred and nineteen diagnosed patients of type 2 diabetes mellitus were enrolled in the study from the outpatient Endocrinology Department of the MH Rawalpindi. Fifty disease-free controls were also included. Fasting blood samples of the patients and controls were analysed for creatinine by Jaffé's kinetic method and estimated GFR was calculated using MDRD-based equation for GFR. Serum cystatin C was estimated by quantitative turbidimetric method. Serum cystatin C was higher in the diabetic group (mean = 1.022 ±0.33 mg/dl) as compared to the control group (mean = 0.63 ±0.14 mg/dl). ROC curve analysis, keeping less than 60 ml/min/1.73 m2 GFR (CKD-MDRD based) as reference value of the stat variable/gold standard; revealed an area under the curve of 0.914 (95% CI 0.85-0.98) and at optimal sensitivity of 88.2% and specificity of 84.8% the established cut-off of serum cystatin C was 1.26 mg/L. Cystatin C is an accurate biomarker of diabetic kidney disease with good sensitivity and specificity.

Age- and sex-specific reference limits for creatinine, cystatin C and the estimated glomerular filtration rate.

PubMed

Hannemann, Anke; Friedrich, Nele; Dittmann, Kathleen; Spielhagen, Christin; Wallaschofski, Henri; Völzke, Henry; Rettig, Rainer; Endlich, Karlhans; Lendeckel, Uwe; Stracke, Sylvia; Nauck, Matthias

2011-11-14

Early detection of patients with chronic kidney disease is of great importance. This study developed reference limits for serum creatinine and serum cystatin C concentrations and for the estimated glomerular filtration rate (eGFR) in healthy subjects from the general population aged 25-65 years. This study defined a reference population including 985 subjects from the first follow-up of the Study of Health in Pomerania. Serum creatinine was measured with a modified kinetic Jaffé method. Serum cystatin C was measured with a nephelometric assay. The eGFR was calculated from serum creatinine according to the Cockcroft-Gault (eGFR(CG)) and the Modification of Diet in Renal Disease (eGFR(MDRD)) equation, respectively, as well as from serum cystatin C according to the formula by Larsson (eGFR(Larsson)). Non-parametric quantile regression was used to estimate the reference limits. For serum creatinine and serum cystatin C the 95th percentile and for eGFR(CG), eGFR(MDRD) and eGFR(Larsson) the 5th percentile were selected as reference limits. All data was weighted to reflect the age- and sex-structure of the German population in 2008. The reference limits for serum creatinine (men: 1.11-1.23 mg/dL; women: 0.93-1.00 mg/dL) and serum cystatin C levels (men: 0.92-1.04 mg/L; women: 0.84-1.02 mg/L) increased with advancing age. The reference limits for eGFR decreased with increasing age (eGFR(CG) men: 106.0-64.7 mL/min, women 84.4-57.9 mL/min; eGFR(MDRD) men: 82.5-62.2 mL/min/1.73 m², women 75.0-58.2 mL/min/1.73 m²; eGFR(Larsson) men: 85.5-72.9 mL/min, women 94.5-75.7 mL/min). This study presents age- and sex-specific reference limits for five measures of renal function based on quantile regression models.

The Effects of Schema-Based Instruction on the Proportional Thinking of Students With Mathematics Difficulties With and Without Reading Difficulties.

PubMed

Jitendra, Asha K; Dupuis, Danielle N; Star, Jon R; Rodriguez, Michael C

2016-07-01

This study examined the effect of schema-based instruction (SBI) on the proportional problem-solving performance of students with mathematics difficulties only (MD) and students with mathematics and reading difficulties (MDRD). Specifically, we examined the responsiveness of 260 seventh grade students identified as MD or MDRD to a 6-week treatment (SBI) on measures of proportional problem solving. Results indicated that students in the SBI condition significantly outperformed students in the control condition on a measure of proportional problem solving administered at posttest (g = 0.40) and again 6 weeks later (g = 0.42). The interaction between treatment group and students' difficulty status was not significant, which indicates that SBI was equally effective for both students with MD and those with MDRD. Further analyses revealed that SBI was particularly effective at improving students' performance on items related to percents. Finally, students with MD significantly outperformed students with MDRD on all measures of proportional problem solving. These findings suggest that interventions designed to include effective instructional features (e.g., SBI) promote student understanding of mathematical ideas. © Hammill Institute on Disabilities 2014.

Chronic kidney disease among high school students of Kinshasa

PubMed Central

2012-01-01

Background Chronic kidney disease (CKD) is a major worldwide health problem. However, its burden among adolescents and young adults is unknown, especially in sub-Saharan Africa. The aim of this study was to investigate its prevalence in the school environment. The concordance of usual formulas used to estimate renal function was also assessed. Methods In an epidemiological cross sectional study, a random sample of 524 pupils (263 boys, mean age of 18.7 ± 1.4 years) from school environment of Kinshasa were studied. Recorded parameters of interest were anthropometric, proteinuria, serum creatinine and estimated glomerular filtration rate (eGFR) according to the Schwartz formula using uncalibrated creatinine levels from one random measurement. CKD was defined as the presence of kidney damage (daily proteinuria ≥ 300 mg) and/or reduced kidney function (eGFR < 60 ml/min/1.73 m2). Concordances between eGFR according to Schwartz, Cockcroft-Gault (C-G) indexed for BSA and modification of diet in renal disease (MDRD) study equations were computed using the kappa coefficient. Results The prevalence of CKD by the Schwartz formula was 1.5%. By stage, 0.8% had CKD stage 1 (proteinuria with normal eGFR) and 0.8% had CKD stage 3 (eGFR, 30 to 59 ml/min/1.73 m2). The prevalence of proteinuria ≥ 300 mg/day was 1% (one case had 2.7g/day). Agreement between eGFR according to Schwartz formula and the MDRD formula was excellent (kappa: 88.8%). Although correlations between all formulas were excellent (0.99; 0.87, and 0.89), agreement was poor between eGFR according to Schwartz and C-G indexed BSA equation (kappa: 52.7%) and, poorer with C-G unadjusted for BSA (kappa: 26.9%). Conclusion In the large African city of Kinshasa, 2% of high school students have CKD. This high prevalence rate emphasizes the need for appropriate detection and prevention measures in this vulnerable young age population group. PMID:22559052

Concurrent use of methotrexate and celecoxib increases risk of silent liver fibrosis in rheumatoid arthritis patients with subclinical reduced kidney function.

PubMed

Park, Jin Su; Park, Min-Chan; Park, Yong-Beom; Lee, Soo-Kon; Lee, Sang-Won

2014-01-01

We evaluated the effects of concurrent use of methotrexate and celecoxib on silent liver and kidney damages in rheumatoid arthritis (RA) patients. We enrolled 92 RA patients with normal laboratory results related to liver and kidney functions, who had received methotrexate and celecoxib concurrently over 6 months. Liver stiffness measurement (LSM) using transient elastography and ultrasonography were performed along with blood and urine tests. Estimated glomerular filtration rate (eGFR) was calculated by both the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and the Modification of Diet in Renal Disease (MDRD) equations. Initial eGFR represented kidney function at the time of the initiation of celecoxib. The cutoff for abnormal LSM values was adopted as 5.3 kPa. The optimal cutoff of each eGFR for abnormal LSM values was also calculated. The median age of patients was 55 years old (74 women). The median LSM was 4.4 kPa and the median eGFRs and median initial eGFRs ranged from 89 to 99 mL/min/1.73 m(2). The cumulative doses of methotrexate and celecoxib and their concurrent administration duration did not affect LSM values and eGFRs. Both eGFRs were significantly associated with LSM values. Patients with initial eGFR(CKD-EPI), initial eGFR(MDRD), and eGFR(CKD-EPI) below each optimal cutoff had significantly high risks for silent liver fibrosis (RR 9.4, 10.3, and 4.4, p < 0.001, respectively). Both initial eGFRs (CKD-EPI and MDRD) and eGFR (CKD-EPI) were significant predictors for the development of silent liver fibrosis in RA patients who had received methotrexate and celecoxib concurrently for at least 6 months.

Effect of a very low-protein diet on outcomes: long-term follow-up of the Modification of Diet in Renal Disease (MDRD) Study.

PubMed

Menon, Vandana; Kopple, Joel D; Wang, Xuelei; Beck, Gerald J; Collins, Allan J; Kusek, John W; Greene, Tom; Levey, Andrew S; Sarnak, Mark J

2009-02-01

The long-term effect of a very low-protein diet on the progression of kidney disease is unknown. We examined the effect of a very low-protein diet on the development of kidney failure and death during long-term follow-up of the Modification of Diet in Renal Disease (MDRD) Study. Long-term follow-up of study B of the MDRD Study (1989-1993). The MDRD Study examined the effects of dietary protein restriction and blood pressure control on progression of kidney disease. This analysis includes 255 trial participants with predominantly stage 4 nondiabetic chronic kidney disease. A low-protein diet (0.58 g/kg/d) versus a very low-protein diet (0.28 g/kg/d) supplemented with a mixture of essential keto acids and amino acids (0.28 g/kg/d). Kidney failure (initiation of dialysis therapy or transplantation) and all-cause mortality until December 31, 2000. Kidney failure developed in 227 (89%) participants, 79 (30.9%) died, and 244 (95.7%) reached the composite outcome of either kidney failure or death. Median duration of follow-up until kidney failure, death, or administrative censoring was 3.2 years, and median time to death was 10.6 years. In the low-protein group, 117 (90.7%) participants developed kidney failure, 30 (23.3%) died, and 124 (96.1%) reached the composite outcome. In the very low-protein group, 110 (87.3%) participants developed kidney failure, 49 (38.9%) died, and 120 (95.2%) reached the composite outcome. After adjustment for a priori-specified covariates, hazard ratios were 0.83 (95% confidence interval, 0.62 to 1.12) for kidney failure, 1.92 (95% confidence interval, 1.15 to 3.20) for death, and 0.89 (95% confidence interval, 0.67 to 1.18) for the composite outcome in the very low-protein diet group compared with the low-protein diet group. Lack of dietary protein measurements during follow-up. In long-term follow-up of the MDRD Study, assignment to a very low-protein diet did not delay progression to kidney failure, but appeared to increase the risk of death.

Factors affecting the incidence of contrast-induced nephropathy in patients undergoing computed tomography.

PubMed

Heras Benito, M; Garrido Blázquez, M; Gómez Sanz, Y; Bernardez Mardomingo, M; Ruiz Cacho, J; Rodríguez Recio, F J; Fernández-Reyes Luis, M J

2018-05-17

To analyze the incidence of contrast-induced nephropathy in a cohort of patients undergoing computed tomography (CT) with intravenous iodinated contrast material. To evaluate the efficacy of N-acetylcysteine in preventing contrast-induced nephropathy. This prospective observational study was carried out in the months comprising March 2016 through July 2016. We selected the first five patients scheduled to undergo CT examination each day who agreed to participate and signed the informed consent form. We recorded patients' cardiovascular histories, chronic treatments, and indications for the CT examination. We measured blood levels of creatinine and urea before and after the CT examination. We used the Modification of Diet in Renal Disease (MDRD-4) equation to estimate the glomerular filtration rate. We analyzed the type and dose of contrast material. We recorded whether N-acetylcysteine was administered before the CT examination. We used SPSS 15.0 ® to compare means and proportions. Statistical significance was set at p < 0.05. No incidents of contrast-induced nephropathy were detected in any of the 202 patients included [mean age, 63.92 ± 12 years (range 22-87); 57.4% male; 21.8% diabetic; 39.6% hypertensive; 87.1% had MDRD4 ≥ 60 ml/min/1.73 m 2 (89.45 ± 14, range 62.36-134.14) and 12.9% had MDRD4 < 60 ml/min/1.73 m 2 (45.38 ± 11, range 9.16-58.90)]. The most common indication for CT examinations was oncologic (81.2%). The only contrast agent administered was iopamidol; the mean dose was 107.83 ± 11 ml (range 70-140). The mean interval between pre-CT and post-CT laboratory tests was 4.06 ± 1 days. Only 13 patients received N-acetylcysteine; 9 of these had MDRD < 60 ml/min/1.73 m 2 and 4 had MDRD4 ≥ 60 ml/min/1.73 m 2 (p = 0.000). The incidence of contrast-induced nephropathy was not significant in patients with glomerular filtration rates greater than 30 ml/min/1.73 m 2 : these favorable results might be due to analyzing only scheduled examinations and to using relatively low doses of a "nonionic" iodinated contrast agent. Copyright © 2018 SERAM. Publicado por Elsevier España, S.L.U. All rights reserved.

Interest and limits of glomerular filtration rate (GFR) estimation with formulae using creatinine or cystatin C in the malnourished elderly population.

PubMed

Fabre, Emmanuelle E; Raynaud-Simon, Agathe; Golmard, Jean-Louis; Gourgouillon, Nadège; Beaudeux, Jean-Louis; Nivet-Antoine, Valérie

2010-01-01

Renal function is often altered in elderly patients. A lot of formulae are proposed to estimate GFR to adjust drug posology. French guidelines recommend the Cockcroft-Gault formula corrected with the body surface area (cCG), but the initially described unadjusted Cockcroft-Gault equation (CG) is mainly used in geriatric clinical practice. International recommendations have proposed the modification of diet in renal disease (MDRD) formula, since several authors recommended the Rule formula using cystatin C (cystC) in particular population. To appreciate the most accurate GFR estimation for posology adaptation in an elderly polypathological population, a cross-sectional study with prospective inclusion was carried out in Charles Foix Hospital. Plasma glucose levels (PGL), creatinine (CREA) levels and serum cystC, albumin (ALB), transthyretin (TTR), C-reactive protein (CRP), orosomucoid (ORO) total cholesterol (tCHOL) levels were determined among 193 elderly patients aged 70 and older. The results showed that in a malnourished, inflamed old population, CG, MDRD and Rule formulae resulted in different estimations of GFR, depending on nutritional and inflammatory parameters. Only cCG estimation was shown to be independent from these parameters. To conclude, cCG seems to be the most accurate and appropriate formula in a polypathological elderly population to evaluate renal function in order to adapt drug posology. Copyright (c) 2009 Elsevier Ireland Ltd. All rights reserved.

Metabolomic Alterations Associated with Cause of CKD.

PubMed

Grams, Morgan E; Tin, Adrienne; Rebholz, Casey M; Shafi, Tariq; Köttgen, Anna; Perrone, Ronald D; Sarnak, Mark J; Inker, Lesley A; Levey, Andrew S; Coresh, Josef

2017-11-07

Causes of CKD differ in prognosis and treatment. Metabolomic indicators of CKD cause may provide clues regarding the different physiologic processes underlying CKD development and progression. Metabolites were quantified from serum samples of participants in the Modification of Diet in Renal Disease (MDRD) Study, a randomized controlled trial of dietary protein restriction and BP control, using untargeted reverse phase ultraperformance liquid chromatography tandem mass spectrometry quantification. Known, nondrug metabolites ( n =687) were log-transformed and analyzed to discover associations with CKD cause (polycystic kidney disease, glomerular disease, and other cause). Discovery was performed in Study B, a substudy of MDRD with low GFR ( n =166), and replication was performed in Study A, a substudy of MDRD with higher GFR ( n =423). Overall in MDRD, average participant age was 51 years and 61% were men. In the discovery study (Study B), 29% of participants had polycystic kidney disease, 28% had glomerular disease, and 43% had CKD of another cause; in the replication study (Study A), the percentages were 28%, 24%, and 48%, respectively. In the discovery analysis, adjusted for demographics, randomization group, body mass index, hypertensive medications, measured GFR, log-transformed proteinuria, and estimated protein intake, seven metabolites (16-hydroxypalmitate, kynurenate, homovanillate sulfate, N2,N2-dimethylguanosine, hippurate, homocitrulline, and 1,5-anhydroglucitol) were associated with CKD cause after correction for multiple comparisons ( P <0.0008). Five of these metabolite associations (16-hydroxypalmitate, kynurenate, homovanillate sulfate, N2,N2-dimethylguanosine, and hippurate) were replicated in Study A ( P <0.007), with all replicated metabolites exhibiting higher levels in polycystic kidney disease and lower levels in glomerular disease compared with CKD of other causes. Metabolomic profiling identified several metabolites strongly associated with cause of CKD. Copyright © 2017 by the American Society of Nephrology.

New treatment for IgA nephropathy: enteric budesonide targeted to the ileocecal region ameliorates proteinuria.

PubMed

Smerud, Hilde Kloster; Bárány, Peter; Lindström, Karin; Fernström, Anders; Sandell, Anna; Påhlsson, Peter; Fellström, Bengt

2011-10-01

Systemic corticosteroid treatment has been shown to exert some protection against renal deterioration in IgA nephropathy (IgAN) but is not commonly recommended for long-term use due to the well-known systemic side effects. In this study, we investigated the efficacy and safety of a new enteric formulation of the locally acting glucocorticoid budesonide (Nefecon®), designed to release the active compound in the ileocecal region. The primary objective was to evaluate the efficacy of targeted release budesonide on albuminuria. Budesonide 8 mg/day was given to 16 patients with IgAN for 6 months, followed by a 3-month follow-up period. The efficacy was measured as change in 24-h urine albumin excretion, serum creatinine and estimated glomerular filtration rate (eGFR). The median relative reduction in urinary albumin excretion was 23% during the treatment period (interquartile range: -0.36 to -0.04, P = 0.04) with pretreatment values ranging from 0.3 to 6 g/24 h (median: 1.5 g/24 h). The median reduction in urine albumin peaked at 40% (interquartile range: -0.58 to -0.15) 2 months after treatment discontinuation. Serum creatinine was reduced by 6% (interquartile range: -0.12 to -0.02; P = 0.003), and eGFR [Modification of Diet in Renal Disease (MDRD)] increased ∼8% (interquartile range: 0.02-0.16, P = 0.003) during treatment. No major corticosteroid-related side effects were observed. In the present pilot study, enteric budesonide targeted to the ileocecal region had a significant effect on urine albumin excretion, accompanied by a minor reduction of serum creatinine and a modest increase of eGFR calculated by the MDRD equation, while eGFR calculated from Cockcroft-Gault equation and cystatin C was not changed. Enteric budesonide may represent a new treatment of IgAN warranting further investigation.

The Correlation Between Urinary 8-Iso-Prostaglandin F2α and Hydrogen Peroxide Toward Renal Function in T2DM Patients Consuming Sulfonylurea and Combination of Metformin-Sulfonylurea.

PubMed

Sauriasari, Rani; Wulandari, Fitri; Nurifahmi, Rahmaningtyas; Sekar, Andisyah P; Susilo, Veronika Y

2018-01-01

Renal dysfunction is a common complication in type 2 diabetes mellitus patients associated with oxidative damage which could be characterized by 8-iso-prostaglandin F2α and hydrogen peroxide level as oxidative stress markers. The aim of our study is to determine if there is a difference in 8-iso-prostaglandin F2α and hydrogen peroxide levels between sulfonylurea and combination of metformin-sulfonylurea in diabetic patients. We also wanted to determine if these oxidative stress markers correlate with the estimated Glomerular Filtration Rate (eGFR). We conducted a cross-sectional study with inclusion of 55 patients with type 2 diabetes mellitus in Dr. Sitanala Tangerang Hospital, Indonesia with purposive sampling. The value of eGFR was obtained by serum creatinine levels, while the level of 8-iso-prostaglandin F2α was measured by ELISA and urinary hydrogen peroxide using FOX-1 (Ferrous Ion Oxidation Xylenol Orange 1). There was no difference in 8-iso-prostaglandin F2α and hydrogen peroxide level between the two groups (p=0.088 and p=0.848). Moreover, there was no difference in eGFR values between the two groups, measured by Cockroft-Gault, MDRD, and CKD-EPI. 8-iso-prostaglandin F2α (n=55) was positively correlated with eGFR based on Cockroft-Gault (r=0.382; p=0.009), whereas urinary hydrogen peroxide (n=47) also generate significant positive correlation with eGFR based on the MDRD equation (r=0.326; p=0.021). Linear regression analysis showed that 8-iso-prostaglandin F2α is the most predictive factor and the only significant factor for eGFR in Cockroft-Gault, MDRD and also CKDEPI, even after controlled by gender, age, BMI, HbA1c, systole, and H2O2. The two treatments did not have any significant differences in antioxidant activity. However, an increase of urinary 8-iso-prostaglandin F2. and hydrogen peroxide which correlates with eGFR in the total sample may play a significant role in the pathophysiology of diabetic nephropathy. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Cognitive and Mathematical Profiles for Different Forms of Learning Difficulties

PubMed Central

Cirino, Paul T.; Fuchs, Lynn S.; Elias, John T.; Powell, Sarah R.; Schumacher, Robin F.

2014-01-01

The purpose of this study was to compare subgroups of students with various forms of learning difficulties (< 25th percentile) on cognitive and mathematics characteristics. Students with mathematics difficulty (MD, n = 105), reading difficulty (RD, n = 65), both (MDRD, n = 87), or neither (NoLD, n = 403) were evaluated on an array of cognitive measures (e.g., working memory and language) and on mathematics measures of foundational numerical competencies, computation, and problem solving. Results revealed expected level differences among groups in both domains: NoLD outperformed RD, and MD outperformed MDRD. Profile differences were noted among pairs of subgroups on cognitive measures. On mathematics measures, profile differences were noted between RD and other subgroups, but not between MD and MDRD subgroups. The most discriminating cognitive measures were processing speed and language; the most discriminating mathematics measures depended on the subgroups being compared. Results were further evaluated according to more severe (< 10th percentile) criteria for MD and RD, which generally affected level differences more than the profile patterns. Results have implications for understanding comorbid MD and RD and for conceptualizing core deficits in MD. PMID:23851137

Detection and prognostic impact of renal dysfunction in patients with chronic heart failure and normal serum creatinine.

PubMed

Scrutinio, Domenico; Passantino, Andrea; Lagioia, Rocco; Santoro, Daniela; Cacciapaglia, Erasmo

2011-03-03

Accurate identification of renal dysfunction (RD) is crucial to risk stratification in chronic heart failure (CHF). Patients with CHF are at special risk of having RD despite normal serum creatinine (SCr), owing to a decreased Cr generation. At low levels of SCr, the equations estimating renal function are less accurate. This study was aimed to assess and compare the prognostic value of formulas estimating renal function in CHF patients with normal SCr. We studied 462 patients with systolic CHF and normal SCr. Creatinine clearance was estimated by the Cockcroft-Gault (eCrCl) and glomerular filtration rate by the 4-variable MDRD equation (eGFR); eCrCl normalized for body-surface area (eCrCl(BSA)) was calculated. The primary outcome was all-cause mortality at 2 years. Seventy five patients died. At multivariate Cox regression analysis, only eCrCl(BSA) was significantly associated with mortality (p = 0.006); eGFR (p = 0.24), eCrCl (p = 0.09) and BUN (p = 0.14) were not statistically significant predictors. The patients in the lowest eCrCl(BSA) quartile had an adjusted 2.1-fold (CI: 1.06-4.1) increased risk of mortality, compared with those in the referent quartile. Two-year survival was 70.4% in the lowest eCrCl(BSA) quartile and 89.7% in the referent quartile. Other independent predictors of mortality were ischemic etiology (RR: 2.16 [CI: 1.3-3.5], p = 0.0017), NYHA III/IV class (RR: 2.45 [CI: 1.51-3.97], p = 0.0003), LVEF <0.25 (RR: 3.38 [CI: 1.69-6.75], p = 0.014), and anemia (RR: 1.86 [CI: 1.16-2.99], p = 0.009). A sizeable proportion of CHF patients have prognostically significant RD despite normal SCr. Such patients represent a high-risk subgroup and can more accurately be identified by the CG formula corrected for BSA than the MDRD. Copyright © 2009 Elsevier B.V. All rights reserved.

Augmented renal clearance is not a risk factor for mortality in Enterobacteriaceae bloodstream infections treated with appropriate empiric antimicrobials.

PubMed

Burnham, Jason P; Micek, Scott T; Kollef, Marin H

2017-01-01

The main objective of the study was to assess whether augmented renal clearance was a risk factor for mortality in a cohort of patients with Enterobacteriaceae sepsis, severe sepsis, or septic shock that all received appropriate antimicrobial therapy within 12 hours. Using a retrospective cohort from Barnes-Jewish Hospital, a 1,250-bed teaching hospital, we collected data on individuals with Enterobacteriaceae sepsis, severe sepsis, and septic shock who received appropriate initial antimicrobial therapy between June 2009 and December 2013. Clinical outcomes were compared according to renal clearance, as assessed by Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formulas, sepsis classification, demographics, severity of illness, and comorbidities. We identified 510 patients with Enterobacteriaceae bacteremia and sepsis, severe sepsis, or septic shock. Sixty-seven patients (13.1%) were nonsurvivors. Augmented renal clearance was uncommon (5.1% of patients by MDRD and 3.0% by CKD-EPI) and was not associated with increased mortality. Our results are limited by the absence of prospective determination of augmented renal clearance. However, in this small cohort, augmented renal clearance as assessed by MDRD and CKD-EPI does not seem to be a risk factor for mortality in patients with Enterobacteriaceae sepsis. Future studies should assess this finding prospectively.

Cognitive and mathematical profiles for different forms of learning difficulties.

PubMed

Cirino, Paul T; Fuchs, Lynn S; Elias, John T; Powell, Sarah R; Schumacher, Robin F

2015-01-01

The purpose of this study was to compare subgroups of students with various forms of learning difficulties (< 25th percentile) on cognitive and mathematics characteristics. Students with mathematics difficulty (MD, n = 105), reading difficulty (RD, n = 65), both (MDRD, n = 87), or neither (NoLD, n = 403) were evaluated on an array of cognitive measures (e.g., working memory and language) and on mathematics measures of foundational numerical competencies, computation, and problem solving. Results revealed expected level differences among groups in both domains: NoLD outperformed RD, and MD outperformed MDRD. Profile differences were noted among pairs of subgroups on cognitive measures. On mathematics measures, profile differences were noted between RD and other subgroups, but not between MD and MDRD subgroups. The most discriminating cognitive measures were processing speed and language; the most discriminating mathematics measures depended on the subgroups being compared. Results were further evaluated according to more severe (< 10th percentile) criteria for MD and RD, which generally affected level differences more than the profile patterns. Results have implications for understanding comorbid MD and RD and for conceptualizing core deficits in MD. © Hammill Institute on Disabilities 2013.

[Differences between MDRD-4 and CG in the prevalence of renal failure and its associated variables in type2 diabetic patients].

PubMed

Dalmau Llorca, Maria Rosa; Boira Costa, Míriam; López Pablo, Carlos; Pepió Vilaubí, Josep Maria; Aguilar Martin, Carina; Forcadell Drago, Emma

2016-11-01

To estimate the prevalence of occult renal failure (RF) in DM2, by comparing two formulas for estimating glomerular filtration rate (GFR): Modification of Diet in Renal Disease 4 (MDRD-4) and Cockcroft-Gault (CG), as well as their associated clinical variables. Multicentre analytical cross-sectional. Two basic Primary Care areas in Terres de l'Ebre, in North-Eastern Spain. A total of 493 DM2 patients with age >18years with an assigned doctor in the areas studied. There was a loss of 9 and 11 cases in each formula due to lack of variables necessary for the GFR. Estimated GFR using the two formulas, plasma creatinine values, classification of patients with established RF, occult RF and without RF, and possible clinical-pathological variables associated with RF. Of the total, 45.2% were men, the mean age was 70.4 years, and mean time since onset of diabetes of 7.5 years. The prevalence of occult RF with MDRD-4 was 18%, and 22.6% with CG. The cases detected by GC and not by MDRD-4 were higher, and with lower weight. In both formulas, occult RF patients had more chronic diseases, hypertension, and cardiovascular events (CV) than those without RF. Risk factors associated with occult RF were female, increasing age, and LDL cholesterol. The prevalence of occult RF was 20% in DM2, independently of the formula. A poorer control of cardiovascular risk factors was observed, which makes them a group at higher risk of suffering a CV event. Copyright © 2016 Elsevier España, S.L.U. All rights reserved.

Assessment of the RIFLE criteria for the diagnosis of Acute Kidney Injury; a retrospective study in South-Western Ghana.

PubMed

Ephraim, Richard K D; Darkwah, Kwame O; Sakyi, Samuel A; Ephraim, Mabel; Antoh, Enoch O; Adoba, Prince

2016-07-26

Acute kidney injury (AKI) affects 3-7 % of patients admitted to the hospital and approximately 25-30 % of patients in the intensive care unit. RIFLE, a newly developed international consensus classification for AKI, defines three grades of severity-class R (risk), I (injury) and F (failure). The aim of this study was to evaluate whether the RIFLE system of classification can detect the incidence of AKI using retrospective data of in-patients at the Effia-Nkwanta Regional Hospital. A total of 1070 in-patients' records spanning a period of 6 months, from July 2014 to December 2014, was used. Demographic data and hospital admission serum creatinine of each participant were used for the calculation of estimated glomerular filtration rate (eGFR) using the 4-variable modification of diet in renal disease (MDRD) equation. Also, the baseline serum creatinine was estimated assuming a standard GFR of 75 ml/min/1.73 m(2) using the simplified MDRD equation. Males had higher serum creatinine, eGFR, and baseline serum creatinine than females (P < 0.0001). However, the level of increase in baseline serum creatinine was higher in females than males (P = 0.0212). The percentage ratios of the various classes from the SCr/ePCr (hospital admission serum creatinine/estimated plasma creatinine) criteria (R-1.45, I-1.53 and F-3.26) were higher than that of the eGFR criteria (R-0.34, I-0.11, F-0.12). The SCr/ePCr criteria gave more risk (89.7 %) than that of the eGFR criteria (23.1 %). The number of Injury and normal patients from the eGFR criteria was higher than the SCr/ePCr criteria. AKI was common in the ICU population with SCr/ePCr detecting more AKI than the eGFR criteria. Males had more injury and failure than females using the eGFR criteria whereas the SCr/ePCr gave females more risk and injury than males. A prospective cohort study must be employed in subsequent studies using the RIFLE criteria to assess the incidence of AKI in hospitalized patients with known diseases or medical conditions.

Novel Filtration Markers for GFR Estimation

PubMed Central

Inker, Lesley A.; Coresh, Josef; Levey, Andrew S.; Eckfeldt, John H.

2017-01-01

Creatinine-based glomerular filtration rate estimation (eGFRcr) has been improved and refined since the 1970s through both the Modification of Diet in Renal Disease (MDRD) Study equation in 1999 and the CKD Epidemiology Collaboration (CKD-EPI) equation in 2009, with current clinical practice dependent primarily on eGFR for accurate assessment of GFR. However, researchers and clinicians have recognized limitations of relying on creatinine as the only filtration marker, which can lead to inaccurate GFR estimates in certain populations due to the influence of non-GFR determinants of serum or plasma creatinine. Therefore, recent literature has proposed incorporation of multiple serum or plasma filtration markers into GFR estimation to improve precision and accuracy and decrease the impact of non-GFR determinants for any individual biomarker. To this end, the CKD-EPI combined creatinine-cystatin C equation (eGFRcr-cys) was developed in 2012 and demonstrated superior accuracy to equations relying on creatinine or cystatin C alone (eGFRcr or eGFRcys). Now, the focus has broadened to include additional novel filtration markers to further refine and improve GFR estimation. Beta-2-microglobulin (B2M) and beta-trace-protein (BTP) are two filtration markers with established assays that have been proposed as candidates for improving both GFR estimation and risk prediction. GFR estimating equations based on B2M and BTP have been developed and validated, with the CKD-EPI combined BTP-B2M equation (eGFRBTP-B2M) demonstrating similar performance to eGFR and eGFR. Additionally, several studies have demonstrated that both B2M and BTP are associated with outcomes in CKD patients, including cardiovascular events, ESRD and mortality. This review will primarily focus on these two biomarkers, and will highlight efforts to identify additional candidate biomarkers through metabolomics-based approaches. PMID:29333147

High creatinine clearance in critically ill patients with community-acquired acute infectious meningitis.

PubMed

Lautrette, Alexandre; Phan, Thuy-Nga; Ouchchane, Lemlih; Aithssain, Ali; Tixier, Vincent; Heng, Anne-Elisabeth; Souweine, Bertrand

2012-09-27

A high dose of anti-infective agents is recommended when treating infectious meningitis. High creatinine clearance (CrCl) may affect the pharmacokinetic / pharmacodynamic relationships of anti-infective drugs eliminated by the kidneys. We recorded the incidence of high CrCl in intensive care unit (ICU) patients admitted with meningitis and assessed the diagnostic accuracy of two common methods used to identify high CrCl. Observational study performed in consecutive patients admitted with community-acquired acute infectious meningitis (defined by >7 white blood cells/mm3 in cerebral spinal fluid) between January 2006 and December 2009 to one medical ICU. During the first 7 days following ICU admission, CrCl was measured from 24-hr urine samples (24-hr-UV/P creatinine) and estimated according to Cockcroft-Gault formula and the simplified Modification of Diet in Renal Disease (MDRD) equation. High CrCl was defined as CrCl >140 ml/min/1.73 m2 by 24-hr-UV/P creatinine. Diagnostic accuracy was performed with ROC curves analysis. Thirty two patients were included. High CrCl was present in 8 patients (25%) on ICU admission and in 15 patients (47%) during the first 7 ICU days for a median duration of 3 (1-4) days. For the Cockcroft-Gault formula, the best threshold to predict high CrCl was 101 ml/min/1.73 m2 (sensitivity: 0.96, specificity: 0.75, AUC = 0.90 ± 0.03) with a negative likelihood ratio of 0.06. For the simplified MDRD equation, the best threshold to predict high CrCl was 108 ml/min/1.73 m2 (sensitivity: 0.91, specificity: 0.80, AUC = 0.88 ± 0.03) with a negative likelihood ratio of 0.11. There was no difference between the estimated methods in the diagnostic accuracy of identifying high CrCl (p = 0.30). High CrCl is frequently observed in ICU patients admitted with community-acquired acute infectious meningitis. The estimated methods of CrCl could be used as a screening tool to identify high CrCl.

Estimated glomerular filtration rate is an early biomarker of cardiac surgery-associated acute kidney injury.

PubMed

Candela-Toha, Ángel; Pardo, María Carmen; Pérez, Teresa; Muriel, Alfonso; Zamora, Javier

2018-04-20

and objective Acute kidney injury (AKI) diagnosis is still based on serum creatinine and diuresis. However, increases in creatinine are typically delayed 48h or longer after injury. Our aim was to determine the utility of routine postoperative renal function blood tests, to predict AKI one or 2days in advance in a cohort of cardiac surgery patients. Using a prospective database, we selected a sample of patients who had undergone major cardiac surgery between January 2002 and December 2013. The ability of the parameters to predict AKI was based on Acute Kidney Injury Network serum creatinine criteria. A cohort of 3,962 cases was divided into 2groups of similar size, one being exploratory and the other a validation sample. The exploratory group was used to show primary objectives and the validation group to confirm results. The ability to predict AKI of several kidney function parameters measured in routine postoperative blood tests, was measured with time-dependent ROC curves. The primary endpoint was time from measurement to AKI diagnosis. AKI developed in 610 (30.8%) and 623 (31.4%) patients in the exploratory and validation samples, respectively. Estimated glomerular filtration rate using the MDRD-4 equation showed the best AKI prediction capacity, with values for the AUC ROC curves between 0.700 and 0.946. We obtained different cut-off values for estimated glomerular filtration rate depending on the degree of AKI severity and on the time elapsed between surgery and parameter measurement. Results were confirmed in the validation sample. Postoperative estimated glomerular filtration rate using the MDRD-4 equation showed good ability to predict AKI following cardiac surgery one or 2days in advance. Copyright © 2018 Sociedad Española de Nefrología. Published by Elsevier España, S.L.U. All rights reserved.

[Prevalence and factors associated with renal disease among patients with newly diagnoses of HIV in Brazzaville, Republic of Congo].

PubMed

Ekat, M H; Courpotin, C; Diafouka, M; Akolbout, M; Mahambou-Nsonde, D; Bitsindou, P R; Nzounza, P; Simon, B

2013-05-01

The aim of this study was to determine the prevalence of kidney disease in patients newly diagnosed as HIV-positive in Brazzaville and to identify the associated risk factors. Descriptive and analytical study of patients diagnosed with HIV infection at the Ambulatory Treatment Center in Brazzaville, Republic of Congo, from January 1, 2009, through December 31, 2010. Estimated glomerular filtration rate (eGFR) was assessed with the Modification of Diet in Renal Disease equation (MDRD-GFR), and kidney disease was defined by an eGFR less than 60 mL/min/1.73 m(2). We conducted a univariate and then a multivariate logistic regression analysis to determine the factors associated with kidney disease in this population. The study included 562 patients newly identified as HIV-infected, 66.13% of whom were women. Their median age was 38.84 years interquartile range (IQR): 33.18-46.23) and their median body mass index (BMI) 20.31 kg/m(2) (IQR: 17.97-22.89). Their median CD4 count was 192 cells/mm(3) (IQR: 81-350), and 70.8% were at WHO stage III/IV. Finally, the median MDRD-GFR was 95.59 (IQR: 78.76-114.92) mL/min/1.73 m(2) and 8.5% had a GFR less than 60 mL/min/1.73 m(2), that is, moderate impairment of kidney function. The only factor associated with kidney disease in the multivariate analysis was a BMI less than 18.5 kg/m(2) (adjusted odds ratio: 2.54, 95% confidence interval: 1.25-5.15, p = 0.01). The prevalence of kidney disease in patients newly diagnosed with HIV in Brazzaville is relatively high. The only factor associated with it in the multivariate analysis was a BMI less than 18.5 kg/m(2).

Relationship of glomerular filtration rate and serum CK activity after resistance exercise in women.

PubMed

Machado, Marco; Zini, Elida N; Valadão, Samara D; Amorim, Mayra Z; Barroso, Tiago Z; de Oliveira, Wilkes

2012-04-01

The aim of study was to assess the correlation between the changes in serum CK activity after a resistance exercise and renal function measured by glomerular filtration rate (eGFR). Twenty-nine trained women (32 ± 10 years; 157 ± 4 cm; 58.8 ± 6.4 kg) performed a resistance exercise session with 17 exercises with 3 × 12 repetitions in a circuit training fashion. Subjects provided blood samples prior to exercise session (PRE), and at 24, 48, and 72 h following exercise session for creatine kinase (CK) and creatinine. 24-Urine samples were collected before and 72 h after exercises. eGFR was obtained by the three most recommended methods (MDRD; MCQE; Cockcroft-Gault). After the exercise session, serum CK activity increase up 1.68 times (P < 0.01). Serum creatinine increased 25.5% (P = 0.0000) while urinary creatinine decreased on average 6.4% (P = 0.0422). eGFR decreased in all formulas: MDRD by 21.5%, MCQE by 14.2%, and C-G by 17% (all with P < 0.01). Ccr also decreased (-22.9%, P < 0.01). The index of correlation was significant for MDRD (r = -0.924; P < 0.01), C-G (r = -0.884; P < 0.01), and MQCE (r = -0.644; P < 0.05). In conclusion, we observed a significant negative correlation between CK activity and the eGFR indices of renal function.

Are cystatin C-based equations superior to creatinine-based equations for estimating GFR in Chinese elderly population?

PubMed

Pei, Xiaohua; Liu, Qiao; He, Juan; Bao, Lihua; Yan, Chengjing; Wu, Jianqing; Zhao, Weihong

2012-12-01

Cystatin C has been proposed as a surrogate marker of kidney function. The elderly population accounts for the largest proportion of chronic kidney disease (CKD) patients. The aim of this study was to assess the diagnostic value of serum cystatin C and compare the applicability of cystatin C-based equations with serum creatinine (Scr)-based equations for estimating glomerular filtration rate (GFR). The estimated GFR (eGFR) values from six cystatin C-based equations (Tan, MacIsaac, Ma, Stevens1-3) and three Scr-based equations (CG, MDRD, CKD-EPI) were compared with the reference GFR (rGFR) values from 99mTc-DTPA renal dynamic imaging method. A total of 110 elderly Chinese (60-92 year, 71.05±7.62 year) were enrolled. Cystatin C had better diagnostic value than Scr (relationship coefficient with rGFR: cystatin C -0.847 vs. Scr -0.729, P<0.01; sensitivity: cystatin C 0.90 vs. Scr 0.55, P<0.01; AUCROC: cystatin C 0.857 vs. Scr 0.757, P<0.01). All the equations predicted GFR more accurately for rGFR≥60 ml/min/1.73 m2 than for rGFR<60 ml/min/1.73 m2. Most equations had acceptable accuracy. The cystatin C-based equations deviated from rGFR by -12.78 ml/min/1.73 m2 to -2.12 ml/min/1.73 m2, with accuracy varying from 64.6 to 82.7%. The Scr-based equations deviated from rGFR by -5.37 ml/min/1.73 m2 to -0.68 ml/min/1.73 m2, with accuracy varying from 77.3 to 79.1%. The CKD-EPI, MacIsaac and Ma equations predicted no bias with rGFR (P>0.05), with higher accuracy and lower deviation in the total group. The MacIsaac, CKD-EPI and Stevens3 equations could be optimal for those with normal and mildly impaired kidney function, whereas the Ma equation for those with CKD. Cystatin C is a promising kidney function marker. However, not all cystatin C-based equations could be superior to the Scr-equations.

Do word-problem features differentially affect problem difficulty as a function of students' mathematics difficulty with and without reading difficulty?

PubMed

Powell, Sarah R; Fuchs, Lynn S; Fuchs, Douglas; Cirino, Paul T; Fletcher, Jack M

2009-01-01

This study examined whether and, if so, how word-problem features differentially affect problem difficulty as a function of mathematics difficulty (MD) status: no MD (n = 109), MD only (n = 109), or MD in combination with reading difficulties (MDRD; n = 109). The problem features were problem type (total, difference, or change) and position of missing information in the number sentence representing the word problem (first, second, or third position). Students were assessed on 14 word problems near the beginning of third grade. Consistent with the hypothesis that mathematical cognition differs as a function of MD subtype, problem type affected problem difficulty differentially for MDRD versus MD-only students; however, the position of missing information in word problems did not. Implications for MD subtyping and for instruction are discussed.

Differences in urine cadmium associations with kidney outcomes based on serum creatinine and cystatin C

PubMed Central

Weaver, Virginia M.; Kim, Nam-Soo; Lee, Byung-Kook; Parsons, Patrick J.; Spector, June; Fadrowski, Jeffrey; Jaar, Bernard G.; Steuerwald, Amy J.; Todd, Andrew C.; Simon, David; Schwartz, Brian S.

2011-01-01

Cadmium is a well known nephrotoxicant; chronic exposure increases risk for chronic kidney disease. Recently, however, associations between urine cadmium and higher creatinine-based estimated glomerular filtration rate (eGFR) have been reported. Analyses utilizing alternate biomarkers of kidney function allow evaluation of potential mechanisms for these observations. We compared associations of urine cadmium with kidney function measures based on serum cystatin C to those with serum creatinine in 712 lead workers. Mean (standard deviation) molybdenum-corrected urine cadmium, Modification of Diet in Renal Disease (MDRD) eGFR and multi-variable cystatin C eGFR were 1.02 (0.65) μg/g creatinine, and 97.4 (19.2) and 112.0 (17.7) mL/min/1.73 m2, respectively. The eGFR measures were moderately correlated (rs = 0.5; p less than 0.001). After adjustment, ln(urine cadmium) was not associated with serum cystatin-C-based measures. However, higher ln(urine cadmium) was associated with higher creatinine-based eGFRs including the MDRD and an equation incorporating serum cystatin C and creatinine (beta-coefficient = 4.1 ml/min/1.73 m2; 95% confidence interval =1.6, 6.6). Urine creatinine was associated with serum creatinine-based but not cystatin-C-based eGFRs. These results support a biomarker-specific, rather than a kidney function, effect underlying the associations observed between higher urine cadmium and creatinine-based kidney function measures. Given the routine use of serum and urine creatinine in kidney and biomarker research, additional research to elucidate the mechanism(s) for these associations is essential. PMID:21871619

Association Between Optic Disc Hemorrhage and Renal Function in South Korea.

PubMed

Lee, Jae Yeun; Kim, Joon Mo; Shim, Seong Hee; Lee, Jin Young; Yoo, Chungkwon; Won, Yu Sam; Hyun, Young Youl; Park, Ki Ho

2018-03-01

The purpose of this article is to investigate the relationship between renal function and disc hemorrhage (DH). This retrospective cross-sectional survey was conducted at Kangbuk Samsung Hospital Health Screening Center between August 2012 and July 2013, and a total of 168,044 participants at least 20 years of age who voluntarily visited the health screening center for systemic and ophthalmologic examinations, including fundus photography, were enrolled. All subjects underwent a physical examination and provided samples for laboratory analysis. Digital fundus photographs of both eyes were taken and reviewed. Estimated glomerular filtration rate (eGFR) was calculated from serum creatinine concentration using the Modification of Diet in Renal Disease (MDRD) formula and Cockcroft-Gault (CG) formula. Subjects were stratified by eGFR into quartiles. Among participants, 220 (0.1%) showed DH, and 2376 (1.6%) showed glaucomatous retinal nerve fiber layer defects. The DH group showed higher creatinine and lower eGFR than the non-DH group. A significant trend was observed among higher creatinine, decreased eGFR as obtained by the MDRD and CG formulas, and the prevalence of DH (P for trend ≤0.003, logistic regression analysis). A multiple logistic regression model adjusted for age, sex, hypertension, diabetes, and hyperlipidemia showed that the lowest eGFR quartiles estimated by MDRD and CG were significantly associated with DH compared with the highest eGFR quartile (adjusted odds ratio, 1.96; 95% confidence interval, 1.22-3.14 by CG, 1.86; 95% confidence interval, 1.17-2.96 by MDRD). Renal function impairment was independently associated with a higher prevalence of DH in a South Korean population.

Change in Renal Function among HIV-Infected Koreans Receiving Tenofovir Disoproxil Fumarate-Backbone Antiretroviral Therapy: A 3-Year Follow-Up Study.

PubMed

Lee, Kyoung Hwa; Lee, Ji Un; Ku, Nam Su; Jeong, Su Jin; Han, Sang Hoon; Choi, Jun Yong; Song, Young Goo; Kim, June Myung

2017-07-01

Tenofovir disoproxil fumarate (TDF) is commonly prescribed as a fixed-dose, co-formulated antiretroviral drug for HIV-1 infection. The major concern of long-term TDF use is renal dysfunction. However, little is known about the long-term patterns of changes in renal function in HIV-infected Koreans receiving TDF. We prospectively followed 50 HIV-infected Koreans, performing laboratory tests every 3 months during the first year and every 6 months for the next 2 years. Urine N-acetyl-β-D-glucosaminidase (NAG) and plasma cystatin-C were measured using samples collected in the first year. Data on renal function were retrospectively collected on HIV-infected patients receiving first-line TDF (n=40) and in antiretroviral therapy (ART)-naïve patients (n=24) for 3 years. Renal function was evaluated as estimated glomerular filtration rate (eGFR) from serum creatinine [Modification of Diet in Renal Disease (MDRD)] and cystatin-C. The eGFR (cystatin-C) showed significant changes from 0 to 48 wks (p=0.002), with the lowest levels at 24 wks (84.3±18.8 mL/min vs. 90.3±22.5 mL/min, p=0.021 by post hoc test). Urine NAG levels did not differ at 0, 12, 24, and 48 wks, although eGFR (MDRD) significantly decreased from 0 (98.7±18.9 mL/min/1.73 m²) to 144 wks (89.0±14.7 mL/min/1.73 m²) (p=0.010). The first-line TDF group had significantly lower eGFR (MDRD) than the ART-naïve group at 144 wks (89.7 mL/min/1.73 m² vs. 98.4 mL/min/1.73 m², p=0.036). Thirteen (26%) participants experienced a decrease in renal impairment of 10 mL/min/1.73 m² in eGFR (MDRD) at 144 wks. These data suggest that clinically meaningful renal injury can develop in HIV-infected Koreans receiving long-term TDF. © Copyright: Yonsei University College of Medicine 2017

Serum cystatin C is independently associated with renal impairment and high sensitivity C-reactive protein in systemic lupus erythematosus.

PubMed

Chew, Christine; Pemberton, Philip W; Husain, Awal Al-M; Haque, Sahena; Bruce, Ian N

2013-01-01

In systemic lupus erythematosus (SLE) patients, glomerular filtration rate (GFR) is usually estimated using the modified Cockcroft-Gault (mCG) and Modification of Diet in Renal Disease (MDRD) equations. We aimed to study cystatin C (sCysC) in SLE to assess its agreement with standard renal indices and investigate factors affecting sCysC in SLE. SLE patients (≥4 ACR criteria) and healthy women from Greater Manchester were recruited and clinical assessments were undertaken. SCysC was measured using R & D Systems' ELISA. Agreement between renal measures was assessed using Deming plots and factors associated with sCysC in SLE were examined by multiple linear regression analyses. 178 patients and 68 controls had median (IQR) ages of 53 (46-61) and 50 (39-60) years, respectively. In an age-adjusted analysis, SLE patients had higher sCysC (1.16 [0.98-1.36] vs. 0.950 [0.73-1.13] mg/l; p<0.0001) and within SLE those with a history of lupus nephritis had higher sCysC (1.31 [1.10-1.66] vs. 1.11 [0.95-1.29] mg/l; p<0.005). SCysC correlated positively with serum creatinine, and inversely to renal measures (r=-0.530; p<0.0001 [mCG], and r=-0.620; p<0.0001 [MDRD]). There was closer agreement between the two eGFR measures than between either eGFR measures and sCysC. In addition to age and serum creatinine, a multivariate analysis (β, p) found that high-sensitivity C-reactive protein (hs-CRP) (0.03, 0.026) was also independently associated with sCysC in SLE. In SLE, sCysC may be influenced by low grade inflammation as well as by renal dysfunction. Therefore, SCysC should not supplant current assessment of renal dysfunction in SLE.

Differences in urine cadmium associations with kidney outcomes based on serum creatinine and cystatin C

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

Weaver, Virginia M., E-mail: vweaver@jhsph.edu; Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD; Welch Center for Prevention, Epidemiology and Clinical Research, Johns Hopkins Medical Institutions, Baltimore, MD

Cadmium is a well-known nephrotoxicant; chronic exposure increases risk for chronic kidney disease. Recently, however, associations between urine cadmium and higher creatinine-based estimated glomerular filtration rate (eGFR) have been reported. Analyses utilizing alternate biomarkers of kidney function allow evaluation of potential mechanisms for these observations. We compared associations of urine cadmium with kidney function measures based on serum cystatin C to those with serum creatinine in 712 lead workers. Mean (standard deviation) molybdenum-corrected urine cadmium, Modification of Diet in Renal Disease (MDRD) eGFR and multi-variable cystatin C eGFR were 1.02 (0.65) {mu}g/g creatinine, and 97.4 (19.2) and 112.0 (17.7) mL/min/1.73more » m{sup 2}, respectively. The eGFR measures were moderately correlated (r{sub s}=0.5; p<0.001). After adjustment, ln (urine cadmium) was not associated with serum cystatin-C-based measures. However, higher ln (urine cadmium) was associated with higher creatinine-based eGFRs including the MDRD and an equation incorporating serum cystatin C and creatinine (beta-coefficient=4.1 mL/min/1.73 m{sup 2}; 95% confidence interval=1.6, 6.6). Urine creatinine was associated with serum creatinine-based but not cystatin-C-based eGFRs. These results support a biomarker-specific, rather than a kidney function, effect underlying the associations observed between higher urine cadmium and creatinine-based kidney function measures. Given the routine use of serum and urine creatinine in kidney and biomarker research, additional research to elucidate the mechanism(s) for these associations is essential.« less

Effects of Fact Retrieval Tutoring on Third-Grade Students with Math Difficulties with and without Reading Difficulties.

PubMed

Powell, Sarah R; Fuchs, Lynn S; Fuchs, Douglas; Cirino, Paul T; Fletcher, Jack M

2009-01-01

The purpose of this study was to assess the efficacy of fact retrieval tutoring as a function of math difficulty (MD) subtype, that is, whether students have MD alone (MD-only) or have concurrent difficulty with math and reading (MDRD). Third graders (n = 139) at two sites were randomly assigned, blocking by site and MD subtype, to four tutoring conditions: fact retrieval practice, conceptual fact retrieval instruction with practice, procedural computation/estimation instruction, and control (no tutoring). Tutoring occurred for 45 sessions over 15weeks for 15-25 minutes per session. Results provided evidence of an interaction between tutoring condition and MD subtype status for assessment of fact retrieval. For MD-only students, students in both fact retrieval conditions achieved comparably and outperformed MD-only students in the control group as well as those in the procedural computation/estimation instruction group. By contrast, for MDRD students, there were no significant differences among intervention conditions.

Effects of Fact Retrieval Tutoring on Third-Grade Students with Math Difficulties with and without Reading Difficulties

PubMed Central

Powell, Sarah R.; Fuchs, Lynn S.; Fuchs, Douglas; Cirino, Paul T.; Fletcher, Jack M.

2009-01-01

The purpose of this study was to assess the efficacy of fact retrieval tutoring as a function of math difficulty (MD) subtype, that is, whether students have MD alone (MD-only) or have concurrent difficulty with math and reading (MDRD). Third graders (n = 139) at two sites were randomly assigned, blocking by site and MD subtype, to four tutoring conditions: fact retrieval practice, conceptual fact retrieval instruction with practice, procedural computation/estimation instruction, and control (no tutoring). Tutoring occurred for 45 sessions over 15weeks for 15–25 minutes per session. Results provided evidence of an interaction between tutoring condition and MD subtype status for assessment of fact retrieval. For MD-only students, students in both fact retrieval conditions achieved comparably and outperformed MD-only students in the control group as well as those in the procedural computation/estimation instruction group. By contrast, for MDRD students, there were no significant differences among intervention conditions. PMID:19448840

Serum 6-Bromotryptophan Levels Identified as a Risk Factor for CKD Progression.

PubMed

Tin, Adrienne; Nadkarni, Girish; Evans, Anne M; Winkler, Cheryl A; Bottinger, Erwin; Rebholz, Casey M; Sarnak, Mark J; Inker, Lesley A; Levey, Andrew S; Lipkowitz, Michael S; Appel, Lawrence J; Arking, Dan E; Coresh, Josef; Grams, Morgan E

2018-05-18

Background Metabolite levels reflect physiologic homeostasis and may serve as biomarkers of disease progression. Identifying metabolites associated with APOL1 risk alleles-genetic variants associated with CKD risk commonly present in persons of African descent-may reveal novel markers of CKD progression relevant to other populations. Methods We evaluated associations between the number of APOL1 risk alleles and 760 serum metabolites identified via untargeted profiling in participants of the African American Study of Kidney Disease and Hypertension (AASK) ( n =588; Bonferroni significance threshold P <6.5×10 -5 ) and replicated findings in 678 black participants with CKD in Bio Me , an electronic medical record-linked biobank. We tested the metabolite association with CKD progression in AASK, Bio Me , and the Modification of Diet in Renal Disease (MDRD) Study. Results One metabolite, 6-bromotryptophan, was significant in AASK ( P =4.7×10 -5 ) and replicated in Bio Me ( P =5.7×10 -3 ) participants, with lower levels associated with more APOL1 risk alleles. Lower levels of 6-bromotryptophan were associated with CKD progression in AASK and Bio Me participants and in white participants in the MDRD Study, independent of demographics and clinical characteristics, including baseline GFR (adjusted hazard ratio per two-fold higher 6-bromotryptophan level, AASK, 0.76; 95% confidence interval [95% CI], 0.64 to 0.91; Bio Me , 0.61; 95% CI, 0.43 to 0.85; MDRD, 0.52; 95% CI, 0.34 to 0.79). The interaction between the APOL1 risk alleles and 6-bromotryptophan was not significant. The identity of 6-bromotryptophan was confirmed in experiments comparing its molecular signature with that of authentic standards of other bromotryptophan isomers. Conclusions Serum 6-bromotryptophan is a consistent and novel risk factor for CKD progression. Copyright © 2018 by the American Society of Nephrology.

Performance of Chronic Kidney Disease Epidemiology Collaboration Creatinine-Cystatin C Equation for Estimating Kidney Function in Cirrhosis

PubMed Central

Mindikoglu, Ayse L.; Dowling, Thomas C.; Weir, Matthew R.; Seliger, Stephen L.; Christenson, Robert H.; Magder, Laurence S.

2013-01-01

Conventional creatinine-based glomerular filtration rate (GFR) equations are insufficiently accurate for estimating GFR in cirrhosis. The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) recently proposed an equation to estimate GFR in subjects without cirrhosis using both serum creatinine and cystatin C levels. Performance of the new CKD-EPI creatinine-cystatin C equation (2012) was superior to previous creatinine- or cystatin C-based GFR equations. To evaluate the performance of the CKD-EPI creatinine-cystatin C equation in subjects with cirrhosis, we compared it to GFR measured by non-radiolabeled iothalamate plasma clearance (mGFR) in 72 subjects with cirrhosis. We compared the “bias”, “precision” and “accuracy” of the new CKD-EPI creatinine-cystatin C equation to that of 24-hour urinary creatinine clearance (CrCl), Cockcroft-Gault (CG) and previously reported creatinine- and/or cystatin C-based GFR-estimating equations. Accuracy of CKD-EPI creatinine-cystatin C equation as quantified by root mean squared error of difference scores [differences between mGFR and estimated GFR (eGFR) or between mGFR and CrCl, or between mGFR and CG equation for each subject] (RMSE=23.56) was significantly better than that of CrCl (37.69, P=0.001), CG (RMSE=36.12, P=0.002) and GFR-estimating equations based on cystatin C only. Its accuracy as quantified by percentage of eGFRs that differed by greater than 30% with respect to mGFR was significantly better compared to CrCl (P=0.024), CG (P=0.0001), 4-variable MDRD (P=0.027) and CKD-EPI creatinine 2009 (P=0.012) equations. However, for 23.61% of the subjects, GFR estimated by CKD-EPI creatinine-cystatin C equation differed from the mGFR by more than 30%. CONCLUSIONS The diagnostic performance of CKD-EPI creatinine-cystatin C equation (2012) in patients with cirrhosis was superior to conventional equations in clinical practice for estimating GFR. However, its diagnostic performance was substantially worse than reported in subjects without cirrhosis. PMID:23744636

Probability of reduced renal function after contrast-enhanced CT: a model based on serum creatinine level, patient age, and estimated glomerular filtration rate.

PubMed

Herts, Brian R; Schneider, Erika; Obuchowski, Nancy; Poggio, Emilio; Jain, Anil; Baker, Mark E

2009-08-01

The objectives of our study were to develop a model to predict the probability of reduced renal function after outpatient contrast-enhanced CT (CECT)--based on patient age, sex, and race and on serum creatinine level before CT or directly based on estimated glomerular filtration rate (GFR) before CT--and to determine the relationship between patients with changes in creatinine level that characterize contrast-induced nephropathy and patients with reduced GFR after CECT. Of 5,187 outpatients who underwent CECT, 963 (18.6%) had serum creatinine levels obtained within 6 months before and 4 days after CECT. The estimated GFR was calculated before and after CT using the four-variable Modification of Diet in Renal Disease (MDRD) Study equation. Pre-CT serum creatinine level, age, race, sex, and pre-CT estimated GFR were tested using multiple-variable logistic regression models to determine the probability of having an estimated GFR of < 60 and < 45 mL/min/1.73 m(2) after CECT. Two thirds of the patients were used to create and one third to test the models. We also determined discordance between patients who met standard definitions of contrast-induced nephropathy and those with a reduced estimated GFR after CECT. Significant (p < 0.002) predictors for a post-CT estimated GFR of < 60 mL/min/1.73 m(2) were age, race, sex, pre-CT serum creatinine level, and pre-CT estimated GFR. Sex, serum creatinine level, and pre-CT estimated GFR were significant factors (p < 0.001) for predicting a post-CT estimated GFR of < 45 mL/min/1.73 m(2). The probability is [exp(y) / (1 + exp(y))], where y = 6.21 - (0.10 x pre-CT estimated GFR) for an estimated GFR of < 60 mL/min/1.73 m(2), and y = 3.66 - (0.087 x pre-CT estimated GFR) for an estimated GFR of < 45 mL/min/1.73 m(2). A discrepancy between those who met contrast-induced nephropathy criteria by creatinine changes and those with a post-CT estimated GFR of < 60 mL/min/1.73 m(2) was detected in 208 of the 963 patients (21.6%). The probability of a reduced estimated GFR after CECT can be predicted by the pre-CT estimated GFR using the four-variable MDRD equation. Furthermore, standard criteria for contrast-induced nephropathy are poor predictors of poor renal function after CECT. Criteria need to be established for what is an acceptable risk to manage patients undergoing CECT.

[Renal insufficiency and clinical outcomes in patients with acute coronary syndrome undergoing percutaneous coronary intervention: a multi-centre study].

PubMed

Huo, Yong; Ho, Wa

2007-12-18

To investigate the association of renal insufficiency and clinical outcomes in patients with acute coronary syndrome(ACS). The study was a multi-centre register study including 3,589 ACS patients coming from 39 centers across China who had received percutaneous coronary intervention(PCI) prior to 1st February, 2007. Estimated glomerular filtration rate (eGFR) was calculated for all patients using the 4-variable MDRD equation with the serum creatinine obtained before angiography. The association between renal insufficiency and clinical outcomes and the presence of in-hospital death and bleeding was studied by Fisher's exact test. Multi-variable analysis on the risk factors of in-hospital bleeding was done by logistic regression test. The mean age of the study population was (61.74+/-11.37) years (ranging from 23 years to 92 years)and 76.5% (2,746/3,589) of the population was male. Only 90 patients (2.51%) were known to have chronic kidney disease at the time of admission and 144 patients(4.01%) had serum creatinine levels above 133 micromol/L. However, after the evaluation of renal status by the MDRD equation, 2,250 patients (63.1%)showed a reduction in eGFR of less than 90 mL/min, of whom, 472 (13.1%) even reached the level of moderate renal insufficiency (eGFR<60 mL/min) and above. Seven patients(0.20%) were proved to have chronic total occlusion lesions(CTO) and eight (0.22%) needed shift to coronary artery bypass grafting (CABG) after angiography. Both the presence of CTO lesions and CABG were proved to be associated with decrease of renal function through Fisher's exact test (P= 0.005 8 and 0.041, respectively). The in-hospital mortality rate was 0.47%(17/3 589) which was associated with the degree of renal insufficiency (P=0.001 3). A total of 75 patients(2.09%) of in-hospital bleeding were recorded with 26 patients(0.72%) diagnosed as major bleeding events. 92% (69/75) of the bleeding events occurred after PCI. Bleeding was found to be associated with the degree of renal insufficiency in every type of antithrombotic therapy (P<0.001). After adjusting with other variables by logistic regression test, renal insufficiency (eGFR per 10 mL/min decrease, OR=1.133, 95% CI 1.011- 1.27, P=0.032)and age (above 65 years, OR=1.907, 95% CI 1.107-3.28, P=0.02) were proved to be the risk factors of in-hospital bleeding. Renal insufficiency is very common in ACS patients but self-report rate is low among this population. Renal function evaluated by eGFR should be carried out for every patient hospitalized for ACS for risk stratification. Patients with severer renal insufficiency usually have more complicated clinical manifestations and a higher rate of in-hospital bleeding.

Proenkephalin, Neutrophil Gelatinase-Associated Lipocalin, and Estimated Glomerular Filtration Rates in Patients With Sepsis.

PubMed

Kim, Hanah; Hur, Mina; Lee, Seungho; Marino, Rossella; Magrini, Laura; Cardelli, Patrizia; Struck, Joachim; Bergmann, Andreas; Hartmann, Oliver; Di Somma, Salvatore

2017-09-01

Proenkephalin (PENK) has been suggested as a novel biomarker for kidney function. We investigated the diagnostic and prognostic utility of plasma PENK in comparison with neutrophil gelatinase-associated lipocalin (NGAL) and estimated glomerular filtration rates (eGFR) in septic patients. A total of 167 septic patients were enrolled: 99 with sepsis, 37 with septic shock, and 31 with suspected sepsis. PENK and NGAL concentrations were measured and GFR was estimated by using the isotope dilution mass spectrometry traceable-Modification of Diet in Renal Disease (MDRD) Study and three Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations: CKD-EPI(Cr), CDK-EPI(CysC), and CKD-EPI(Cr-CysC). The PENK, NGAL, and eGFR results were compared according to sepsis severity, presence or absence of acute kidney injury (AKI), and clinical outcomes. The PENK, NGAL, and eGFR results were significantly associated with sepsis severity and differed significantly between patients with and without AKI only in the sepsis group (all P<0.05). PENK was superior to NGAL in predicting AKI (P=0.022) and renal replacement therapy (RRT) (P=0.0085). Regardless of the variable GFR category by the different eGFR equations, PENK showed constant and significant associations with all eGFR equations. Unlike NGAL, PENK was not influenced by inflammation and predicted the 30-day mortality. PENK is a highly sensitive and objective biomarker of AKI and RRT and is useful for prognosis prediction in septic patients. With its diagnostic robustness and predictive power for survival, PENK constitutes a promising biomarker in critical care settings including sepsis. © The Korean Society for Laboratory Medicine

Baseline renal insufficiency and risk of death among HIV-infected adults on antiretroviral therapy in Lusaka, Zambia

PubMed Central

Mulenga, Lloyd B.; Kruse, Gina; Lakhi, Shabir; Cantrell, Ronald A.; Reid, Stewart E.; Zulu, Isaac; Stringer, Elizabeth M.; Krishnasami, Zipporah; Mwinga, Alwyn; Saag, Michael S.; Stringer, Jeffrey S. A.; Chi, Benjamin H.

2009-01-01

Objective To examine the association between baseline renal insufficiency and mortality among adults initiating antiretroviral therapy (ART) in urban African setting. Design Open cohort evaluation Methods We examined mortality according to baseline renal function among adults initiating ART in Lusaka, Zambia. Renal function was assessed by the Cockcroft-Gault method, the Modification of Diet in Renal Disease (MDRD) equation, and serum creatinine. Results From April 2004 to September 2007, 25,779 individuals started ART with an available creatinine measurement at baseline. When creatinine clearance was calculated by the Cockcroft-Gault method, 8,456 (33.5%) had renal insufficiency: 73.5% were mild (60-89 mL/min), 23.4% moderate (30-59 mL/min), and 3.1% severe (<30 mL/min). Risk for mortality at or before 90 days was elevated for those with mildly (adjusted hazard ratio [AHR]=1.7; 95%CI=1.5-1.9), moderately (AHR=2.3; 95%CI=2.0-2.7), and severely (AHR=4.1; 95%CI=3.1-5.5) reduced creatinine clearance. Mild (AHR=1.4; 95%CI=1.2-1.6), moderate (AHR=1.9; 95%CI=1.5-2.3), and severe (AHR=3.6; 95%CI=2.4-5.5) insufficiency were also associated with increased mortality after 90 days, when compared to those with normal renal function. Trends were similar when renal function was estimated with MDRD or serum creatinine. Conclusions Renal insufficiency at time of ART initiation was prevalent and associated with increased mortality risk among adults in this population. These results have particular relevance for settings like Zambia, where tenofovir - a drug with known nephrotoxicity - has been adopted as part of first-line therapy. This emphasizes the need for resource-appropriate screening algorithms for renal disease, both as part of ART eligibility and pre-treatment assessment. PMID:18753939

[Impaired renal function: be aware of exogenous factors].

PubMed

van der Meijden, Wilbert A G; Smak Gregoor, Peter J H

2013-01-01

Renal function is currently estimated using the Modification of Diet in Renal Disease (MDRD) formula, which is partly based on the serum creatinine level. Patients with impaired renal function are referred to nephrologists in accordance with the Dutch national transmural agreement for 'Chronic renal impairment'. A 54-year-old woman without significant history was referred to analyse a coincidentally found decline in the estimated glomerular filtration rate (eGFR). The patient had no complaints and used no medication except creatine supplements. Additional diagnostic testing showed no abnormalities. After cessation of creatine supplementation, the calculated renal function normalized. Serum creatinine is a reflection of muscle mass. The use of creatine-containing dietary supplements, such as creatine ethyl ester, can influence serum creatinine levels and therefore the eGFR as calculated with the MDRD formula. The use of supplements deserves attention when taking the history.

Factors associated with renal function compensation after donor nephrectomy.

PubMed

Burballa, Carla; Crespo, Marta; Redondo-Pachón, Dolores; Pérez-Sáez, María José; Arias-Cabrales, Carlos; Mir, Marisa; Francés, Albert; Fumadó, Lluís; Cecchini, Lluís; Pascual, Julio

2018-05-14

Kidney transplant donors lose 50% of their renal mass after nephrectomy. The remaining kidney compensates for this loss and it is estimated that 70% of the baseline renal function prior to donation is recovered. Factors associated with post-donation renal compensation are not well understood. Retrospective study of 66 consecutive kidney donors (mean age 48.8 years, 74.2% women). We analysed the potential factors associated with the compensatory mechanisms of the remaining kidney by comparing donors according to their renal compensation rate (RCR) (Group A, infra-compensation [<70%]; Group B, normal compensation [>70%]). We compared Group A (n=38) and group B (n=28). Predictors for RCR>70% were higher baseline creatinine (A vs B: 0.73±0.14 vs 0.82±0.11; P=.03) and a lower baseline glomerular filtration rate (GFR), estimated both by MDRD-4 (A vs B: 97.7±18.8 vs 78.6±9.6ml/min; P<.001) and CKD-EPI (A vs B: 101.7±15 vs. 88.3±11.7ml/min; P≤.001). Age, gender, smoking, hypertension and GFR measured by Tc-DTPA did not show any correlation with the RCR. The multivariate analysis confirmed baseline estimated glomerular filtration rate (eGFR) to be a predictor of compensation: the higher the baseline eGFR, the lower the likelihood of >70% compensation (MDRD-4, OR=0.94 [95% CI 0.8-0.9], P=.01). The compensation rate decreased by 0.4% (P<.001) and 0.3% (P=.006) for every ml/min increase in baseline eGFR estimated by MDRD-4 and CKD-EPI, respectively. One year after living donor nephrectomy, the remaining kidney partially compensates baseline renal function. In our experience, baseline eGFR is inversely proportional to the one-year renal compensation rate. Copyright © 2018 Sociedad Española de Nefrología. Published by Elsevier España, S.L.U. All rights reserved.

Relation of N-terminal pro-brain natriuretic peptide levels and their prognostic power in chronic stable heart failure to obesity status.

PubMed

Frankenstein, Lutz; Remppis, Andrew; Nelles, Manfred; Schaelling, Bernd; Schellberg, Dieter; Katus, Hugo; Zugck, Christian

2008-11-01

To investigate the relationship between body mass index (BMI) and N-terminal pro-brain natriuretic peptide (NTproBNP) level and resultant prognostic capacity in chronic heart failure (CHF) controlled for known confounders. We formed 206 triplets of patients (n = 618) with stable systolic CHF matched with respect to age, sex, renal function (MDRD, modification of diet in renal disease formula), and NYHA class, each with a BMI >30 kg/m(2) (group 3), 20-24.9 kg/m(2) (group 1), and 25-29.9 kg/m(2) (group 2). BMI conveys a 4% drop in NTproBNP per unit increase. This influence remained significant after correction for age, sex, MDRD, NYHA, heart rate, rhythm, and ejection fraction. NTproBNP remained an independent predictor of adverse outcome after correction for age, sex, BMI, NYHA, MDRD, and ejection fraction. Despite numerical differences, prognostic power was comparable between BMI groups (log-transformed NTproBNP; group 1: hazard ratio (HR) 1.435, 95% CI 1.046-1.967, chi(2) 5.02, P = 0.03; group 2: HR 1.604, 95% CI 1.203-2.138, chi(2) 10.36, P = 0.001; group 3: HR 1.735, 95% CI 1.302-2.313, chi(2) 14.12, P = 0.0002) (P = NS, all). An NTproBNP correction factor was calculated. Even matched for NYHA, age, sex, and renal function, BMI exerts a significant and independent inverse influence on NTproBNP in patients with stable CHF. NTproBNP retained equal statistical power in all three BMI groups.

The association of genetic variants of type 2 diabetes with kidney function.

PubMed

Franceschini, Nora; Shara, Nawar M; Wang, Hong; Voruganti, V Saroja; Laston, Sandy; Haack, Karin; Lee, Elisa T; Best, Lyle G; Maccluer, Jean W; Cochran, Barbara J; Dyer, Thomas D; Howard, Barbara V; Cole, Shelley A; North, Kari E; Umans, Jason G

2012-07-01

Type 2 diabetes is highly prevalent and is the major cause of progressive chronic kidney disease in American Indians. Genome-wide association studies identified several loci associated with diabetes but their impact on susceptibility to diabetic complications is unknown. We studied the association of 18 type 2 diabetes genome-wide association single-nucleotide polymorphisms (SNPs) with estimated glomerular filtration rate (eGFR; MDRD equation) and urine albumin-to-creatinine ratio in 6958 Strong Heart Study family and cohort participants. Center-specific residuals of eGFR and log urine albumin-to-creatinine ratio, obtained from linear regression models adjusted for age, sex, and body mass index, were regressed onto SNP dosage using variance component models in family data and linear regression in unrelated individuals. Estimates were then combined across centers. Four diabetic loci were associated with eGFR and one locus with urine albumin-to-creatinine ratio. A SNP in the WFS1 gene (rs10010131) was associated with higher eGFR in younger individuals and with increased albuminuria. SNPs in the FTO, KCNJ11, and TCF7L2 genes were associated with lower eGFR, but not albuminuria, and were not significant in prospective analyses. Our findings suggest a shared genetic risk for type 2 diabetes and its kidney complications, and a potential role for WFS1 in early-onset diabetic nephropathy in American Indian populations.

Measuring and Estimating GFR and Treatment Effect in ADPKD Patients: Results and Implications of a Longitudinal Cohort Study

PubMed Central

Cannata, Antonio; Carrara, Fabiola; Cella, Claudia; Ferrari, Silvia; Stucchi, Nadia; Prandini, Silvia; Ene-Iordache, Bogdan; Diadei, Olimpia; Perico, Norberto; Ondei, Patrizia; Pisani, Antonio; Buongiorno, Erasmo; Messa, Piergiorgio; Dugo, Mauro; Remuzzi, Giuseppe

2012-01-01

Trials failed to demonstrate protective effects of investigational treatments on glomerular filtration rate (GFR) reduction in Autosomal Dominant Polycystic Kidney Disease (ADPKD). To assess whether above findings were explained by unreliable GFR estimates, in this academic study we compared GFR values centrally measured by iohexol plasma clearance with corresponding values estimated by Chronic Kidney Disease Epidemiology Collaboration (CKD-Epi) and abbreviated Modification of Diet in Renal Disease (aMDRD) formulas in ADPKD patients retrieved from four clinical trials run by a Clinical Research Center and five Nephrology Units in Italy. Measured baseline GFRs and one-year GFR changes averaged 78.6±26.7 and 8.4±10.3 mL/min/1.73 m2 in 111 and 71 ADPKD patients, respectively. CKD-Epi significantly overestimated and aMDRD underestimated baseline GFRs. Less than half estimates deviated by <10% from measured values. One-year estimated GFR changes did not detect measured changes. Both formulas underestimated GFR changes by 50%. Less than 9% of estimates deviated <10% from measured changes. Extent of deviations even exceeded that of measured one-year GFR changes. In ADPKD, prediction formulas unreliably estimate actual GFR values and fail to detect their changes over time. Direct kidney function measurements by appropriate techniques are needed to adequately evaluate treatment effects in clinics and research. PMID:22393413

Renal volume assessed by magnetic resonance imaging volumetry correlates with renal function in living kidney donors pre- and postdonation: a retrospective cohort study.

PubMed

Lange, Daniel; Helck, Andreas; Rominger, Axel; Crispin, Alexander; Meiser, Bruno; Werner, Jens; Fischereder, Michael; Stangl, Manfred; Habicht, Antje

2018-07-01

Renal function of potential living kidney donors is routinely assessed with scintigraphy. Kidney anatomy is evaluated by imaging techniques such as magnetic resonance imaging (MRI). We evaluated if a MRI-based renal volumetry is a good predictor of kidney function pre- and postdonation. We retrospectively analyzed the renal volume (RV) in a MRI of 100 living kidney donors. RV was correlated with the tubular excretion rate (TER) of MAG3-scintigraphy, a measured creatinine clearance (CrCl), and the estimated glomerular filtration rate (eGFR) by Cockcroft-Gault (CG), CKD-EPI, and modification of diet in renal disease (MDRD) formula pre- and postdonation during a follow-up of 3 years. RV correlated significantly with the TER (total: r = 0.6735, P < 0.0001). Correlation between RV and renal function was the highest for eGFR by CG (r = 0.5595, P < 0.0001), in comparison with CrCl, MDRD-GFR, and CKD-EPI-GFR predonation. RV significantly correlated with CG-GFR postdonation and predicted CG-GFR until 3 years after donation. MRI renal volumetry might be an alternative technique for the evaluation of split renal function and prediction of renal function postdonation in living kidney donors. © 2018 Steunstichting ESOT.

[Chronic kidney disease in Primary Health Care: prevalence and associated risk factors].

PubMed

Salvador González, Betlem; Rodríguez Pascual, Mercedes; Ruipérez Guijarro, Laura; Ferré González, Antonia; Cunillera Puertolas, Oriol; Rodríguez Latre, Luisa M

2015-04-01

To determine the prevalence of chronic kidney disease and associated risk factors in subjects over 60 years of age, as well as its staging by determining the glomerular filtration rate (GFR). Cross-sectional observational study. Primary Health Care. Patients≥60 years of age who were seen in 40 Primary Health Care centres with serum creatinine measured in a central laboratory between January 1 and December 31, 2010. kidney transplant, home care. Social-demographic and anthropometric data, cardiovascular risk factors, and diseases established according to electronic clinical records. Serum creatinine was measured using standardised Jaffe kinetic method, and GFR estimated with MDRD-4-IDMS and CKD-EPI. A total of 97,665 subjects (57.3% women, median age 70.0 years [Q1: 65.0, Q3: 77.0]). GFR-MDRD prevalence<60=15.1% (16.6% in women, 13.2% in men; P<.001) and increased with age. Multivariate analysis showed a positive association between GFR-MDRD<60 and age (OR=1.74; 95% CI 1.70 to 1.77), hypertension (OR=2.18; 95% CI 2.08 to 2.30), heart failure (OR=2.03; 95% CI 1.83 to 2.25), atrial fibrillation (OR=1.57; 95% CI 1.41 to 1.76), ischaemic heart disease (OR=1.40; 95% CI 1.30 to 1.50), peripheral arterial disease (OR=1.31; 95% CI 1.09 to 1.57), dyslipidaemia (OR=1.28; 95% CI 1.23 to 1.33), diabetes (OR=1.26; 95% CI 1.17 to 1.34), and stroke (OR=1.17; 95% CI 1.09 to 1.25). The GFR-CKD-EPI model showed an increase in OR with age and male sex, that became significant as a chronic kidney disease risk factor. Chronic kidney disease has considerable prevalence in subjects≥60 years seen in Primary Health Care, more in women, and increasing with age. Hypertension, more than diabetes, was the main associated cardiovascular risk factor. Copyright © 2014 Elsevier España, S.L.U. All rights reserved.

Serum metabolites are associated with all-cause mortality in chronic kidney disease.

PubMed

Hu, Jiun-Ruey; Coresh, Josef; Inker, Lesley A; Levey, Andrew S; Zheng, Zihe; Rebholz, Casey M; Tin, Adrienne; Appel, Lawrence J; Chen, Jingsha; Sarnak, Mark J; Grams, Morgan E

2018-06-02

Chronic kidney disease (CKD) involves significant metabolic abnormalities and has a high mortality rate. Because the levels of serum metabolites in patients with CKD might provide insight into subclinical disease states and risk for future mortality, we determined which serum metabolites reproducibly associate with mortality in CKD using a discovery and replication design. Metabolite levels were quantified via untargeted liquid chromatography and mass spectroscopy from serum samples of 299 patients with CKD in the Modification of Diet in Renal Disease (MDRD) study as a discovery cohort. Six among 622 metabolites were significantly associated with mortality over a median follow-up of 17 years after adjustment for demographic and clinical covariates, including urine protein and measured glomerular filtration rate. We then replicated associations with mortality in 963 patients with CKD from the African American Study of Kidney Disease and Hypertension (AASK) cohort over a median follow-up of ten years. Three of the six metabolites identified in the MDRD cohort replicated in the AASK cohort: fumarate, allantoin, and ribonate, belonging to energy, nucleotide, and carbohydrate pathways, respectively. Point estimates were similar in both studies and in meta-analysis (adjusted hazard ratios 1.63, 1.59, and 1.61, respectively, per doubling of the metabolite). Thus, selected serum metabolites were reproducibly associated with long-term mortality in CKD beyond markers of kidney function in two well characterized cohorts, providing targets for investigation. Copyright © 2018 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.

Prevalence of renal insufficiency in elderly cancer patients in a tertiary cancer center

PubMed Central

Pontes, Lucíola de Barros; Antunes, Yuri Philippe Pimentel Vieira; Bugano, Diogo Diniz Gomes; Karnakis, Theodora; del Giglio, Auro; Kaliks, Rafael Aliosha

2014-01-01

Objective To estimate the prevalence of abnormal glomerular filtration rate in elderly patients with solid tumors. Methods A retrospective study with patients aged >65 years diagnosed with solid tumors between January 2007 and December 2011 in a cancer center. The following data were collected: sex, age, serum creatinine at the time of diagnosis and type of tumor. Renal function was calculated using abbreviated Modification of Diet in Renal Disease (MDRD) formulae and then staged in accordance with the clinical practice guidelines published by the Working Group of the National Kidney Foundation. Results A total of 666 patients were included and 60% were male. The median age was 74.2 years (range: 65 to 99 years). The most prevalent diagnosis in the study population were colorectal (24%), prostate (20%), breast (16%) and lung cancer (16%). The prevalence of elevated serum creatinine (>1.0mg/dL) was 30%. However, when patients were assessed using abbreviated MDRD formulae, 66% had abnormal renal function, stratified as follows: 45% with stage 2, 18% with stage 3, 3% with stage 4 and 0.3% with stage 5. Conclusion To the best of our knowledge, this was the first study to estimate the frequency of renal insufficiency in elderly cancer patients in Brazil. The prevalence of abnormal renal function among our cohort was high. As suspected, the absolute creatinine level does underestimate renal function impairment and should not be used as predictor of chemotherapy metabolism, excretion and consequent toxicity. PMID:25295449

Math Disabilities: A Selective Meta-Analysis of the Literature

ERIC Educational Resources Information Center

Swanson, H. Lee; Jerman, Olga

2006-01-01

This article synthesizes published literature comparing the cognitive functioning of children who have math disabilities (MD) with that of (a) average-achieving children; (b) children who have reading disabilities (RD); and (c) children who have co-morbid disabilities (MD+RD). Average achievers outperformed children with MD on measures of verbal…

Neurobiological Underpinnings of Math and Reading Learning Disabilities

ERIC Educational Resources Information Center

Ashkenazi, Sarit; Black, Jessica M.; Abrams, Daniel A.; Hoeft, Fumiko; Menon, Vinod

2013-01-01

The primary goal of this review is to highlight current research and theories describing the neurobiological basis of math (MD), reading (RD), and comorbid math and reading disability (MD+RD). We first describe the unique brain and cognitive processes involved in acquisition of math and reading skills, emphasizing similarities and differences in…

PubMed

Medina Arnaudo, Gisel Ivana

2017-09-08

Resumen: La valoración del Índice de Filtrado Glomerular (IFG) es fundamental para la selección de potenciales donantes renales. Para su medición existen métodos poco prácticos y complejos, por lo cual se han desarrollado ecuaciones de estimación del IFG. Objetivo: Evaluar el rendimiento diagnóstico de ecuaciones de estimación del IFG a partir de Creatinina y Cistatina C en una población de adultos sanos candidatos a donantes renales. Materiales y métodos: Se llevó a cabo un estudio transversal en 72 pacientes de ambos sexos de entre 18 y 75 años de edad, candidatos a donantes renales. Se les midió el IFG a través del clearance de Iotalamato no marcado (IFGm). Se evaluaron cuatro ecuaciones de estimación del FG (IFGe): MDRD, del estudio "Modification of Diet in Renal Disease"; CKD-EPI-Creatinina (CKD-EPI-CREAT) y CKD-EPI-Creatinina y Cistatina C (CKD-EPI-CREAT+CIS), desarrolladas por el grupo "Chronic Kidney Disease Epidemiology Collaboration"; y la que incluye Creatinina y Cistatina C propuesta por Stevens y col. (STEVENS-CREAT+CIS). Se analizó el desempeño de cada ecuación con respecto al IFGm. Resultados: Las ecuaciones CKD-EPI-CREAT+CIS, STEVENS-CREAT+CIS y CKD-EPI-CREAT mostraron ser más exactas (bias= 1,93; -0,71; -1,53 mL/min/1,73m2 respectivamente) que MDRD (bias= -10,36 mL/min/1,73m2). El mejor rendimiento diagnóstico lo mostró  el IFGe CKD-EPI-CREAT+CIS (LR(+)=9,8; "Positive Likelihood Ratios"), seguido por IFGe STEVENS-CREAT+CIS (LR(+)=4,7) y luego por IFGe CKD-EPI-CREAT (LR(+)=3,7). Discusión: Las ecuaciones CKD-EPI-CREAT+CIS, STEVENS-CREAT+CIS y CKD-EPI-CREAT demostraron tener un desempeño claramente superior a MDRD para estimar el IFG en la población estudiada.

Assessing glomerular filtration rate (GFR) in critically ill patients with acute kidney injury - true GFR versus urinary creatinine clearance and estimating equations

PubMed Central

2013-01-01

Introduction Estimation of kidney function in critically ill patients with acute kidney injury (AKI), is important for appropriate dosing of drugs and adjustment of therapeutic strategies, but challenging due to fluctuations in kidney function, creatinine metabolism and fluid balance. Data on the agreement between estimating and gold standard methods to assess glomerular filtration rate (GFR) in early AKI are lacking. We evaluated the agreement of urinary creatinine clearance (CrCl) and three commonly used estimating equations, the Cockcroft Gault (CG), the Modification of Diet in Renal Disease (MDRD) and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations, in comparison to GFR measured by the infusion clearance of chromium-ethylenediaminetetraacetic acid (51Cr-EDTA), in critically ill patients with early AKI after complicated cardiac surgery. Methods Thirty patients with early AKI were studied in the intensive care unit, 2 to 12 days after complicated cardiac surgery. The infusion clearance for 51Cr-EDTA obtained as a measure of GFR (GFR51Cr-EDTA) was calculated from the formula: GFR (mL/min/1.73m2) = (51Cr-EDTA infusion rate × 1.73)/(arterial 51Cr-EDTA × body surface area) and compared with the urinary CrCl and the estimated GFR (eGFR) from the three estimating equations. Urine was collected in two 30-minute periods to measure urine flow and urine creatinine. Urinary CrCl was calculated from the formula: CrCl (mL/min/1.73m2) = (urine volume × urine creatinine × 1.73)/(serum creatinine × 30 min × body surface area). Results The within-group error was lower for GFR51Cr-EDTA than the urinary CrCl method, 7.2% versus 55.0%. The between-method bias was 2.6, 11.6, 11.1 and 7.39 ml/min for eGFRCrCl, eGFRMDRD, eGFRCKD-EPI and eGFRCG, respectively, when compared to GFR51Cr-EDTA. The error was 103%, 68.7%, 67.7% and 68.0% for eGFRCrCl, eGFRMDRD, eGFRCKD-EPI and eGFRCG, respectively, when compared to GFR51Cr-EDTA. Conclusions The study demonstrated poor precision of the commonly utilized urinary CrCl method for assessment of GFR in critically ill patients with early AKI, suggesting that this should not be used as a reference method when validating new methods for assessing kidney function in this patient population. The commonly used estimating equations perform poorly when estimating GFR, with high biases and unacceptably high errors. PMID:23767877

Enhancing the 'real world' prediction of cardiovascular events and major bleeding with the CHA2DS2-VASc and HAS-BLED scores using multiple biomarkers.

PubMed

Roldán, Vanessa; Rivera-Caravaca, José Miguel; Shantsila, Alena; García-Fernández, Amaya; Esteve-Pastor, María Asunción; Vilchez, Juan Antonio; Romera, Marta; Valdés, Mariano; Vicente, Vicente; Marín, Francisco; Lip, Gregory Y H

2018-02-01

Atrial fibrillation (AF)-European guidelines suggest the use of biomarkers to stratify patients for stroke and bleeding risks. We investigated if a multibiomarker strategy improved the predictive performance of CHA 2 DS 2 -VASc and HAS-BLED in anticoagulated AF patients. We included consecutive patients stabilized for six months on vitamin K antagonists (INRs 2.0-3.0). High sensitivity troponin T, NT-proBNP, interleukin-6, von Willebrand factor concentrations and glomerular filtration rate (eGFR; using MDRD-4 formula) were quantified at baseline. Time in therapeutic range (TTR) was recorded at six months after inclusion. Patients were follow-up during a median of 2375 (IQR 1564-2887) days and all adverse events were recorded. In 1361 patients, adding four blood biomarkers, TTR and MDRD-eGFR, the predictive value of CHA 2 DS 2 -VASc increased significantly by c-index (0.63 vs. 0.65; p = .030) and IDI (0.85%; p < .001), but not by NRI (-2.82%; p < .001). The predictive value of HAS-BLED increased up to 1.34% by IDI (p < .001). Nevertheless, the overall predictive value remains modest (c-indexes approximately 0.65) and decision curve analyses found lower net benefit compared with the originals scores. Addition of biomarkers enhanced the predictive value of CHA 2 DS 2 -VASc and HAS-BLED, although the overall improvement was modest and the added predictive advantage over original scores was marginal. Key Messages Recent atrial fibrillation (AF)-European guidelines for the first time suggest the use of biomarkers to stratify patients for stroke and bleeding risks, but their usefulness in real world for risk stratification is still questionable. In this cohort study involving 1361 AF patients optimally anticoagulated with vitamin K antagonists, adding high sensitivity troponin T, N-terminal pro-B-type natriuretic peptide, interleukin 6, von Willebrand factor, glomerular filtration rate (by the MDRD-4 formula) and time in therapeutic range, increased the predictive value of CHA 2 DS 2 -VASc for cardiovascular events, but not the predictive value of HAS-BLED for major bleeding. Reclassification analyses did not show improvement adding multiple biomarkers. Despite the improvement observed, the added predictive advantage is marginal and the clinical usefulness and net benefit over current clinical scores is lower.

Dietary Protein Intake and Chronic Kidney Disease

PubMed Central

Ko, Gang Jee; Obi, Yoshitsugu; Tortoricci, Amanda R.; Kalantar-Zadeh, Kamyar

2018-01-01

Purpose of review High protein intake may lead to increased intraglomerular pressure and glomerular hyperfiltration. This can cause damage to glomerular structure leading to or aggravating chronic kidney disease (CKD). Hence, a low protein diet (LPD) of 0.6–0.8 g/kg/day is often recommended for the management of CKD. We reviewed the effect of protein intake on incidence and progression of CKD and the role of LPD the CKD management. Recent findings Actual dietary protein consumption in CKD patients remain substantially higher than the recommendations for LPD. Notwithstanding the inconclusive results of the Modification of Diet in Renal Disease (MDRD) study, the largest randomized controlled trial to examine protein restriction in CKD, several prior and subsequent studies and meta-analyses including secondary analyses of the MDRD data appear to support the role of LPD on retarding progression of CKD and delaying initiation of maintenance dialysis therapy. LPD can also be used to control metabolic derangements in CKD. Supplemented LPD with essential amino acids or their keto-analogs may be used for incremental transition to dialysis especially in non-dialysis days. An LPD management in lieu of dialysis therapy can reduce costs, enhance psychological adaptation, and preserve residual renal function upon transition to dialysis. Adherence and adequate protein and energy intake should be ensured to avoid protein-energy wasting. Summary A balanced and individualized dietary approach based on LPD should be elaborated with periodic dietitian counselling and surveillance to optimize management of CKD, to assure adequate protein and energy intake and to avoid or correct protein-energy wasting. PMID:27801685

Comparing the association of GFR estimated by the CKD-EPI and MDRD study equations and mortality: the third national health and nutrition examination survey (NHANES III)

PubMed Central

2012-01-01

Background The Chronic Kidney Disease Epidemiology Collaboration equation for estimation of glomerular filtration rate (eGFRCKD-EPI) improves GFR estimation compared with the Modification of Diet in Renal Disease Study equation (eGFRMDRD) but its association with mortality in a nationally representative population sample in the US has not been studied. Methods We examined the association between eGFR and mortality among 16,010 participants of the Third National Health and Nutrition Examination Survey (NHANES III). Primary predictors were eGFRCKD-EPI and eGFRMDRD. Outcomes of interest were all-cause and cardiovascular disease (CVD) mortality. Improvement in risk categorization with eGFRCKD-EPI was evaluated using adjusted relative hazard (HR) and Net Reclassification Improvement (NRI). Results Overall, 26.9% of the population was reclassified to higher eGFR categories and 2.2% to lower eGFR categories by eGFRCKD-EPI, reducing the proportion of prevalent CKD classified as stage 3–5 from 45.6% to 28.8%. There were 3,620 deaths (1,540 from CVD) during 215,082 person-years of follow-up (median, 14.3 years). Among those with eGFRMDRD 30–59 ml/min/1.73 m2, 19.4% were reclassified to eGFRCKD-EPI 60–89 ml/min/1.73 m2 and these individuals had a lower risk of all-cause mortality (adjusted HR, 0.53; 95% CI, 0.34-0.84) and CVD mortality (adjusted HR, 0.51; 95% CI, 0.27-0.96) compared with those not reclassified. Among those with eGFRMDRD >60 ml/min/1.73 m2, 0.5% were reclassified to lower eGFRCKD-EPI and these individuals had a higher risk of all-cause (adjusted HR, 1.31; 95% CI, 1.01-1.69) and CVD (adjusted HR, 1.42; 95% CI, 1.01-1.99) mortality compared with those not reclassified. Risk prediction improved with eGFRCKD-EPI; NRI was 0.21 for all-cause mortality (p < 0.001) and 0.22 for CVD mortality (p < 0.001). Conclusions eGFRCKD-EPI categories improve mortality risk stratification of individuals in the US population. If eGFRCKD-EPI replaces eGFRMDRD in the US, it will likely improve risk stratification. PMID:22702805

Creatinine measurement on dry blood spot sample for chronic kidney disease screening.

PubMed

Silva, Alan Castro Azevedo E; Gómez, Juan Fidel Bencomo; Lugon, Jocemir Ronaldo; Graciano, Miguel Luis

2016-03-01

Chronic kidney disease (CKD) screening is advisable due to its high morbidity and mortality and is usually performed by sampling blood and urine. Here we present an innovative and simpler method, by measuring creatinine on a dry blood spot on filter paper. One-hundred and six individuals at high risk for CKD were enrolled. The creatinine values obtained using both tests and the demographic data of each participant allowed us to determinate the eGFR. The adopted cutoff for CKD was an eGFR < 60 ml/min. Mean age was 57 ± 12 years, 74% were female, 40% white, and 60% non-white. Seventy-six percent were hypertensive, 30% diabetic, 37% had family history of CKD, and 22% of smoking. The BMI was 29.5 ± 6.9 kg/m2, median systolic blood pressure was 125 mmHg (IQR 120-140 mmHg) and median diastolic blood pressure was 80 mmHg (IQR 70-80 mmHg). According to MDRD equation, sensitivity was 96%, specificity 55%, predictive positive value 96%, predictive negative value 55% and accuracy 92%. By the CKD-EPI equation the sensitivity was 94%, specificity 55%, predictive positive value 94%, predictive negative value 55% and accuracy 90%. A Bland and Altman analysis showed a relatively narrow range of creatinine values differences (+ 0.68mg/dl to -0.55mg/dl) inside the ± 1.96 SD, without systematic differences. Measurement of creatinine on dry blood sample is an easily feasible non-invasive diagnostic test with good accuracy that may be useful to screen chronic kidney disease.

Community-based study on CKD subjects and the associated risk factors.

PubMed

Chen, Nan; Wang, Weiming; Huang, Yanping; Shen, Pingyan; Pei, Daoling; Yu, Haijin; Shi, Hao; Zhang, Qianying; Xu, Jing; Lv, Yilun; Fan, Qishi

2009-07-01

The study was performed to investigate the prevalence, awareness and the risk factors of chronic kidney disease (CKD) in the community population in Shanghai, China. A total of 2596 residents were randomly recruited from the community population in Shanghai, China. All were screened for albuminuria, haematuria, morning spot urine albumin-to-creatinine ratio and renal function. Serum creatinine, uric acid, cholesterol, triglyceride and haemoglobin were assessed. A simplified MDRD equation was used to estimate the glomerular filtration rate (eGFR). All studied subjects were screened by kidney ultrasound. Haematuria, if present in the morning spot urine dipstick test, was confirmed by microscopy. The associations among the demographic characteristics, health characteristics and indicators of kidney damage were examined. Two thousand five hundred and fifty-four residents (n = 2554), after giving informed consent and with complete data, were entered into this study. Albuminuria and haematuria were detected in 6.3% and 1.2% of all the studied subjects, respectively, whereas decreased kidney function was found in 5.8% of all studied subjects. Approximately 11.8% of subjects had at least one indicator of kidney damage. The rate of awareness of CKD was 8.2%. The logistic regression model showed that age, central obesity, hypertension, diabetes, anaemia, hyperuricaemia and nephrolithiasis each contributed to the development of CKD. This is the first Shanghai community-based epidemiological study data on Chinese CKD patients. The prevalence of CKD in the community population in Shanghai is 11.8%, and the rate of awareness of CKD is 8.2%. All the factors including age, central obesity, hypertension, diabetes, anaemia, hyperuricaemia and nephrolithiasis are positively correlated with the development of CKD in our studied subjects.

QT dispersion increases with low glomerular filtration rate in patients with coronary artery disease

PubMed Central

Celik, Murat; Yuksel, UygarCagdas; Gokoglan, Yalcin; Bugan, Baris; Yalcinkaya, Emre; Unal, HilmiUmut; Celik, Turgay; Iyisoy, Atila; Kilic, Selim

2014-01-01

Objective: We aimed to evaluate the relationship between estimated glomerular filtration rate (eGFR) and QT dispersion (QTd) in patients with coronary artery disease (CAD). Methods: Sixty patients(mean age 62.72 ± 12.48 years) included 46 male, (mean age 60.89 ± 12.70 years)and 14 female (mean age 68.71± 9.86 years) were enrolled in this study. Patients were divided into 2 groups according to their eGFR using the 6 variable MDRD equation. Group 1 consisted of patients with estimated eGFR<60 ml/min/1.73m2 and Group 2 consisted of patients witheGFR ≥ 60 ml/min/1.73m2. Results: Baseline patient characteristics were homogeneous in both groups except for age, gender and smoking.Also, the extent of CAD was similar in both groups (p > 0.05) QTd values were found higher in group 1 than those of group 2 (57.23 ± 40.65 ms vs. 31.23 ± 14.47 ms, p = 0.002). After adjustment for age, gender and smoking using one-way ANCOVA test, statistically significant difference in QTd still existedbetween the groups (p=0.038). Conclusion:QTd tends to be higher in patients with poor renal function independent of severity of angiographical CAD. QTd may be a potentially useful non-invasive test in the management of patients with poor renal function, especially those with CAD. PMID:24772124

Inflammation, homocysteine and carotid intima-media thickness.

PubMed

Baptista, Alexandre P; Cacdocar, Sanjiva; Palmeiro, Hugo; Faísca, Marília; Carrasqueira, Herménio; Morgado, Elsa; Sampaio, Sandra; Cabrita, Ana; Silva, Ana Paula; Bernardo, Idalécio; Gome, Veloso; Neves, Pedro L

2008-01-01

Cardiovascular disease is the main cause of morbidity and mortality in chronic renal patients. Carotid intima-media thickness (CIMT) is one of the most accurate markers of atherosclerosis risk. In this study, the authors set out to evaluate a population of chronic renal patients to determine which factors are associated with an increase in intima-media thickness. We included 56 patients (F=22, M=34), with a mean age of 68.6 years, and an estimated glomerular filtration rate of 15.8 ml/min (calculated by the MDRD equation). Various laboratory and inflammatory parameters (hsCRP, IL-6 and TNF-alpha) were evaluated. All subjects underwent measurement of internal carotid artery intima-media thickness by high-resolution real-time B-mode ultrasonography using a 10 MHz linear transducer. Intima-media thickness was used as a dependent variable in a simple linear regression model, with the various laboratory parameters as independent variables. Only parameters showing a significant correlation with CIMT were evaluated in a multiple regression model: age (p=0.001), hemoglobin (p=00.3), logCRP (p=0.042), logIL-6 (p=0.004) and homocysteine (p=0.002). In the multiple regression model we found that age (p=0.001) and homocysteine (p=0.027) were independently correlated with CIMT. LogIL-6 did not reach statistical significance (p=0.057), probably due to the small population size. The authors conclude that age and homocysteine correlate with carotid intima-media thickness, and thus can be considered as markers/risk factors in chronic renal patients.

Renal Function in De Novo Liver Transplant Recipients Receiving Different Prolonged-Release Tacrolimus Regimens-The DIAMOND Study.

PubMed

TruneČka, P; Klempnauer, J; Bechstein, W O; Pirenne, J; Friman, S; Zhao, A; Isoniemi, H; Rostaing, L; Settmacher, U; Mönch, C; Brown, M; Undre, N; Tisone, G

2015-07-01

DIAMOND: multicenter, 24-week, randomized trial investigating the effect of different once-daily, prolonged-release tacrolimus dosing regimens on renal function after de novo liver transplantation. Arm 1: prolonged-release tacrolimus (initial dose 0.2mg/kg/day); Arm 2: prolonged-release tacrolimus (0.15-0.175mg/kg/day) plus basiliximab; Arm 3: prolonged-release tacrolimus (0.2mg/kg/day delayed until Day 5) plus basiliximab. All patients received MMF plus a bolus of corticosteroid (no maintenance steroids). eGFR (MDRD4) at Week 24. Secondary endpoints: composite efficacy failure, BCAR and AEs. Baseline characteristics were comparable. Tacrolimus trough levels were readily achieved posttransplant; initially lower in Arm 2 versus 1 with delayed initiation in Arm 3. eGFR (MDRD4) was higher in Arms 2 and 3 versus 1 (p = 0.001, p = 0.047). Kaplan-Meier estimates of composite efficacy failure-free survival were 72.0%, 77.6%, 73.9% in Arms 1-3. BCAR incidence was significantly lower in Arm 2 versus 1 and 3 (p = 0.016, p = 0.039). AEs were comparable. Prolonged-release tacrolimus (0.15-0.175mg/kg/day) immediately posttransplant plus basiliximab and MMF (without maintenance corticosteroids) was associated with lower tacrolimus exposure, and significantly reduced renal function impairment and BCAR incidence versus prolonged-release tacrolimus (0.2mg/kg/day) administered immediately posttransplant. Delayed higher-dose prolonged-release tacrolimus initiation significantly reduced renal function impairment compared with immediate posttransplant administration, but BCAR incidence was comparable. © 2015 The Authors. American Journal of Transplantation published by Wiley Periodicals Inc.

Repeated serum creatinine measurement in primary care: Not all patients have chronic renal failure.

PubMed

Gentille Lorente, Delicia; Gentille Lorente, Jorge; Salvadó Usach, Teresa

2015-01-01

To assess the prevalence of kidney failure in patients from a primary care centre in a basic healthcare district with laboratory availability allowing serum creatinine measurements. An observational descriptive cross-sectional study. A basic healthcare district serving 23,807 people aged ≥ 18 years. Prevalence of kidney failure among 17,240 patients having at least one laboratory measurement available was 8.5% (mean age 77.6 ± 12.05 years). In 33.2% of such patients an occult kidney failure was found (98.8% were women). Prevalence of chronic kidney failure among 10,011 patients having at least 2 laboratory measurements available (≥ 3 months apart) was 5.5% with mean age being 80.1 ± 10.0 years (most severely affected patients were those aged 75 to 84); 59.7% were men and 76.3% of cases were in stage 3. An occult kidney failure was found in 5.3% of patients with women being 86.2% of them (a glomerular filtration rate<60 ml/min was estimated for plasma creatinine levels of 0.9 mg/dl or higher). Comparison of present findings to those previously reported demonstrates the need for further studies on the prevalence of overall (chronic and acute) kidney failure in Spain in order to estimate the real scope of the disease. Primary care physicians play a critical role in disease detection, therapy, control and recording (in medical records). MDRD equation is useful and practical to estimate glomerular filtration rate. Copyright © 2015 The Authors. Published by Elsevier España, S.L.U. All rights reserved.

A retrospective evaluation of furosemide and mannitol for prevention of cisplatin-induced nephrotoxicity.

PubMed

Mach, C M; Kha, C; Nguyen, D; Shumway, J; Meaders, K M; Ludwig, M; Williams-Brown, M Y; Anderson, M L

2017-06-01

Nephrotoxicity is a recognized side effect of cisplatin chemotherapy. However, the optimal strategy for preventing cisplatin-induced nephrotoxicity, if any, remains unclear. The primary objective for this study was to determine whether mannitol or furosemide provides better nephroprotection when administered with hydration prior to weekly, low-dose cisplatin concurrently with whole pelvic radiotherapy. Clinical data were abstracted from all women who underwent chemoradiation for FIGO IB2-IVA cervical cancer at a regional safety net health system between January 2009 and December 2014. Creatinine clearance was estimated using the IDMS-traceable MDRD Study Equation. Descriptive statistics were used to summarize patient demographics. Cox proportional hazard models were used to identify factors associated with hypomagnesemia and survival. A total of 133 women received 656 weekly doses of single-agent cisplatin (40 mg/m 2 ) concomitant with whole pelvic radiation. Furosemide (20 mg) was administered intravenously prior to 341 cisplatin doses, whereas mannitol (24 g) was administered prior to 315 doses. Significant magnesium wasting was observed after the second weekly cisplatin infusion regardless of whether furosemide or mannitol was utilized. Repetitive low-dose cisplatin infusion had no impact on measured levels of serum creatinine or estimated glomerular filtration rate. Prior history of hypertension, diabetes mellitus, hepatitis C infection and acute gastrointestinal toxicity were each associated with early onset of hypomagnesemia. Repetitive administration of low-dose cisplatin concurrent with whole pelvic radiation is associated with magnesium wasting. However, choice of diuretic with pretreatment hydration had no significant impact on the severity of this adverse effect. © 2017 John Wiley & Sons Ltd.

Assessment of renal perfusion with contrast-enhanced ultrasound: Preliminary results in early diabetic nephropathies.

PubMed

Dong, Yi; Wang, Wen-Ping; Lin, Pan; Fan, Peili; Mao, Feng

2016-01-01

We performed a prospective study to evaluate the value of contrast-enhanced ultrasound (CEUS) in quantitative evaluation of renal cortex perfusion in patients suspected of early diabetic nephropathies (DN), with the estimated GFR (MDRD equation) as the gold standard. The study protocol was approved by the hospital review board; each patient gave written informed consent. Our study included 46 cases (21 males and 25 females, mean age 55.6 ± 4.14 years) of clinical confirmed early DN patients. After intravenous bolus injection of 1 ml sulfur hexafluoride microbubbles of ultrasound contrast agent, real time CEUS of renal cortex was performed successively using a 2-5 MHz convex probe. Time-intensity curves (TICs) and quantitative indexes were created with Qlab software. Receiver operating characteristic (ROC) curves were used to predict the diagnostic criteria of CEUS quantitative indexes, and their diagnostic efficiencies were compared with resistance index (RI) and peak systolic velocity (PSV) of renal segmental arteries by chi square test. Our control group included forty-five healthy volunteers. Difference was considered statistically significant with P <  0.05. Changes of area under curve (AUC), derived peak intensity (DPI) were statistically significant (P <  0.05). DPI less than 12 and AUC greater than 1400 had high utility in DN, with 71.7% and 67.3% sensitivity, 77.8% and 80.0% specificity. These results were significantly better than those obtained with RI and PSV which had no significant difference in early stage of DN (P > 0.05). CEUS might be helpful to improve early diagnosis of DN by quantitative analyses. AUC and DPI might be valuable quantitative indexes.

[Cardiorenal syndrome type 1 in the intensive coronary care unit of the Hospital Nacional Arzobispo Loayza].

PubMed

Preza, Paul M; Hurtado, Abdías; Armas, Victoria; Cárcamo, César P

2015-01-01

This study sought to evaluate the incidence of cardiorenal syndrome (CRS) type 1 in a coronary care unit and its association with hospital mortality within 30 days of admission, as well as other epidemiological characteristics. The medical records of all the patients who were hospitalized with the diagnosis of acute heart failure in a 4-year period were reviewed. CRS type 1 was characterized by the presence of acute heart failure and an elevation of serum creatinine ≥0.3mg/dL in comparison to the baseline creatinine calculated by the MDRD75 equation and/or the elevation of ≥50% of the admission serum creatinine within a 48 h period. The incidence of CRS type 1 was 27.87%, 95% CI: 20.13-36.71 (34 of 122). There was a higher frequency of CRS type 1 in those patients who were admitted with the diagnosis of cardiogenic shock (adjusted RR 2.02, 95% CI: 1.20-3.93, p=0.0378) and in those with higher hemoglobin levels (p=0.0412). The CRS type 1 was associated with an increase of 30-day mortality (HR: 4.11, 95% CI: 1.20-14.09, p=0.0244). The incidence of CRS type 1 in the coronary care unit found in our study is similar to those found in foreign studies. The history of stroke and the higher values of hemoglobin were associated with a higher incidence of cardiorenal syndrome type 1. Patients with CRS type 1 had a higher hospital mortality within 30 days of admission. Copyright © 2014 Instituto Nacional de Cardiología Ignacio Chávez. Published by Masson Doyma México S.A. All rights reserved.

BP Control and Long-Term Risk of ESRD and Mortality

PubMed Central

Gassman, Jennifer; Appel, Lawrence J.; Smogorzewski, Miroslaw; Sarnak, Mark J.; Glidden, David V.; Bakris, George; Gutiérrez, Orlando M.; Hebert, Lee A.; Ix, Joachim H.; Lea, Janice; Lipkowitz, Michael S.; Norris, Keith; Ploth, David; Pogue, Velvie A.; Rostand, Stephen G.; Siew, Edward D.; Sika, Mohammed; Tisher, C. Craig; Toto, Robert; Wright, Jackson T.; Wyatt, Christina; Hsu, Chi-yuan

2017-01-01

We recently showed an association between strict BP control and lower mortality risk during two decades of follow-up of prior participants in the Modification of Diet in Renal Disease (MDRD) trial. Here, we determined the risk of ESRD and mortality during extended follow-up of the African American Study of Kidney Disease and Hypertension (AASK) trial. We linked 1067 former AASK participants with CKD previously randomized to strict or usual BP control (mean arterial pressure ≤92 mmHg or 102–107 mmHg, respectively) to the US Renal Data System and Social Security Death Index; 397 patients had ESRD and 475 deaths occurred during a median follow-up of 14.4 years from 1995 to 2012. Compared with the usual BP arm, the strict BP arm had unadjusted and adjusted relative risks of ESRD of 0.92 (95% confidence interval [95% CI], 0.75 to 1.12) and 0.95 (95% CI, 0.78 to 1.16; P=0.64), respectively, and unadjusted and adjusted relative risks of death of 0.92 (95% CI, 0.77 to 1.10) and 0.81 (95% CI, 0.68 to 0.98; P=0.03), respectively. In meta-analyses of individual-level data from the MDRD and the AASK trials, unadjusted relative risk of ESRD was 0.88 (95% CI, 0.78 to 1.00) and unadjusted relative risk of death was 0.87 (95% CI, 0.76 to 0.99) for strict versus usual BP arms. Our findings suggest that, during long–term follow-up, strict BP control does not delay the onset of ESRD but may reduce the relative risk of death in CKD. PMID:27516235

Dosing of cytotoxic chemotherapy: impact of renal function estimates on dose.

PubMed

Dooley, M J; Poole, S G; Rischin, D

2013-11-01

Oncology clinicians are now routinely provided with an estimated glomerular filtration rate on pathology reports whenever serum creatinine is requested. The utility of using this for the dose determination of renally excreted drugs compared with other existing methods is needed to inform practice. Renal function was determined by [Tc(99m)]DTPA clearance in adult patients presenting for chemotherapy. Renal function was calculated using the 4-variable Modification of Diet in Renal Disease (4v-MDRD), Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI), Cockcroft and Gault (CG), Wright and Martin formulae. Doses for renal excreted cytotoxic drugs, including carboplatin, were calculated. The concordance of the renal function estimates according to the CKD classification with measured Tc(99m)DPTA clearance in 455 adults (median age 64.0 years: range 17-87 years) for the 4v-MDRD, CKD-EPI, CG, Martin and Wright formulae was 47.7%, 56.3%, 46.2%, 56.5% and 60.2%, respectively. Concordance for chemotherapy dose for these formulae was 89.0%, 89.5%, 85.1%, 89.9% and 89.9%, respectively. Concordance for carboplatin dose specifically was 66.4%, 71.4%, 64.0%, 73.8% and 73.2%. All bedside formulae provide similar levels of concordance in dosage selection for the renal excreted chemotherapy drugs when compared with the use of a direct measure of renal function.

Estimated GFR reporting is associated with decreased nonsteroidal anti-inflammatory drug prescribing and increased renal function.

PubMed

Wei, Li; MacDonald, Thomas M; Jennings, Claudine; Sheng, Xia; Flynn, Robert W; Murphy, Michael J

2013-07-01

Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used; however, they are also nephrotoxic with both acute and chronic effects on kidney function. Here we determined NSAID prescribing before and after estimated GFR (eGFR) reporting and evaluate renal function in patients who used NSAIDs but stopped these after their first eGFR report. A population-based longitudinal analysis using a record-linkage database was conducted with the GFR estimated using the four-variable equation from the MDRD study and analyzed by trend test, paired t-test, and logistic regression modeling. Prescriptions for NSAIDs significantly decreased from 39,459 to 35,415 after implementation of eGFR reporting from the second quarter of 2005 compared with the first quarter of 2007. Reporting eGFR was associated with reduced NSAID prescriptions (adjusted odds ratio, 0.78). NSAID prescription rates in the 6 months before April 2006 were 18.8, 15.4, and 7.0% in patients with CKD stages 3, 4, and 5 and 15.5, 10.7, and 6.3%, respectively, after eGFR reporting commenced. In patients who stopped NSAID treatment, eGFR significantly increased from 45.9 to 46.9, 23.9 to 27.1, and 12.4 to 26.4 ml/min per 1.73 m(2) in 1340 stage 3 patients, 162 stage 4 patients, and 9 stage 5 patients, respectively. Thus, NSAID prescribing decreased after the implementation of eGFR reporting, and there were significant improvements in estimated renal function in patients who stopped taking NSAIDs. Hence, eGFR reporting may result in safer prescribing.

Changes in urinary amino acids excretion in relationship with muscle activity markers over a professional cycling stage race: in search of fatigue markers.

PubMed

Corsetti, Roberto; Barassi, Alessandra; Perego, Silvia; Sansoni, Veronica; Rossi, Alessandra; Damele, Clara Anna Linda; Melzi D'Eril, Gianlodovico; Banfi, Giuseppe; Lombardi, Giovanni

2016-01-01

The aim of this study was to identify the relationship between metabolic effort, muscular damage/activity indices, and urinary amino acids profile over the course of a strenuous prolonged endurance activity, as a cycling stage race is, in order to identify possible fatigue markers. Nine professional cyclists belonging to a single team, competing in the Giro d'Italia cycling stage race, were anthropometrically characterized and sampled for blood and urine the day before the race started, and on days 12 and 23 of the race. Diet was kept the same over the race, and power output and energy expenditure were recorded. Sera were assayed for muscle markers (lactate dehydrogenase, aspartate aminotransferase, and creatine kinase activities, and blood urea nitrogen), and creatinine, all corrected for plasma volume changes. Urines were profiled for amino acid concentrations, normalized on creatinine excretion. Renal function, in terms of glomerular filtration rate, was monitored by MDRD equation corrected on body surface area. Creatine kinase activity and blood urea were increased during the race as did serum creatinine while kidney function remained stable. Among the amino acids, taurine, glycine, cysteine, leucine, carnosine, 1-methyl histidine, and 3-methyl histidine showed a net decreased, while homocysteine was increased. Taurine and the dipeptide carnosine (β-alanyl-L-histidine) were significantly correlated with the muscle activity markers and the indices of effort. In conclusion, the metabolic profile is modified strikingly due to the effort. Urinary taurine and carnosine seem useful tools to evaluate the muscle damage and possibly the fatigue status on a long-term basis.

Cardiovascular Disease Outcomes Related to Early Stage Renal Impairment Following Liver Transplantation.

PubMed

VanWagner, Lisa B; Montag, Samantha; Zhao, Lihui; Allen, Norrina B; Lloyd-Jones, Donald M; Das, Arighno; Skaro, Anton I; Hohmann, Samuel; Friedewald, John J; Levitsky, Josh

2018-03-20

In the general population, even mild renal disease is associated with increased cardiovascular (CV) complications. Whether this is true in liver transplant recipients (LTR) is unknown. This was a retrospective cohort study of 671 LTR (2002-2012) from a large urban tertiary care center and 37,322 LTR using Vizient hospitalization data linked to the United Network for Organ Sharing. The MDRD4 equation estimated GFR (eGFR). Outcomes were 1-year CV complications (death/hospitalization from myocardial infarction, heart failure, atrial fibrillation, cardiac arrest, pulmonary embolism or stroke) and mortality. Latent mixture modeling identified trajectories in eGFR in the first LT year in the 671 patients. Mean(SD) eGFR was 72.1(45.7) ml/min/1.73m. Six distinct eGFR trajectories were identified in the local cohort (n=671): qualitatively Normal-Slow Decrease (4% of cohort), Normal-Rapid Decrease (4%), Mild-Stable (18%), Mild-Slow Decrease (35%), Moderate-Stable (30%), and Severe-Stable (9%). In multivariable analyses adjusted for confounders and baseline eGFR, the greatest odds of 1-year CV complications were in the Normal-Rapid Decrease group (OR, 95% CI: 10.6, 3.0-36.9). Among the national cohort, each 5-unit lower eGFR at LT was associated with a 2% and 5% higher hazard of all-cause and CV-mortality, respectively (p<0.0001) independent of multiple confounders. Even mild renal disease at the time of LT is a risk factor for posttransplant all-cause and CV mortality. More rapid declines in eGFR soon after LT correlate with risk of adverse CV outcomes, highlighting the need to study whether early renal preservation interventions also reduce CV complications.

Heritability of Measures of Kidney Disease Among Zuni Indians: The Zuni Kidney Project

PubMed Central

MacCluer, Jean W.; Scavini, Marina; Shah, Vallabh O.; Cole, Shelley A.; Laston, Sandra L.; Voruganti, V. Saroja; Paine, Susan S.; Eaton, Alfred J.; Comuzzie, Anthony G.; Tentori, Francesca; Pathak, Dorothy R.; Bobelu, Arlene; Bobelu, Jeanette; Ghahate, Donica; Waikaniwa, Mildred; Zager, Philip G.

2010-01-01

Background The long-term goal of the GKDZI (Genetics of Kidney Disease in Zuni Indians) Study is to identify genes, environmental factors, and genetic-environmental interactions that modulate susceptibility to renal disease and intermediate phenotypes. Study Design A community-based participatory research approach was used to recruit family members of individuals with kidney disease. Setting & Participants The study was conducted in the Zuni Indians, a small endogamous tribe located in rural New Mexico. We recruited members of extended families, ascertained through a proband with kidney disease and at least 1 sibling with kidney disease. 821 participants were recruited, comprising 7,702 relative pairs. Predictor Outcomes & Measurements Urine albumin-creatinine ratio (UACR) and hematuria were determined in 3 urine samples and expressed as a true ratio. Glomerular filtration rate (GFR) was estimated using the Modification of Diet in Renal Disease (MDRD) Study equation modified for American Indians. Probands were considered to have kidney disease if UACR was ≥0.2 in 2 or more of 3 spot urine samples or estimated GFR was decreased according to the CRIC (Chronic Renal Insufficiency Cohort) Study criteria. Results Kidney disease was identified in 192 participants (23.4%). There were significant heritabilities for estimated GFR, UACR, serum creatinine, serum urea nitrogen, and uric acid and a variety of phenotypes related to obesity, diabetes, and cardiovascular disease. There were significant genetic correlations of some kidney-related phenotypes with these other phenotypes. Limitations Limitations include absence of renal biopsy, possible misclassification bias, lack of direct GFR measurements, and failure to include all possible environmental interactions. Conclusions Many phenotypes related to kidney disease showed significant heritabilities in Zuni Indians, and there were significant genetic correlations with phenotypes related to obesity, diabetes, and cardiovascular disease. The study design serves as a paradigm for the conduct of research in relatively isolated, endogamous, underserved populations. PMID:20646805

Relationship of Estimated GFR and Coronary Artery Calcification in the (CRIC) Chronic Renal Insufficiency Cohort Study

PubMed Central

Budoff, Matthew J; Rader, Daniel J; Reilly, Muredach P.; Mohler, Emile R.; Lash, Jim; Yang, Wei; Rosen, Leigh; Glenn, Melanie; Teal, Valerie; Feldman, Harold I.

2011-01-01

Background Coronary artery calcification (CAC) is associated with increased mortality risk in the general population. Although individuals with chronic kidney disease (CKD) are at markedly increased mortality risk, the incidence, prevalence, and prognosis of CAC in CKD is not well-understood. Study Design Cross-sectional observational study. Setting and Participants Analysis of 1,908 participants who underwent coronary calcium scanning as part of the multi-ethnic CRIC (Chronic Renal Insufficiency Cohort) Study. Predictor Estimated glomerular filtration rate (eGFR) computed using the Modification of Diet in Renal Disease (MDRD) Study equation, stratified by race, sex and diabetic status. eGFR was treated as a continous variable and a categorical variable compared to the reference range of >60 ml/min/1.73 m2 Measurements CAC detected using CT scans using either an Imatron C-300 electron beam computed tomography scanner or multi-detector CT scanner. CAC was computed using the Agatston score, as a categorical variable. Analyses were performed using ordinal logistic regression. Results We found a strong and graded relationship between lower eGFR and increasing CAC. In unadjusted models, ORs increased from 1.68 (95% CI, 1.23–2.31) for eGFR from 50–59 to 2.82 (95% CI, 2.06–3.85) for eGFR of <30. Multivariable adjustment only partially attenuated the results (OR, 1.53; 95% CI, 1.07–2.20) for eGFR<30. Limitations Use of eGFR rather than measured GFR. Conclusions We demonstrated a graded relationship between severity of CKD and CAC, independent of traditional risk factors. These findings supports recent guidelines that state that if vascular calcification is present, it should be considered as a complementary component to be included in the decision making required for individualizing treatment of CKD. PMID:21783289

Concealed renal failure and adverse drug reactions in older patients with type 2 diabetes mellitus.

PubMed

Corsonello, Andrea; Pedone, Claudio; Corica, Francesco; Mazzei, Bruno; Di Iorio, Angelo; Carbonin, Pierugo; Incalzi, Raffaele Antonelli

2005-09-01

In elderly patients serum creatinine may be normal despite decreased glomerular filtration rate (GFR). The aim of this study was to evaluate the prevalence of this "concealed" renal failure, i.e., renal failure with normal serum creatinine levels, in elderly diabetic patients, and to verify whether it is a risk factor for adverse drug reactions (ADR) to hydrosoluble drugs. We used data on 2257 hospitalized patients with type 2 diabetes mellitus enrolled in the Gruppo Italiano di Farmacovigilanza nell'Anziano study. On the basis of serum creatinine and calculated GFR, patients were grouped as follows: normal renal function (normal serum creatinine levels and normal GFR), concealed (normal serum creatinine levels and reduced GFR), or overt (increased creatinine levels and reduced GFR) renal failure. GFR was calculated using the Modification of Diet in Renal Disease (MDRD) equation. The outcome of the study was the incidence of ADR to hydrosoluble drugs during the hospital stay. The relationship between renal function and ADR was evaluated using Cox regression analysis including potential confounders. Concealed renal failure was observed in 363 (16.1%) of patients studied. Patients with concealed or overt renal failure were older, had more frequently cognitive impairment and polypharmacy, and had lower serum albumin levels than did those with normal renal function. Both concealed (hazard ratio = 1.90; 95% confidence interval, 1.04-3.48; p =.036) and overt (hazard ratio = 2.23; 95% confidence interval, 1.40-3.55; p =.001) renal failure were significantly associated with ADR to hydrosoluble drugs. The use of more than four drugs also qualified as an independent risk factor for ADRs to hydrosoluble drugs during hospital stay. Older diabetic patients should be systematically screened to ascertain the presence of concealed renal failure in an attempt to optimize the pharmacological treatment and reduce the risk of ADRs.

Monitoring of patients with type 2 diabetes and nephropathy in a specialized diabetic nephropathy clinic seems to be beneficial.

PubMed

Vallianou, N; Stratigou, T; Paikopoulou, A; Apostolou, T; Vlassopoulou, B; Tsagarakis, S; Ioannidis, G

2018-04-13

The purpose of this study was to evaluate the outcome of DM2 patients with nephropathy when they are under surveillance of a joined clinic run by endocrinologists & nephrologists. A cohort of 106 patients with DM2, 42-83 years of age, and eGFR < 60 ml/min/m 2 were included. Age, sex, duration of diabetes, duration of attending our clinic, smoking habits, BMI, data regarding ischemic heart disease and induction of hemodialysis, urine albumin excretion (UAE) levels, eGFR (MDRD equation) and values of various biochemical parameters were recorded too. Follow-up period ranged from one to 25 years. Paired samples t-test and non-parametrical Kruskal-Wallis test were used for the analyses of the data. Fifty percent of patients had no further progression, 25.9% improvement, while 24.1% had worsening of the UAE levels. During the follow-up in the joined clinic, there was a smaller than the expected from the medical literature decrease in median eGFR, i.e. 2,3 ml/min/m 2 and a statistically significant improvement in glycosylated hemoglobin levels from 8.0% to 7.4% (p = 0.016). Time in years of follow-up in the joined clinic of our hospital appeared to be the most significant factor in the improvement or stabilization against deterioration of the UAE levels (p = 0.018). Close follow-up of DM2 patients with eGFR < 60 ml/min/m 2 has resulted in a minor annual eGFR decrease. Monitoring of these patients in a specialized diabetic nephropathy clinic is beneficial for this group of patients for delaying the occurrence of end-stage renal disease. Copyright © 2018 Diabetes India. Published by Elsevier Ltd. All rights reserved.

The pharmacokinetics of peginterferon lambda-1a following single dose administration to subjects with impaired renal function.

PubMed

Hruska, Matthew W; Adamczyk, Robert; Colston, Elizabeth; Hesney, Michael; Stonier, Michele; Myler, Heather; Bertz, Richard

2015-09-01

This open label study was conducted to assess the effect of renal impairment (RI) on the pharmacokinetics (PK) of peginterferon lambda-1a (Lambda). Subjects (age 18-75 years, BMI 18-35 kg m(-2) ) were enrolled into one of five renal function groups: normal (n = 12), mild RI (n = 8), moderate RI (n = 8), severe RI (n = 7), end-stage renal disease (ESRD, n = 8) based on estimated glomerular filtration rate (eGFR) calculated using the Modification of Diet in Renal Disease (MDRD) equation. Subjects received a single dose of Lambda (180 µg) subcutaneously on day 1 followed by PK serum sample collections through day 29. Safety, tolerability and immunogenicity data were collected through day 43. PK parameters were estimated and summarized by group. Geometric mean ratios (GMR) and 90% confidence intervals (CIs) were calculated between normal and RI groups. With decreasing eGFR, Lambda exposure (Cmax , AUC) increased while apparent clearance (CL/F) and apparent volume of distribution (V/F) decreased. Relative to subjects with normal renal function (geometric mean AUC = 99.5 ng ml(-1) h), Lambda exposure estimates (AUC) were slightly increased in the mild RI group (geometric mean [90% CI]: 1.20 [0.82, 1.77]) and greater in the moderate (1.95 [1.35, 2.83]), severe RI (1.95 [1.30, 2.93]) and ESRD (1.88 [1.30, 2.73]) groups. Lambda was generally well tolerated. The results demonstrated that RI reduces the clearance of Lambda and suggests that dose modifications may not be required in patients with mild RI but may be required in patients with moderate to severe RI or ESRD. © 2015 The British Pharmacological Society.

Body Composition Analysis Allows the Prediction of Urinary Creatinine Excretion and of Renal Function in Chronic Kidney Disease Patients.

PubMed

Donadio, Carlo

2017-05-28

The aim of this study was to predict urinary creatinine excretion (UCr), creatinine clearance (CCr) and the glomerular filtration rate (GFR) from body composition analysis. Body cell mass (BCM) is the compartment which contains muscle mass, which is where creatinine is generated. BCM was measured with body impedance analysis in 165 chronic kidney disease (CKD) adult patients (72 women) with serum creatinine (SCr) 0.6-14.4 mg/dL. The GFR was measured ( 99m Tc-DTPA) and was predicted using the Modification of Diet in Renal Disease (MDRD) formula. The other examined parameters were SCr, 24-h UCr and measured 24-h CCr (mCCr). A strict linear correlation was found between 24-h UCr and BCM ( r = 0.772). Multiple linear regression (MR) indicated that UCr was positively correlated with BCM, body weight and male gender, and negatively correlated with age and SCr. UCr predicted using the MR equation (MR-UCr) was quite similar to 24-h UCr. CCr predicted from MR-UCr and SCr (MR-BCM-CCr) was very similar to mCCr with a high correlation ( r = 0.950), concordance and a low prediction error (8.9 mL/min/1.73 m²). From the relationship between the GFR and the BCM/SCr ratio, we predicted the GFR (BCM GFR). The BCM GFR was very similar to the GFR with a high correlation ( r = 0.906), concordance and a low prediction error (12.4 mL/min/1.73 m²). In CKD patients, UCr, CCr and the GFR can be predicted from body composition analysis.

Body Composition Analysis Allows the Prediction of Urinary Creatinine Excretion and of Renal Function in Chronic Kidney Disease Patients

PubMed Central

Donadio, Carlo

2017-01-01

The aim of this study was to predict urinary creatinine excretion (UCr), creatinine clearance (CCr) and the glomerular filtration rate (GFR) from body composition analysis. Body cell mass (BCM) is the compartment which contains muscle mass, which is where creatinine is generated. BCM was measured with body impedance analysis in 165 chronic kidney disease (CKD) adult patients (72 women) with serum creatinine (SCr) 0.6–14.4 mg/dL. The GFR was measured (99mTc-DTPA) and was predicted using the Modification of Diet in Renal Disease (MDRD) formula. The other examined parameters were SCr, 24-h UCr and measured 24-h CCr (mCCr). A strict linear correlation was found between 24-h UCr and BCM (r = 0.772). Multiple linear regression (MR) indicated that UCr was positively correlated with BCM, body weight and male gender, and negatively correlated with age and SCr. UCr predicted using the MR equation (MR-UCr) was quite similar to 24-h UCr. CCr predicted from MR-UCr and SCr (MR-BCM-CCr) was very similar to mCCr with a high correlation (r = 0.950), concordance and a low prediction error (8.9 mL/min/1.73 m2). From the relationship between the GFR and the BCM/SCr ratio, we predicted the GFR (BCM GFR). The BCM GFR was very similar to the GFR with a high correlation (r = 0.906), concordance and a low prediction error (12.4 mL/min/1.73 m2). In CKD patients, UCr, CCr and the GFR can be predicted from body composition analysis. PMID:28555040

Evaluating the efficacy, safety and evolution of renal function with early initiation of everolimus-facilitated tacrolimus reduction in de novo liver transplant recipients: Study protocol for a randomized controlled trial.

PubMed

Nashan, Bjorn; Schemmer, Peter; Braun, Felix; Dworak, Markus; Wimmer, Peter; Schlitt, Hans

2015-03-26

Introduction of calcineurin inhibitors had led to improved survival rates in liver transplant recipients. However, long-term use of calcineurin inhibitors is associated with a higher risk of chronic renal failure, neurotoxicity, de novo malignancies, recurrence of hepatitis C viral (HCV) infection and hepatocellular carcinoma. Several studies have shown that everolimus has the potential to provide protection against viral replication, malignancy, and progression of fibrosis, as well as preventing nephrotoxicity by facilitating calcineurin inhibitor reduction without compromising efficacy. The Hephaistos study evaluates the beneficial effects of early initiation of everolimus in de novo liver transplant recipients. Hephaistos is an ongoing 12-month, multi-center, open-label, controlled study aiming to enroll 330 de novo liver transplant recipients from 15 centers across Germany. Patients are randomized in a 1:1 ratio (7-21 days post-transplantation) to receive everolimus (trough levels 3-8 ng/mL) with reduced tacrolimus (trough levels <5 ng/mL), or standard tacrolimus (trough levels 6-10 ng/mL) after entering a run-in period (3-5 days post-transplantation). In the run-in period, patients are treated with induction therapy, mycophenolate mofetil, tacrolimus, and corticosteroids according to local practice. Randomization is stratified by HCV status and model of end-stage liver disease scores at transplantation. The primary objective of the study is to exhibit superior renal function (estimated glomerular filtration rate assessed by the Modification of Diet in Renal Disease (MDRD)-4 formula) with everolimus plus reduced tacrolimus compared to standard tacrolimus at Month 12. Other objectives are: to assess the incidence of treated biopsy-proven acute rejection, graft loss, or death; the incidences of components of the composite efficacy endpoint; renal function via estimated glomerular filtration rate using various formulae (MDRD-4, Nankivell, Cockcroft-Gault, chronic kidney disease epidemiology collaboration and Hoek formulae); the incidence of proteinuria; the incidence of adverse events and serious adverse events; the incidence and severity of cytomegalovirus and HCV infections and HCV-related fibrosis. This study aims to demonstrate superior renal function, comparable efficacy, and safety in de novo liver transplant recipients receiving everolimus with reduced tacrolimus compared with standard tacrolimus. This study also evaluates the antiviral benefit by early initiation of everolimus. NCT01551212 .

Evaluation of urine biomarkers of kidney injury in Polycystic Kidney Disease

PubMed Central

Parikh, Chirag R.; Dahl, Neera K.; Chapman, Arlene; Bost, James E.; Edelstein, Charles L.; Comer, Diane M.; Zeltner, Raoul; Tian, Xin; Grantham, Jared J.; Somlo, Stefan

2012-01-01

Progressive disruption of renal tubular integrity in the setting of increased cellular proliferation and apoptosis is a feature of ADPKD. Here we evaluated the effect of these processes on the expression of NGAL and IL-18, markers of tubular injury, in rodent models and in the cyst fluid and urine of patients with ADPKD. Two mouse models where Pkd2 was inactivated which resulted in early or adult onset cysts, were used to evaluate NGAL levels. Further, the Han:SPRD rat model of polycystic disease was used to study IL-18 levels. In four annual serial urine samples from 107 patients with ADPKD in the Consortium for Radiologic Imaging for the Study of Polycystic Kidney Disease (CRISP) study, NGAL and IL-18 excretion rates were determined in conjunction with measures of total kidney volume and estimated GFR (eGFR) by the MDRD equation. Kidneys from affected mice and rats showed prominent expression of NGAL and IL-18/IL-18R, respectively, in epithelial cells lining kidney cysts. In human ADPKD cyst fluid, both NGAL and IL-18 were elevated. In CRISP patients, the mean percentage increase in total kidney volume was 5.4 /year and the mean decline in eGFR 2.4 mL/min/year. The trend of increased mean urine NGAL and IL-18 over three years was statistically significant; however, there was no association of tertiles of IL-18 or quartiles of NGAL and the change in total kidney volume or eGFR over this period. Thus, urinary NGAL and IL-18 excretion are mildly and stably elevated in ADPKD, but do not correlate with changes in total kidney volume or kidney function. This may be due, in part, to the lack of communication between individual cysts and the urinary collecting system in this disorder. PMID:22258321

Does pretransplant soluble CD30 serum concentration affect deceased-donor kidney graft function 3 years after transplantation?

PubMed

Kovac, J; Arnol, M; Vidan-Jeras, B; Bren, A F; Kandus, A

2008-06-01

Elevated serum concentrations of soluble CD30 molecule (sCD30) have been related to acute cellular rejection and poor graft outcomes in kidney transplantation. This historical cohort study investigated the association of pretransplant sCD30 serum concentrations with kidney graft function expressed as estimated glomerular filtration rate (GFR) at 3 years after transplantation. Pretransplant sera from 176 adult deceased-donor kidney graft recipients were tested for sCD30 content using a commercially available automated enzyme-linked immunosorbent assay. The immunosuppression consisted of induction therapy with monoclonal anti-CD25 antibodies and a maintenance regimen of cyclosporine (CsA)-based therapy. GFR was estimated (eGFR) by the four-variable Modification of Diet in Renal Disease (MDRD) Study equation. According to the distribution of pretransplant sCD30 levels (median 66.7 U/mL; interquartile range, 46.6 to 98.6 U/mL), a concentration of 66 U/mL or higher was defined as high (n = 89) and below 66 U/mL as low (n = 87). Three years after transplantation, eGFR was not significantly different among recipients in high versus low sCD30 groups (69 +/- 23 mL/min/1.73m2 vs 66 +/- 21 mL/min/1.73m2; P = .327) and there was no correlation between eGFR and pretransplant sCD30 levels (r2 = 0.001; P = .73). Upon multivariate regression analysis, donor age, recipient body mass index at transplantation, and acute rejection episodes were independent variables affecting eGFR at 3 years after transplantation. This study showed that pretransplant sCD30 serum concentrations were not associated with deceased-donor kidney graft function at 3 years after transplantation. The immunosuppression with anti-CD25 antibodies and a triple CsA-based maintenance regimen could possibly be decisive for our findings.

Association between GFR, proteinuria, and adverse outcomes among White, Chinese, and South Asian individuals in Canada.

PubMed

Conley, Joslyn; Tonelli, Marcello; Quan, Hude; Manns, Braden J; Palacios-Derflingher, Luz; Bresee, Lauren C; Khan, Nadia; Hemmelgarn, Brenda R

2012-03-01

We investigated the association between proteinuria, estimated glomerular filtration rate (eGFR), and risk of mortality and kidney failure in white, Chinese, and South Asian populations. Population-based cohort study. Participants from Alberta, Canada, with a serum creatinine and urine protein dipstick measurement from January 1, 2005, to December 31, 2005. White, Chinese, or South Asian ethnicity. Prevalence of proteinuria by level of eGFR (estimated using the MDRD [Modification of Diet in Renal Disease] Study equation) and the association between eGFR, proteinuria, and all-cause mortality and kidney failure. Rates of all-cause mortality and kidney failure per 1,000 person-years were calculated using Poisson regression by ethnicity, eGFR level, and proteinuria level while adjusting for sociodemographic variables and comorbid conditions. Of 491,729 participants, 5.3% were Chinese and 4.7% were South Asian. For participants with eGFR <60 mL/min/1.73 m(2), the prevalence of heavy proteinuria was higher in Chinese and South Asians compared with whites. Compared with whites, adjusted rates of death were significantly lower for Chinese and South Asian populations (rate ratios, 0.67 [95% CI, 0.56-0.80] and 0.73 [95% CI, 0.59-0.88], respectively); these rate ratios did not vary by eGFR and proteinuria levels. Using surname to identify ethnicity has the potential for misclassification due to name changes and identical last names from different ethnic groups. Also, to be eligible for inclusion, participants had to have a measurement of serum creatinine and urine dipstick proteinuria. Although increasing proteinuria and lower eGFR predicted mortality and progression to kidney failure in all 3 ethnic groups, both Chinese and South Asian populations experienced a lower risk of death and similar risk of kidney failure compared with whites at all eGFR and proteinuria levels. Studies exploring this association further are required. Copyright © 2012 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

How we estimate GFR--a pitfall of using a serum creatinine-based formula.

PubMed

Refaie, R; Moochhala, S H; Kanagasundaram, N S

2007-10-01

Chronic kidney disease (CKD) is defined using the estimated glomerular filtration rate (eGFR). This has led to a large increase in the diagnosis of CKD in the United Kingdom, the majority of which is in its earlier stages and is detected in non-hospital settings. It is important to be aware that eGFR calculations will reflect inaccuracies in the measured serum creatinine, as the latter is an important component of the calculation. We report a case in which a patient with high muscle-mass who had consumed large quantities of a creatine-containing nutritional supplement presented with apparently reduced renal function on the basis of the serum creatinine and therefore also the eGFR calculation (MDRD equation). Creatine is an amino acid which is a precursor of creatinine, and is known to transiently increase serum creatinine. 6 weeks after discontinuing creatine ingestion, serum creatinine had fallen but still gave rise to an apparently abnormal calculated eGFR. In fact, renal function was shown to be normal when estimated using 24-hour urinary creatinine clearance. This case demonstrates that the upper extreme of muscle mass and ingestion of creatine can affect not only serum creatinine but also the calculated eGFR. Knowledge of common confounding factors and their effects on serum creatinine and eGFR will allow appreciation of the limitations of these measures of renal function, and can prevent unnecessary over-investigation of such patients.

Changes in renal function after discontinuation of vitamin D analogues in advanced chronic kidney disease.

PubMed

Caravaca, Francisco; Caravaca-Fontán, Fernando; Azevedo, Lilia; Luna, Enrique

In routine clinical practice, the prescription of vitamin D analogues (VDA) in patients with chronic kidney disease (CKD) is often associated with a decline of the estimated renal function. The reason for this is not fully understood. To analyse the effects of VDA discontinuation in advanced CKD and to determine the factors associated with changes in renal function. Retrospective cohort study of adult patients with advanced CKD. The case subgroup was treated with VDA and this medication was discontinued at baseline (the first visit). The control subgroup was not treated with VDA and they were selected according to comparability principles for CKD progression by propensity score matching. The primary outcome measure was a change to both the estimated glomerular filtration rate (MDRD-GFR) and the measured glomerular filtration rate (mGFR by combined creatinine and urea clearances). Baseline parameters related to mineral metabolism and creatinine generation were analysed as potential determinants of renal function changes. The study sample consisted of 67 cases and 67 controls. Renal function improved in 67% of cases and worsened in 72% of controls (p<0.0001). Changes in MDRD-GFR for the case subgroup and the control subgroup were +0.455±0.997 vs. -0.436±1.103ml/min/1.73 m 2 /month (p<0.0001), respectively. Total creatinine excretion was slightly higher in cases than in controls but the difference was not significant. According to multivariate logistic and linear regression analyses, baseline total serum calcium was one of the best determinants of both renal function recovery (Odds ratio=3.49; p=0.001), and of the extent of renal function recovery (beta=0.276; p=0.001). Discontinuation of VDA treatment in CKD patients is associated with significant recovery of estimated renal function. The extent of these changes is mainly associated with baseline total serum calcium. Copyright © 2017 Sociedad Española de Nefrología. Published by Elsevier España, S.L.U. All rights reserved.

A Population Pharmacokinetic Model for 51Cr EDTA to Estimate Renal Function.

PubMed

Kuan, Isabelle H S; Duffull, Stephen B; Putt, Tracey L; Schollum, John B W; Walker, Robert J; Wright, Daniel F B

2017-06-01

51 Cr EDTA clearance (CL) from plasma is used to estimate glomerular filtration rate (GFR). We propose that current methods for analysing the raw 51 Cr EDTA measurements over-simplifies the disposition of 51 Cr EDTA and therefore could produce biased GFR estimates. The aim of this study was to develop a population pharmacokinetic model for 51 Cr EDTA disposition and to compare model-predicted GFR to other methods of estimating renal function. Data from 40 individuals who received ~7.4 MBq of 51 Cr EDTA, as an intravenous bolus, were available for analysis. Plasma radioactivity (counts/min) was measured from timed collection points at 2, 4, 6 and 24 h after the dose. A population analysis was conducted using NONMEM ® version 7.2. Model-predicted GFR was compared with other methods for estimating renal function using mean prediction error (MPE). A two-compartment pharmacokinetic model with first-order elimination best fit the data. Compared with the model predictions, creatinine CL from 24 h urine data was unbiased. The commonly used 'slope-intercept' method for estimating isotopic GFR was positively biased compared with the model (MPE 15.5 mL/min/1.73 m 2 [95% confidence interval {CI} 8.9-22.2]. The Cockcroft Gault, Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease Epidemiology Collaboration (CKD-Epi) equations led to negatively biased GFR estimates (MPE -19.0 [95% CI -25.4 to -12.7], -20.1 [95% CI -27.2 to -13.1] and -16.5 [95% CI -22.2 to -10.1] mL/min/1.73 m 2 , respectively). The biased GFR estimates were most obvious in patients with relatively normal renal function. This may lead to inaccurate dosing in patients who are receiving drugs with a narrow therapeutic range where dosing is adjusted according to GFR estimates (e.g. carboplatin). The study is registered with the Australian New Zealand Clinical Trials Registry (ANZCTR), number: ACTRN 12611000035921.

Chronic Kidney Disease and Risk of Presenting with Acute Myocardial Infarction versus Stable Exertional Angina in Adults with Coronary Heart Disease

PubMed Central

Go, Alan S.; Bansal, Nisha; Chandra, Malini; Lathon, Phenius V.; Fortmann, Stephen P.; Iribarren, Carlos; Hsu, Chi-yuan; Hlatky, Mark A.

2011-01-01

Objective To examine whether kidney dysfunction is associated with the type of clinical presentation of coronary heart disease (CHD). Background Reduced kidney function increases risk of developing CHD, but it is not known whether it also influences the acuity of clinical presentation, which has important prognostic implications. Methods We conducted a case-control study of subjects whose first clinical presentation of CHD was either acute myocardial infarction or stable exertional angina between October 2001-December 2003. Glomerular filtration rate (eGFR) before the incident event was estimated using calibrated serum creatinine and the abbreviated MDRD equation. Patient characteristics and use of medications were ascertained from self-report and health plan databases. We used multivariable logistic regression to examine the association of reduced eGFR and CHD presentation. Results We studied 803 adults with incident acute myocardial infarction and 419 adults with incident stable exertional angina who had a baseline eGFR ≤130 ml/min/1.73 m2. Mean eGFR was lower among subjects with acute myocardial infarction compared with stable angina. Compared with eGFR 90–130 ml/min/1.73 m2, we found a strong, graded independent association between reduced eGFR and presenting with acute myocardial infarction: adjusted odds ratio (OR) 1.36 (95% CI: 0.99 to 1.86) for eGFR 60–89 ml/min/1.73 m2, OR 1.55 (0.92 to 2.62) for eGFR 45–59 ml/min/1.73 m2 and OR 3.82 (1.55 to 9.46) for eGFR <45 ml/min/1.73 m2 (P<0.001 for trend). Conclusion eGFR less than 45 ml/min/1.73 m2 is a strong, independent predictor of presenting with acute myocardial infarction versus stable angina as the initial manifestation of CHD. PMID:21958887

Prevalence, evolution, and related risk factors of kidney disease among Spanish HIV-infected individuals

PubMed Central

Juega-Mariño, Javier; Bonjoch, Anna; Pérez-Alvarez, Nuria; Negredo, Eugenia; Bayes, Beatriu; Bonet, Josep; Clotet, Buenaventura; Romero, Ramon

2017-01-01

Abstract Prevalence of kidney disease (KD) is increasing among human immunodeficiency virus (HIV)-infected population. Different factors have been related, varying on different published series. The objectives were to study prevalence of KD in those patients, its evolution, and associated risk factors. An observational cohort study of 1596 HIV-positive patients with cross-sectional data collection in 2008 and 2010 was conducted. We obtained clinical and laboratory markers, and registered previous or current treatment with tenofovir (TDF) and indinavir (IDV). The sample was divided according to estimated glomerular filtration rate (eGFR) by modification of diet in renal disease (MDRD) equation. Group 1: eGFR ≤60 mL/min/1.73 m2; group 2: eGFR >60 mL/min/1.73 m2. Among the patients, 76.4% were men, mean age (SD) 45 ± 9 years, time since diagnose of HIV 14 ± 7 years, and 47.2% of the patients received previous treatment with TDF and 39.1% with IDV. In 2008, eGFR ≤60: 4.9% (91.4% of them in chronic kidney disease [CKD] stage 3, eGFR 59–30 mL/min); this group was older, presented higher fibrinogen levels, and more patients were treated previously with TDF and IDV. In 2010, eGFR ≤60: 3.9% (87.1% stage 3 CKD). The 2.4% of cohort showed renal improvement and 1.3% decline of renal function over time. The absence of hypertension and treatment with TDF were associated with improvement in eGFR. Increased age, elevated fibrinogen, decreased albumin, diabetes mellitus, hyperTG, and worse virological control were risk factors for renal impairment. The HIV-positive patients in our area have a CKD prevalence of 4% to 5% (90% stage 3 CKD) associated with ageing, inflammation, worse immune control of HIV, TDF treatment, and metabolic syndrome. PMID:28906351

Comparison of Associations of Urine Protein-Creatinine Ratio Versus Albumin-Creatinine Ratio With Complications of CKD: A Cross-sectional Analysis

PubMed Central

Fisher, Herrick; Hsu, Chi-yuan; Vittinghoff, Eric; Lin, Feng; Bansal, Nisha

2013-01-01

Background Urine albumin-creatinine ratio (ACR) and protein-creatinine ratio (PCR) are important markers of kidney damage and are utilized for prognosis in persons with chronic kidney disease (CKD). Despite how commonly these measurements are done in clinical practice, relatively few studies have directly compared the performance of these two measures with regard to associations with clinical outcomes, which may inform clinicians about which measure of urinary protein excretion is best. We studied the association of ACR and PCR with common complications of CKD. Study Design Cross-sectional study. Setting & Participants 3,481 participants with CKD in the Chronic Renal Insufficiency Cohort (CRIC) study. Predictors ACR and PCR. Outcomes We examined the association between ACR and PCR with measures of common CKD complications: serum hemoglobin, bicarbonate, parathyroid hormone, phosphorus, potassium and albumin. Measurements Restricted cubic spline analyses adjusted for estimated glomerular filtration rate (eGFR; calculated by the MDRD [Modification of Diet in Renal Disease] Study Equation) were performed to study the continuous association with our predictors with each outcome. Results Mean eGFR was 43 ± 13 (SD) ml/min/1.73 m2 and median levels of PCR and ACR were 140 and 46 mg/g, respectively. In continuous analyses adjusted for eGFR, higher ACR and PCR were comparable and both were associated with lower levels of serum hemoglobin, bicarbonate, and albumin and higher levels of parathyroid hormone, phosphorus, and potassium. Across all outcomes, the associations of ACR and PCR were comparable with only small, absolute differences in the outcome measure. Similar associations were seen in patients with diabetes mellitus. Limitations Participants largely had moderate CKD with low levels of ACR and PCR, so results may not be generalizable to all CKD populations. Conclusions In persons with CKD, ACR and PCR are relatively comparable in their associations with common complications of CKD. Thus routine measurement of PCR may provide similar information as ACR in managing immediate complications of CKD. PMID:24041612

The influence of genetic polymorphisms of cytochrome P450 3A5 and ABCB1 on starting dose- and weight-standardized tacrolimus trough concentrations after kidney transplantation in relation to renal function.

PubMed

Mourad, Michel; Wallemacq, Pierre; De Meyer, Martine; Brandt, Dimitri; Van Kerkhove, Valérie; Malaise, Jacques; Chaïb Eddour, Djamila; Lison, Dominique; Haufroid, Vincent

2006-01-01

Cytochrome P450 3A5 (CYP3A5) and ABCB1 polymorphisms have been shown to influence tacrolimus (Tc) blood concentrations in the stable phase after organ transplantation. We hypothesized that Tc pharmacokinetics may be affected by genetic mutations subsequent to starting doses. We retrospectively analyzed data from a cohort of 59 kidney transplant recipients, in whom CYP3A5 (intron 3) and ABCB1 (exons 12, 21 and 26) genotypes were correlated to dose- and weight-standardized Tc trough concentrations obtained after initial Tc doses. Renal function, expressed as glomerular filtration rate (GFR) (MDRD equation), on days 7 and 14 after transplantation was evaluated and its relationship with Tc concentrations was analyzed. Dose- and weight-standardized Tc trough concentrations were lower in patients carrying the CYP3A5 *1 allele (p<0.01). There was no statistically significant association with ABCB1 polymorphisms. In a multivariate analysis, both the presence of at least one CYP3A5 *1 allele (p=0.006) and age at the time of transplantation (p=0.010) were significant independent variables affecting Tc trough blood concentrations standardized to the first dosages (model r2=0.23). GFR was not affected by Tc concentrations. Prospective trials are needed to prove that a genetic approach to Tc pharmacokinetics and its related side effects during the early period after grafting may improve patient outcome.

Prediction of two-sample (99m)Tc-diethylene triamine pentaacetic acid plasma clearance from single-sample method.

PubMed

Zuo, Li; Ying-Chun; Wang, Mei; Zhang, Chun-Li; Wang, Rong-Fu; Wang, Hai-Yan

2005-07-01

To develop an equation to predict dual plasma sample method (DPSM) (99m)Tc-diethylene triamine pentaacetic acid ((99m)Tc-DTPA) plasma clearance from single plasma sample method (SPSM), and to clarify the condition in which DPSM can be substituted by SPSM in measurement of glomerular filtration rate (GFR). Patients with chronic kidney disease (CKD) were selected. Watson modified Christensen and Groth equation was used to calculate (99m)Tc-DTPA plasma clearance by SPSM (sGFR). The equation recommended by the Nephrourology Committee of the Society of Nuclear Medicine was used to calculate (99m)Tc-DTPA plasma clearance by DPSM (tGFR) in each patient. The difference between sGFR and tGFR was expressed as percent of the average of these two methods, and tGFR was predicted from sGFR. Plasma creatinine was measured by the kinetic picrate method, and GFR estimated by abbreviated modification of diet in renal disease (MDRD) equation (aGFR) and Cockcroft-Gault equation (cGFR) were evaluated as criteria in selection of DPSM and SPSM. Three hundred and sixty-nine patients with CKD were selected (208 male and 161 female). The average age and body weight were 51.4 +/- 15.5 years and 67.2 +/- 12.5 kg, respectively. The causes of CKD were glomerular disease, renal arterial stenosis, chronic tubulointerstitial disease, and other causes or causes unknown. The average tGFR was 62.9 +/- 36.5 ml/min/1.73 m2, ranging from 1-180 ml/min/1.73 m2. sGFR was significantly correlated with tGFR (r = 0.9194, p < 0.001), but widely scattered when tGFR <30 ml/min/1.73 m2; in contrast, then tGFR was > or =30 ml/min/1.73 m2, the difference was constant (-1.1%, 95% confidence interval -18.3%, 16.1%), and tGFR could be predicted from sGFR using the equation: predicted tGFR (ml/min/1.73 m2) = 7.4244 + 0.7318 x sGFR + 0.0022 x sGFR2 (n = 299, r2 = 0.9428, p < 0.001), and the difference decreased to 0.1%, 95% confidence interval (-15.8%, 16.0%). aGFR was better than cGFR in diagnosis of tGFR <30 ml/min/1.73 m2, the diagnostic sensitivity of a cut off value of aGFR = 45 ml/min/1.73 m2 was 91.8%, and recommended as a criterion in the selection of DPSM and SPSM. When GFR > or =30 ml/min/1.73 m2, tGFR can be predicted from sGFR, which will simplify the reference GFR measurement in clinical trials. sGFR becomes widely scattered when tGFR is less than 30 ml/min/1.73 m2. To obtain reliable reference GFR values, it is recommended that DPSM be used in clinical trials when aGFR is less than 45 ml/min/1.73 m2.

Neurobiological Underpinnings of Math and Reading Learning Disabilities

PubMed Central

Ashkenazi, Sarit; Black, Jessica M.; Abrams, Daniel A.; Hoeft, Fumiko; Menon, Vinod

2013-01-01

The primary goal of this review is to highlight current research and theories describing the neurobiological basis of math (MD), reading (RD), and comorbid math and reading disability (MD+RD). We first describe the unique brain and cognitive processes involved in acquisition of math and reading skills, emphasizing similarities and differences in each domain. Next we review functional imaging studies of MD and RD in children, integrating relevant theories from experimental psychology and cognitive neuroscience to characterize the functional neuroanatomy of cognitive dysfunction in MD and RD. We then review recent research on the anatomical correlates of MD and RD. Converging evidence from morphometry and tractography studies are presented to highlight distinct patterns of white matter pathways which are disrupted in MD and RD. Finally, we examine how the intersection of MD and RD provides a unique opportunity to clarify the unique and shared brain systems which adversely impact learning and skill acquisition in MD and RD, and point out important areas for future work on comorbid learning disabilities. PMID:23572008

A comparison of the extended-release and standard-release formulations of tacrolimus in de novo kidney transplant recipients: a 12-month outcome study.

PubMed

Fanous, Helen; Zheng, Rebecca; Campbell, Carolyn; Huang, Michael; Nash, Michelle M; Rapi, Lindita; Zaltzman, Jeffrey S; Prasad, G V Ramesh

2013-02-01

BACKGROUND: Limited comparative data are available on the outcomes between extended-release and standard-release tacrolimus when used de novo in kidney transplant recipients (KTRs). METHODS: We identified KTRs transplanted at our institution during 2009-10 routinely prescribed extended-release tacrolimus and compared them with those transplanted during 2008-09 prescribed standard-release tacrolimus. Graft function (eGFR by MDRD-7 equation) at 12 months post-transplant (primary outcome); new-onset diabetes and other cardiovascular risk factors, BK viremia incidence, acute rejection, and graft survival to 12 months (secondary outcomes) were compared by intent-to-treat analysis. Time-to-steady-state concentration and number of dose adjustments required to attain steady state were recorded. RESULTS: There were no important demographic differences between the extended-release (N = 106) and standard-release (N = 95) cohorts. The estimated glomerular filtration rate (eGFR) at 12 months was similar (58.8 ± 17 versus 59.2 ± 18 mL/min/1.73 m(2), P = 0.307). There was no difference in new-onset diabetes (17 versus 20%, P = 0.581), BK viremia (10 versus 7%, P = 0.450), acute rejection (7 versus 16%, P = 0.067) or graft survival (97 versus 95%, P = 0.301). Time-to-steady state was similar (9.2 ± 1.1 versus 8.1 ± 4.7 days, P = 0.490) although extended-release patients required fewer adjustments to attain steady state (1.2 ± 1.7 [0-8] versus 1.7 ± 1.5 [0-7], P = 0.030) but a similar dose (7.2 ± 2.4 [2-17] versus 7 ± 2.7 [2-16] mg/day, P = 0.697). CONCLUSION: De novo KTRs prescribed extended-release or standard-release tacrolimus demonstrate similar 12-month outcomes.

Association of ABCB1 genetic variants with renal function in Africans and in Caucasians

PubMed Central

Bochud, Murielle; Eap, Chin B; Maillard, Marc; Johnson, Toby; Vollenweider, Peter; Bovet, Pascal; Elston, Robert C; Bergmann, Sven; Beckmann, Jacques S; Waterworth, Dawn M; Mooser, Vincent; Gabriel, Anne; Burnier, Michel

2008-01-01

Background The P-glycoprotein, encoded by the ABCB1 gene, is expressed in human endothelial and mesangial cells, which contribute to control renal plasma flow and glomerular filtration rate. We investigated the association of ABCB1 variants with renal function in African and Caucasian subjects. Methods In Africans (290 subjects from 62 pedigrees), we genotyped the 2677G>T and 3435 C>T ABCB1 polymorphisms. Glomerular filtration rate (GFR) was measured using inulin clearance and effective renal plasma flow (ERPF) using para-aminohippurate clearance. In Caucasians (5382 unrelated subjects), we analyzed 30 SNPs located within and around ABCB1, using data from the Affymetrix 500 K chip. GFR was estimated using the simplified Modification of the Diet in Renal Disease (MDRD) and Cockcroft-Gault equations. Results In Africans, compared to the reference genotype (GG or CC), each copy of the 2677T and 3435T allele was associated, respectively, with: GFR higher by 10.6 ± 2.9 (P < 0.001) and 4.4 ± 2.3 (P = 0.06) mL/min; ERPF higher by 47.5 ± 11.6 (P < 0.001) and 28.1 ± 10.5 (P = 0.007) mL/min; and renal resistances lower by 0.016 ± 0.004 (P < 0.001) and 0.011 ± 0.004 (P = 0.004) mm Hg/mL/min. In Caucasians, we identified 3 polymorphisms in the ABCB1 gene that were strongly associated with all estimates of GFR (smallest P value = 0.0006, overall P = 0.014 after multiple testing correction). Conclusion Variants of the ABCB1 gene were associated with renal function in both Africans and Caucasians and may therefore confer susceptibility to nephropathy in humans. If confirmed in other studies, these results point toward a new candidate gene for nephropathy in humans. PMID:18518969

Awareness, self-management behaviors, health literacy and kidney function relationships in specialty practice

PubMed Central

Devraj, Radhika; Borrego, Matthew E; Vilay, A Mary; Pailden, Junvie; Horowitz, Bruce

2018-01-01

AIM To determine the relationship between chronic kidney disease (CKD) awareness (CKD-A), self-management behaviors (CKD-SMB) knowledge, performance of CKD-SMBs, health literacy (HL) and kidney function. METHODS Participants were eligible patients attending an outpatient nephrology clinic. Participants were administered: Newest Vital Sign to measure HL, CKD self-management knowledge tool (CKD-SMKT) to assess knowledge, past performance of CKD-SMB, CKD-A. Estimated GFR (eGFR) was determined using the MDRD-4 equation. Duration of clinic participation and CKD cause were extracted from medical charts. RESULTS One-hundred-fifty patients participated in the study. eGFRs ranged from 17-152 mL/min per 1.73 m2. Majority (83%) of respondents had stage 3 or 4 CKD, low HL (63%), and were CKD aware (88%). Approximately 40% (10/25) of patients in stages 1 and 2 and 6.4% (8/125) in stages 3 and 4 were unaware of their CKD. CKD-A differed with stage (P < 0.001) but not by HL level, duration of clinic participation, or CKD cause. Majority of respondents (≥ 90%) correctly answered one or more CKD-SMKT items. Knowledge of one behavior, “controlling blood pressure” differed significantly by CKD-A. CKD-A was associated with past performance of two CKD-SMBs, “controlling blood pressure” (P = 0.02), and “keeping healthy body weight” (P = 0.01). Adjusted multivariate analyses between CKD-A and: (1) HL; and (2) CKD-SMB knowledge were non-significant. However, there was a significant relationship between CKD-A and kidney function after controlling for demographics, HL, and CKD-SMB (P < 0.05). CONCLUSION CKD-A is not associated with HL, or better CKD-SMBs. CKD-A is significantly associated with kidney function and substantially lower eGFR, suggesting the need for focused patient education in CKD stages 1. PMID:29359119

Associations of blood lead, cadmium, and mercury with estimated glomerular filtration rate in the Korean general population: Analysis of 2008-2010 Korean National Health and Nutrition Examination Survey data

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

Kim, Yangho; Lee, Byung-Kook, E-mail: bklee@sch.ac.kr

Introduction: The objective of this study was to evaluate associations between blood lead, cadmium, and mercury levels with estimated glomerular filtration rate in a general population of South Korean adults. Methods: This was a cross-sectional study based on data obtained in the Korean National Health and Nutrition Examination Survey (KNHANES) (2008-2010). The final analytical sample consisted of 5924 participants. Estimated glomerular filtration rate (eGFR) was calculated using the MDRD Study equation as an indicator of glomerular function. Results: In multiple linear regression analysis of log2-transformed blood lead as a continuous variable on eGFR, after adjusting for covariates including cadmium andmore » mercury, the difference in eGFR levels associated with doubling of blood lead were -2.624 mL/min per 1.73 m Superscript-Two (95% CI: -3.803 to -1.445). In multiple linear regression analysis using quartiles of blood lead as the independent variable, the difference in eGFR levels comparing participants in the highest versus the lowest quartiles of blood lead was -3.835 mL/min per 1.73 m Superscript-Two (95% CI: -5.730 to -1.939). In a multiple linear regression analysis using blood cadmium and mercury, as continuous or categorical variables, as independent variables, neither metal was a significant predictor of eGFR. Odds ratios (ORs) and 95% CI values for reduced eGFR calculated for log2-transformed blood metals and quartiles of the three metals showed similar trends after adjustment for covariates. Discussion: In this large, representative sample of South Korean adults, elevated blood lead level was consistently associated with lower eGFR levels and with the prevalence of reduced eGFR even in blood lead levels below 10 {mu}g/dL. In conclusion, elevated blood lead level was associated with lower eGFR in a Korean general population, supporting the role of lead as a risk factor for chronic kidney disease.« less

Nutritional status and body composition in patients early after renal transplantation.

PubMed

Netto, M C A S; Alves-Filho, G; Mazzali, M

2012-10-01

After renal transplantation recovery in nutritional status occurs during the first year. We assessed the changes in nutritional status after transplantation in 145 transplant recipients (94 males, 51 females). Patients were evaluated immediately after renal transplant (baseline data) and at 6 months' follow-up. Analysis included body mass index (BMI), body composition (skin fold and arm circumference), and estimated body composition (calculated percent of fat, arm circumference, arm muscle circumference, and arm muscle area). Other data obtained from medical records included renal function (MDRD) serum albumin and lipid profile. At baseline evaluation (21 ± 15 days posttransplant), mean BMI was 23.9 ± 3.9 kg/m(2), serum albumin was 3.7 ± 0.7 g/dL, and lipid profile showed (cholesterol 158.5 ± 52.7 mg% and triglycerides 135.9 ± 91.8 mg%. Body composition analysis showed better adaptation of muscle mass in females [AC (91 ± 10.2 × 98 ± 14.6; male × female, P < .05) arm muscle circumference (92.6 ± 1.4 × 102.3% ± 2.9%, male × female, P < .05) and arm muscle area (87.1 ± 22.3 × 105.5% ± 25.9%, male × female, P < .05)]. Body fat was above the recommended levels in 80% of patients, especially females. After 6 months we divided the groups according to BMI, observing better renal function in the normal weight group compared with obese subjects (60 ± 17.2 × 39.5 ± 19.8 mL/min MDRD, P < .05), despite comparable estimated glomerular filtration rate at baseline. The nutritional assessment of patients with end-stage renal disease early after renal transplantation, showed inadequate body composition, with increased fat and reduced lean body mass. The lower glomerular filtration rate after 6 months may be attributed to relatively inadequate renal mass or to obesity-induced hyperfiltration. Copyright © 2012 Elsevier Inc. All rights reserved.

Prediction of cardiovascular outcome by estimated glomerular filtration rate and estimated creatinine clearance in the high-risk hypertension population of the VALUE trial.

PubMed

Ruilope, Luis M; Zanchetti, Alberto; Julius, Stevo; McInnes, Gordon T; Segura, Julian; Stolt, Pelle; Hua, Tsushung A; Weber, Michael A; Jamerson, Ken

2007-07-01

Reduced renal function is predictive of poor cardiovascular outcomes but the predictive value of different measures of renal function is uncertain. We compared the value of estimated creatinine clearance, using the Cockcroft-Gault formula, with that of estimated glomerular filtration rate (GFR), using the Modification of Diet in Renal Disease (MDRD) formula, as predictors of cardiovascular outcome in 15 245 high-risk hypertensive participants in the Valsartan Antihypertensive Long-term Use Evaluation (VALUE) trial. For the primary end-point, the three secondary end-points and for all-cause death, outcomes were compared for individuals with baseline estimated creatinine clearance and estimated GFR < 60 ml/min and > or = 60 ml/min using hazard ratios and 95% confidence intervals. Coronary heart disease, left ventricular hypertrophy, age, sex and treatment effects were included as covariates in the model. For each end-point considered, the risk in individuals with poor renal function at baseline was greater than in those with better renal function. Estimated creatinine clearance (Cockcroft-Gault) was significantly predictive only of all-cause death [hazard ratio = 1.223, 95% confidence interval (CI) = 1.076-1.390; P = 0.0021] whereas estimated GFR was predictive of all outcomes except stroke. Hazard ratios (95% CIs) for estimated GFR were: primary cardiac end-point, 1.497 (1.332-1.682), P < 0.0001; myocardial infarction, 1.501 (1.254-1.796), P < 0.0001; congestive heart failure, 1.699 (1.435-2.013), P < 0.0001; stroke, 1.152 (0.952-1.394) P = 0.1452; and all-cause death, 1.231 (1.098-1.380), P = 0.0004. These results indicate that estimated glomerular filtration rate calculated with the MDRD formula is more informative than estimated creatinine clearance (Cockcroft-Gault) in the prediction of cardiovascular outcomes.

A lower baseline glomerular filtration rate predicts high mortality and newly cerebrovascular accidents in acute ischemic stroke patients.

PubMed

Dong, Kai; Huang, Xiaoqin; Zhang, Qian; Yu, Zhipeng; Ding, Jianping; Song, Haiqing

2017-02-01

Chronic kidney disease (CKD) is gradually recognized as an independent risk factor for cardiovascular and cardio-/cerebrovascular disease. This study aimed to examine the association of the estimated glomerular filtration rate (eGFR) and clinical outcomes at 3 months after the onset of ischemic stroke in a hospitalized Chinese population.Totally, 972 patients with acute ischemic stroke were enrolled into this study. Modified of Diet in Renal Disease (MDRD) equations were used to calculate eGFR and define CKD. The site and degree of the stenosis were examined. Patients were followed-up for 3 months. Endpoint events included all-cause death and newly ischemic events. The multivariate logistic model was used to determine the association between renal dysfunction and patients' outcomes.Of all patients, 130 patients (13.4%) had reduced eGFR (<60 mL/min/1.73 m), and 556 patients had a normal eGFR (≥90 mL/min/1.73 m). A total of 694 patients suffered from cerebral artery stenosis, in which 293 patients only had intracranial artery stenosis (ICAS), 110 only with extracranial carotid atherosclerotic stenosis (ECAS), and 301 with both ICAS and ECAS. The patients with eGFR <60 mL/min/1.73m had a higher proportion of death and newly ischemic events compared with those with a relatively normal eGFR. Multivariate analysis revealed that a baseline eGFR <60 mL/min/1.73 m increased the risk of mortality by 3.089-fold and newly ischemic events by 4.067-fold. In further analysis, a reduced eGFR was associated with increased rates of mortality and newly events both in ICAS patients and ECAS patients. However, only an increased risk of newly events was found as the degree of renal function deteriorated in ICAS patients (odds ratio = 8.169, 95% confidence interval = 2.445-14.127).A low baseline eGFR predicted a high mortality and newly ischemic events at 3 months in ischemic stroke patients. A low baseline eGFR was also a strong independent predictor for newly ischemic events in ICAS patients.

Association of APOE polymorphism with chronic kidney disease in a nationally representative sample: a Third National Health and Nutrition Examination Survey (NHANES III) Genetic Study

PubMed Central

Chu, Audrey Y; Parekh, Rulan S; Astor, Brad C; Coresh, Josef; Berthier-Schaad, Yvette; Smith, Michael W; Shuldiner, Alan R; Kao, Wen Hong L

2009-01-01

Background Apolipoprotein E polymorphisms (APOE) have been associated with lowered glomerular filtration rate (GFR) and chronic kidney disease (CKD) with e2 allele conferring risk and e4 providing protection. However, few data are available in non-European ethnic groups or in a population-based cohort. Methods The authors analyzed 5,583 individuals from the Third National Health and Nutrition Examination Survey (NHANES III) to determine association with estimated GFR by the Modification of Diet in Renal Disease (MDRD) equation and low-GFR cases. Low-GFR cases were defined as GFR <75 ml/min/1.73 m2; additionally, GFR was analyzed continuously. Results In univariate analysis, the e4 allele was negatively associated with low-GFR cases in non-Hispanic whites, odds ratio (OR): 0.76, 95% confidence interval (CI): 0.60, 0.97. In whites, there was a significant association between increasing APOE score (indicating greater number of e2 alleles) and higher prevalence of low-GFR cases (OR: 1.21, 95%CI: 1.01, 1.45). Analysis of continuous GFR in whites found the e4 allele was associated with higher levels of continuous GFR (β-coefficient: 2.57 ml/min/1.73 m2, 95%CI: 0.005, 5.14); in non-Hispanic blacks the e2 allele was associated with lower levels of continuous GFR (β-coefficient: -3.73 ml/min/1.73 m2, 95%CI: -6.61, -0.84). APOE e2 and e4 alleles were rare and not associated with low-GFR cases or continuous GFR in Mexican Americans. Conclusion In conclusion, the authors observed a weak association between the APOE e4 allele and low-GFR cases and continuous GFR in non-Hispanic whites, and the APOE e2 allele and continuous GFR in non-Hispanic blacks, but found no association with either measure of kidney function in Mexican Americans. Larger studies including multiethnic groups are needed to determine the significance of this association. PMID:19852818

Numerical Magnitude Representation in Children With Mathematical Difficulties With or Without Reading Difficulties.

PubMed

Tobia, Valentina; Fasola, Anna; Lupieri, Alice; Marzocchi, Gian Marco

2016-01-01

This study aimed to explore the spatial numerical association of response codes (SNARC), the flanker, and the numerical distance effects in children with mathematical difficulties. From a sample of 720 third, fourth, and fifth graders, 60 children were selected and divided into the following three groups: typically developing children (TD; n = 29), children with mathematical difficulties only (MD only; n = 21), and children with mathematical and reading difficulties (MD+RD; n = 10). Children were tested with a numerical Eriksen task that was built to assess SNARC, numerical distance, and flanker (first and second order congruency) effects. Children with MD only showed stronger SNARC and second order congruency effects than did TD children, whereas the numerical distance effects were similar across the three groups. Finally, the first order congruency effect was associated with reading difficulties. These results showed that children with mathematical difficulties with or without reading difficulties were globally more impaired when spatial incompatibilities were presented. © Hammill Institute on Disabilities 2014.

Percutaneous Coronary Intervention versus Coronary Artery Bypass Grafting in Patients with Diabetic Nephropathy and Left Main Coronary Artery Disease.

PubMed

Li, Hsin-Ru; Hsu, Chiao-Po; Sung, Shih-Hsien; Shih, Chun-Che; Lin, Shing-Jong; Chan, Wan-Leong; Wu, Cheng-Hsueh; Lu, Tse-Min

2017-03-01

Patients with diabetic nephropathy and unprotected left main (LM) coronary artery disease suffer from high cardiovascular morbidity and mortality. Although surgical revascularization is currently recommended in this special patient population, the optimal revascularization method for this distinct patient group has remained unclear. We collected 99 consecutive patients with unprotected LM disease and diabetic nephropathy, including 46 patients who had undergone percutaneous coronary intervention (PCI), and 53 who had coronary artery bypass grafting (CABG), with a mean age of 72 ± 10; with 80.8% male. Diabetic nephropathy was defined as overt proteinuria (proteinuria > 500 mg/day) and estimated glomerular filtration rate (eGFR) by the modified Modification of Diet in Renal Disease (MDRD) equation of less than 60 mL/min/1.73 m 2 . The baseline characteristics, angiographic results and long-term clinical outcomes were retrospectively analyzed. The baseline characteristic of all patients were similar except for smokers, low density lipoprotein (LDL) level and extension of coronary artery disease involvement. The median follow-up period was 3.8 years. There were 73 patients (74%) considered as high risk with additive European System for Cardiac Operative Risk Evaluation (EuroSCORE) ≥ 6. During follow-up period, the long term rate of all-cause death (PCI vs. CABG: 45.7% vs. 58.5%, p = 0.20) and all-cause death/myocardial infarction (MI)/stroke (PCI vs. CABG: 52.2% vs. 60.4%, p = 0.41) were comparable between the PCI and CABG group, whereas the repeat revascularization rate was significantly higher in the PCI group (PCI vs. CABG: 32.6% vs. 9.4%, p < 0.01). eGFR remained an independent predictor for all-cause death [hazard ratio: 0.97, 95% confidence interval: 0.96 to 0.99; p = 0.002] in multivariate logistic regression. In the real-world practice of high-risk patients with unprotected LM disease and diabetic nephropathy, we found that PCI was a comparable alternative to CABG in terms of long-term risks of all-cause death/MI/stroke, with significantly higher repeat revascularization rate. Given the small patient number and retrospective nature, our findings should be validated by larger-scale randomized studies.

Numerical and arithmetical cognition: a longitudinal study of process and concept deficits in children with learning disability.

PubMed

Geary, D C; Hamson, C O; Hoard, M K

2000-11-01

Based on the stability and level of performance on standard achievement tests in first and second grade (mean age in first grade = 82 months), children with IQ scores in the low-average to high-average range were classified as learning disabled (LD) in mathematics (MD), reading (RD), or both (MD/RD). These children (n = 42), a group of children who showed variable achievement test performance across grades (n = 16), and a control group of academically normal peers (n = 35) were administered a series of experimental and psychometric tasks. The tasks assessed number comprehension and production skills, counting knowledge, arithmetic skills, working memory, the ease of activation of phonetic representations of words and numbers, and spatial abilities. The children with variable achievement test performance did not differ from the academically normal children in any cognitive domain, whereas the children in the LD groups showed specific patterns of cognitive deficit, above and beyond the influence of IQ. Discussion focuses on the similarities and differences across the groups of LD children. Copyright 2000 Academic Press.

Type 2 diabetes mellitus in elderly institutionalized patients.

PubMed

Cano Megias, M; Guisado Vasco, P

2014-12-01

A 93-year-old woman is admitted to a conventional hospital ward for an acute respiratory infection. The patient has type 2 diabetes mellitus of approximately 15 years evolution and has no other associated comorbidities, except for progressive dependence due to senescence and a previous hospitalization for pneumonia 6 months ago. She is currently in an assisted-living residence. A recent laboratory test revealed an HbA1c level of 7.8%, with a serum creatinine level of 1.3mg/dl (MDRD, 45ml/min). Her standard treatment consists of 5mg of glibenclamide a day and 850mg of metformin every 12hours. What regimen should we follow once she is hospitalized? Does she require any change in her treatment at discharge? Copyright © 2013 Elsevier España, S.L.U. All rights reserved.

Arterial stiffness, body fat compartments, central hemodynamics, renal function and left atrial size.

PubMed

Katulska, Katarzyna; Milewska, Agata; Wykretowicz, Mateusz; Krauze, Tomasz; Przymuszala, Dagmara; Piskorski, Jaroslaw; Stajgis, Marek; Guzik, Przemyslaw; Wysocki, Henryk; Wykrętowicz, Andrzej

2013-10-01

Left atrial (LA) size is an important predictor of stroke, death, and atrial fibrillation. It was demonstrated recently that body fat, arterial stiffness and renal functions are associated with LA diameter. However, data are lacking for comprehensive assessments of all these risk factors in a single population. Therefore, the aim of the present study was to investigate the association between LA size and different fat descriptors, central hemodynamics, arterial stiffness, and renal function in healthy subjects. To this end, body fat percentage, abdominal, subcutaneous fat, and general descriptors of body fat were estimated in 162 healthy subjects (mean age 51 years). Echocardiography was performed to assess LA diameter. Arterial stiffness and peripheral and central hemodynamics were estimated by digital volume pulse analysis and pulse wave analysis. Glomerular filtration rate was estimated by MDRD formula. There were significant (p < 0.05) bivariate correlations between LA diameter and all descriptors of body fat (except subcutaneous fat). Arterial stiffness and estimated glomerular filtration rate (eGFR) were also significantly correlated with LA size. Multiple regression analysis including all significant confounders, such as sex, mean arterial pressure, arterial stiffness, eGFR and body fat descriptors, explained 35% of variance in LA diameter. In conclusion, the present study reveals significant, independent relationships between body fat, arterial stiffness, and LA size.

Glomerular Filtration Rate is Unchanged By Ultramarathon.

PubMed

Wołyniec, Wojciech; Ratkowski, Wojciech; Kasprowicz, Katarzyna; Jastrzębski, Zbigniew; Małgorzewicz, Sylwia; Witek, Konrad; Grzywacz, Tomasz; Żmijewski, Piotr; Renke, Marcin

2017-12-27

Acute kidney injury (AKI) is reported as a common complication of marathon and ultramarathon running. In previous studies AKI was diagnosed on the basis of the creatinine level in serum and estimated glomerular filtration rate (eGFR). In the present study we calculated eGFR and also measured creatinine clearance after every 25 km of a 100 km run. 20 healthy, amateur runners (males, mean age 40.75 ± 7.15 years, mean weight 76.87 ± 8.39 kg) took part in a 100 km run on a track. Blood and urine were collected before the run, after every 25 km and 12 hours after the run. 17 runners completed the study. There was increase in creatinine, urea and uric acid observed after 100 km (p < 0.05). The mean increase in creatinine was 0.21 mg/dl (24.53%). 5 runners fulfilled the Acute Kidney Injury Network (AKIN) criteria of AKI. The eGFR according to the MDRD (modification of diet in renal disease), CKD-EPI (chronic kidney disease epidemiology collaboration) and Cockcroft-Gault formulas was significantly decreased after the run (p < 0.05). Otherwise, creatinine clearance calculated from creatinine level in both serum and urine remained stable. In contrast to the majority of previous studies, we did not observe any decrease in the kidney function during an ultramarathon. In this study the creatinine clearance, which is the best routine laboratory method to determine glomerular filtration rate was used. There is no evidence that long running is harmful for kidney.

Higher risk of renal impairment associated with tenofovir use amongst people living with HIV in India: a comparative cohort analysis between Western India and United Kingdom.

PubMed

Pujari, Sanjay N; Smith, Colette; Makane, Abhimanyu; Youle, Mike; Johnson, Margaret; Bele, Vivek; Joshi, Kedar; Dabhade, Digamber; Bhagani, Sanjay

2014-03-29

Data on the renal safety of Tenofovir (TDF) in Low and Middle Income Countries (LMICs) is scarce. We compared development of various forms of renal impairment with use of TDF-containing antiretroviral therapy (ART) between a cohort from the Institute of Infectious Diseases (IID) Pune, Western India and the Royal Free Hospital (RFH) London, UK. This is a retrospective analysis of change in estimated glomerular filtration rates (eGFRs) at 6, 12 and 24 months post TDF initiation using the Modification of Diet in Renal Disease (MDRD) equation. In people living with Human Immunodeficiency virus (PLHIV) with pre-TDF eGFR > 90 ml/min/1.73 m2 time to development of and factors associated with progression to eGFR < 60 ml/min/1.73 m2 were calculated using standard survival methods. A total of 574 (59% Caucasian) at the RFH, and 708 (100% Indian ethnicity) PLHIV from IID were included. Baseline median eGFR were similar; RFH 102 (IQR 89, 117), IID 100 (82, 119). At 24 months, mean (SD) decline in eGFR was -7(21) at RFH (p < 0.0001) and -7(40) at IID (p = 0.001). Amongst those with pre-TDF eGFR > 90 ml/min/1.73 m2 PLHIV at IID were more likely to develop an eGFR < 60 ml/min/1.73 m2 (aHR = 7.6 [95% CI 3.4, 17.4] p < 0.0001) and had a faster rate of progression estimated using Kaplan Meier methods. Risk factors included age (per 10 years older: aHR = 2.21 [1.6, 3.0] p < 0.0001) and receiving concomitant ritonavir boosted Protease Inhibitor (PI/r) (aHR = 2.4 [1.2, 4.8] p = 0.01). There is higher frequency of treatment limiting renal impairment events amongst PLHIV receiving TDF in Western India. As TDF scale up progresses, programs need to develop capacity for monitoring and treatment of renal impairment associated with TDF.

[Hypoglycemic treatment in type 2 diabetes patients suffering from moderate to severe renal failure in France. Aim of the study].

PubMed

Bouée, Stéphane; Gaudin, Anne-Françoise; Amelineau, Elisabeth; Bonnet, Fabrice

2013-01-01

The purpose of this study is to describe the hypoglycemic agents prescribed to type 2 diabetes patients (T2D) with renal impairment (RI). Data were extracted from the database LPD-CEGEDIM, based on a sample of 1200 general practitioners. The analysis focused on T2D patients with RI, defined by a glomerular filtration rate (GFR) below 60 mL/min/1.73 m², estimated by the MDRD formula. Of the 36 255 patients identified with T2D, a GFR was calculated for 8 647 patients (23.9%), 1 472 (22%) with a moderate RI (GFR=[30mL/min/1.73 m²-60mL/min/1.73 m²]) and 86 (1.0%) with a severe RI (GFR=[15mL/min/1.73 m-30mL/min/1.73 m²]); 47,6% of T2D patients with a moderate RI and 52,3% of T2D patients with a severe RI were treated with at least one drug contraindicated in patients with moderate or severe RI. These findings suggest better informing doctors of these contraindications and show the value of having new hypoglycemic drugs that can be used in case of RI. © 2013 Société Française de Pharmacologie et de Thérapeutique.

Dietary protein intake and chronic kidney disease.

PubMed

Ko, Gang Jee; Obi, Yoshitsugu; Tortorici, Amanda R; Kalantar-Zadeh, Kamyar

2017-01-01

High-protein intake may lead to increased intraglomerular pressure and glomerular hyperfiltration. This can cause damage to glomerular structure leading to or aggravating chronic kidney disease (CKD). Hence, a low-protein diet (LPD) of 0.6-0.8 g/kg/day is often recommended for the management of CKD. We reviewed the effect of protein intake on incidence and progression of CKD and the role of LPD in the CKD management. Actual dietary protein consumption in CKD patients remains substantially higher than the recommendations for LPD. Notwithstanding the inconclusive results of the 'Modification of Diet in Renal Disease' (MDRD) study, the largest randomized controlled trial to examine protein restriction in CKD, several prior and subsequent studies and meta-analyses appear to support the role of LPD on retarding progression of CKD and delaying initiation of maintenance dialysis therapy. LPD can also be used to control metabolic derangements in CKD. Supplemented LPD with essential amino acids or their ketoanalogs may be used for incremental transition to dialysis especially on nondialysis days. The LPD management in lieu of dialysis therapy can reduce costs, enhance psychological adaptation, and preserve residual renal function upon transition to dialysis. Adherence and adequate protein and energy intake should be ensured to avoid protein-energy wasting. A balanced and individualized dietary approach based on LPD should be elaborated with periodic dietitian counseling and surveillance to optimize management of CKD, to assure adequate protein and energy intake, and to avoid or correct protein-energy wasting.

Relationship between renal function and renal volume in autosomal dominant polycystic kidney disease: cross-sectional study.

PubMed

Torres-Sánchez, M J; Ávila-Barranco, E; Esteban de la Rosa, R J; Fernández-Castillo, R; Esteban, M A; Carrero, J J; García-Valverde, M; Bravo-Soto, J A

2016-03-01

To determine in patients with autosomal dominant polycystic kidney disease the relationship between total renal volume (the sum of both kidneys, TRV) as measured by magnetic resonance and renal function; and its behaviour according to sex and the presence of arterial hypertension, hypercholesterolaemia and hyperglycemia. Cross-sectional study including patients with autosomal dominant polycystic kidney disease who underwent periodic reviews at Nephrology external consultations at Hospital de las Nieves de Granada, and who underwent an magnetic resonance to estimate renal volume between January 2008 and March 2011. We evaluated 67 patients (59.7% women, average age of 48±14.4 years) and found a significant positive association between TRV and serum creatinine or urea, which was reversed compared with estimated glomerular filtration by MDRD-4 and Cockcroft-Gault. Women showed an average serum creatinine level and a significantly lower TRV level compared with males. Subgroups affected by arterial hypertension and hyperuricemia presented average values for serum creatinine and urea, higher for TRV and lower for estimated glomerular filtration. The hypercholesterolaemia subgroup showed higher average values for urea and lower for estimated glomerular filtration, without detecting significant differences compared with TRV. The volume of polycystic kidneys measured by magnetic resonance is associated with renal function, and can be useful as a complementary study to monitor disease progression. The presence of arterial hypertension, hyperuricemia or hypercholesterolaemia is associated with a poorer renal function. Copyright © 2015 Elsevier España, S.L.U. y Sociedad Española de Medicina Interna (SEMI). All rights reserved.

Poor concordance between different definitions of worsening renal function in patients with acute exacerbation of chronic heart failure: a retrospective study.

PubMed

De Vecchis, Renato; Baldi, Cesare; Di Biase, Giuseppina

2016-04-01

Approximately one-third of patients with acute decompensated heart failure (ADHF) treated with an intravenous (iv) loop diuretic at a relatively high dose (>80 mg/day of furosemide, or an equivalent dose of another loop diuretic), exhibit worsening renal function (WRF) after a single course of iv infusions or iv bolus injections maintained for several days. WRF is currently defined as an increase in serum creatinine >0.3 mg/dL (WRF-Cr) or a decrease in the estimated glomerular filtration rate of ≥20% (WRF-GFR) compared to baseline measurements. Furthermore, small increases in serum creatinine in the high-normal range of its values are indicative of significant reductions in estimated glomerular filtration rate (eGFR) due to the exponential relationship between serum creatinine and eGFR. Therefore, underestimating this relationship could lead to an erroneous quantitative estimate of new-onset renal dysfunction, diuretic-related. The relationship between baseline serum creatinine (exposure variable) and the risk of diuretic-related WRF (dichotomous outcome variable), expressed either as WRF-Cr or as WRF-GFR, was assessed by logistic regression analysis. For this purpose, medical records with a diagnosis of previous ADHF were collated, and retrospectively analyzed. The eGFR was calculated using the equation "Modification of Diet in Renal Disease" (MDRD). The WRF was inferred from measurements of serum creatinine that had been made daily during the scheduled courses of intravenous diuretic therapy. Thirty-eight patients with chronic heart failure (CHF) and history of a previous episode of ADHF were enrolled in the study. An increase higher than 0.3 mg/dL of serum creatinine (WRF-Cr) was detected in 14 of 38 patients (36.8%). In addition, a decrease of ≥20% in GFR (WRF-GFR) was detected in 14 of 38 patients (36.8%). However, a poor concordance between the two criteria was found (Cohen's Kappa =0.208, 95% CI: -0.110 to 0.526). WRF-Cr and WRF-GFR showed opposing relations with baseline serum creatinine. In fact, the risk of WRF-Cr appeared positively associated with baseline serum creatinine (odds ratio =33.56; 95% CI:2.93- 384.18 P=0.0047), while the risk of WRF-GFR was inversely associated with the same analyte (odds ratio =0.0393; 95% CI: 0.0039 to 0.3966 P=0.0061). The criterion to discontinue the iv diuretic or to reduce its dosage in the presence of WRF-Cr for patients with ADHF or resistance to oral diuretic should be joined with the useful notion that this finding indicates a significant reduction of eGFR only for values of serum creatinine in the normal or near-normal ranges.

Left ventricular hypertrophy and geometry in type 2 diabetes patients with chronic kidney disease. An echocardiographic study.

PubMed

Bayauli, M P; Lepira, F B; Kayembe, P K; M'buyamba-Kabangu, J R

2012-03-01

We assessed left ventricular structural alterations associated with chronic kidney disease (CKD) in Congolese patients with type 2 diabetes. This was a cross-sectional study of a case series. We obtained anthropometric, clinical, biological and echocardiographic measurements in 60 consecutive type 2 diabetes patients (37 females, 62% ) aged 20 years or older from the diabetes outpatient clinic, University of Kinshasa Hospital, DRC. We computed creatinine clearance rate according to the MDRD equation and categorised patients into mild (CrCl > 60 ml/min per 1.73 m(2)), moderate (CrCl 30-60 ml/min per 1.73 m(2)) and severe CKD (< 30 ml/min per 1.73 m(2)). Left ventricular hypertrophy (LVH) was indicated by a LV mass index (LVMI) > 51 g/m(2.7) and LV geometry was defined as normal, or with concentric remodelling, eccentric or concentric hypertrophy, using relative wall thickness (RWT) and LVMI. Compared to patients with normal kidney function, CKD patients had higher uric acid levels (450 ± 166 vs 306 ± 107 µmol/l; p ≤ 0.001), a greater proportion of LVH (37 vs 14%; p ≤ 0.05) and longstanding diabetes (13 ± 8 vs 8 ± 6 years; p ≤ 0.001). Their left ventricular internal diameter, diastolic (LVIDD) was (47.00 ± 6.00 vs 43.00 ± 7.00 mm; p ≤ 0.001), LVMI was (47 ± 19 vs 36.00 ± 15 g/m2.7; p ≤ 0.05) and proportions of concentric (22 vs 11%; p ≤ 0.05) or eccentric (15 vs 3%; p ≤ 0.05) LVH were also greater. Severe CKD was associated with increased interventricular septum, diastolic (IVSD) (12.30 ± 3.08 vs 9.45 ± 1.94 mm; p ≤ 0.05), posterior wall thickness, diastolic (PWTD) (11.61 ± 2.78 vs 9.52 ± 1.77 mm; p ≤ 0.01), relative wall thickness (RWT) (0.52 ± 0.17 vs 0.40 ± 0.07; p ≤ 0.01) rate of LVH (50 vs 30%; p ≤ 0.05), and elevated proportions of concentric remodelling (25 vs 15%; p ≤ 0.05) and concentric LVH (42 vs 10%; p ≤ 0.05) in comparison with patients with moderate CKD. In multivariable adjusted analysis, hyperuricaemia emerged as the only predictor of the presence of LVH in patients with CKD (adjusted OR 9.10; 95% CI: 2.40-33.73). In keeping with a higher rate of cardiovascular events usually reported in patients with impaired renal function, CKD patients exhibited LVH and abnormal LV geometry.

Higher risk of renal impairment associated with tenofovir use amongst people living with HIV in India: A comparative cohort analysis between Western India and United Kingdom

PubMed Central

2014-01-01

Background Data on the renal safety of Tenofovir (TDF) in Low and Middle Income Countries (LMICs) is scarce. We compared development of various forms of renal impairment with use of TDF-containing antiretroviral therapy (ART) between a cohort from the Institute of Infectious Diseases (IID) Pune, Western India and the Royal Free Hospital (RFH) London, UK. Methods This is a retrospective analysis of change in estimated glomerular filtration rates (eGFRs) at 6, 12 and 24 months post TDF initiation using the Modification of Diet in Renal Disease (MDRD) equation. In people living with Human Immunodeficiency virus (PLHIV) with pre-TDF eGFR > 90 ml/min/1.73 m2 time to development of and factors associated with progression to eGFR < 60 ml/min/1.73 m2 were calculated using standard survival methods. Results A total of 574 (59% Caucasian) at the RFH, and 708 (100% Indian ethnicity) PLHIV from IID were included. Baseline median eGFR were similar; RFH 102 (IQR 89, 117), IID 100 (82, 119). At 24 months, mean (SD) decline in eGFR was -7(21) at RFH (p < 0.0001) and -7(40) at IID (p = 0.001). Amongst those with pre-TDF eGFR > 90 ml/min/1.73 m2 PLHIV at IID were more likely to develop an eGFR < 60 ml/min/1.73 m2 (aHR = 7.6 [95% CI 3.4, 17.4] p < 0.0001) and had a faster rate of progression estimated using Kaplan Meier methods. Risk factors included age (per 10 years older: aHR = 2.21 [1.6, 3.0] p < 0.0001) and receiving concomitant ritonavir boosted Protease Inhibitor (PI/r) (aHR = 2.4 [1.2, 4.8] p = 0.01). Conclusions There is higher frequency of treatment limiting renal impairment events amongst PLHIV receiving TDF in Western India. As TDF scale up progresses, programs need to develop capacity for monitoring and treatment of renal impairment associated with TDF. PMID:24679159

An analysis of chronic kidney disease risk factors in a Louisiana nursing home population: a cross-sectional study.

PubMed

Aguilar, Erwin A; Ashraf, Hina; Frontini, Maria; Ruiz, Marco; Reske, Thomas M; Cefalu, Charles

2013-01-01

Chronic Kidney Disease (CKD) and its progression are associated with multiple risk factors. CKD is prevalent in nursing homes residents, but factors related to CKD in this setting have not been defined. A cross-sectional study was conducted (n=103). Data was abstracted using standardized forms and analyzed (SAS 9.2). Chi square and t-test statistics were used to compare proportions and means; correlation coefficients were used to describe associations. Logistic models were fit to the data to determine multivariate associations. Modification of Diet in Renal Disease (MDRD) formula was used to estimate GFR. CKD was defined according to established standards. A cutoff point of 60 was chosen for further analysis. Twenty-three percent of subjects had CKD. Mean age for eGFR <60 was 70.8 +/- 13 and for eGFR >60 was 61.7 +/-14. Frequent co-morbidities were hypertension (75%), GERD (40%), obesity (39%), dyslipidemia (35%), depression (34%), anemia (32%), and diabetes (32%). Our population is unique in terms of its age and reasons for nursing home admission. Factors associated with CKD in our study include age >65 years old, being male, having a positive history of cardiovascular disease (including congestive heart failure and coronary artery disease,) anemia, polypharmacy, and being obese (BMI >30). Further analysis showed that age and anemia are the strongest factors associated with CKD in our population. Management targeted at CKD risk factor reduction may play a vital role in controlling the magnitude of this disease. Prospective studies to investigate the relationship between gender, a BMI greater than 30, cardiovascular disease, and CKD and its complications are warranted.

Comparison of Three Methods Estimating Baseline Creatinine For Acute Kidney Injury in Hospitalized Patients: a Multicentre Survey in Third-Level Urban Hospitals of China.

PubMed

Lang, Xia-Bing; Yang, Yi; Yang, Ju-Rong; Wan, Jian-Xin; Yu, Sheng-Qiang; Cui, Jiong; Tang, Xiao-Jing; Chen, Jianghua

2018-01-01

A lack of baseline serum creatinine (SCr) data leads to underestimation of the burden caused by acute kidney injury (AKI) in developing countries. The goal of this study was to investigate the effects of various baseline SCr analysis methods on the current diagnosis of AKI in hospitalized patients. Patients with at least one SCr value during their hospital stay between January 1, 2011 and December 31, 2012 were retrospectively included in the study. The baseline SCr was determined either by the minimum SCr (SCrMIN) or the estimated SCr using the MDRD formula (SCrGFR-75). We also used the dynamic baseline SCr (SCrdynamic) in accordance with the 7 day/48 hour time window. AKI was defined based on the KDIGO SCr criteria. Of 562,733 hospitalized patients, 350,458 (62.3%) had at least one SCr determination, and 146,185 (26.0%) had repeat SCr tests. AKI was diagnosed in 13,883 (2.5%) patients using the SCrMIN, 21,281 (3.8%) using the SCrGFR-75 and 9,288 (1.7%) using the SCrdynamic. Compared with the non-AKI patients, AKI patients had a higher in-hospital mortality rate regardless of the baseline SCr analysis method. Because of the scarcity of SCr data, imputation of the baseline SCr is necessary to remedy the missing data. The detection rate of AKI varies depending on the different imputation methods. SCrGFR-75 can identify more AKI cases than the other two methods. © 2018 The Author(s). Published by S. Karger AG, Basel.

Lack of Serum Creatinine Decrease After Coronary Angiography Despite Prophylactic Hydration After Routine Coronary Angiography/Angioplasty in Stable Angina Patients--Pilot Study.

PubMed

Burchardt, Pawel; Rzezniczak, Janusz; Synowiec, Tomasz; Angerer, Dariusz; Palasz, Anna; Zurawski, Jakub

2016-01-01

To prevent contrast induced renal dysfunction a periprocedural prophylactic hydration is applied. Due to dilution it should cause a drop in serum creatinine concentration (SCR). Surprisingly, no reduction in SCR after contrast admission is found in up to 25% of patients as early as 12-18 hours after coronary angiography/angioplasty. This study aims to find a clinical explanation as well as predict circumstances for this phenomenon. Retrospective clinical and laboratory data was used from 341 patients who underwent elective coronary angiography/angioplasty, received a prophylactic hydration, and had serum creatinine concentration measured prior to, and 12-18 hours after invasive procedure with iodine contrast administration. To exclude an improper hydration due to no creatinine decrease, the number of red blood cells was analysed as well as hemoglobin and hematocrit in blood donations collected during the study time points. The resulting lack of serum creatinine reduction could be explained by dehydration (measured by increase in number of RBC, HGB and HCT) only in 13.5% , 10.8%, and 20% of cases, respectively. Any form of abnormal glucose metabolism combined with either baseline serum creatinine concentration <0.87 mg/dL or creatinine clearance >86.77 mL/min, or GFR by CKD EPI >80.08 mL/min/1.73 m2, or GFR by MDRD >74.48 mL/min/1.73 m2 were the predictors for no creatinine decrease at outcome. Additionally, it was demonstrated that the lack of creatinine decrease was more often observed among those patients whose initial renal function was better than in the subjects with reduction of SCR. This observation requires further prospective investigation on extended group of patients. © 2016 The Author(s) Published by S. Karger AG, Basel.

Differences in the clinical presentation and the frequency of complications between elderly and non-elderly scrub typhus patients.

PubMed

Jang, Mi-Ok; Kim, Ji Eun; Kim, Uh Jin; Ahn, Joon Hwan; Kang, Seung-Ji; Jang, Hee-Chang; Jung, Sook-In; Park, Kyung-Hwa

2014-01-01

Age can affect the clinical features and severity of infectious disorders, such as scrub typhus. We performed this study to examine differences between elderly and non-elderly scrub typhus patients, and to identify risk factors predictive of disease outcomes. This retrospective study included patients admitted to a tertiary hospital with scrub typhus between 2001 and 2011. A total of 615 patients were enrolled in this study, 328 of which were >65 years of age. Of the elderly patients, 46.0% (151/328) experienced at least one complication compared to only 23.0% (66/287) in younger patients. A linear trend was observed between age and complication rates (p=0.002). The most common complication in elderly patients was acute kidney injury (75, 22.9%). Treatment failure was reported in 10 elderly patients (3.0%) compared to one non-elderly patient (0.3%). Mental confusion and dyspnea of clinical manifestations at admission were common in elderly patients. Frequency of fever, rash, and eschar were similar in both groups. The following four factors were significantly associated with severe scrub typhus in elderly patients: (1) white blood cell (WBC) counts>10,000/mm(3) (OR=2.569, CI=1.298-5.086), (2) MDRD GFR<60mL/min (OR=3.525, CI=1.864-6.667), (3) albumin≤3.0g/dL (OR=4.976, CI=2.664-9.294), and (4) acute physiology and chronic health evaluation II (APACHE II) score>10 points (OR=3.304, CI=1.793-60.87). Complications and mortality were more common in elderly patients, often associated with delays in diagnosis and treatment. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Late onset azotemia from RAAS blockade in CKD patients with normal renal arteries and no precipitating risk factors.

PubMed

Onuigbo, Macaulay A C; Onuigbo, Nnonyelum T C

2008-01-01

Despite proven renoprotection from RAAS blockade and its increased application since the early 1990s, we have experienced an increasing CKD/ESRD epidemic, especially among U.S. diabetics. Consequently, some concerns regarding iatrogenic azotemia from RAAS blockade have surfaced. We hypothesized that susceptible CKD patients with normal renal arteries on conventional angiography, including MRA, but who have microvascular arteriolar narrowing in the renal circulation - mimicking large vessel renal artery stenosis, even without precipitating risk factors - could experience worsening azotemia after periods of time exceeding three months on stable doses of RAAS blockade. Between September 2002 and February 2005, as part of a larger prospective study of renal failure in CKD patients on RAAS blockade, we studied five patients with >25% higher serum creatinine and normal MRA without precipitating factors. RAAS blockade was discontinued. eGFR by MDRD was monitored. Five Caucasians (M:F = 1:4; age 68 years) were enrolled and followed-up at 29.6 months. The duration of RAAS blockade at enrollment was 34.6 months. The baseline eGFR had decreased from 28.4 +/- 7.1 to 17.0 +/- 7.4 ml/min/1.73 m(2) BSA (p < 0.001) at enrollment. One required temporary hemodialysis; no deaths occurred. eGFR increased from 17.0 +/- 7.4 to 24.6 +/- 9.5 ml/min/1.73 m(2) BSA (p = 0.009), 29.6 (20-43) months after stopping the RAAS blockade. We conclude that worsening azotemia occurs in susceptible CKD patients on stable doses of RAAS blockade after long periods of time, despite normal renal arteries without precipitating risk factors. We submit that microvascular renal arteriolar narrowing is the pathophysiologic mechanism. These observations call for further study.

[Chronic kidney disease in 5 708 people receiving physical examination].

PubMed

Xu, Guo; Chen, Zhiheng; Zhang, Hao; Gong, Ni; Wang, Yan

2014-04-01

To investigate chronic kidney disease (CKD) and its risk factors in people receiving physical examination. This retrospective study included people over 20 years old who had physical examination in the Health Management Center of Third Xiangya Hospital from Janurary 2008 to June 2011. CKD and its risk factors as well as questionnaire were recorded. The risk factors were analyzed by multivariate logistic analysis. CKD was defined by kidney damage (microalbuminuria≥30 mg/L) and/or hematuria and/or reduced kidney function [evaluate glomerular filtration rate (eGFR)<60 mL/(min.1.73 m2)]. We counted eGFR according to the modification of diet in renal disease (MDRD). A total of 5 708 physical examination reports were included. The detection rate of albuminuria, reduced renal function and hematuria was 25.0%, 1.7% and 1.1%. The detection rate of CKD was 25.6%, and detection rate of CKD stage 1-5 was 17.8%, 6.7%, 1.1%, 0 and 0, respectively. Multivariate logistic analysis indicated that diabetes mellitus, hypertension, hypercholesterolemia, male, age, and smoking were the risk factors for CKD. Increasing physical activity was the protective factor against CKD. High prevalence of CKD in people receiving physical examination is found in Changsha, especially stage 1 and 2 CKD. Physical examination is important to screen CKD. Stopping smoking, control of blood glucose, blood pressure, blood lipids and increasing physical activity may help reduce the prevalence of CKD.

The progress of inflammation and oxidative stress in patients with chronic kidney disease.

PubMed

Xu, Gaosi; Luo, Kaiping; Liu, Huixin; Huang, Tianlun; Fang, Xiangdong; Tu, Weiping

2015-02-01

The variations and their correlation of inflammation and oxidative stress in chronic kidney disease (CKD) have not been thoroughly understood. Biomarkers of inflammation and oxidative stress were measured in a cohort of 176 patients with CKD ranging from stage 1 to 5 and 67 healthy controls. Correlation analysis in levels between inflammation and oxidative stress was also performed with estimated glomerular filtration rate (eGFR) using the Modification of Diet in Renal Disease (MDRD) formula. Concentrations of serum creatinine (Scr), hs-CRP (hypersensitive C reactive protein) and MDA (malondialdehyde) of these participants were measured again after 12 month follow-up. In the present study, with the development of CKD, serum levels of hs-CRP, interleukin-6 (IL-6) and MDA were significantly increased, and the serum levels of SOD (superoxide dismutase) and GSH-PX (glutathione peroxidase) were significantly decreased in these participants. eGFR was inversely associated with MDA and positively with SOD and GSH-PX when adjusting for age and hypertension therapy. IL-6 and hs-CRP were positively correlated with MDA, and negatively associated with SOD and GSH-PX. Notably, after 12-month follow-up, the increase in Scr was positively associated with the increase in hs-CRP (p < 0.01) and MDA (p < 0.05), respectively. Inflammation and oxidative stress interacted with each other and played pivotal roles in the development of CKD. Variation in eGFR was parallel with the changes of oxidative stress and inflammation when CKD developing.

Role of traditional risk factors and antiretroviral drugs in the incidence of chronic kidney disease, ANRS CO3 Aquitaine cohort, France, 2004-2012.

PubMed

Morlat, Philippe; Vivot, Alexandre; Vandenhende, Marie-Anne; Dauchy, Frédéric-Antoine; Asselineau, Julien; Déti, Edouard; Gerard, Yann; Lazaro, Estibaliz; Duffau, Pierre; Neau, Didier; Bonnet, Fabrice; Chêne, Geneviève

2013-01-01

To examine the role of antiretroviral drugs (ART), HIV-related and traditional risk factors on the incidence of chronic kidney disease (CKD) in HIV-infected patients. Prospective hospital-based cohort of HIV-infected patients from 2004 to 2012. CKD was defined using MDRD equation as an estimated glomerular filtration rate (eGFR) less than 60 ml/mn/1.73 m(2) at 2 consecutive measurements ≥3 months apart. Poisson regression models were used to study determinants of CKD either measured at baseline or updated. ART exposure was classified as ever or never. We additionally tested the role of tenofovir (TDF), whether or not prescribed concomitantly with a Protease Inhibitor (PI), taking into account the cumulative exposure to the drug. 4,350 patients (74% men) with baseline eGFR>60 ml/mn/1.73 m(2) were followed for a median of 5.8 years. At the end of follow-up, 96% had received ART, one third of them (35%) jointly received TDF and a PI. Average incidence rate of CKD was 0.95% person-years of follow-up. Incidence of CKD was higher among women (IRR = 2.2), older patients (>60 y vs <45 y: IRR = 2.5 and 45-60 y: IRR = 1.7), those with diabetes (IRR = 1.9), high blood pressure (IRR = 1.5), hyperlipidemia (IRR = 1.5), AIDS stage (IRR = 1.4), low baseline eGFR (IRR = 15.8 for 6090 and IRR = 7.1 for 70500/mm(3) (IRR = 2.5), and exposure to TDF (IRR = 2.0). Exposure to TDF was even strongly associated with CKD when co-administered with PIs (IRR = 3.1 vs 1.3 when not, p<0,001). A higher risk of CKD was found when tenofovir exposure was >12 months [IRR = 3.0 with joint PIs vs 1.3 without (p<0.001)]. A vast majority of those developing CKD (76.6%) had a baseline eGFR between 60 and 80 ml/mn/1.73 m(2). In patients with eGFR between 60 and 80 mL/min/1.73 m(2), a thorough control of CKD risk factors is warranted. The use of TDF, especially when co-administered with PIs, should be mentioned as a relative contraindication in presence of at least one of these risk factors.

Pretransplant urinary proteome analysis does not predict development of chronic kidney disease after liver transplantation.

PubMed

Milongo, David; Bascands, Jean-Loup; Huart, Antoine; Esposito, Laure; Breuil, Benjamin; Moulos, Panagiotis; Siwy, Justyna; Ramírez-Torres, Adela; Ribes, David; Lavayssière, Laurence; Del Bello, Arnaud; Muscari, Fabrice; Alric, Laurent; Bureau, Christophe; Rostaing, Lionel; Schanstra, Joost P; Kamar, Nassim

2015-07-01

Chronic kidney disease (CKD) is a common complication after liver transplantation. Kidney biopsies cannot be easily performed before liver transplantation to predict patients at high risk for CKD. The aim of our study was to determine whether pre-, peri- and post-transplant factors, as well as peptides present in preliver transplant urine samples were associated with loss in kidney function at 6 months post-transplantation using proteome analysis. Eighty patients who underwent a liver transplantation and that had pretransplant glomerular filtration rate (GFR) value of ≥60 mL/min/1.73 m² (MDRD) were included in the study. GFR decreased significantly after transplantation. At month 6 post-transplantation, 40 patients displayed a CKD, i.e. eGFR of <60 mL/min/1.73 m², while the other 40 patients did not. Although thousands of peptides were identified, none was significantly associated with the development of CKD at 6 months after liver transplantation. Moreover, using a urinary peptidome classifier to detect preexisting CKD, no difference was found in CKD scores between the 2 groups. After analysis of a large number of pre-, peri- and post-transplant parameters, viral hepatitis as a cause for liver transplantation was the sole independent predictive factor for CKD. No difference in peptides with differential urinary abundance between patients who received a graft for virus related liver disease vs. all other causes of liver disease was observed. Urinary peptidome analysis before liver transplantation failed to identify a peptide pattern associated with the development of CKD at 6 months after liver transplantation. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Low thyroid function is not associated with an accelerated deterioration in renal function.

PubMed

Meuwese, Christiaan L; van Diepen, Merel; Cappola, Anne R; Sarnak, Mark J; Shlipak, Michael G; Bauer, Douglas C; Fried, Linda P; Iacoviello, Massimo; Vaes, Bert; Degryse, Jean; Khaw, Kay-Tee; Luben, Robert N; Åsvold, Bjørn O; Bjøro, Trine; Vatten, Lars J; de Craen, Anton J M; Trompet, Stella; Iervasi, Giorgio; Molinaro, Sabrina; Ceresini, Graziano; Ferrucci, Luigi; Dullaart, Robin P F; Bakker, Stephan J L; Jukema, J Wouter; Kearney, Patricia M; Stott, David J; Peeters, Robin P; Franco, Oscar H; Völzke, Henry; Walsh, John P; Bremner, Alexandra; Sgarbi, José A; Maciel, Rui M B; Imaizumi, Misa; Ohishi, Waka; Dekker, Friedo W; Rodondi, Nicolas; Gussekloo, Jacobijn; den Elzen, Wendy P J

2018-04-18

Chronic kidney disease (CKD) is frequently accompanied by thyroid hormone dysfunction. It is currently unclear whether these alterations are the cause or consequence of CKD. This study aimed at studying the effect of thyroid hormone alterations on renal function in cross-sectional and longitudinal analyses in individuals from all adult age groups. Individual participant data (IPD) from 16 independent cohorts having measured thyroid stimulating hormone, free thyroxine levels and creatinine levels were included. Thyroid hormone status was defined using clinical cut-off values. Estimated glomerular filtration rates (eGFR) were calculated by means of the four-variable Modification of Diet in Renal Disease (MDRD) formula. For this IPD meta-analysis, eGFR at baseline and eGFR change during follow-up were computed by fitting linear regression models and linear mixed models in each cohort separately. Effect estimates were pooled using random effects models. A total of 72 856 individuals from 16 different cohorts were included. At baseline, individuals with overt hypothyroidism (n = 704) and subclinical hypothyroidism (n = 3356) had a average (95% confidence interval) -4.07 (-6.37 to -1.78) and -2.40 (-3.78 to -1.02) mL/min/1.73 m2 lower eGFR as compared with euthyroid subjects (n = 66 542). In (subclinical) hyperthyroid subjects (n = 2254), average eGFR was 3.01 (1.50-4.52) mL/min/1.73 m2 higher. During 329 713 patient years of follow-up, eGFR did not decline more rapidly in individuals with low thyroid function compared with individuals with normal thyroid function. Low thyroid function is not associated with a deterioration of renal function. The cross-sectional association may be explained by renal dysfunction causing thyroid hormone alterations.

Microstructures in striato-thalamo-orbitofrontal circuit in methamphetamine users.

PubMed

Li, Yadi; Dong, Haibo; Li, Feng; Wang, Gaoyan; Zhou, Wenhua; Yu, Rongbin; Zhang, Lingjun

2017-11-01

Background Striato-thalamo-orbitofrontal (STO) circuit plays a key role in the development of drug addiction. Few studies have investigated its microstructural abnormalities in methamphetamine (MA) users. Purpose To evaluate the microstructural changes and relevant clinical relevance of the STO circuit in MA users using diffusion tensor imaging (DTI). Material and Methods Twenty-eight MA users and 28 age-matched normal volunteers were enrolled. 3T magnetic resonance imaging (MRI) was employed to obtain structural T1-weighted (T1W) imaging and diffusion-tensor imaging (DTI) data. Freesurfer software was used for automated segmentation of the bilateral nucleus accumbens (NAc), thalami, and orbitofrontal cortex (OFC). Four DTI measures maps, fractional anisotropy (FA), mean diffusivity (MD), axial diffusion (AD), and radial diffusion (RD) were generated and non-linearly co-registered to structural space. Comparisons of DTI measures of the STO circuit were carried out between MA and controls using repeated measures analysis of variance. Correlation analyses were performed between STO circuit DTI measures and clinical characteristics. Results The MA group had significant FA reduction in the bilateral NAc, OFC, and right thalamus ( P < 0.05). Lower left OFC FA and right NAc FA/AD were associated with longer duration of MA use. Lower right OFC FA was associated with younger age at first MA use. Higher FA and lower MD/RD in the thalamus, as well as higher left OFC RD, were associated with increased psychiatric symptoms. Conclusion The STO circuit has reduced microstructural integrity in MA users. Microstructural changes in the thalamus may compensate for dysfunction in functionally connected cortices, which needs further investigation.

One-Year Conservative Care Using Sodium Bicarbonate Supplementation Is Associated with a Decrease in Electronegative LDL in Chronic Kidney Disease Patients: A Pilot Study.

PubMed

Rizzetto, Felipe; Mafra, Denise; Barra, Ana Beatriz; Pires de Melo, Gisella; Abdalla, Dulcinéia Saes Parra; Leite, Maurilo

2017-10-01

Chronic kidney disease (CKD) patients develop metabolic acidosis when approaching stages 3 and 4, a period in which accelerated atherogenesis may ensue. Studies in vitro show that low pH may increase low-density lipoprotein (LDL) oxidation, suggesting a role for chronic metabolic acidosis in atherosclerosis. The present study attempted to evaluate the effects of conservative care using oral sodium bicarbonate (NaHCO 3 ) supplementation on the electronegative LDL [LDL(-)], a minimally oxidized LDL, plasma levels in CKD patients. Thirty-one CKD patients were followed by a multidisciplinary team during 15 months of care in which 1.0 mmol/kg/day oral NaHCO 3 supplementation was first given in the third month. Blood samples were collected 3 months before the initiation of oral NaHCO 3 supplementation (T1), at the time of the beginning of supplementation (T2), and thereafter, each 4 months (T3, T4 and T5) until month 15 of care. Blood parameters and LDL(-) were measured from these collections. After 12 months of conservative care, creatinine clearance (MDRD) was kept stable, and serum bicarbonate (HCO 3 - ) increased from 20.5 ± 2.9 to 22.6 ± 1.1 mM ( p < 0.003). LDL(-) plasma levels declined from 4.5 ± 3.3 to 2.1 ± 0.9 U/L ( p < 0.007) after reaching mean serum HCO 3 - levels of 22.6 ± 1.1 mM. Conservative care using oral NaHCO 3 supplementation was able to stabilize renal function and decrease serum levels of LDL(-), a modified proatherogenic lipoprotein, only when mean serum HCO 3 - levels approached 22 mM. This study constitutes evidence that alkali therapy, in addition to its beneficial effect on renal disease progression, might serve as a preventive strategy to attenuate atherogenesis in CKD patients.

Prevalence of chronic kidney disease and progression of disease over time among patients enrolled in the Houston West Nile virus cohort.

PubMed

Nolan, Melissa S; Podoll, Amber S; Hause, Anne M; Akers, Katherine M; Finkel, Kevin W; Murray, Kristy O

2012-01-01

In experimental models of West Nile virus (WNV) infection, animals develop chronic kidney infection with histopathological changes in the kidney up to 8-months post-infection. However, the long term pathologic effects of acute infection in humans are largely unknown. The purpose of this study was to assess renal outcomes following WNV infection, specifically the development of chronic kidney disease (CKD). In a cohort of 139 study participants with a previous diagnosis of WNV infection, we investigated the prevalence of CKD using the Kidney Disease Outcomes Quality Initiative (KDOQI) criteria based on the Modification of Diet in Renal Disease (MDRD) formula and urinary abnormalities, and assessed various risk factors and biomarkers. Study participants were primarily male (60%) and non-Hispanic white (86%) with a mean age of 57 years. Most (83%) were four to nine years post-infection at the time of this study. Based on the KDOQI definition, 40% of participants had evidence of CKD, with 10% having Stage III or greater and 30% having Stage I-II. By urinary dipstick testing, 26% of patients had proteinuria and 23% had hematuria. Plasma NGAL levels were elevated in 14% of participants while MCP-1 levels were increased in 12%. Over 1.5 years, the average change in eGFR was -3.71 mL/min/1.73 m(2). Only a history of Neuroinvasive WNV disease was independently associated with CKD following multivariate analysis. We found a high prevalence of CKD after long term follow-up in a cohort of participants previously infected with WNV. The majority of those with CKD are in Stage I-II indicating early stages of renal disease. Traditional risk factors were not associated with the presence of CKD in this population. Therefore, clinicians should regularly evaluate all patients with a history of WNV for evidence of CKD.

Renal, efficacy and safety outcomes following late conversion of kidney transplant patients from calcineurin inhibitor therapy to everolimus: the randomized APOLLO study.

PubMed

Budde, Klemens; Rath, Thomas; Sommerer, Claudia; Haller, Hermann; Reinke, Petra; Witzke, Oliver; Suwelack, Barbara; Baeumer, Daniel; May, Christoph; Porstner, Martina; Arns, Wolfgang

2015-01-01

The primary objective of this trial was to demonstrate, based on the estimated glomerular filtration rate (eGFR), superior renal function at month 12 after conversion of maintenance kidney transplant patients from calcineurin inhibitor (CNI) therapy to everolimus, compared to continuing a standard CNI regimen. APOLLO was an open-label, 12-month, prospective, multicenter study in which 93 maintenance kidney transplant patients were randomized to convert from CNI to everolimus (n = 46) or remain on standard CNI-based immunosuppression (n = 47). The primary efficacy variable was eGFR (Nankivell formula) 12 months after randomization. The study was terminated prematurely due to slow recruitment and was thus underpowered. Mean time post-transplant was 83.5 months with everolimus and 70.1 months with CNI. Adjusted values for eGFR (Nankivell) at month 12 were 61.6 (95% CI 58.1, 65.1) mL/ min/1.73 m² with everolimus and 58.8 (95% CI 55.2, 62.3) mL/min/1.73 m² with CNI, a difference of 2.8 (95% CI -1.0, 6.7) mL/ min/1.73 m² (p = 0.145) i.e., the primary objective was not met. Using the modification of diet in renal disease (MDRD) formula, adjusted eGFR at month 12 was significantly higher with everolimus (p = 0.030). In the subpopulation who remained on the study drug (n = 52), the difference in the adjusted change from randomization was 6.6 (95% CI 1.5, 11.6) mL/min/1.73 m² (p = 0.013) in favor of everolimus. There was no biopsyproven acute rejection and no graft losses. Adverse events led to discontinuation of everolimus and CNI in 32.6% and 10.6% of patients, respectively. Conversion from CNI to everolimus to preserve renal function can be considered several years after kidney transplantation and does not compromise immunosuppressive efficacy.

An Evaluation of the Kernel Equating Method: A Special Study with Pseudotests Constructed from Real Test Data. Research Report. ETS RR-06-02

ERIC Educational Resources Information Center

von Davier, Alina A.; Holland, Paul W.; Livingston, Samuel A.; Casabianca, Jodi; Grant, Mary C.; Martin, Kathleen

2006-01-01

This study examines how closely the kernel equating (KE) method (von Davier, Holland, & Thayer, 2004a) approximates the results of other observed-score equating methods--equipercentile and linear equatings. The study used pseudotests constructed of item responses from a real test to simulate three equating designs: an equivalent groups (EG)…

Encouraging Students to Think Strategically when Learning to Solve Linear Equations

ERIC Educational Resources Information Center

Robson, Daphne; Abell, Walt; Boustead, Therese

2012-01-01

Students who are preparing to study science and engineering need to understand equation solving but adult students returning to study can find this difficult. In this paper, the design of an online resource, Equations2go, for helping students learn to solve linear equations is investigated. Students learning to solve equations need to consider…

Middle School Students' Conceptual Understanding of Equations: Evidence From Writing Story Problems. WCER Working Paper No. 2009-3

ERIC Educational Resources Information Center

Alibali, Martha W.; Kao, Yvonne S.; Brown, Alayna N.; Nathan, Mitchell J.; Stephens, Ana C.

2009-01-01

This study investigated middle school students' conceptual understanding of algebraic equations. Participants in the study--257 sixth- and seventh-grade students--were asked to solve one set of algebraic equations and to generate story problems corresponding with another set of equations. Structural aspects of the equations, including the number…

Effects of oral vitamin D3 supplementation in stage 3 chronic kidney disease subjects: insulin resistance syndrome and hormonal disturb interactions.

PubMed

Tahar, Amina; Zerdoumi, Faiza; Saidani, Messaoud; Griene, Lakhdar; Koceir, Elhadj-Ahmed

2018-04-16

The 1-25-hydroxyvitamine D (1-25OHD) or calcitriol deficiency in chronic kidney disease (CKD) patients was associated with increases vascular calcification risk, nephrons reduction, bone deficit and cardiovascular mortality by atherosclerosis. The objective of this study was to investigate the pleiotropic effects of 200.000 IU (D 200 group) every 3 months versus 30.000 IU (D 30 group) every month dose vitamin D supplementation in stage 3 CKD patients. A cohort of 132 adult subjects was randomized into 2 groups according to dose vitamin D supplementation in deficient subjects (25OHD <50 nmol/L or <20 ng/mL). Serum 25OHD levels were assessed before and after 6 and 12 months of vitamin D supplementation. Patients were phenotyped for IRS according to NCEP/ATPIII. Glomerular filtration rate (GFR) by the MDRD formula. Insulin resistance was evaluated by the Homa-IR model. IRS clusters by Cobas Integra 400®. PTH, Cortisol and IGF-1 were determined by radioimmunologic methods. The 25OHD profile was analyzed by LC-MS/MS. Results showed that vitamin D supplementation increased serum 25OHD concentrations (>75 nmol/L or >30 ng/mL) in both groups; however, the supplementation benefits are more significant in D 30 group than in D 200 group. We noted a highlighted improvement of kidney function, an inhibition of GFR collaps, a safe reduction of proteinuria, a significant PTH and C-reactive protein (inflammation) levels attenuation, concomitantly with cortisolemia normalization and decreased IGF-1 depletion. Nevertheless, homocysteine and Lp(a) concentrations remain increased, not modulated by vitamin D treatment. This study shows that continuous low doses (30.000 IU every month) are recommended for intermittent high doses (200.000 IU every 3 months) vitamin D supplementation. Our study suggests that the serum 25OHD profile can be considered a reliable biomarker in the bioclinic CKD status to stage stabilization and inhibit its evolution.

Effectiveness and safety of anakinra in gout patients with stage 4-5 chronic kidney disease or kidney transplantation: a multicentre, retrospective study.

PubMed

Loustau, Clotilde; Rosine, Nicolas; Forien, Marine; Ottaviani, Sébastien; Juge, Pierre-Antoine; Lioté, Frédéric; Bardin, Thomas; Richette, Pascal; Dieudé, Philippe; Richez, Christophe; Bannwarth, Bernard; Schaeverbeke, Thierry; Ea, Hang-Korng; Truchetet, Marie-Elise

2018-04-11

Interleukin (IL)-1β blocking is effective for the treatment of gout flares and is recommended in patients with contraindications to the standard of care, such as stage 4-5 chronic kidney disease (CKD) patients. However, efficacy and safety data regarding these agents are lacking in this population. We aimed to investigate the efficacy and safety of anakinra for the treatment of gout flares in patients with stage 4-5 CKD or renal transplantation. This retrospective study encompassing 3 academic centres included consecutive patients with stage 4-5 CKD or kidney transplantation who received anakinra for the treatment of acute gouty arthritis and completed at least one follow-up visit. Efficacy, occurrence of infection, and renal function variations were recorded. Of the 31 included patients (24 men, mean age 72 ± 11 years), 25 were non-transplant subjects with stage 4-5 CKD (mean estimated glomerular filtration rate, MDRD formula (eGFR) 22.7 ± 6.5mL/min/1.73 m 2 ), and 6 had undergone kidney transplantation (mean eGFR 41.5 ± 22.8mL/min/1.73 m 2 ). Median gout duration was 3.5 years, and the mean serum urate (SUA) level was 8.7mg/dL. Twenty-one (68%) patients had tophi, and 21 had gout arthropathy. Anakinra was efficacious in all patients (final VAS 10 and CRP level 10mg/L). Ten patients (32%) were anakinra dependent (i.e., required prolonged treatment with anakinra). A serious infection was recorded in only one patient, occurring 3 months after starting anakinra. No significant variation in renal function was observed. Anakinra may be a safe therapeutic option for gout patients with advanced CKD. Further randomized controlled studies are required to confirm our results. Copyright © 2018. Published by Elsevier SAS.

Urine Potassium Excretion, Kidney Failure, and Mortality in CKD.

PubMed

Leonberg-Yoo, Amanda K; Tighiouart, Hocine; Levey, Andrew S; Beck, Gerald J; Sarnak, Mark J

2017-03-01

Low urine potassium excretion, as a surrogate for dietary potassium intake, is associated with higher risk for hypertension and cardiovascular disease in a general population. Few studies have investigated the relationship of urine potassium with clinical outcomes in chronic kidney disease (CKD). Longitudinal cohort study. The MDRD (Modification of Diet in Renal Disease) Study was a randomized controlled trial (N = 840) conducted in 1989 to 1993 to examine the effects of blood pressure control and dietary protein restriction on kidney disease progression in adults aged 18 to 70 years with CKD stages 2 to 4. This post hoc analysis included 812 participants. The primary predictor variable was 24-hour urine potassium excretion, measured at baseline and at multiple time points (presented as time-updated average urine potassium excretion). Kidney failure, defined as initiation of dialysis therapy or transplantation, was determined from US Renal Data System data. All-cause mortality was assessed using the National Death Index. Median follow-up for kidney failure was 6.1 (IQR, 3.5-11.7) years, with 9 events/100 patient-years. Median all-cause mortality follow-up was 19.2 (IQR, 10.8-20.6) years, with 3 deaths/100 patient-years. Baseline mean urine potassium excretion was 2.39±0.89 (SD) g/d. Each 1-SD higher baseline urine potassium level was associated with an adjusted HR of 0.95 (95% CI, 0.87-1.04) for kidney failure and 0.83 (95% CI, 0.74-0.94) for all-cause mortality. Results were consistent using time-updated average urine potassium measurements. Analyses were performed using urine potassium excretion as a surrogate for dietary potassium intake. Results are obtained from a primarily young, nondiabetic, and advanced CKD population and may not be generalizable to the general CKD population. Higher urine potassium excretion was associated with lower risk for all-cause mortality, but not kidney failure. Copyright © 2016 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

Equating TIMSS Mathematics Subtests with Nonlinear Equating Methods Using NEAT Design: Circle-Arc Equating Approaches

ERIC Educational Resources Information Center

Ozdemir, Burhanettin

2017-01-01

The purpose of this study is to equate Trends in International Mathematics and Science Study (TIMSS) mathematics subtest scores obtained from TIMSS 2011 to scores obtained from TIMSS 2007 form with different nonlinear observed score equating methods under Non-Equivalent Anchor Test (NEAT) design where common items are used to link two or more test…

Turbulent fluid motion 3: Basic continuum equations

NASA Technical Reports Server (NTRS)

Deissler, Robert G.

1991-01-01

A derivation of the continuum equations used for the analysis of turbulence is given. These equations include the continuity equation, the Navier-Stokes equations, and the heat transfer or energy equation. An experimental justification for using a continuum approach for the study of turbulence is given.

Comparison of nephrotoxicity between two gadolinium-contrasts, gadodiamide and gadopentetate in patients with mildly diminished renal failure.

PubMed

Naito, Shokichi; Tazaki, Hiromi; Okamoto, Tomoko; Takeuchi, Kazuhiro; Kan, Shinichi; Takeuchi, Yasuo; Kamata, Kouju

2017-01-01

Although gadolinium (Gd)-based contrast media have been found to be nephrotoxic, their nephrotoxicity, and the dependence of nephrotoxicity on chelate types, have not been assessed in patients with normal or mildly diminished renal failure. This prospective, randomized study compared the nephrotoxicity of low doses of the nonionic Gd-based contrast medium gadodiamide (Omniscan®) and the ionic Gd-based contrast medium gadopentetate (Magnevist®) in patients with serum creatinine < 1.6 mg/dL. Patients aged 20 to 80 years, weighing 45 to 70 kg and with normal or < 1.6 mg/dL Serum-creatinine in the 3 months prior to undergoing magnetic resonance imaging (MRI) of brain, were enrolled. Patients were randomized to receive 0.1 mol/kg gadodiamide or gadopentetate. Serum-creatinine, serum cystatin-C, estimated glomerular filtration rate (eGFR) using the Modification of Diet in Renal Disease (MDRD) formula, and estimated creatinine clearance rate (eCCr) using the Cockcroft-Gault formula were measured just before and 16-80 hr after MRI. Groups were compared statistically by Mann-Whitney U-tests and Wilcoxon signed-rank tests. There were no significant differences in clinical characteristics between the gadodiamide (n = 43) and gadopentetate (n = 59) groups. Serum-creatinine, eGFR and eCCr before and 16-80 hr after MRI did not differ significantly within either group or between the two groups. Serum cystatin-C was significantly higher 16-80 hr after than before MRI only in the gadodiamide group (0.79 ± 0.21 vs. 0.74 ± 0.14 mg/L, p = 0.028). The ionic contrast medium, gadopentetate, did not affect renal function during MRI, whereas the nonionic contrast medium, gadodiamide, affected renal function transiently.

Precision Medicine for Hypertension Management in Chronic Kidney Disease: Relevance of SPRINT for Therapeutic Targets in Nondiabetic Renal Disease.

PubMed

Ruzicka, Marcel; Burns, Kevin D; Hiremath, Swapnil

2017-05-01

In this review we evaluate the literature to determine if lower blood pressure (BP) targets are beneficial for patients with nondiabetic chronic kidney disease (CKD). Modification of Diet in Renal Disease (MDRD), African American Study of Kidney Disease and Hypertension (AASK), and Ramipril Efficacy in Nephropathy-2 (REIN-2), designed to assess the benefit of lower BP on progression of nondiabetic CKD, generally came to the same negative conclusion. They were not designed and powered to assess an effect of lower BP on cardiovascular outcomes. The Systolic Blood Pressure Intervention Trial (SPRINT) was the first trial designed and powered to address this issue, and showed a clear benefit of a lower targeted and achieved BP. SPRINT did not show any renal benefits from lower BP, and it was not designed to assess this outcome, and it enrolled patients with less "renal risk" per se. A distinguishing feature of SPRINT compared with other large trials is that it highlighted the importance of precise BP measurement methods in defining targets in hypertension treatment. Accordingly, we propose that SPRINT is truly a "game-changing" clinical trial that sets the bar for management of hypertension in select patients with nondiabetic CKD. In these patients, systolic BP target depends critically on the BP measurement method: < 140 mm Hg when derived from 3 readings using a mercury sphygmomanometer after 5 minutes of rest, < 130 mm Hg when calculated from at a minimum of 3 readings using an automated oscillometric device, and < 120 mm Hg when taken using an automated oscillometric device after 5 minutes of unattended rest. Copyright © 2017 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.

Prevalence of chronic kidney disease in a population in southern Brazil (Pro-Renal Study).

PubMed

Piccolli, Ana Paula; Nascimento, Marcelo Mazza do; Riella, Miguel Carlos

2017-01-01

Chronic kidney disease (CKD) affects 10-12% of the adult population in many countries. In Brazil, there is no reliable information about the actual prevalence of CKD. To determine the prevalence of CKD by estimated glomerular filtration rate (eGFR) and proteinuria/albuminuria in an urban population randomly selected in Southern Brazil. Patients and. 5,216 individuals were randomly selected out of a pool of 10,000 individuals identified from the database of a local energy company. The screening consisted of collection of demographic data, history of diabetes mellitus, hypertension, kidney/cardiovascular disease in the family and obesity through the body mass index - BMI (CKD risk factors). Blood samples were collected for determination of serum creatinine and subsequent eGFR estimation by the MDRD formula and urine samples for determination of albuminuria by dipstick. Albuminuria was further evaluated by HemoCue© in a selected CKD risk group. The population was predominantly Caucasians (93%), 64% were females and the mean age of participants was 45 years old (18-87). BMI (kg/m2) was 27±5. Albuminuria was found in 5.25% of individuals. 88.6% of this population had no CKD (eGFR > 60 ml/min/1.73m2 & normoalbuminuria) and 11.4% were identified as having CKD, with majority on stages 3A (7.2%) and 3B (1.1%). Hypertension, diabetes, older age and obesity was associated with a higher prevalence of CKD (p < 0.001). The prevalence of CKD in an urban population in southern Brazil mirrors other developed countries and indicates that kidney disease is an important public health problem in Brazil.

[The Role of Urinary Lipocalin in Prognostication of Hospital Complications in Patients With Ischemic Heart Disease After Coronary Artery Bypass Grafting].

PubMed

Shafranskaya, K S; Kuzmina, O K; Sumin, D A; Krivoshapova, K Ye; Uchasova, Ye G; Ivanov, S V; Zykov, M V; Kashtalap, V V; Barbarash, O L

2016-10-01

To assess significance of urinary neutrophil gelatinase-associated lipocalin (NGAL) for predicting hospital complications in subjects with ischemic heart disease (IHD) after coronary artery bypass grafting (CABG). The study included 720 subjects who underwent CABG between 03/2011 and 04/2012. Blood serum creatinine level, glomerular filtration rate (GFR) (MDRD formula) and NGAL concentration were measured before and on day 7 after CABG. The following unfavorable outcomes of operative intervention: myocardial infarction (MI), stroke or transient ischemic attack, acute or progression of chronic renal disease, remediastinotomy were registered during in-hospital period. Additive EuroSCORE was calculated for all patients. There were no significant differences in serum creatinine level and GFR both before and on day 7 after CABG between groups of patients with different risk assessed by EuroSCORE, and with complicated and uncomplicated postoperative course. Urine NGAL level before and on day 7 after CABG was significantly higher in high and medium compared with low EuroSCORE risk groups. Preoperative NGAL urine level was significantly higher in patients with than in those without MI or stroke after CABG. NGAL urine level was also higher in patients with development of acute renal failure (ARF) compared with those without ARF. Both pre- and postoperative NGAL urine levels were higher in patients with unfavorable outcome while there were no significant differences in serum creatinine levels and CRF between patients with favorable and unfavorable outcomes. Preoperative measurement of urinary NGAL - a preclinical marker of acute kidney injury - allowed to predict more accurately the hospital risk of development of adverse cardiovascular and renal complications of CABG.

Numerical study of the Kadomtsev-Petviashvili equation and dispersive shock waves

NASA Astrophysics Data System (ADS)

Grava, T.; Klein, C.; Pitton, G.

2018-02-01

A detailed numerical study of the long time behaviour of dispersive shock waves in solutions to the Kadomtsev-Petviashvili (KP) I equation is presented. It is shown that modulated lump solutions emerge from the dispersive shock waves. For the description of dispersive shock waves, Whitham modulation equations for KP are obtained. It is shown that the modulation equations near the soliton line are hyperbolic for the KPII equation while they are elliptic for the KPI equation leading to a focusing effect and the formation of lumps. Such a behaviour is similar to the appearance of breathers for the focusing nonlinear Schrödinger equation in the semiclassical limit.

[Robotic assisted laparoscopic living donor nephrectomy: preoperative assessment and results of 100 cases].

PubMed

Laplace, B; Ladrière, M; Claudon, M; Eschwege, P; Kessler, M; Hubert, J

2014-04-01

To assess short term morbidity and renal function after robotic laparoscopic living donor nephrectomy. We performed a retrospective analysis of 100 consecutives patients undergoing a robotic laparoscopic living donors nephrectomy. We analyzed isotopic measure of the renal function before and 4 months after surgery, the side, the number of arteries, the blood loss, the operative time and warm ischemia time. In the outcomes, we collected the complications, the length of stay, and for the receiver, the renal function recovery time, dialysis, survival and renal function at one year. Left kidney nephrectomy was performed in 85 patients and we observed 25 multiples renal arteries. Mean estimated blood loss was 0,8 g/dL. Mean operative time and warm ischemia time were respectively 174 ± 30 and 4.8 ± 1.7 minutes. Seven complications occured, with 2 major (Clavien-Dindo System). Mean length of stay was 5.1 ± 1.9 days. Mean glomerular filtration decrease was 26% and remains stable at one year after surgery. Grafts had an immediate renal function recovery for 99%, and were all functional after one year, with mean MDRD clearance of 57 ± 14mL/min. Robotic procedure in laparoscopic living donor nephrectomy seems to guarantee low morbidity and the stability of the renal function decrease of 26%. Copyright © 2013. Published by Elsevier Masson SAS.

Selection of site specific vibration equation by using analytic hierarchy process in a quarry

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

Kalayci, Ulku, E-mail: ukalayci@istanbul.edu.tr; Ozer, Umit, E-mail: uozer@istanbul.edu.tr

This paper presents a new approach for the selection of the most accurate SSVA (Site Specific Vibration Attenuation) equation for blasting processes in a quarry located near settlements in Istanbul, Turkey. In this context, the SSVA equations obtained from the same study area in the literature were considered in terms of distance between the shot points and buildings and the amount of explosive charge. In this purpose, 11 different SSVA equations obtained from the study area in the past 12 years, forecasting capabilities according to designated new conditions, using 102 vibration records as test data obtained from the study areamore » was investigated. In this study, AHP (Analytic Hierarchy Process) was selected as an analysis method in order to determine the most accurate equation among 11 SSAV equations, and the parameters such as year, distance, charge, and r{sup 2} of the equations were used as criteria for AHP. Finally, the most appropriate equation was selected among the existing ones, and the process of selecting according to different target criteria was presented. Furthermore, it was noted that the forecasting results of the selected equation is more accurate than that formed using the test results. - Highlights: • The optimum Site Specific Vibration Attenuation equation for blasting in a quarry located near settlements was determined. • It is indicated that SSVA equations changing over the years don’t give always accurate estimates at changing conditions. • Selection of the blast induced SSVA equation was made using AHP. • Equation selection method was highlighted based on parameters such as charge, distance, and quarry geometry changes (year).« less

Validity of Bioelectrical Impedance Analysis to Estimation Fat-Free Mass in the Army Cadets.

PubMed

Langer, Raquel D; Borges, Juliano H; Pascoa, Mauro A; Cirolini, Vagner X; Guerra-Júnior, Gil; Gonçalves, Ezequiel M

2016-03-11

Bioelectrical Impedance Analysis (BIA) is a fast, practical, non-invasive, and frequently used method for fat-free mass (FFM) estimation. The aims of this study were to validate predictive equations of BIA to FFM estimation in Army cadets and to develop and validate a specific BIA equation for this population. A total of 396 males, Brazilian Army cadets, aged 17-24 years were included. The study used eight published predictive BIA equations, a specific equation in FFM estimation, and dual-energy X-ray absorptiometry (DXA) as a reference method. Student's t-test (for paired sample), linear regression analysis, and Bland-Altman method were used to test the validity of the BIA equations. Predictive BIA equations showed significant differences in FFM compared to DXA (p < 0.05) and large limits of agreement by Bland-Altman. Predictive BIA equations explained 68% to 88% of FFM variance. Specific BIA equations showed no significant differences in FFM, compared to DXA values. Published BIA predictive equations showed poor accuracy in this sample. The specific BIA equations, developed in this study, demonstrated validity for this sample, although should be used with caution in samples with a large range of FFM.

Modelling with Difference Equations Supported by GeoGebra: Exploring the Kepler Problem

ERIC Educational Resources Information Center

Kovacs, Zoltan

2010-01-01

The use of difference and differential equations in the modelling is a topic usually studied by advanced students in mathematics. However difference and differential equations appear in the school curriculum in many direct or hidden ways. Difference equations first enter in the curriculum when studying arithmetic sequences. Moreover Newtonian…

Additive noise-induced Turing transitions in spatial systems with application to neural fields and the Swift Hohenberg equation

NASA Astrophysics Data System (ADS)

Hutt, Axel; Longtin, Andre; Schimansky-Geier, Lutz

2008-05-01

This work studies the spatio-temporal dynamics of a generic integral-differential equation subject to additive random fluctuations. It introduces a combination of the stochastic center manifold approach for stochastic differential equations and the adiabatic elimination for Fokker-Planck equations, and studies analytically the systems’ stability near Turing bifurcations. In addition two types of fluctuation are studied, namely fluctuations uncorrelated in space and time, and global fluctuations, which are constant in space but uncorrelated in time. We show that the global fluctuations shift the Turing bifurcation threshold. This shift is proportional to the fluctuation variance. Applications to a neural field equation and the Swift-Hohenberg equation reveal the shift of the bifurcation to larger control parameters, which represents a stabilization of the system. All analytical results are confirmed by numerical simulations of the occurring mode equations and the full stochastic integral-differential equation. To gain some insight into experimental manifestations, the sum of uncorrelated and global additive fluctuations is studied numerically and the analytical results on global fluctuations are confirmed qualitatively.

A Harmonic Solution for the Hyperbolic Heat Conduction Equation and Its Relationship to the Guyer-Krumhansl Equation

NASA Astrophysics Data System (ADS)

Zhukovsky, K. V.

2018-01-01

A particular solution of the hyperbolic heat-conduction equation was constructed using the method of operators. The evolution of a harmonic solution is studied, which simulates the propagation of electric signals in long wire transmission lines. The structures of the solutions of the telegraph equation and of the Guyer-Krumhansl equation are compared. The influence of the phonon heat-transfer mechanism in the environment is considered from the point of view of heat conductivity. The fulfillment of the maximum principle for the obtained solutions is considered. The frequency dependences of heat conductivity in the telegraph equation and in an equation of the Guyer-Krumhansl type are studied and compared with each other. The influence of the Knudsen number on heat conductivity in the model of thin films is studied.

A genome-wide search for linkage of estimated glomerular filtration rate (eGFR) in the Family Investigation of Nephropathy and Diabetes (FIND).

PubMed

Thameem, Farook; Igo, Robert P; Freedman, Barry I; Langefeld, Carl; Hanson, Robert L; Schelling, Jeffrey R; Elston, Robert C; Duggirala, Ravindranath; Nicholas, Susanne B; Goddard, Katrina A B; Divers, Jasmin; Guo, Xiuqing; Ipp, Eli; Kimmel, Paul L; Meoni, Lucy A; Shah, Vallabh O; Smith, Michael W; Winkler, Cheryl A; Zager, Philip G; Knowler, William C; Nelson, Robert G; Pahl, Madeline V; Parekh, Rulan S; Kao, W H Linda; Rasooly, Rebekah S; Adler, Sharon G; Abboud, Hanna E; Iyengar, Sudha K; Sedor, John R

2013-01-01

Estimated glomerular filtration rate (eGFR), a measure of kidney function, is heritable, suggesting that genes influence renal function. Genes that influence eGFR have been identified through genome-wide association studies. However, family-based linkage approaches may identify loci that explain a larger proportion of the heritability. This study used genome-wide linkage and association scans to identify quantitative trait loci (QTL) that influence eGFR. Genome-wide linkage and sparse association scans of eGFR were performed in families ascertained by probands with advanced diabetic nephropathy (DN) from the multi-ethnic Family Investigation of Nephropathy and Diabetes (FIND) study. This study included 954 African Americans (AA), 781 American Indians (AI), 614 European Americans (EA) and 1,611 Mexican Americans (MA). A total of 3,960 FIND participants were genotyped for 6,000 single nucleotide polymorphisms (SNPs) using the Illumina Linkage IVb panel. GFR was estimated by the Modification of Diet in Renal Disease (MDRD) formula. The non-parametric linkage analysis, accounting for the effects of diabetes duration and BMI, identified the strongest evidence for linkage of eGFR on chromosome 20q11 (log of the odds [LOD] = 3.34; P = 4.4 × 10(-5)) in MA and chromosome 15q12 (LOD = 2.84; P = 1.5 × 10(-4)) in EA. In all subjects, the strongest linkage signal for eGFR was detected on chromosome 10p12 (P = 5.5 × 10(-4)) at 44 cM near marker rs1339048. A subsequent association scan in both ancestry-specific groups and the entire population identified several SNPs significantly associated with eGFR across the genome. The present study describes the localization of QTL influencing eGFR on 20q11 in MA, 15q21 in EA and 10p12 in the combined ethnic groups participating in the FIND study. Identification of causal genes/variants influencing eGFR, within these linkage and association loci, will open new avenues for functional analyses and development of novel diagnostic markers for DN.

A Genome-Wide Search for Linkage of Estimated Glomerular Filtration Rate (eGFR) in the Family Investigation of Nephropathy and Diabetes (FIND)

PubMed Central

Thameem, Farook; Igo, Robert P.; Freedman, Barry I.; Langefeld, Carl; Hanson, Robert L.; Schelling, Jeffrey R.; Elston, Robert C.; Duggirala, Ravindranath; Nicholas, Susanne B.; Goddard, Katrina A. B.; Divers, Jasmin; Guo, Xiuqing; Ipp, Eli; Kimmel, Paul L.; Meoni, Lucy A.; Shah, Vallabh O.; Smith, Michael W.; Winkler, Cheryl A.; Zager, Philip G.; Knowler, William C.; Nelson, Robert G.; Pahl, Madeline V.; Parekh, Rulan S.; Kao, W. H. Linda; Rasooly, Rebekah S.; Adler, Sharon G.; Abboud, Hanna E.; Iyengar, Sudha K.; Sedor, John R.

2013-01-01

Objective Estimated glomerular filtration rate (eGFR), a measure of kidney function, is heritable, suggesting that genes influence renal function. Genes that influence eGFR have been identified through genome-wide association studies. However, family-based linkage approaches may identify loci that explain a larger proportion of the heritability. This study used genome-wide linkage and association scans to identify quantitative trait loci (QTL) that influence eGFR. Methods Genome-wide linkage and sparse association scans of eGFR were performed in families ascertained by probands with advanced diabetic nephropathy (DN) from the multi-ethnic Family Investigation of Nephropathy and Diabetes (FIND) study. This study included 954 African Americans (AA), 781 American Indians (AI), 614 European Americans (EA) and 1,611 Mexican Americans (MA). A total of 3,960 FIND participants were genotyped for 6,000 single nucleotide polymorphisms (SNPs) using the Illumina Linkage IVb panel. GFR was estimated by the Modification of Diet in Renal Disease (MDRD) formula. Results The non-parametric linkage analysis, accounting for the effects of diabetes duration and BMI, identified the strongest evidence for linkage of eGFR on chromosome 20q11 (log of the odds [LOD] = 3.34; P = 4.4×10−5) in MA and chromosome 15q12 (LOD = 2.84; P = 1.5×10−4) in EA. In all subjects, the strongest linkage signal for eGFR was detected on chromosome 10p12 (P = 5.5×10−4) at 44 cM near marker rs1339048. A subsequent association scan in both ancestry-specific groups and the entire population identified several SNPs significantly associated with eGFR across the genome. Conclusion The present study describes the localization of QTL influencing eGFR on 20q11 in MA, 15q21 in EA and 10p12 in the combined ethnic groups participating in the FIND study. Identification of causal genes/variants influencing eGFR, within these linkage and association loci, will open new avenues for functional analyses and development of novel diagnostic markers for DN. PMID:24358131

The Effect of Tutoring With Nonstandard Equations for Students With Mathematics Difficulty.

PubMed

Powell, Sarah R; Driver, Melissa K; Julian, Tyler E

2015-01-01

Students often misinterpret the equal sign (=) as operational instead of relational. Research indicates misinterpretation of the equal sign occurs because students receive relatively little exposure to equations that promote relational understanding of the equal sign. No study, however, has examined effects of nonstandard equations on the equation solving and equal-sign understanding of students with mathematics difficulty (MD). In the present study, second-grade students with MD (n = 51) were randomly assigned to standard equations tutoring, combined tutoring (standard and nonstandard equations), and no-tutoring control. Combined tutoring students demonstrated greater gains on equation-solving assessments and equal-sign tasks compared to the other two conditions. Standard tutoring students demonstrated improved skill on equation solving over control students, but combined tutoring students' performance gains were significantly larger. Results indicate that exposure to and practice with nonstandard equations positively influence student understanding of the equal sign. © Hammill Institute on Disabilities 2013.

A numerical study of the 3-periodic wave solutions to KdV-type equations

NASA Astrophysics Data System (ADS)

Zhang, Yingnan; Hu, Xingbiao; Sun, Jianqing

2018-02-01

In this paper, by using the direct method of calculating periodic wave solutions proposed by Akira Nakamura, we present a numerical process to calculate the 3-periodic wave solutions to several KdV-type equations: the Korteweg-de Vries equation, the Sawada-Koterra equation, the Boussinesq equation, the Ito equation, the Hietarinta equation and the (2 + 1)-dimensional Kadomtsev-Petviashvili equation. Some detailed numerical examples are given to show the existence of the three-periodic wave solutions numerically.

Cable logging production rate equations for thinning young-growth Douglas-fir

Treesearch

Chris B. LeDoux; Lawson W. Starnes

1986-01-01

A cable logging thinning simulation model and field study data from cable thinning production studies have been assembled and converted into a set of simple equations. These equations can be used to estimate the hourly production rates of various cable thinning machines operating in the mountainous terrain of western Oregon and western Washington. The equations include...

Equations as Guides to Thinking and Problem Solving

ERIC Educational Resources Information Center

Hewitt, Paul G.

2011-01-01

Science is the study of nature's rules. The most basic of these are the laws of physics, most of which are expressed in equation form. Physics equations show how concepts connect to one another. But does a study of these equations enhance student understanding? Not always, for too often in an introductory course students are tempted (or even…

A Comparison of the Kernel Equating Method with Traditional Equating Methods Using SAT[R] Data

ERIC Educational Resources Information Center

Liu, Jinghua; Low, Albert C.

2008-01-01

This study applied kernel equating (KE) in two scenarios: equating to a very similar population and equating to a very different population, referred to as a distant population, using SAT[R] data. The KE results were compared to the results obtained from analogous traditional equating methods in both scenarios. The results indicate that KE results…

Non-Archimedean reaction-ultradiffusion equations and complex hierarchic systems

NASA Astrophysics Data System (ADS)

Zúñiga-Galindo, W. A.

2018-06-01

We initiate the study of non-Archimedean reaction-ultradiffusion equations and their connections with models of complex hierarchic systems. From a mathematical perspective, the equations studied here are the p-adic counterpart of the integro-differential models for phase separation introduced by Bates and Chmaj. Our equations are also generalizations of the ultradiffusion equations on trees studied in the 1980s by Ogielski, Stein, Bachas, Huberman, among others, and also generalizations of the master equations of the Avetisov et al models, which describe certain complex hierarchic systems. From a physical perspective, our equations are gradient flows of non-Archimedean free energy functionals and their solutions describe the macroscopic density profile of a bistable material whose space of states has an ultrametric structure. Some of our results are p-adic analogs of some well-known results in the Archimedean setting, however, the mechanism of diffusion is completely different due to the fact that it occurs in an ultrametric space.

Predictive Variables of Half-Marathon Performance for Male Runners

PubMed Central

Gómez-Molina, Josué; Ogueta-Alday, Ana; Camara, Jesus; Stickley, Christoper; Rodríguez-Marroyo, José A.; García-López, Juan

2017-01-01

The aims of this study were to establish and validate various predictive equations of half-marathon performance. Seventy-eight half-marathon male runners participated in two different phases. Phase 1 (n = 48) was used to establish the equations for estimating half-marathon performance, and Phase 2 (n = 30) to validate these equations. Apart from half-marathon performance, training-related and anthropometric variables were recorded, and an incremental test on a treadmill was performed, in which physiological (VO2max, speed at the anaerobic threshold, peak speed) and biomechanical variables (contact and flight times, step length and step rate) were registered. In Phase 1, half-marathon performance could be predicted to 90.3% by variables related to training and anthropometry (Equation 1), 94.9% by physiological variables (Equation 2), 93.7% by biomechanical parameters (Equation 3) and 96.2% by a general equation (Equation 4). Using these equations, in Phase 2 the predicted time was significantly correlated with performance (r = 0.78, 0.92, 0.90 and 0.95, respectively). The proposed equations and their validation showed a high prediction of half-marathon performance in long distance male runners, considered from different approaches. Furthermore, they improved the prediction performance of previous studies, which makes them a highly practical application in the field of training and performance. Key points The present study obtained four equations involving anthropometric, training, physiological and biomechanical variables to estimate half-marathon performance. These equations were validated in a different population, demonstrating narrows ranges of prediction than previous studies and also their consistency. As a novelty, some biomechanical variables (i.e. step length and step rate at RCT, and maximal step length) have been related to half-marathon performance. PMID:28630571

Characterization of Free Phenytoin Concentrations in End-Stage Renal Disease Using the Winter-Tozer Equation.

PubMed

Soriano, Vincent V; Tesoro, Eljim P; Kane, Sean P

2017-08-01

The Winter-Tozer (WT) equation has been shown to reliably predict free phenytoin levels in healthy patients. In patients with end-stage renal disease (ESRD), phenytoin-albumin binding is altered and, thus, affects interpretation of total serum levels. Although an ESRD WT equation was historically proposed for this population, there is a lack of data evaluating its accuracy. The objective of this study was to determine the accuracy of the ESRD WT equation in predicting free serum phenytoin concentration in patients with ESRD on hemodialysis (HD). A retrospective analysis of adult patients with ESRD on HD and concurrent free and total phenytoin concentrations was conducted. Each patient's true free phenytoin concentration was compared with a calculated value using the ESRD WT equation and a revised version of the ESRD WT equation. A total of 21 patients were included for analysis. The ESRD WT equation produced a percentage error of 75% and a root mean square error of 1.76 µg/mL. Additionally, 67% of the samples had an error >50% when using the ESRD WT equation. A revised equation was found to have high predictive accuracy, with only 5% of the samples demonstrating >50% error. The ESRD WT equation was not accurate in predicting free phenytoin concentration in patients with ESRD on HD. A revised ESRD WT equation was found to be significantly more accurate. Given the small study sample, further studies are required to fully evaluate the clinical utility of the revised ESRD WT equation.

Gestational diabetes mellitus (GDM) in the Republic of Kosovo: a retrospective pilot study.

PubMed

Daci, Armond; Elshani, Brikene; Giangiacomo, Beretta

2013-01-01

GDM is a condition in which women without previously diagnosed diabetes exhibit high blood glucose levels during pregnancy. Pregnancy causes some insulin resistance in all women, but only a few develop GDM. To test the hypothesis that women with GDM have impaired regulation of blood iron storage and transport, decreased renal function due to decreased glomerular filtration rate and occurrence of urinary tract infection (UTI). Incidence of blood iron storage was investigated in n=30 pregnant kosovar women with GDM after mild of pregnancy and in n=30 pregnant women without GDM (years 2010-2012). Baby weights, both systolic and diastolic BP, creatinine, albumin, lymphocytes, monocytes, WBC and granulocytes in both groups were within their normal ranges in both groups. Compared to control group, glucose was higher in women with GDM (mean +/- SD: 7.43 +/- 2.23 mg/dL vs. 4.33 +/- 0.63 mg/dL; P < 0.001). Women with GDM had also higher RBC (mean +/- SD: 4.4 +/- 0.8% vs. 3.8 +/- 0.3%; P < 0.005) and HGB (mean +/- SD: 13.0 +/- 3.2 g/dL vs. 11.2 +/- 1.4 mg/dL; P < 0.05), and decreased renal functionality (MDRD-GFR: 92.8 +/- 25.8 g/dL vs. 108.2 +/- 38.2 g/dL; P < .05). There is a potential association between iron status and GDM. The role of iron from diet and/or from supplementation in GDM pathogenesis needs still to be examined. In addition we have observed a decrease of glomerular filtration rate in women with GDM. Due to the lack of studies on the relationships between GDM and UTI, and to the retrospective design of the present investigation, it is difficult to establish whether UTI may be a GDM causal factor or a consequence of GDM symptoms, signs and/or of its correlated pathologies.

Prevalence and nature of anaemia in a prospective, population-based sample of people with diabetes: Teesside anaemia in diabetes (TAD) study.

PubMed

Jones, S C; Smith, D; Nag, S; Bilous, M T; Winship, S; Wood, A; Bilous, R W

2010-06-01

Anaemia occurs in 25% of people attending hospital diabetes clinics, but this may not be representative of all people with diabetes. We aimed to determine the prevalence of anaemia in a prospective population-based sample stratified by estimated glomerular filtration rate (eGFR) using the 4-point Modification of Diet in Renal Disease (MDRD) formula. All 7331 patients on our district register were stratified by eGFR. Seven hundred and thirty were approached by letter on two occasions. Two hundred and thirty-four (32%) returned questionnaires and blood samples. Responders (R), non-responders (NR) and the whole cohort (C) were similar: mean +/- sd age R 61.7 +/- 12.7 years; NR 61.3 +/- 15.1 years; C 61.8 +/- 14.2 years; diabetes duration R 8.8 +/- 8.6 years; NR 8.2 +/- 7.9 years; C 7.5 +/- 7.8 years, Type 1 diabetes R 10.1%, NR 10.8%, C 9.4%. Anaemia was defined using World Health Organization criteria: haemoglobin < 13 g/dl for men, < 12 g/dl for women. Previously undiagnosed anaemia was present in 15% of the whole group, 36% with eGFR < 60 ml/min per 1.73 m(2) and 9% of those with eGFR > 60 ml/min per 1.73 m(2). Anaemia was as a result of erythropoietin deficiency in 34%, abnormal haematinics in 40% and was unexplained in 26% of patients. Five per cent of the patients had anaemia below the treatment threshold of 11 g/dl. The prevalence of unrecognized anaemia in population-based cohorts is lower than that in hospital-based studies. Current clinical surveillance in the UK is failing to detect anaemia in stage 3-5 chronic kidney disease (eGFR < 60 ml/min per 1.73 m(2)) and current guidelines will not detect 9% of diabetic patients with anaemia and an eGFR > 60 ml/min per 1.73 m(2).

Stochastic Evolution Equations Driven by Fractional Noises

DTIC Science & Technology

2016-11-28

rate of convergence to zero or the error and the limit in distribution of the error fluctuations. We have studied time discrete numerical schemes...error fluctuations. We have studied time discrete numerical schemes based on Taylor expansions for rough differential equations and for stochastic...variations of the time discrete Taylor schemes for rough differential equations and for stochastic differential equations driven by fractional Brownian

Computation techniques and computer programs to analyze Stirling cycle engines using characteristic dynamic energy equations

NASA Technical Reports Server (NTRS)

Larson, V. H.

1982-01-01

The basic equations that are used to describe the physical phenomena in a Stirling cycle engine are the general energy equations and equations for the conservation of mass and conversion of momentum. These equations, together with the equation of state, an analytical expression for the gas velocity, and an equation for mesh temperature are used in this computer study of Stirling cycle characteristics. The partial differential equations describing the physical phenomena that occurs in a Stirling cycle engine are of the hyperbolic type. The hyperbolic equations have real characteristic lines. By utilizing appropriate points along these curved lines the partial differential equations can be reduced to ordinary differential equations. These equations are solved numerically using a fourth-fifth order Runge-Kutta integration technique.

An Evaluation of Kernel Equating: Parallel Equating with Classical Methods in the SAT Subject Tests[TM] Program. Research Report. ETS RR-09-06

ERIC Educational Resources Information Center

Grant, Mary C.; Zhang, Lilly; Damiano, Michele

2009-01-01

This study investigated kernel equating methods by comparing these methods to operational equatings for two tests in the SAT Subject Tests[TM] program. GENASYS (ETS, 2007) was used for all equating methods and scaled score kernel equating results were compared to Tucker, Levine observed score, chained linear, and chained equipercentile equating…

Smoothing and Equating Methods Applied to Different Types of Test Score Distributions and Evaluated with Respect to Multiple Equating Criteria. Research Report. ETS RR-11-20

ERIC Educational Resources Information Center

Moses, Tim; Liu, Jinghua

2011-01-01

In equating research and practice, equating functions that are smooth are typically assumed to be more accurate than equating functions with irregularities. This assumption presumes that population test score distributions are relatively smooth. In this study, two examples were used to reconsider common beliefs about smoothing and equating. The…

A Comparison of Kernel Equating and Traditional Equipercentile Equating Methods and the Parametric Bootstrap Methods for Estimating Standard Errors in Equipercentile Equating

ERIC Educational Resources Information Center

Choi, Sae Il

2009-01-01

This study used simulation (a) to compare the kernel equating method to traditional equipercentile equating methods under the equivalent-groups (EG) design and the nonequivalent-groups with anchor test (NEAT) design and (b) to apply the parametric bootstrap method for estimating standard errors of equating. A two-parameter logistic item response…

Exact solution of some linear matrix equations using algebraic methods

NASA Technical Reports Server (NTRS)

Djaferis, T. E.; Mitter, S. K.

1977-01-01

A study is done of solution methods for Linear Matrix Equations including Lyapunov's equation, using methods of modern algebra. The emphasis is on the use of finite algebraic procedures which are easily implemented on a digital computer and which lead to an explicit solution to the problem. The action f sub BA is introduced a Basic Lemma is proven. The equation PA + BP = -C as well as the Lyapunov equation are analyzed. Algorithms are given for the solution of the Lyapunov and comment is given on its arithmetic complexity. The equation P - A'PA = Q is studied and numerical examples are given.

Investigation of supersonic jet plumes using an improved two-equation turbulence model

NASA Technical Reports Server (NTRS)

Lakshmanan, B.; Abdol-Hamid, Khaled S.

1994-01-01

Supersonic jet plumes were studied using a two-equation turbulence model employing corrections for compressible dissipation and pressure-dilatation. A space-marching procedure based on an upwind numerical scheme was used to solve the governing equations and turbulence transport equations. The computed results indicate that two-equation models employing corrections for compressible dissipation and pressure-dilatation yield improved agreement with the experimental data. In addition, the numerical study demonstrates that the computed results are sensitive to the effect of grid refinement and insensitive to the type of velocity profiles used at the inflow boundary for the cases considered in the present study.

Local Linear Observed-Score Equating

ERIC Educational Resources Information Center

Wiberg, Marie; van der Linden, Wim J.

2011-01-01

Two methods of local linear observed-score equating for use with anchor-test and single-group designs are introduced. In an empirical study, the two methods were compared with the current traditional linear methods for observed-score equating. As a criterion, the bias in the equated scores relative to true equating based on Lord's (1980)…

Multi-Component Diffusion with Application To Computational Aerothermodynamics

NASA Technical Reports Server (NTRS)

Sutton, Kenneth; Gnoffo, Peter A.

1998-01-01

The accuracy and complexity of solving multicomponent gaseous diffusion using the detailed multicomponent equations, the Stefan-Maxwell equations, and two commonly used approximate equations have been examined in a two part study. Part I examined the equations in a basic study with specified inputs in which the results are applicable for many applications. Part II addressed the application of the equations in the Langley Aerothermodynamic Upwind Relaxation Algorithm (LAURA) computational code for high-speed entries in Earth's atmosphere. The results showed that the presented iterative scheme for solving the Stefan-Maxwell equations is an accurate and effective method as compared with solutions of the detailed equations. In general, good accuracy with the approximate equations cannot be guaranteed for a species or all species in a multi-component mixture. 'Corrected' forms of the approximate equations that ensured the diffusion mass fluxes sum to zero, as required, were more accurate than the uncorrected forms. Good accuracy, as compared with the Stefan- Maxwell results, were obtained with the 'corrected' approximate equations in defining the heating rates for the three Earth entries considered in Part II.

Methods for Equating Mental Tests.

DTIC Science & Technology

1984-11-01

1983) compared conventional and IRT methods for equating the Test of English as a Foreign Language ( TOEFL ) after chaining. Three conventional and...three IRT equating methods were examined in this study; two sections of TOEFL were each (separately) equated. The IRT methods included the following: (a...group. A separate base form was established for each of the six equating methods. Instead of equating the base-form TOEFL to itself, the last (eighth

An Exploration of Kernel Equating Using SAT® Data: Equating to a Similar Population and to a Distant Population. Research Report. ETS RR-07-17

ERIC Educational Resources Information Center

Liu, Jinghua; Low, Albert C.

2007-01-01

This study applied kernel equating (KE) in two scenarios: equating to a very similar population and equating to a very different population, referred to as a distant population, using SAT® data. The KE results were compared to the results obtained from analogous classical equating methods in both scenarios. The results indicate that KE results are…

Thermodynamic properties of oxygen and nitrogen III

NASA Technical Reports Server (NTRS)

Stewart, R. B.; Jacobsen, R. T.; Myers, A. F.

1972-01-01

The final equation for nitrogen was determined. In the work on the equation of state for nitrogen, coefficients were determined by constraining the critical point to selected critical point parameters. Comparisons of this equation with all the P-density-T data were made, as well as comparisons to all other thermodynamic data reported in the literature. The extrapolation of the equation of state was studied for vapor to higher temperatures and lower temperatures, and for the liquid surface to the saturated liquid and the fusion lines. A new vapor pressure equation was also determined which was constrained to the same critical temperature, pressure, and slope (dP/dT) as the equation of state. Work on the equation of state for oxygen included studies for improving the equation at the critical point. Comparisons of velocity of sound data for oxygen were also made between values calculated with a preliminary equation of state and experimental data. Functions for the calculation of the derived thermodynamic properties using the equation of state are given, together with the derivative and integral functions for the calculation of the thermodynamic properties using the equations of state. Summary tables of the thermodynamic properties of nitrogen and oxygen are also included to serve as a check for those preparing computer programs using the equations of state.

Validity of one-repetition maximum predictive equations in men with spinal cord injury.

PubMed

Ribeiro Neto, F; Guanais, P; Dornelas, E; Coutinho, A C B; Costa, R R G

2017-10-01

Cross-sectional study. The study aimed (a) to test the cross-validation of current one-repetition maximum (1RM) predictive equations in men with spinal cord injury (SCI); (b) to compare the current 1RM predictive equations to a newly developed equation based on the 4- to 12-repetition maximum test (4-12RM). SARAH Rehabilitation Hospital Network, Brasilia, Brazil. Forty-five men aged 28.0 years with SCI between C6 and L2 causing complete motor impairment were enrolled in the study. Volunteers were tested, in a random order, in 1RM test or 4-12RM with 2-3 interval days. Multiple regression analysis was used to generate an equation for predicting 1RM. There were no significant differences between 1RM test and the current predictive equations. ICC values were significant and were classified as excellent for all current predictive equations. The predictive equation of Lombardi presented the best Bland-Altman results (0.5 kg and 12.8 kg for mean difference and interval range around the differences, respectively). The two created equation models for 1RM demonstrated the same and a high adjusted R 2 (0.971, P<0.01), but different SEE of measured 1RM (2.88 kg or 5.4% and 2.90 kg or 5.5%). All 1RM predictive equations are accurate to assess individuals with SCI at the bench press exercise. However, the predictive equation of Lombardi presented the best associated cross-validity results. A specific 1RM prediction equation was also elaborated for individuals with SCI. The created equation should be tested in order to verify whether it presents better accuracy than the current ones.

Basic lubrication equations

NASA Technical Reports Server (NTRS)

Hamrock, B. J.; Dowson, D.

1981-01-01

Lubricants, usually Newtonian fluids, are assumed to experience laminar flow. The basic equations used to describe the flow are the Navier-Stokes equation of motion. The study of hydrodynamic lubrication is, from a mathematical standpoint, the application of a reduced form of these Navier-Stokes equations in association with the continuity equation. The Reynolds equation can also be derived from first principles, provided of course that the same basic assumptions are adopted in each case. Both methods are used in deriving the Reynolds equation, and the assumptions inherent in reducing the Navier-Stokes equations are specified. Because the Reynolds equation contains viscosity and density terms and these properties depend on temperature and pressure, it is often necessary to couple the Reynolds with energy equation. The lubricant properties and the energy equation are presented. Film thickness, a parameter of the Reynolds equation, is a function of the elastic behavior of the bearing surface. The governing elasticity equation is therefore presented.

On supporting students' understanding of solving linear equation by using flowchart

NASA Astrophysics Data System (ADS)

Toyib, Muhamad; Kusmayadi, Tri Atmojo; Riyadi

2017-05-01

The aim of this study was to support 7th graders to gradually understand the concepts and procedures of solving linear equation. Thirty-two 7th graders of a Junior High School in Surakarta, Indonesia were involved in this study. Design research was used as the research approach to achieve the aim. A set of learning activities in solving linear equation with one unknown were designed based on Realistic Mathematics Education (RME) approach. The activities were started by playing LEGO to find a linear equation then solve the equation by using flowchart. The results indicate that using the realistic problems, playing LEGO could stimulate students to construct linear equation. Furthermore, Flowchart used to encourage students' reasoning and understanding on the concepts and procedures of solving linear equation with one unknown.

Bifurcations of solitary wave solutions for (two and three)-dimensional nonlinear partial differential equation in quantum and magnetized plasma by using two different methods

NASA Astrophysics Data System (ADS)

Khater, Mostafa M. A.; Seadawy, Aly R.; Lu, Dianchen

2018-06-01

In this research, we study new two techniques that called the extended simple equation method and the novel (G‧/G) -expansion method. The extended simple equation method depend on the auxiliary equation (dϕ/dξ = α + λϕ + μϕ2) which has three ways for solving depends on the specific condition on the parameters as follow: When (λ = 0) this auxiliary equation reduces to Riccati equation, when (α = 0) this auxiliary equation reduces to Bernoulli equation and when (α ≠ 0, λ ≠ 0, μ ≠ 0) we the general solutions of this auxiliary equation while the novel (G‧/G) -expansion method depends also on similar auxiliary equation (G‧/G)‧ = μ + λ(G‧/G) + (v - 1)(G‧/G) 2 which depend also on the value of (λ2 - 4 (v - 1) μ) and the specific condition on the parameters as follow: When (λ = 0) this auxiliary equation reduces to Riccati equation, when (μ = 0) this auxiliary equation reduces to Bernoulli equation and when (λ2 ≠ 4 (v - 1) μ) we the general solutions of this auxiliary equation. This show how both of these auxiliary equation are special cases of Riccati equation. We apply these methods on two dimensional nonlinear Kadomtsev-Petviashvili Burgers equation in quantum plasma and three-dimensional nonlinear modified Zakharov-Kuznetsov equation of ion-acoustic waves in a magnetized plasma. We obtain the exact traveling wave solutions of these important models and under special condition on the parameters, we get solitary traveling wave solutions. All calculations in this study have been established and verified back with the aid of the Maple package program. The executed method is powerful, effective and straightforward for solving nonlinear partial differential equations to obtain more and new solutions.

Governing equations for electro-conjugate fluid flow

NASA Astrophysics Data System (ADS)

Hosoda, K.; Takemura, K.; Fukagata, K.; Yokota, S.; Edamura, K.

2013-12-01

An electro-conjugation fluid (ECF) is a kind of dielectric liquid, which generates a powerful flow when high DC voltage is applied with tiny electrodes. This study deals with the derivation of the governing equations for electro-conjugate fluid flow based on the Korteweg-Helmholtz (KH) equation which represents the force in dielectric liquid subjected to high DC voltage. The governing equations consist of the Gauss's law, charge conservation with charge recombination, the KH equation, the continuity equation and the incompressible Navier-Stokes equations. The KH equation consists of coulomb force, dielectric constant gradient force and electrostriction force. The governing equation gives the distribution of electric field, charge density and flow velocity. In this study, direct numerical simulation (DNS) is used in order to get these distribution at arbitrary time. Successive over-relaxation (SOR) method is used in analyzing Gauss's law and constrained interpolation pseudo-particle (CIP) method is used in analyzing charge conservation with charge recombination. The third order Runge-Kutta method and conservative second-order-accurate finite difference method is used in analyzing the Navier-Stokes equations with the KH equation. This study also deals with the measurement of ECF ow generated with a symmetrical pole electrodes pair which are made of 0.3 mm diameter piano wire. Working fluid is FF-1EHA2 which is an ECF family. The flow is observed from the both electrodes, i.e., the flow collides in between the electrodes. The governing equation successfully calculates mean flow velocity in between the collector pole electrode and the colliding region by the numerical simulation.

Heavy use of equations impedes communication among biologists.

PubMed

Fawcett, Tim W; Higginson, Andrew D

2012-07-17

Most research in biology is empirical, yet empirical studies rely fundamentally on theoretical work for generating testable predictions and interpreting observations. Despite this interdependence, many empirical studies build largely on other empirical studies with little direct reference to relevant theory, suggesting a failure of communication that may hinder scientific progress. To investigate the extent of this problem, we analyzed how the use of mathematical equations affects the scientific impact of studies in ecology and evolution. The density of equations in an article has a significant negative impact on citation rates, with papers receiving 28% fewer citations overall for each additional equation per page in the main text. Long, equation-dense papers tend to be more frequently cited by other theoretical papers, but this increase is outweighed by a sharp drop in citations from nontheoretical papers (35% fewer citations for each additional equation per page in the main text). In contrast, equations presented in an accompanying appendix do not lessen a paper's impact. Our analysis suggests possible strategies for enhancing the presentation of mathematical models to facilitate progress in disciplines that rely on the tight integration of theoretical and empirical work.

Comparing the IRT Pre-equating and Section Pre-equating: A Simulation Study.

ERIC Educational Resources Information Center

Hwang, Chi-en; Cleary, T. Anne

The results obtained from two basic types of pre-equatings of tests were compared: the item response theory (IRT) pre-equating and section pre-equating (SPE). The simulated data were generated from a modified three-parameter logistic model with a constant guessing parameter. Responses of two replication samples of 3000 examinees on two 72-item…

The Examination of the Classification of Students into Performance Categories by Two Different Equating Methods

ERIC Educational Resources Information Center

Keller, Lisa A.; Keller, Robert R.; Parker, Pauline A.

2011-01-01

This study investigates the comparability of two item response theory based equating methods: true score equating (TSE), and estimated true equating (ETE). Additionally, six scaling methods were implemented within each equating method: mean-sigma, mean-mean, two versions of fixed common item parameter, Stocking and Lord, and Haebara. Empirical…

Performance of bed-load transport equations relative to geomorphic significance: Predicting effective discharge and its transport rate

Treesearch

Jeffrey J. Barry; John M. Buffington; Peter Goodwin; John .G. King; William W. Emmett

2008-01-01

Previous studies assessing the accuracy of bed-load transport equations have considered equation performance statistically based on paired observations of measured and predicted bed-load transport rates. However, transport measurements were typically taken during low flows, biasing the assessment of equation performance toward low discharges, and because equation...

Dynamics of one- and two-dimensional fronts in a bistable equation with time-delayed global feedback: Propagation failure and control mechanisms

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

Boubendir, Yassine; Mendez, Vicenc; Rotstein, Horacio G.

2010-09-15

We study the evolution of fronts in a bistable equation with time-delayed global feedback in the fast reaction and slow diffusion regime. This equation generalizes the Hodgkin-Grafstein and Allen-Cahn equations. We derive a nonlinear equation governing the motion of fronts, which includes a term with delay. In the one-dimensional case this equation is linear. We study the motion of one- and two-dimensional fronts, finding a much richer dynamics than for the previously studied cases (without time-delayed global feedback). We explain the mechanism by which localized fronts created by inhibitory global coupling loose stability in a Hopf bifurcation as the delaymore » time increases. We show that for certain delay times, the prevailing phase is different from that corresponding to the system in the absence of global coupling. Numerical simulations of the partial differential equation are in agreement with the analytical predictions.« less

Application of integral equation theory to analyze stability of electric field in multimode microwave heating cavity

NASA Astrophysics Data System (ADS)

Tang, Zhengming; Hong, Tao; Chen, Fangyuan; Zhu, Huacheng; Huang, Kama

2017-10-01

Microwave heating uniformity is mainly dependent on and affected by electric field. However, little study has paid attention to its stability characteristics in multimode cavity. In this paper, this problem is studied by the theory of Freedholm integral equation. Firstly, Helmholtz equation and the electric dyadic Green's function are used to derive the electric field integral equation. Then, the stability of electric field is demonstrated as the characteristics of solutions to Freedholm integral equation. Finally, the stability characteristics are obtained and verified by finite element calculation. This study not only can provide a comprehensive interpretation of electric field in multimode cavity but also help us make better use of microwave energy.

Nonlocal nonlinear Schrödinger equations and their soliton solutions

NASA Astrophysics Data System (ADS)

Gürses, Metin; Pekcan, Aslı

2018-05-01

We study standard and nonlocal nonlinear Schrödinger (NLS) equations obtained from the coupled NLS system of equations (Ablowitz-Kaup-Newell-Segur (AKNS) equations) by using standard and nonlocal reductions, respectively. By using the Hirota bilinear method, we first find soliton solutions of the coupled NLS system of equations; then using the reduction formulas, we find the soliton solutions of the standard and nonlocal NLS equations. We give examples for particular values of the parameters and plot the function |q(t, x)|2 for the standard and nonlocal NLS equations.

Protein electrostatics: a review of the equations and methods used to model electrostatic equations in biomolecules--applications in biotechnology.

PubMed

Neves-Petersen, Maria Teresa; Petersen, Steffen B

2003-01-01

The molecular understanding of the initial interaction between a protein and, e.g., its substrate, a surface or an inhibitor is essentially an understanding of the role of electrostatics in intermolecular interactions. When studying biomolecules it is becoming increasingly evident that electrostatic interactions play a role in folding, conformational stability, enzyme activity and binding energies as well as in protein-protein interactions. In this chapter we present the key basic equations of electrostatics necessary to derive the equations used to model electrostatic interactions in biomolecules. We will also address how to solve such equations. This chapter is divided into two major sections. In the first part we will review the basic Maxwell equations of electrostatics equations called the Laws of Electrostatics that combined will result in the Poisson equation. This equation is the starting point of the Poisson-Boltzmann (PB) equation used to model electrostatic interactions in biomolecules. Concepts as electric field lines, equipotential surfaces, electrostatic energy and when can electrostatics be applied to study interactions between charges will be addressed. In the second part we will arrive at the electrostatic equations for dielectric media such as a protein. We will address the theory of dielectrics and arrive at the Poisson equation for dielectric media and at the PB equation, the main equation used to model electrostatic interactions in biomolecules (e.g., proteins, DNA). It will be shown how to compute forces and potentials in a dielectric medium. In order to solve the PB equation we will present the continuum electrostatic models, namely the Tanford-Kirkwood and the modified Tandord-Kirkwood methods. Priority will be given to finding the protonation state of proteins prior to solving the PB equation. We also present some methods that can be used to map and study the electrostatic potential distribution on the molecular surface of proteins. The combination of graphical visualisation of the electrostatic fields combined with knowledge about the location of key residues on the protein surface allows us to envision atomic models for enzyme function. Finally, we exemplify the use of some of these methods on the enzymes of the lipase family.

Modified Maturity Offset Prediction Equations: Validation in Independent Longitudinal Samples of Boys and Girls.

PubMed

Kozieł, Sławomir M; Malina, Robert M

2018-01-01

Predicted maturity offset and age at peak height velocity are increasingly used with youth athletes, although validation studies of the equations indicated major limitations. The equations have since been modified and simplified. The objective of this study was to validate the new maturity offset prediction equations in independent longitudinal samples of boys and girls. Two new equations for boys with chronological age and sitting height and chronological age and stature as predictors, and one equation for girls with chronological age and stature as predictors were evaluated in serial data from the Wrocław Growth Study, 193 boys (aged 8-18 years) and 198 girls (aged 8-16 years). Observed age at peak height velocity for each youth was estimated with the Preece-Baines Model 1. The original prediction equations were included for comparison. Predicted age at peak height velocity was the difference between chronological age at prediction and maturity offset. Predicted ages at peak height velocity with the new equations approximated observed ages at peak height velocity in average maturing boys near the time of peak height velocity; a corresponding window for average maturing girls was not apparent. Compared with observed age at peak height velocity, predicted ages at peak height velocity with the new and original equations were consistently later in early maturing youth and earlier in late maturing youth of both sexes. Predicted ages at peak height velocity with the new equations had reduced variation compared with the original equations and especially observed ages at peak height velocity. Intra-individual variation in predicted ages at peak height velocity with all equations was considerable. The new equations are useful for average maturing boys close to the time of peak height velocity; there does not appear to be a clear window for average maturing girls. The new and original equations have major limitations with early and late maturing boys and girls.

Effect of an intensive nutrition intervention of a high protein and low glycemic-index diet on weight of kidney transplant recipients: study protocol for a randomized clinical trial.

PubMed

Pedrollo, Elis Forcellini; Nicoletto, Bruna Bellincanta; Carpes, Larissa Salomoni; de Freitas, Júlia de Melo Cardoso; Buboltz, Julia Roberta; Forte, Cristina Carra; Bauer, Andrea Carla; Manfro, Roberto Ceratti; Souza, Gabriela Corrêa; Leitão, Cristiane Bauermann

2017-09-06

Excessive weight gain is commonly observed within the first year after kidney transplantation and is associated with negative outcomes, such as graft loss and cardiovascular events. The purpose of this study is to evaluate the effect of a high protein and low glycemic-index diet on preventing weight gain after kidney transplantation. We designed a prospective, single-center, open-label, randomized controlled study to compare the efficacy of a high protein (1.3-1.4 g/kg/day) and low-glycemic index diet versus a conventional diet (0.8-1.0 g/kg/day of protein) on preventing weight gain after kidney transplantation. A total of 120 eligible patients 2 months after transplantation will be recruited. Patients with an estimated glomerular filtration rate through the modification of diet of renal disease (MDRD) formula < 30 mL/min/1.73 m 2 or urinary albumin excretion > 300 mg/24 h will be excluded. Patients' diets will be allocated through simple sequential randomization. Patients will be followed-up for 12 months with nine clinic appointments with a dietitian and the evaluations will include nutritional assessment (anthropometrics, body composition, and resting metabolic rate) and laboratory tests. The primary outcome is weight maintenance or body weight gain under 5% after 12 months. Secondary outcomes include body composition, resting metabolic rate, satiety sensation, kidney function, and other metabolic parameters. Diets with higher protein content and lower glycemic index may lead to weight loss because of higher satiety sensation. However, there is a concern about the association of high protein intake and kidney damage. Nevertheless, there is little evidence on the impact of high protein intake on long-term kidney function outcome. Therefore, we designed a study to test if a high protein diet with low-glycemic index will be an effective and safe nutritional intervention to prevent weight gain in kidney transplant patients. ClinicalTrials.gov identifier, NCT02883777 . Registered on 3 August 2016.

Administration of contrast media just before cisplatin-based chemotherapy increases cisplatin-induced nephrotoxicity.

PubMed

Sendur, M A N; Aksoy, S; Yaman, S; Arik, Z; Tugba Kos, F; Akinci, M B; Civelek, B; Yildirim Ozdemir, N; Uncu, D; Zengin, N

2013-01-01

There is a clinical need to predict the probability of cisplatin-induced nephrotoxicity (CIN) in order to make decisions about patient management and relevant preventive measures. The purpose of this study was to develop a risk prediction methodology of CIN. 197 consecutive cancer patients, whose serum creatinine was measured at least 48 h before every cycle of cisplatin-based chemotherapy, were included in the study. Demographic and clinical data were collected from the patient medical records. Renal function was evaluated at least 48 h before treatment (day 0) of each cycle, based on the Modification of Diet in Renal Disease (MDRD) formula. CIN was defined as a decrease of ≥ 25% in glomerular filtration rate (GFR) compared to baseline GFR values. The mean age of the study population was 54.5±9.6 years. Fifty-eight patients (29.4%) whose GFR had decreased by at least 25% compared to baseline values formed the CIN group, and the remaining 139 patients formed the non-CIN group. No significant differences were noted between the CIN and non-CIN groups in terms of age, gender, body mass index and smoking history. Metastatic disease was similar in both groups (p=0.86). History of hypertension (p=0.81), diabetes mellitus (p=0.72), and cardiovascular disease (p=0.58) were similar in the two groups. Chemotherapeutic agents used concurrently with cisplatin were similar in both groups. Significantly more radiologic examinations using contrast media were performed in the CIN group compared with the non-CIN group (p=0.01). In patients exposed to contrast media within a week before cisplatin administration, the risk of CIN was 2.56-fold higher (957 percent; CI 1.28-5.11) than in patients without such exposure (p=0.009). In patients with exposure to contrast media within a week before cisplatin administration, the risk of CIN was significantly higher than in patients without such an exposure. No additional risk factors for CIN were found in this retrospective observational study.

[Chronic kidney disease in the source documentation of the outpatient clinic Department of Nephrology. Part I. Causes of renal failure and characteristics of the studied population].

PubMed

Kopeć, Jerzy; Januszek, Rafał; Wieczorek-Surdacka, Ewa; Sułowicz, Władysław

2009-01-01

During the last years the incidence of chronic kidney disease (CKD) is permanently increasing and has become a global social and economical problem in the world as well as in Poland. The aim of the study was the retrospective analysis of medical records of patients with renal failure under supervision at the outpatient clinic, Department of Nephrology, University Hospital in Cracow. The study population enclosed 1183 patients (640 men and 543 women) aged between 17 and 98 years (mean 64.7) with creatinine concentration >120 micromol/l and/or creatinine clearance <90 ml/min/1.73 m2. Hemoglobin, iron, creatinine, urea, sodium, potasium, calcium, phosphate, magnesium, PTH, uric acid, albumin, total protein, bilirubin, glucose, total cholesterol, LDL and HDL cholesterol, triglicerydes concentration and values of hematocrite, MCV, HbA1, as well as alkaline phosphatase, AspAT, AIAT activity were estimated based on standard laboratory methods. Creatinine clearances were evaluated based on 3 different methods: simplified MDRD formula, Cockcroft-Gault formula and 24-h urine collection. Mean creatinine concentration in the studied population was 172.8 micromol/l (1.95 mg/dl). Hypertension was diagnosed in 65% of patients. In spite of treatment, more than half of the patients (51.9%) have increased systolic blood pressure and above 1/3 (35%) increased diastolic blood pressure. Mean hemoglobin concentration was 13.02 g/dl; more than 12% of patients had decreased hemoglobin below 11 g/dl. Mean values of parameters discovering calcium-phosphate metabolism were: calcium--2.33 mmol/l, phosphate--1.23 mmol/l and parathormon--169.3 pg/ml. Increased value of total serum cholesterol level was noted more than half of the patients (56.5%). Significant positive correlations were found between GFR calculated based on Cockcroft-Gault formula and BMI, hemoglobin, hematocrite, serum iron, diastolic blood pressure, total and LDL serum cholesterol, triglicerydes level, as well as AIAT activity and % values of HbA1c and negative with age, serum potassium, phosphorus, PTH and uric acid.

The renin-angiotensin-aldosterone system blockade in patients with advanced diabetic kidney disease.

PubMed

Bermejo, Sheila; García, Carles Oriol; Rodríguez, Eva; Barrios, Clara; Otero, Sol; Mojal, Sergi; Pascual, Julio; Soler, María José

Diabetic kidney disease is the leading cause of end-stage chronic kidney disease. The renin-angiotensin-aldosterone system (RAAS) blockade has been shown to slow the progression of diabetic kidney disease. Our objectives were: to study the percentage of patients with diabetic kidney disease treated with RAAS blockade, to determine its renal function, safety profile and assess whether its administration is associated with increased progression of CKD after 3 years of follow-up. Retrospective study. 197 diabetic kidney disease patients were included and divided into three groups according to the treatment: patients who had never received RAAS blockade (non-RAAS blockade), patients who at some point had received RAAS blockade (inconstant-RAAS blockade) and patients who received RAAS blockade (constant-RAAS blockade). Clinical characteristics and analytical variables such as renal function, electrolytes, glycosylated haemoglobin and glomerular filtration rate according to chronic kidney disease -EPI and MDRD formulas were assessed. We also studied their clinical course (baseline, 1 and 3 years follow-up) in terms of treatment group, survival, risk factors and renal prognosis. Non-RAAS blockade patients had worse renal function and older age (p<0.05) at baseline compared to RAAS blockade patients. Patients who received RAAS blockade were not found to have greater toxicity or chronic kidney disease progression and no differences in renal prognosis were identified. Mortality was higher in non-RAAS blockade patients, older patients and patients with worse renal function (p<0.05). In the multivariate analysis, older age and worse renal function were risk factors for mortality. Treatment with RAAS blockade is more common in diabetic kidney disease patients with eGFR≥30ml/min/1.73m 2 . In our study, there were no differences in the evolution of renal function between the three groups. Older age and worse renal function were associated with higher mortality in patients who did not receive RAAS blockade. Copyright © 2017 Sociedad Española de Nefrología. Published by Elsevier España, S.L.U. All rights reserved.

Cardiovascular risk prediction tools for populations in Asia.

PubMed

Barzi, F; Patel, A; Gu, D; Sritara, P; Lam, T H; Rodgers, A; Woodward, M

2007-02-01

Cardiovascular risk equations are traditionally derived from the Framingham Study. The accuracy of this approach in Asian populations, where resources for risk factor measurement may be limited, is unclear. To compare "low-information" equations (derived using only age, systolic blood pressure, total cholesterol and smoking status) derived from the Framingham Study with those derived from the Asian cohorts, on the accuracy of cardiovascular risk prediction. Separate equations to predict the 8-year risk of a cardiovascular event were derived from Asian and Framingham cohorts. The performance of these equations, and a subsequently "recalibrated" Framingham equation, were evaluated among participants from independent Chinese cohorts. Six cohort studies from Japan, Korea and Singapore (Asian cohorts); six cohort studies from China; the Framingham Study from the US. 172,077 participants from the Asian cohorts; 25,682 participants from Chinese cohorts and 6053 participants from the Framingham Study. In the Chinese cohorts, 542 cardiovascular events occurred during 8 years of follow-up. Both the Asian cohorts and the Framingham equations discriminated cardiovascular risk well in the Chinese cohorts; the area under the receiver-operator characteristic curve was at least 0.75 for men and women. However, the Framingham risk equation systematically overestimated risk in the Chinese cohorts by an average of 276% among men and 102% among women. The corresponding average overestimation using the Asian cohorts equation was 11% and 10%, respectively. Recalibrating the Framingham risk equation using cardiovascular disease incidence from the non-Chinese Asian cohorts led to an overestimation of risk by an average of 4% in women and underestimation of risk by an average of 2% in men. A low-information Framingham cardiovascular risk prediction tool, which, when recalibrated with contemporary data, is likely to estimate future cardiovascular risk with similar accuracy in Asian populations as tools developed from data on local cohorts.

Choice of Target Population Weights in Rater Comparability Scoring and Equating. Research Report. ETS RR-13-03

ERIC Educational Resources Information Center

Puhan, Gautam

2013-01-01

The purpose of this study was to demonstrate that the choice of sample weights when defining the target population under poststratification equating can be a critical factor in determining the accuracy of the equating results under a unique equating scenario, known as "rater comparability scoring and equating." The nature of data…

Variational objective analysis for cyclone studies

NASA Technical Reports Server (NTRS)

Achtemeier, Gary L.

1989-01-01

Significant accomplishments during 1987 to 1988 are summarized with regard to each of the major project components. Model 1 requires satisfaction of two nonlinear horizontal momentum equations, the integrated continuity equation, and the hydrostatic equation. Model 2 requires satisfaction of model 1 plus the thermodynamic equation for a dry atmosphere. Model 3 requires satisfaction of model 2 plus the radiative transfer equation. Model 4 requires satisfaction of model 3 plus a moisture conservation equation and a parameterization for moist processes.

Whitham modulation theory for (2  +  1)-dimensional equations of Kadomtsev–Petviashvili type

NASA Astrophysics Data System (ADS)

Ablowitz, Mark J.; Biondini, Gino; Rumanov, Igor

2018-05-01

Whitham modulation theory for certain two-dimensional evolution equations of Kadomtsev–Petviashvili (KP) type is presented. Three specific examples are considered in detail: the KP equation, the two-dimensional Benjamin–Ono (2DBO) equation and a modified KP (m2KP) equation. A unified derivation is also provided. In the case of the m2KP equation, the corresponding Whitham modulation system exhibits features different from the other two. The approach presented here does not require integrability of the original evolution equation. Indeed, while the KP equation is known to be a completely integrable equation, the 2DBO equation and the m2KP equation are not known to be integrable. In each of the cases considered, the Whitham modulation system obtained consists of five first-order quasilinear partial differential equations. The Riemann problem (i.e. the analogue of the Gurevich–Pitaevskii problem) for the one-dimensional reduction of the m2KP equation is studied. For the m2KP equation, the system of modulation equations is used to analyze the linear stability of traveling wave solutions.

Generalized Thomas-Fermi equations as the Lampariello class of Emden-Fowler equations

NASA Astrophysics Data System (ADS)

Rosu, Haret C.; Mancas, Stefan C.

2017-04-01

A one-parameter family of Emden-Fowler equations defined by Lampariello's parameter p which, upon using Thomas-Fermi boundary conditions, turns into a set of generalized Thomas-Fermi equations comprising the standard Thomas-Fermi equation for p = 1 is studied in this paper. The entire family is shown to be non integrable by reduction to the corresponding Abel equations whose invariants do not satisfy a known integrability condition. We also discuss the equivalent dynamical system of equations for the standard Thomas-Fermi equation and perform its phase-plane analysis. The results of the latter analysis are similar for the whole class.

The Dirac equation in Schwarzschild black hole coupled to a stationary electromagnetic field

NASA Astrophysics Data System (ADS)

Al-Badawi, A.; Owaidat, M. Q.

2017-08-01

We study the Dirac equation in a spacetime that represents the nonlinear superposition of the Schwarzschild solution to an external, stationary electromagnetic field. The set of equations representing the uncharged Dirac particle in the Newman-Penrose formalism is decoupled into a radial and an angular parts. We obtain exact analytical solutions of the angular equations. We manage to obtain the radial wave equations with effective potentials. Finally, we study the potentials by plotting them as a function of radial distance and examine the effect of the twisting parameter and the frequencies on the potentials.

An efficient numerical scheme for the study of equal width equation

NASA Astrophysics Data System (ADS)

Ghafoor, Abdul; Haq, Sirajul

2018-06-01

In this work a new numerical scheme is proposed in which Haar wavelet method is coupled with finite difference scheme for the solution of a nonlinear partial differential equation. The scheme transforms the partial differential equation to a system of algebraic equations which can be solved easily. The technique is applied to equal width equation in order to study the behaviour of one, two, three solitary waves, undular bore and soliton collision. For efficiency and accuracy of the scheme, L2 and L∞ norms and invariants are computed. The results obtained are compared with already existing results in literature.

Stature estimation equations for South Asian skeletons based on DXA scans of contemporary adults.

PubMed

Pomeroy, Emma; Mushrif-Tripathy, Veena; Wells, Jonathan C K; Kulkarni, Bharati; Kinra, Sanjay; Stock, Jay T

2018-05-03

Stature estimation from the skeleton is a classic anthropological problem, and recent years have seen the proliferation of population-specific regression equations. Many rely on the anatomical reconstruction of stature from archaeological skeletons to derive regression equations based on long bone lengths, but this requires a collection with very good preservation. In some regions, for example, South Asia, typical environmental conditions preclude the sufficient preservation of skeletal remains. Large-scale epidemiological studies that include medical imaging of the skeleton by techniques such as dual-energy X-ray absorptiometry (DXA) offer new potential datasets for developing such equations. We derived estimation equations based on known height and bone lengths measured from DXA scans from the Andhra Pradesh Children and Parents Study (Hyderabad, India). Given debates on the most appropriate regression model to use, multiple methods were compared, and the performance of the equations was tested on a published skeletal dataset of individuals with known stature. The equations have standard errors of estimates and prediction errors similar to those derived using anatomical reconstruction or from cadaveric datasets. As measured by the number of significant differences between true and estimated stature, and the prediction errors, the new equations perform as well as, and generally better than, published equations commonly used on South Asian skeletons or based on Indian cadaveric datasets. This study demonstrates the utility of DXA scans as a data source for developing stature estimation equations and offer a new set of equations for use with South Asian datasets. © 2018 Wiley Periodicals, Inc.

Coulomb Thrusting Application Study

DTIC Science & Technology

2006-01-20

Acceleration Magnitudes To study the relative motion of spacecraft in nearly circular orbits, the Clohessy - Wiltshire - Hill equations are commonly...Modeling The Clohessy - Wiltshire -Hill’s equations12–14 for one of the spacecraft in the 2-craft Coulomb tether formation is given by ẍ1 − 2nẏ1...equa- tion was obtained using the Clohessy - Wiltshire - Hill equations, while the linearized differential equations of ψ and θ were derived from the full

An Investigation of the Sampling Distributions of Equating Coefficients.

ERIC Educational Resources Information Center

Baker, Frank B.

1996-01-01

Using the characteristic curve method for dichotomously scored test items, the sampling distributions of equating coefficients were examined. Simulations indicate that for the equating conditions studied, the sampling distributions of the equating coefficients appear to have acceptable characteristics, suggesting confidence in the values obtained…

Estimating GFR using Serum Cystatin C Alone and in Combination with Serum Creatinine: A Pooled Analysis of 3418 Individuals with CKD

PubMed Central

Stevens, Lesley A; Coresh, Josef; Schmid, Christopher H; Feldman, Harold I.; Froissart, Marc; Kusek, John; Rossert, Jerome; Van Lente, Frederick; Bruce, Robert D.; Zhang, Yaping (Lucy); Greene, Tom; Levey, Andrew S

2008-01-01

Background Serum cystatin C (Scys) has been proposed as a potential replacement for serum creatinine (Scr) in glomerular filtration rate (GFR) estimation. We report development and evaluation of GFR estimating equations using Scys alone and Scys, Scr or both with demographic variables. Study Design Test of diagnostic accuracy. Setting and Participants Participants screened for three chronic kidney disease (CKD) studies in the US (n=2980) and a clinical population in Paris, France (n=438) Reference Test Measured GFR (mGFR). Index Test Estimated GFR using the four new equations based on Scys alone, Scys, Scr or both with age, sex and race. New equations were developed using regression with log GFR as the outcome in 2/3 data from US studies. Internal validation was performed in remaining 1/3 of data from US CKD studies; external validation was performed in the Paris study. Measurements GFR was measured using urinary clearance of 125I-iothalamate in the US studies and chromium-ethylenediaminetetraacetate (51Cr-EDTA) in the Paris study. Scys was measured by Dade Behring assay, standardized Scr. Results Mean mGFR, Scr and Scys were 48 (5th–95th percentile 15–95) ml/min/1.73m2 2.1 mg/dL and 1.8 mg/L respectively. For the new equations, the coefficients for age, sex and race were significant in the equation with Scys but 2 to 4 fold smaller than in the equation with Scr. Measures of performance among new equations were consistent across development, internal and external validation datasets. Percent of eGFR within 30% of mGFR for equations based on Scys alone, Scys, Scr or both with age, sex and race were 81, 83, 85, and 89%, respectively. The equation using Scys alone yields estimates with small biases in age, sex and race subgroups, which are improved in equations including these variables. Limitations Study population composed mainly of patients with CKD. Conclusions Scys alone provides GFR estimates that are nearly as accurate as Scr adjusted for age, sex and race thus providing an alternative GFR estimate that is not linked to muscle mass. An equation including Scys in combination with Scr, age, sex and race provide most accurate estimates. PMID:18295055

Asymptotic of the Solutions of Hyperbolic Equations with a Skew-Symmetric Perturbation

NASA Astrophysics Data System (ADS)

Gallagher, Isabelle

1998-12-01

Using methods introduced by S. Schochet inJ. Differential Equations114(1994), 476-512, we compute the first term of an asymptotic expansion of the solutions of hyperbolic equations perturbated by a skew-symmetric linear operator. That result is first applied to two systems describing the motion of geophysic fluids: the rotating Euler equations and the primitive system of the quasigeostrophic equations. Finally in the last part, we study the slightly compressible Euler equations by application of that same result.

Loop equations and bootstrap methods in the lattice

DOE PAGES

Anderson, Peter D.; Kruczenski, Martin

2017-06-17

Pure gauge theories can be formulated in terms of Wilson Loops by means of the loop equation. In the large-N limit this equation closes in the expectation value of single loops. In particular, using the lattice as a regulator, it becomes a well defined equation for a discrete set of loops. In this paper we study different numerical approaches to solving this equation.

Using the Kernel Method of Test Equating for Estimating the Standard Errors of Population Invariance Measures. Research Report. ETS RR-06-20

ERIC Educational Resources Information Center

Moses, Tim

2006-01-01

Population invariance is an important requirement of test equating. An equating function is said to be population invariant when the choice of (sub)population used to compute the equating function does not matter. In recent studies, the extent to which equating functions are population invariant is typically addressed in terms of practical…

The Equation, the Whole Equation, and Nothing but the Equation! One Approach to the Teaching of Linear Equations.

ERIC Educational Resources Information Center

Pirie, Susan E. B.; Martin, Lyndon

1997-01-01

Presents the results of a case study which looked at the mathematics classroom of one teacher trying to teach mathematics with meaning to pupils or lower ability at the secondary level. Contrasts methods of teaching linear equations to a variety of ability levels and uses the Pirie-Kieren model to account for the successful growth in understanding…

Quantum integrability and functional equations

NASA Astrophysics Data System (ADS)

Volin, Dmytro

2010-03-01

In this thesis a general procedure to represent the integral Bethe Ansatz equations in the form of the Reimann-Hilbert problem is given. This allows us to study in simple way integrable spin chains in the thermodynamic limit. Based on the functional equations we give the procedure that allows finding the subleading orders in the solution of various integral equations solved to the leading order by the Wiener-Hopf technics. The integral equations are studied in the context of the AdS/CFT correspondence, where their solution allows verification of the integrability conjecture up to two loops of the strong coupling expansion. In the context of the two-dimensional sigma models we analyze the large-order behavior of the asymptotic perturbative expansion. Obtained experience with the functional representation of the integral equations allowed us also to solve explicitly the crossing equations that appear in the AdS/CFT spectral problem.

The Forced Hard Spring Equation

ERIC Educational Resources Information Center

Fay, Temple H.

2006-01-01

Through numerical investigations, various examples of the Duffing type forced spring equation with epsilon positive, are studied. Since [epsilon] is positive, all solutions to the associated homogeneous equation are periodic and the same is true with the forcing applied. The damped equation exhibits steady state trajectories with the interesting…

Infinite hierarchy of nonlinear Schrödinger equations and their solutions.

PubMed

Ankiewicz, A; Kedziora, D J; Chowdury, A; Bandelow, U; Akhmediev, N

2016-01-01

We study the infinite integrable nonlinear Schrödinger equation hierarchy beyond the Lakshmanan-Porsezian-Daniel equation which is a particular (fourth-order) case of the hierarchy. In particular, we present the generalized Lax pair and generalized soliton solutions, plane wave solutions, Akhmediev breathers, Kuznetsov-Ma breathers, periodic solutions, and rogue wave solutions for this infinite-order hierarchy. We find that "even- order" equations in the set affect phase and "stretching factors" in the solutions, while "odd-order" equations affect the velocities. Hence odd-order equation solutions can be real functions, while even-order equation solutions are always complex.

Some Exact Solutions of a Nonintegrable Toda-type Equation

NASA Astrophysics Data System (ADS)

Kim, Chanju

2018-05-01

We study a Toda-type equation with two scalar fields which is not integrable and construct two families of exact solutions which are expressed in terms of rational functions. The equation appears in U(1) Chern-Simons theories coupled to two nonrelativistic matter fields with opposite charges. One family of solutions is a trivial embedding of Liouville-type solutions. The other family is obtained by transforming the equation into the Taubes vortex equation on the hyperbolic space. Though the Taubes equation is not integrable, a trivial vacuum solution provides nontrivial solutions to the original Toda-type equation.

Predicting basal metabolic rates in Malaysian adult elite athletes.

PubMed

Wong, Jyh Eiin; Poh, Bee Koon; Nik Shanita, Safii; Izham, Mohd Mohamad; Chan, Kai Quin; Tai, Meng De; Ng, Wei Wei; Ismail, Mohd Noor

2012-11-01

This study aimed to measure the basal metabolic rate (BMR) of elite athletes and develop a gender specific predictive equation to estimate their energy requirements. 92 men and 33 women (aged 18-31 years) from 15 sports, who had been training six hours daily for at least one year, were included in the study. Body composition was measured using the bioimpedance technique, and BMR by indirect calorimetry. The differences between measured and estimated BMR using various predictive equations were calculated. The novel equation derived from stepwise multiple regression was evaluated using Bland and Altman analysis. The predictive equations of Cunningham and the Food and Agriculture Organization/World Health Organization/United Nations University either over- or underestimated the measured BMR by up to ± 6%, while the equations of Ismail et al, developed from the local non-athletic population, underestimated the measured BMR by 14%. The novel predictive equation for the BMR of athletes was BMR (kcal/day) = 669 + 13 (weight in kg) + 192 (gender: 1 for men and 0 for women) (R2 0.548; standard error of estimates 163 kcal). Predicted BMRs of elite athletes by this equation were within 1.2% ± 9.5% of the measured BMR values. The novel predictive equation presented in this study can be used to calculate BMR for adult Malaysian elite athletes. Further studies may be required to validate its predictive capabilities for other sports, nationalities and age groups.

The Jeffcott equations in nonlinear rotordynamics

NASA Technical Reports Server (NTRS)

Zalik, R. A.

1987-01-01

The Jeffcott equations are a system of coupled differential equations representing the behavior of a rotating shaft. This is a simple model which allows investigation of the basic dynamic behavior of rotating machinery. Nolinearities can be introduced by taking into consideration deadband, side force, and rubbing, among others. The properties of the solutions of the Jeffcott equations with deadband are studied. In particular, it is shown how bounds for the solution of these equations can be obtained from bounds for the solutions of the linearized equations. By studying the behavior of the Fourier transforms of the solutions, we are also able to predict the onset of destructive vibrations. These conclusions are verified by means of numerical solutions of the equations, and of power spectrum density (PSD) plots. This study offers insight into a possible detection method to determine pump stability margins during flight and hot fire tests, and was motivated by the need to explain a phenomenon observed in the development phase of the cryogenic pumps of the Space Shuttle, during hot fire ground testing; namely, the appearance of vibrations at frequencies that could not be accounted for by means of linear models.

Renal function in type 2 diabetes with rosiglitazone, metformin, and glyburide monotherapy.

PubMed

Lachin, John M; Viberti, Giancarlo; Zinman, Bernard; Haffner, Steven M; Aftring, R Paul; Paul, Gitanjali; Kravitz, Barbara G; Herman, William H; Holman, Rury R; Kahn, Steven E

2011-05-01

In ADOPT (A Diabetes Outcomes Prevention Trial), initial monotherapy with rosiglitazone provided more durable glycemic control than metformin or glyburide in patients with recently diagnosed type 2 diabetes. Herein, we examine differences in albumin excretion, renal function (estimated GFR), and BP over 5 years between treatment groups. A total of 4351 recently diagnosed, drug-naïve patients with type 2 diabetes were treated and followed for up to 5 years with rosiglitazone, metformin, or glyburide and were examined with periodic assessments of albumin/creatinine ratio (ACR), modification of diet in renal disease (MDRD)-estimated GFR, and BP. The ACR rose slowly with metformin. It fell with rosiglitazone and less so with glyburide over the first 2 years, and then rose slowly over time. Estimated GFR (eGFR) with all therapies rose into the high normal range over the first 3 to 4 years, more so with rosiglitazone, and then declined, more so with glyburide. Systolic BP was stable over time, values with rosiglitazone being lower, and diastolic BP declined over time, more so with rosiglitazone than with metformin or glyburide. There was no difference among groups in the incidence of emergent albuminuria (ACR ≥30 mg/g), hypertension, or impaired eGFR (<60 ml/min per 1.73 m(2)). Over a 5-year period, initial monotherapy with rosiglitazone retards the rise of ACR compared with metformin, preserves eGFR compared with glyburide, and lowers BP relative to both comparators. Copyright © 2011 by the American Society of Nephrology

Breakdown of the conservative potential equation

NASA Technical Reports Server (NTRS)

Salas, M. D.; Gumbert, C. R.

1986-01-01

The conservative full-potential equation is used to study transonic flow over five airfoil sections. The results of the study indicate that once shock are present in the flow, the qualitative approximation is different from that observed with the Euler equations. The difference in behavior of the potential eventually leads to multiple solutions.

Evaluating Equating Accuracy and Assumptions for Groups that Differ in Performance

ERIC Educational Resources Information Center

Powers, Sonya; Kolen, Michael J.

2014-01-01

Accurate equating results are essential when comparing examinee scores across exam forms. Previous research indicates that equating results may not be accurate when group differences are large. This study compared the equating results of frequency estimation, chained equipercentile, item response theory (IRT) true-score, and IRT observed-score…

Equating with Miditests Using IRT

ERIC Educational Resources Information Center

Fitzpatrick, Joseph; Skorupski, William P.

2016-01-01

The equating performance of two internal anchor test structures--miditests and minitests--is studied for four IRT equating methods using simulated data. Originally proposed by Sinharay and Holland, miditests are anchors that have the same mean difficulty as the overall test but less variance in item difficulties. Four popular IRT equating methods…

Students' Equation Understanding and Solving in Iran

ERIC Educational Resources Information Center

Barahmand, Ali; Shahvarani, Ahmad

2014-01-01

The purpose of the present article is to investigate how 15-year-old Iranian students interpret the concept of equation, its solution, and studying the relation between the students' equation understanding and solving. Data from two equation-solving exercises are reported. Data analysis shows that there is a significant relationship between…

The Effect of Repeaters on Equating

ERIC Educational Resources Information Center

Kim, HeeKyoung; Kolen, Michael J.

2010-01-01

Test equating might be affected by including in the equating analyses examinees who have taken the test previously. This study evaluated the effect of including such repeaters on Medical College Admission Test (MCAT) equating using a population invariance approach. Three-parameter logistic (3-PL) item response theory (IRT) true score and…

Applying Meta-Analysis to Structural Equation Modeling

ERIC Educational Resources Information Center

Hedges, Larry V.

2016-01-01

Structural equation models play an important role in the social sciences. Consequently, there is an increasing use of meta-analytic methods to combine evidence from studies that estimate the parameters of structural equation models. Two approaches are used to combine evidence from structural equation models: A direct approach that combines…

W-transform for exponential stability of second order delay differential equations without damping terms.

PubMed

Domoshnitsky, Alexander; Maghakyan, Abraham; Berezansky, Leonid

2017-01-01

In this paper a method for studying stability of the equation [Formula: see text] not including explicitly the first derivative is proposed. We demonstrate that although the corresponding ordinary differential equation [Formula: see text] is not exponentially stable, the delay equation can be exponentially stable.

Study on Heat Transfer Agent Models of Transmission Line and Transformer

NASA Astrophysics Data System (ADS)

Wang, B.; Zhang, P. P.

2018-04-01

When using heat transfer simulation to study the dynamic overload of transmission line and transformer, it needs to establish the mathematical expression of heat transfer. However, the formula is a nonlinear differential equation or equation set and it is not easy to get general solutions. Aiming at this problem, some different temperature change processes caused by different initial conditions are calculated by differential equation and equation set. New agent models are developed according to the characteristics of different temperature change processes. The results show that the agent models have high precision and can solve the problem that the original equation cannot be directly applied in some practical engineers.

Nonlinear Equations of Equilibrium for Elastic Helicopter or Wind Turbine Blades Undergoing Moderate Deformation

NASA Technical Reports Server (NTRS)

Rosen, A.; Friedmann, P. P.

1978-01-01

A set of nonlinear equations of equilibrium for an elastic wind turbine or helicopter blades are presented. These equations are derived for the case of small strains and moderate rotations (slopes). The derivation includes several assumptions which are carefully stated. For the convenience of potential users the equations are developed with respect to two different systems of coordinates, the undeformed and the deformed coordinates of the blade. Furthermore, the loads acting on the blade are given in a general form so as to make them suitable for a variety of applications. The equations obtained in the study are compared with those obtained in previous studies.

Systematic derivation of reaction-diffusion equations with distributed delays and relations to fractional reaction-diffusion equations and hyperbolic transport equations: application to the theory of Neolithic transition.

PubMed

Vlad, Marcel Ovidiu; Ross, John

2002-12-01

We introduce a general method for the systematic derivation of nonlinear reaction-diffusion equations with distributed delays. We study the interactions among different types of moving individuals (atoms, molecules, quasiparticles, biological organisms, etc). The motion of each species is described by the continuous time random walk theory, analyzed in the literature for transport problems, whereas the interactions among the species are described by a set of transformation rates, which are nonlinear functions of the local concentrations of the different types of individuals. We use the time interval between two jumps (the transition time) as an additional state variable and obtain a set of evolution equations, which are local in time. In order to make a connection with the transport models used in the literature, we make transformations which eliminate the transition time and derive a set of nonlocal equations which are nonlinear generalizations of the so-called generalized master equations. The method leads under different specified conditions to various types of nonlocal transport equations including a nonlinear generalization of fractional diffusion equations, hyperbolic reaction-diffusion equations, and delay-differential reaction-diffusion equations. Thus in the analysis of a given problem we can fit to the data the type of reaction-diffusion equation and the corresponding physical and kinetic parameters. The method is illustrated, as a test case, by the study of the neolithic transition. We introduce a set of assumptions which makes it possible to describe the transition from hunting and gathering to agriculture economics by a differential delay reaction-diffusion equation for the population density. We derive a delay evolution equation for the rate of advance of agriculture, which illustrates an application of our analysis.

Schwarz maps of algebraic linear ordinary differential equations

NASA Astrophysics Data System (ADS)

Sanabria Malagón, Camilo

2017-12-01

A linear ordinary differential equation is called algebraic if all its solution are algebraic over its field of definition. In this paper we solve the problem of finding closed form solution to algebraic linear ordinary differential equations in terms of standard equations. Furthermore, we obtain a method to compute all algebraic linear ordinary differential equations with rational coefficients by studying their associated Schwarz map through the Picard-Vessiot Theory.

Predictive Variables of Half-Marathon Performance for Male Runners.

PubMed

Gómez-Molina, Josué; Ogueta-Alday, Ana; Camara, Jesus; Stickley, Christoper; Rodríguez-Marroyo, José A; García-López, Juan

2017-06-01

The aims of this study were to establish and validate various predictive equations of half-marathon performance. Seventy-eight half-marathon male runners participated in two different phases. Phase 1 (n = 48) was used to establish the equations for estimating half-marathon performance, and Phase 2 (n = 30) to validate these equations. Apart from half-marathon performance, training-related and anthropometric variables were recorded, and an incremental test on a treadmill was performed, in which physiological (VO 2max , speed at the anaerobic threshold, peak speed) and biomechanical variables (contact and flight times, step length and step rate) were registered. In Phase 1, half-marathon performance could be predicted to 90.3% by variables related to training and anthropometry (Equation 1), 94.9% by physiological variables (Equation 2), 93.7% by biomechanical parameters (Equation 3) and 96.2% by a general equation (Equation 4). Using these equations, in Phase 2 the predicted time was significantly correlated with performance (r = 0.78, 0.92, 0.90 and 0.95, respectively). The proposed equations and their validation showed a high prediction of half-marathon performance in long distance male runners, considered from different approaches. Furthermore, they improved the prediction performance of previous studies, which makes them a highly practical application in the field of training and performance.

Studying relaxation phenomena via effective master equations

NASA Astrophysics Data System (ADS)

Chan, David; Wan, Jones T. K.; Chu, L. L.; Yu, K. W.

2000-04-01

The real-time dynamics of various relaxation phenomena can be conveniently formulated by a master equation with the enumeration of transition rates between given classes of conformations. To study the relaxation time towards equilibrium, it suffices to solve for the second largest eigenvalue of the resulting eigenvalue equation. Generally speaking, there is no analytic solution for the dynamic equation. Mean-field approaches generally yield misleading results while the presumably exact Monte-Carlo methods require prohibitive time steps in most real systems. In this work, we propose an exact decimation procedure for reducing the number of conformations significantly, while there is no loss of information, i.e., the reduced (or effective) equation is an exact transformed version of the original one. However, we have to pay the price: the initial Markovianity of the evolution equation is lost and the reduced equation contains memory terms in the transition rates. Since the transformed equation has significantly reduced number of degrees of freedom, the systems can readily be diagonalized by iterative means, to obtain the exact second largest eigenvalue and hence the relaxation time. The decimation method has been applied to various relaxation equations with generally desirable results. The advantages and limitations of the method will be discussed.

Nonintegrable semidiscrete Hirota equation: gauge-equivalent structures and dynamical properties.

PubMed

Ma, Li-Yuan; Zhu, Zuo-Nong

2014-09-01

In this paper, we investigate nonintegrable semidiscrete Hirota equations, including the nonintegrable semidiscrete Hirota(-) equation and the nonintegrable semidiscrete Hirota(+) equation. We focus on the topics on gauge-equivalent structures and dynamical behaviors for the two nonintegrable semidiscrete equations. By using the concept of the prescribed discrete curvature, we show that, under the discrete gauge transformations, the nonintegrable semidiscrete Hirota(-) equation and the nonintegrable semidiscrete Hirota(+) equation are, respectively, gauge equivalent to the nonintegrable generalized semidiscrete modified Heisenberg ferromagnet equation and the nonintegrable generalized semidiscrete Heisenberg ferromagnet equation. We prove that the two discrete gauge transformations are reversible. We study the dynamical properties for the two nonintegrable semidiscrete Hirota equations. The exact spatial period solutions of the two nonintegrable semidiscrete Hirota equations are obtained through the constructions of period orbits of the stationary discrete Hirota equations. We discuss the topic regarding whether the spatial period property of the solution to the nonintegrable semidiscrete Hirota equation is preserved to that of the corresponding gauge-equivalent nonintegrable semidiscrete equations under the action of discrete gauge transformation. By using the gauge equivalent, we obtain the exact solutions to the nonintegrable generalized semidiscrete modified Heisenberg ferromagnet equation and the nonintegrable generalized semidiscrete Heisenberg ferromagnet equation. We also give the numerical simulations for the stationary discrete Hirota equations. We find that their dynamics are much richer than the ones of stationary discrete nonlinear Schrödinger equations.

Extremely Fast Numerical Integration of Ocean Surface Wave Dynamics

DTIC Science & Technology

2007-09-30

sub-processor must be added as shown in the blue box of Fig. 1. We first consider the Kadomtsev - Petviashvili (KP) equation ηt + coηx +αηηx + βη ...analytic integration of the so-called “soliton equations ,” I have discovered how the GFT can be used to solved higher order equations for which study...analytical study and extremely fast numerical integration of the extended nonlinear Schroedinger equation for fully three dimensional wave motion

Rayleigh-Plesset equation of the bubble stable cavitation in water: A nonequilibrium all-atom molecular dynamics simulation study

NASA Astrophysics Data System (ADS)

Man, Viet Hoang; Li, Mai Suan; Derreumaux, Philippe; Nguyen, Phuong H.

2018-03-01

The Rayleigh-Plesset (RP) equation was derived from the first principles to describe the bubble cavitation in liquids in terms of macroscopic hydrodynamics. A number of nonequilibrium molecular dynamics studies have been carried out to validate this equation in describing the bubble inertial cavitation, but their results are contradictory and the applicability of the RP equation still remains to be examined, especially for the stable cavitation. In this work, we carry out nonequilibrium all-atom simulation to validate the applicability of the RP equation in the description of the stable cavitation of nano-sized bubbles in water. We show that although microscopic effects are not explicitly included, this equation still describes the dynamics of subnano-bubbles quite well as long as the contributions of various terms including inertial, surface tension, and viscosity are correctly taken into account. These terms are directly and inversely proportional to the amplitude and period of the cavitation, respectively. Thus, their contributions to the RP equation depend on these two parameters. This may explain the discrepancy between the current results obtained using different parameters. Finally, the accuracy of the RP equation in the current mathematical modeling studies of the ultrasound-induced blood-brain-barrier experiments is discussed in some detail.

Unified approach for incompressible flows

NASA Astrophysics Data System (ADS)

Chang, Tyne-Hsien

1995-07-01

A unified approach for solving incompressible flows has been investigated in this study. The numerical CTVD (Centered Total Variation Diminishing) scheme used in this study was successfully developed by Sanders and Li for compressible flows, especially for the high speed. The CTVD scheme possesses better mathematical properties to damp out the spurious oscillations while providing high-order accuracy for high speed flows. It leads us to believe that the CTVD scheme can equally well apply to solve incompressible flows. Because of the mathematical difference between the governing equations for incompressible and compressible flows, the scheme can not directly apply to the incompressible flows. However, if one can modify the continuity equation for incompressible flows by introducing pseudo-compressibility, the governing equations for incompressible flows would have the same mathematical characters as compressible flows. The application of the algorithm to incompressible flows thus becomes feasible. In this study, the governing equations for incompressible flows comprise continuity equation and momentum equations. The continuity equation is modified by adding a time-derivative of the pressure term containing the artificial compressibility. The modified continuity equation together with the unsteady momentum equations forms a hyperbolic-parabolic type of time-dependent system of equations. Thus, the CTVD schemes can be implemented. In addition, the physical and numerical boundary conditions are properly implemented by the characteristic boundary conditions. Accordingly, a CFD code has been developed for this research and is currently under testing. Flow past a circular cylinder was chosen for numerical experiments to determine the accuracy and efficiency of the code. The code has shown some promising results.

Unified approach for incompressible flows

NASA Technical Reports Server (NTRS)

Chang, Tyne-Hsien

1995-01-01

A unified approach for solving incompressible flows has been investigated in this study. The numerical CTVD (Centered Total Variation Diminishing) scheme used in this study was successfully developed by Sanders and Li for compressible flows, especially for the high speed. The CTVD scheme possesses better mathematical properties to damp out the spurious oscillations while providing high-order accuracy for high speed flows. It leads us to believe that the CTVD scheme can equally well apply to solve incompressible flows. Because of the mathematical difference between the governing equations for incompressible and compressible flows, the scheme can not directly apply to the incompressible flows. However, if one can modify the continuity equation for incompressible flows by introducing pseudo-compressibility, the governing equations for incompressible flows would have the same mathematical characters as compressible flows. The application of the algorithm to incompressible flows thus becomes feasible. In this study, the governing equations for incompressible flows comprise continuity equation and momentum equations. The continuity equation is modified by adding a time-derivative of the pressure term containing the artificial compressibility. The modified continuity equation together with the unsteady momentum equations forms a hyperbolic-parabolic type of time-dependent system of equations. Thus, the CTVD schemes can be implemented. In addition, the physical and numerical boundary conditions are properly implemented by the characteristic boundary conditions. Accordingly, a CFD code has been developed for this research and is currently under testing. Flow past a circular cylinder was chosen for numerical experiments to determine the accuracy and efficiency of the code. The code has shown some promising results.

Prediction equation of resting energy expenditure in an adult Spanish population of obese adult population.

PubMed

de Luis, D A; Aller, R; Izaola, O; Romero, E

2006-01-01

The aim of our study was to evaluate the accuracy of the equations to estimate REE in obese patents and develop a new equation in our obese population. A population of 200 obesity outpatients was analyzed in a prospective way. The following variables were specifically recorded: age, weight, body mass index (BMI), waist circumference, and waist-to-hip ratio. Basal glucose, insulin, and TSH (thyroid-stimulating hormone) were measured. An indirect calorimetry and a tetrapolar electrical bioimpedance were performed. REE measured by indirect calorimetry was compared with REE obtained by prediction equations to obese or nonobese patients. The mean age was 44.8 +/- 16.81 years and the mean BMI 34.4 +/- 5.3. Indirect calorimetry showed that, as compared to women, men had higher resting energy expenditure (REE) (1,998.1 +/- 432 vs. 1,663.9 +/- 349 kcal/day; p < 0.05) and oxygen consumption (284.6 +/- 67.7 vs. 238.6 +/- 54.3 ml/min; p < 0.05). Correlation analysis among REE obtained by indirect calorimetry and REE predicted by prediction equations showed the next data; Berstein's equation (r = 0.65; p < 0.05), Harris Benedict's equation (r = 0.58; p < 0.05), Owen's equation (r = 0.56; p < 0.05), Ireton's equation (r = 0.58; p < 0.05) and WHO's equation (r = 0.57; p < 0.05). Both the Berstein's and the Ireton's equations overpredicted REE and showed nonsignificant mean differences form measured REE. The Owen's, WHO's, and Harris Benedict's equations underpredicted REE. Our male prediction equation was REE = 58.6 + (6.1 x weight (kg)) + (1,023.7 x height (m)) - (9.5 x age). The female model was REE = 1,272.5 + (9.8 x weight (kg)) - (61.6 x height (m)) - (8.2 x age). Our prediction equations showed a nonsignificant difference with REE measured (-3.7 kcal/day) with a significant correlation coefficient (r = 0.67; p < 0.05). Previously developed prediction equations overestimated and underestimated REE measured. WHO equation developed in normal weight individuals provided the closest values. The two new equations (male and female equations) developed in our study had a good accuracy. Copyright 2006 S. Karger AG, Basel.

Revised techniques for estimating peak discharges from channel width in Montana

USGS Publications Warehouse

Parrett, Charles; Hull, J.A.; Omang, R.J.

1987-01-01

This study was conducted to develop new estimating equations based on channel width and the updated flood frequency curves of previous investigations. Simple regression equations for estimating peak discharges with recurrence intervals of 2, 5, 10 , 25, 50, and 100 years were developed for seven regions in Montana. The standard errors of estimates for the equations that use active channel width as the independent variables ranged from 30% to 87%. The standard errors of estimate for the equations that use bankfull width as the independent variable ranged from 34% to 92%. The smallest standard errors generally occurred in the prediction equations for the 2-yr flood, 5-yr flood, and 10-yr flood, and the largest standard errors occurred in the prediction equations for the 100-yr flood. The equations that use active channel width and the equations that use bankfull width were determined to be about equally reliable in five regions. In the West Region, the equations that use bankfull width were slightly more reliable than those based on active channel width, whereas in the East-Central Region the equations that use active channel width were slightly more reliable than those based on bankfull width. Compared with similar equations previously developed, the standard errors of estimate for the new equations are substantially smaller in three regions and substantially larger in two regions. Limitations on the use of the estimating equations include: (1) The equations are based on stable conditions of channel geometry and prevailing water and sediment discharge; (2) The measurement of channel width requires a site visit, preferably by a person with experience in the method, and involves appreciable measurement errors; (3) Reliability of results from the equations for channel widths beyond the range of definition is unknown. In spite of the limitations, the estimating equations derived in this study are considered to be as reliable as estimating equations based on basin and climatic variables. Because the two types of estimating equations are independent, results from each can be weighted inversely proportional to their variances, and averaged. The weighted average estimate has a variance less than either individual estimate. (Author 's abstract)

New nonlinear evolution equations from surface theory

NASA Astrophysics Data System (ADS)

Gürses, Metin; Nutku, Yavuz

1981-07-01

We point out that the connection between surfaces in three-dimensional flat space and the inverse scattering problem provides a systematic way for constructing new nonlinear evolution equations. In particular we study the imbedding for Guichard surfaces which gives rise to the Calapso-Guichard equations generalizing the sine-Gordon (SG) equation. Further, we investigate the geometry of surfaces and their imbedding which results in the Korteweg-deVries (KdV) equation. Then by constructing a family of applicable surfaces we obtain a generalization of the KdV equation to a compressible fluid.

On the exact solutions of high order wave equations of KdV type (I)

NASA Astrophysics Data System (ADS)

Bulut, Hasan; Pandir, Yusuf; Baskonus, Haci Mehmet

2014-12-01

In this paper, by means of a proper transformation and symbolic computation, we study high order wave equations of KdV type (I). We obtained classification of exact solutions that contain soliton, rational, trigonometric and elliptic function solutions by using the extended trial equation method. As a result, the motivation of this paper is to utilize the extended trial equation method to explore new solutions of high order wave equation of KdV type (I). This method is confirmed by applying it to this kind of selected nonlinear equations.

Validating Reference Equations for Impulse Oscillometry in Healthy Mexican Children.

PubMed

Gochicoa-Rangel, Laura; Del Río-Hidalgo, Rodrigo; Hernández-Ruiz, Juana; Rodríguez-Moreno, Luis; Martínez-Briseño, David; Mora-Romero, Uri; Cid-Juárez, Silvia; García-Sancho, Cecilia; Torre-Bouscoulet, Luis

2017-09-01

The impulse oscillometry system (IOS) measures the impedance (Z) of the respiratory system, but proper interpretation of its results requires adequate reference values. The objectives of this work were: (1) to validate the reference equations for the IOS published previously by our group and (2) to compare the adjustment of new available reference equations for the IOS from different countries in a sample of healthy children. Subjects were healthy 4-15-y-old children from the metropolitan area of Mexico City, who performed an IOS test. The functional IOS parameters obtained were compared with the predicted values from 12 reference equations determined in studies of different ethnic groups. The validation methods applied were: analysis of the differences between measured and predicted values for each reference equation; correlation and concordance coefficients; adjustment by Z-score values; percentage of predicted value; and the percentage of patients below the lower limit of normality or above the upper limit of normality. Of the 224 participants, 117 (52.3%) were girls, and the mean age was 8.6 ± 2.3 y. The equations that showed the best adjustment for the different parameters were those from the studies by Nowowiejska et al (2008) and Gochicoa et al (2015). The equations proposed by Frei et al (2005), Hellinckx et al (1998), Kalhoff et al (2011), Klug and Bisgaard (1998), de Assumpção et al (2016), and Dencker et al (2006) overestimated the airway resistance of the children in our sample, whereas the equation of Amra et al (2008) underestimated it. In the analysis of the lower and upper limits of normality, Gochicoa et al equation was the closest, since 5% of subjects were below or above percentiles 5 and 95, respectively. The study found that, in general, all of the equations showed greater error at the extremes of the age distribution. Because of the robust adjustment of the present study reference equations for the IOS, it can be recommended for both clinical and research purposes in our population. The differential adjustment of other equations underlines the need to obtain local reference values. Copyright © 2017 by Daedalus Enterprises.

A Study of Multigrid Preconditioners Using Eigensystem Analysis

NASA Technical Reports Server (NTRS)

Roberts, Thomas W.; Swanson, R. C.

2005-01-01

The convergence properties of numerical schemes for partial differential equations are studied by examining the eigensystem of the discrete operator. This method of analysis is very general, and allows the effects of boundary conditions and grid nonuniformities to be examined directly. Algorithms for the Laplace equation and a two equation model hyperbolic system are examined.

Equating Scores from Adaptive to Linear Tests

ERIC Educational Resources Information Center

van der Linden, Wim J.

2006-01-01

Two local methods for observed-score equating are applied to the problem of equating an adaptive test to a linear test. In an empirical study, the methods were evaluated against a method based on the test characteristic function (TCF) of the linear test and traditional equipercentile equating applied to the ability estimates on the adaptive test…

Lie symmetries for systems of evolution equations

NASA Astrophysics Data System (ADS)

Paliathanasis, Andronikos; Tsamparlis, Michael

2018-01-01

The Lie symmetries for a class of systems of evolution equations are studied. The evolution equations are defined in a bimetric space with two Riemannian metrics corresponding to the space of the independent and dependent variables of the differential equations. The exact relation of the Lie symmetries with the collineations of the bimetric space is determined.

Successfully Transitioning to Linear Equations

ERIC Educational Resources Information Center

Colton, Connie; Smith, Wendy M.

2014-01-01

The Common Core State Standards for Mathematics (CCSSI 2010) asks students in as early as fourth grade to solve word problems using equations with variables. Equations studied at this level generate a single solution, such as the equation x + 10 = 25. For students in fifth grade, the Common Core standard for algebraic thinking expects them to…

Revisiting Newtonian and Non-Newtonian Fluid Mechanics Using Computer Algebra

ERIC Educational Resources Information Center

Knight, D. G.

2006-01-01

This article illustrates how a computer algebra system, such as Maple[R], can assist in the study of theoretical fluid mechanics, for both Newtonian and non-Newtonian fluids. The continuity equation, the stress equations of motion, the Navier-Stokes equations, and various constitutive equations are treated, using a full, but straightforward,…

Weak field equations and generalized FRW cosmology on the tangent Lorentz bundle

NASA Astrophysics Data System (ADS)

Triantafyllopoulos, A.; Stavrinos, P. C.

2018-04-01

We study field equations for a weak anisotropic model on the tangent Lorentz bundle TM of a spacetime manifold. A geometrical extension of general relativity (GR) is considered by introducing the concept of local anisotropy, i.e. a direct dependence of geometrical quantities on observer 4‑velocity. In this approach, we consider a metric on TM as the sum of an h-Riemannian metric structure and a weak anisotropic perturbation, field equations with extra terms are obtained for this model. As well, extended Raychaudhuri equations are studied in the framework of Finsler-like extensions. Canonical momentum and mass-shell equation are also generalized in relation to their GR counterparts. Quantization of the mass-shell equation leads to a generalization of the Klein–Gordon equation and dispersion relation for a scalar field. In this model the accelerated expansion of the universe can be attributed to the geometry itself. A cosmological bounce is modeled with the introduction of an anisotropic scalar field. Also, the electromagnetic field equations are directly incorporated in this framework.

Algebro-geometric Solutions for the Derivative Burgers Hierarchy

NASA Astrophysics Data System (ADS)

Hou, Yu; Fan, Engui; Qiao, Zhijun; Wang, Zhong

2015-02-01

Though completely integrable Camassa-Holm (CH) equation and Degasperis-Procesi (DP) equation are cast in the same peakon family, they possess the second- and third-order Lax operators, respectively. From the viewpoint of algebro-geometrical study, this difference lies in hyper-elliptic and non-hyper-elliptic curves. The non-hyperelliptic curves lead to great difficulty in the construction of algebro-geometric solutions of the DP equation. In this paper, we study algebro-geometric solutions for the derivative Burgers (DB) equation, which is derived by Qiao and Li (2004) as a short wave model of the DP equation with the help of functional gradient and a pair of Lenard operators. Based on the characteristic polynomial of a Lax matrix for the DB equation, we introduce a third order algebraic curve with genus , from which the associated Baker-Akhiezer functions, meromorphic function, and Dubrovin-type equations are constructed. Furthermore, the theory of algebraic curve is applied to derive explicit representations of the theta function for the Baker-Akhiezer functions and the meromorphic function. In particular, the algebro-geometric solutions are obtained for all equations in the whole DB hierarchy.

Test Score Equating Using a Mini-Version Anchor and a Midi Anchor: A Case Study Using SAT[R] Data

ERIC Educational Resources Information Center

Liu, Jinghua; Sinharay, Sandip; Holland, Paul W.; Curley, Edward; Feigenbaum, Miriam

2011-01-01

This study explores an anchor that is different from the traditional miniature anchor in test score equating. In contrast to a traditional "mini" anchor that has the same spread of item difficulties as the tests to be equated, the studied anchor, referred to as a "midi" anchor (Sinharay & Holland), has a smaller spread of…

On the conservation laws and solutions of a (2+1) dimensional KdV-mKdV equation of mathematical physics

NASA Astrophysics Data System (ADS)

Motsepa, Tanki; Masood Khalique, Chaudry

2018-05-01

In this paper, we study a (2+1) dimensional KdV-mKdV equation, which models many physical phenomena of mathematical physics. This equation has two integral terms in it. By an appropriate substitution, we convert this equation into two partial differential equations, which do not have integral terms and are equivalent to the original equation. We then work with the system of two equations and obtain its exact travelling wave solutions in form of Jacobi elliptic functions. Furthermore, we employ the multiplier method to construct conservation laws for the system. Finally, we revert the results obtained into the original variables of the (2+1) dimensional KdV-mKdV equation.

Coupled rotor and fuselage equations of motion

NASA Technical Reports Server (NTRS)

Warmbrodt, W.

1979-01-01

The governing equations of motion of a helicopter rotor coupled to a rigid body fuselage are derived. A consistent formulation is used to derive nonlinear periodic coefficient equations of motion which are used to study coupled rotor/fuselage dynamics in forward flight. Rotor/fuselage coupling is documented and the importance of an ordering scheme in deriving nonlinear equations of motion is reviewed. The nature of the final equations and the use of multiblade coordinates are discussed.

Symmetry groups of integro-differential equations for linear thermoviscoelastic materials with memory

NASA Astrophysics Data System (ADS)

Zhou, L.-Q.; Meleshko, S. V.

2017-07-01

The group analysis method is applied to a system of integro-differential equations corresponding to a linear thermoviscoelastic model. A recently developed approach for calculating the symmetry groups of such equations is used. The general solution of the determining equations for the system is obtained. Using subalgebras of the admitted Lie algebra, two classes of partially invariant solutions of the considered system of integro-differential equations are studied.

Stoichiometric network analysis and associated dimensionless kinetic equations. Application to a model of the Bray-Liebhafsky reaction.

PubMed

Schmitz, Guy; Kolar-Anić, Ljiljana Z; Anić, Slobodan R; Cupić, Zeljko D

2008-12-25

The stoichiometric network analysis (SNA) introduced by B. L. Clarke is applied to a simplified model of the complex oscillating Bray-Liebhafsky reaction under batch conditions, which was not examined by this method earlier. This powerful method for the analysis of steady-states stability is also used to transform the classical differential equations into dimensionless equations. This transformation is easy and leads to a form of the equations combining the advantages of classical dimensionless equations with the advantages of the SNA. The used dimensionless parameters have orders of magnitude given by the experimental information about concentrations and currents. This simplifies greatly the study of the slow manifold and shows which parameters are essential for controlling its shape and consequently have an important influence on the trajectories. The effectiveness of these equations is illustrated on two examples: the study of the bifurcations points and a simple sensitivity analysis, different from the classical one, more based on the chemistry of the studied system.

A parameter study of the two-fluid solar wind

NASA Technical Reports Server (NTRS)

Sandbaek, Ornulf; Leer, Egil; Holzer, Thomas E.

1992-01-01

A two-fluid model of the solar wind was introduced by Sturrock and Hartle (1966) and Hartle and Sturrock (1968). In these studies the proton energy equation was integrated neglecting the heat conductive term. Later several authors solved the equations for the two-fluid solar wind model keeping the proton heat conductive term. Methods where the equations are integrated simultaneously outward and inward from the critical point were used. The equations were also integrated inward from a large heliocentric distance. These methods have been applied to cases with low coronal base electron densities and high base temperatures. In this paper we present a method of integrating the two-fluid solar wind equations using an iteration procedure where the equations are integrated separately and the proton flux is kept constant during the integrations. The technique is applicable for a wide range of coronal base densities and temperatures. The method is used to carry out a parameter study of the two-fluid solar wind.

Renal Function and Remission of Hypertension After Bariatric Surgery: a 5-Year Prospective Cohort Study.

PubMed

Neff, Karl J; Baud, Gregory; Raverdy, Violeta; Caiazzo, Robert; Verkindt, Helene; Noel, Christian; le Roux, Carel W; Pattou, François

2017-03-01

This study examines the effect of Roux-en-Y gastric bypass (RYGB) and laparoscopic adjustable gastric banding (LAGB) on renal function for at least 5 years post-operatively in a tertiary referral center for bariatric surgery. This prospective cohort study of patients undergoing RYGB and LAGB measured renal function, blood pressure, and diabetes status pre-operatively and then 1 and 5 years post-operatively. Renal function was assessed using the Modification of Diet in Renal Disease (MDRD), Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI), and Cockcroft-Gault formulae. Hypertension and diabetes were defined by the European Society of Hypertension and European Society of Cardiology joint guidelines and American Diabetes Association guidelines, respectively. A sub-group who had completed 10 years post-operative follow-up was also included. Estimated glomerular filtration rate (eGFR) increased over 5 years after RYGB (N = 190; 94 ± 2 mL/min/1.73 m 2 to 102 ± 22 mL/min/1.73 m 2 , p = 0.01) and LAGB (N = 271; 88 ± 1 to 93 ± 22 mL/min/1.73 m 2 , p = 0.02). In a sub-group with up to 10 years post-operative date, this trend was maintained. In patients with renal impairment, eGFR improved over 5 years (52 ± 2 to 68 ± 7 mL/min/1.73 m 2 , p = 0.01). Remission of hypertension was greater after RYGB than LAGB at 1 year (32 vs. 16 %, p = 0.008) and at 5 years post-operatively (23 vs. 11 %, p = 0.02). Bariatric surgery stabilizes eGFR post-operatively for at least 5 years. In a sub-group with renal impairment, eGFR is increased in the first post-operative year and this is maintained for up to 5 years. RYGB is an effective procedure in achieving blood pressure control.

Three dimensional cylindrical Kadomtsev-Petviashvili equation in a very dense electron-positron-ion plasma

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

Moslem, W. M.; Sabry, R.; Shukla, P. K.

2010-03-15

By using the hydrodynamic equations of ions, Thomas-Fermi electron/positron density distribution, and Poisson equation, a three-dimensional cylindrical Kadomtsev-Petviashvili (CKP) equation is derived for small but finite amplitude ion-acoustic waves. The generalized expansion method is used to analytically solve the CKP equation. New class of solutions admits a train of well-separated bell-shaped periodic pulses is obtained. At certain condition, the latter degenerates to solitary wave solution. The effects of physical parameters on the solitary pulse structures are examined. Furthermore, the energy integral equation is used to study the existence regions of the localized pulses. The present study might be helpful tomore » understand the excitation of nonlinear ion-acoustic waves in a very dense astrophysical objects such as white dwarfs.« less

Unified approach for incompressible flows

NASA Astrophysics Data System (ADS)

Chang, Tyne-Hsien

1993-12-01

An unified approach for solving both compressible and incompressible flows was investigated in this study. The difference in CFD code development between incompressible and compressible flows is due to the mathematical characteristics. However, if one can modify the continuity equation for incompressible flows by introducing pseudocompressibility, the governing equations for incompressible flows would have the same mathematical characters as compressible flows. The application of a compressible flow code to solve incompressible flows becomes feasible. Among numerical algorithms developed for compressible flows, the Centered Total Variation Diminishing (CTVD) schemes possess better mathematical properties to damp out the spurious oscillations while providing high-order accuracy for high speed flows. It leads us to believe that CTVD schemes can equally well solve incompressible flows. In this study, the governing equations for incompressible flows include the continuity equation and momentum equations. The continuity equation is modified by adding a time-derivative of the pressure term containing the artificial compressibility. The modified continuity equation together with the unsteady momentum equations forms a hyperbolic-parabolic type of time-dependent system of equations. The continuity equation is modified by adding a time-derivative of the pressure term containing the artificial compressibility. The modified continuity equation together with the unsteady momentum equations forms a hyperbolic-parabolic type of time-dependent system of equations. Thus, the CTVD schemes can be implemented. In addition, the boundary conditions including physical and numerical boundary conditions must be properly specified to obtain accurate solution. The CFD code for this research is currently in progress. Flow past a circular cylinder will be used for numerical experiments to determine the accuracy and efficiency of the code before applying this code to more specific applications.

Personal computer study of finite-difference methods for the transonic small disturbance equation

NASA Technical Reports Server (NTRS)

Bland, Samuel R.

1989-01-01

Calculation of unsteady flow phenomena requires careful attention to the numerical treatment of the governing partial differential equations. The personal computer provides a convenient and useful tool for the development of meshes, algorithms, and boundary conditions needed to provide time accurate solution of these equations. The one-dimensional equation considered provides a suitable model for the study of wave propagation in the equations of transonic small disturbance potential flow. Numerical results for effects of mesh size, extent, and stretching, time step size, and choice of far-field boundary conditions are presented. Analysis of the discretized model problem supports these numerical results. Guidelines for suitable mesh and time step choices are given.

Oblique scattering from radially inhomogeneous dielectric cylinders: An exact Volterra integral equation formulation

NASA Astrophysics Data System (ADS)

Tsalamengas, John L.

2018-07-01

We study plane-wave electromagnetic scattering by radially and strongly inhomogeneous dielectric cylinders at oblique incidence. The method of analysis relies on an exact reformulation of the underlying field equations as a first-order 4 × 4 system of differential equations and on the ability to restate the associated initial-value problem in the form of a system of coupled linear Volterra integral equations of the second kind. The integral equations so derived are discretized via a sophisticated variant of the Nyström method. The proposed method yields results accurate up to machine precision without relying on approximations. Numerical results and case studies ably demonstrate the efficiency and high accuracy of the algorithms.

A DRBEM for steady infiltration from periodic semi-circular channels with two different types of roots distribution

NASA Astrophysics Data System (ADS)

Solekhudin, Imam; Sumardi

2017-05-01

In this study, problems involving steady Infiltration from periodic semicircular channels with root-water uptake function are considered. These problems are governed by Richards equation. This equation can be studied more conveniently by transforming the equation into a modified Helmholtz equation. In these problems, two different types of root-water uptake are considered. A dual reciprocity boundary element method (DRBEM) with a predictor-corrector scheme is used to solve the modified Helmholtz equation numerically. Using the solution obtained, numerical values of suction potential and root-water uptake function can be computed. In addition, amount of water absorbed by the different plant roots distribution can also be computed and compared.

Multiple and exact soliton solutions of the perturbed Korteweg-de Vries equation of long surface waves in a convective fluid via Painlevé analysis, factorization, and simplest equation methods.

PubMed

Selima, Ehab S; Yao, Xiaohua; Wazwaz, Abdul-Majid

2017-06-01

In this research, the surface waves of a horizontal fluid layer open to air under gravity field and vertical temperature gradient effects are studied. The governing equations of this model are reformulated and converted to a nonlinear evolution equation, the perturbed Korteweg-de Vries (pKdV) equation. We investigate the latter equation, which includes dispersion, diffusion, and instability effects, in order to examine the evolution of long surface waves in a convective fluid. Dispersion relation of the pKdV equation and its properties are discussed. The Painlevé analysis is applied not only to check the integrability of the pKdV equation but also to establish the Bäcklund transformation form. In addition, traveling wave solutions and a general form of the multiple-soliton solutions of the pKdV equation are obtained via Bäcklund transformation, the simplest equation method using Bernoulli, Riccati, and Burgers' equations as simplest equations, and the factorization method.

Comparison of the One- and Bi-Direction Chained Equipercentile Equating

ERIC Educational Resources Information Center

Oh, Hyeonjoo; Moses, Tim

2012-01-01

This study investigated differences between two approaches to chained equipercentile (CE) equating (one- and bi-direction CE equating) in nearly equal groups and relatively unequal groups. In one-direction CE equating, the new form is linked to the anchor in one sample of examinees and the anchor is linked to the reference form in the other…

A new multi-symplectic scheme for the generalized Kadomtsev-Petviashvili equation

NASA Astrophysics Data System (ADS)

Li, Haochen; Sun, Jianqiang

2012-09-01

We propose a new scheme for the generalized Kadomtsev-Petviashvili (KP) equation. The multi-symplectic conservation property of the new scheme is proved. Back error analysis shows that the new multi-symplectic scheme has second order accuracy in space and time. Numerical application on studying the KPI equation and the KPII equation are presented in detail.

Cross-validation of generalised body composition equations with diverse young men and women: the Training Intervention and Genetics of Exercise Response (TIGER) Study

USDA-ARS?s Scientific Manuscript database

Generalised skinfold equations developed in the 1970s are commonly used to estimate laboratory-measured percentage fat (BF%). The equations were developed on predominately white individuals using Siri's two-component percentage fat equation (BF%-GEN). We cross-validated the Jackson-Pollock (JP) gene...

Evaluating Students' Conceptual Understanding of Balanced Equations and Stoichiometric Ratios Using a Particulate Drawing

ERIC Educational Resources Information Center

Sanger, Michael J.

2005-01-01

A total of 156 students were asked to provide free-response balanced chemical equations for a classic multiple-choice particulate-drawing question first used by Nurrenbern and Pickering. The balanced equations and the number of students providing each equation are reported in this study. The most common student errors included a confusion between…

Additive nonlinear biomass equations: A likelihood-based approach

Treesearch

David L. R. Affleck; Ulises Dieguez-Aranda

2016-01-01

Since Parresol’s (Can. J. For. Res. 31:865-878, 2001) seminal article on the topic, it has become standard to develop nonlinear tree biomass equations to ensure compatibility among total and component predictions and to fit these equations using multistep generalized least-squares methods. In particular, many studies have specified equations for total tree...

Kernel and Traditional Equipercentile Equating with Degrees of Presmoothing. Research Report. ETS RR-07-15

ERIC Educational Resources Information Center

Moses, Tim; Holland, Paul

2007-01-01

The purpose of this study was to empirically evaluate the impact of loglinear presmoothing accuracy on equating bias and variability across chained and post-stratification equating methods, kernel and percentile-rank continuization methods, and sample sizes. The results of evaluating presmoothing on equating accuracy generally agreed with those of…

Impact of Inclusion of Varying Percentages of Repeaters on Equating

ERIC Educational Resources Information Center

Rogers, W. Todd; Radwan, Nizam

2015-01-01

Restricted equating samples are often used to equate test results. Previously eligible students may be excluded because this group of students is not stable from year to year and their inclusion may bias the results. The present study evaluated the impact of including previously eligible students in the equating samples, where the percentage of…

Technological pedagogical content knowledge of junior high school mathematics teachers in teaching linear equation

NASA Astrophysics Data System (ADS)

Wati, S.; Fitriana, L.; Mardiyana

2018-04-01

Linear equation is one of the topics in mathematics that are considered difficult. Student difficulties of understanding linear equation can be caused by lack of understanding this concept and the way of teachers teach. TPACK is a way to understand the complex relationships between teaching and content taught through the use of specific teaching approaches and supported by the right technology tools. This study aims to identify TPACK of junior high school mathematics teachers in teaching linear equation. The method used in the study was descriptive. In the first phase, a survey using a questionnaire was carried out on 45 junior high school mathematics teachers in teaching linear equation. While in the second phase, the interview involved three teachers. The analysis of data used were quantitative and qualitative technique. The result PCK revealed teachers emphasized developing procedural and conceptual knowledge through reliance on traditional in teaching linear equation. The result of TPK revealed teachers’ lower capacity to deal with the general information and communications technologies goals across the curriculum in teaching linear equation. The result indicated that PowerPoint constitutes TCK modal technological capability in teaching linear equation. The result of TPACK seems to suggest a low standard in teachers’ technological skills across a variety of mathematics education goals in teaching linear equation. This means that the ability of teachers’ TPACK in teaching linear equation still needs to be improved.

A Comparative Structural Equation Modeling Investigation of the Relationships among Teaching, Cognitive and Social Presence

ERIC Educational Resources Information Center

Kozan, Kadir

2016-01-01

The present study investigated the relationships among teaching, cognitive, and social presence through several structural equation models to see which model would better fit the data. To this end, the present study employed and compared several different structural equation models because different models could fit the data equally well. Among…

Collateral Information for Equating in Small Samples: A Preliminary Investigation

ERIC Educational Resources Information Center

Kim, Sooyeon; Livingston, Samuel A.; Lewis, Charles

2011-01-01

This article describes a preliminary investigation of an empirical Bayes (EB) procedure for using collateral information to improve equating of scores on test forms taken by small numbers of examinees. Resampling studies were done on two different forms of the same test. In each study, EB and non-EB versions of two equating methods--chained linear…

Test Score Equating Using Discrete Anchor Items versus Passage-Based Anchor Items: A Case Study Using "SAT"® Data. Research Report. ETS RR-14-14

ERIC Educational Resources Information Center

Liu, Jinghua; Zu, Jiyun; Curley, Edward; Carey, Jill

2014-01-01

The purpose of this study is to investigate the impact of discrete anchor items versus passage-based anchor items on observed score equating using empirical data.This study compares an "SAT"® critical reading anchor that contains more discrete items proportionally, compared to the total tests to be equated, to another anchor that…

On the Boltzmann Equation with Stochastic Kinetic Transport: Global Existence of Renormalized Martingale Solutions

NASA Astrophysics Data System (ADS)

Punshon-Smith, Samuel; Smith, Scott

2018-02-01

This article studies the Cauchy problem for the Boltzmann equation with stochastic kinetic transport. Under a cut-off assumption on the collision kernel and a coloring hypothesis for the noise coefficients, we prove the global existence of renormalized (in the sense of DiPerna/Lions) martingale solutions to the Boltzmann equation for large initial data with finite mass, energy, and entropy. Our analysis includes a detailed study of weak martingale solutions to a class of linear stochastic kinetic equations. This study includes a criterion for renormalization, the weak closedness of the solution set, and tightness of velocity averages in {{L}1}.

Initial singularity and pure geometric field theories

NASA Astrophysics Data System (ADS)

Wanas, M. I.; Kamal, Mona M.; Dabash, Tahia F.

2018-01-01

In the present article we use a modified version of the geodesic equation, together with a modified version of the Raychaudhuri equation, to study initial singularities. These modified equations are used to account for the effect of the spin-torsion interaction on the existence of initial singularities in cosmological models. Such models are the results of solutions of the field equations of a class of field theories termed pure geometric. The geometric structure used in this study is an absolute parallelism structure satisfying the cosmological principle. It is shown that the existence of initial singularities is subject to some mathematical (geometric) conditions. The scheme suggested for this study can be easily generalized.

Density-Dependent Conformable Space-time Fractional Diffusion-Reaction Equation and Its Exact Solutions

NASA Astrophysics Data System (ADS)

Hosseini, Kamyar; Mayeli, Peyman; Bekir, Ahmet; Guner, Ozkan

2018-01-01

In this article, a special type of fractional differential equations (FDEs) named the density-dependent conformable fractional diffusion-reaction (DDCFDR) equation is studied. Aforementioned equation has a significant role in the modelling of some phenomena arising in the applied science. The well-organized methods, including the \\exp (-φ (\\varepsilon )) -expansion and modified Kudryashov methods are exerted to generate the exact solutions of this equation such that some of the solutions are new and have been reported for the first time. Results illustrate that both methods have a great performance in handling the DDCFDR equation.

Whitham modulation theory for the two-dimensional Benjamin-Ono equation.

PubMed

Ablowitz, Mark; Biondini, Gino; Wang, Qiao

2017-09-01

Whitham modulation theory for the two-dimensional Benjamin-Ono (2DBO) equation is presented. A system of five quasilinear first-order partial differential equations is derived. The system describes modulations of the traveling wave solutions of the 2DBO equation. These equations are transformed to a singularity-free hydrodynamic-like system referred to here as the 2DBO-Whitham system. Exact reductions of this system are discussed, the formulation of initial value problems is considered, and the system is used to study the transverse stability of traveling wave solutions of the 2DBO equation.

Lie Symmetry Analysis and Explicit Solutions of the Time Fractional Fifth-Order KdV Equation

PubMed Central

Wang, Gang wei; Xu, Tian zhou; Feng, Tao

2014-01-01

In this paper, using the Lie group analysis method, we study the invariance properties of the time fractional fifth-order KdV equation. A systematic research to derive Lie point symmetries to time fractional fifth-order KdV equation is performed. In the sense of point symmetry, all of the vector fields and the symmetry reductions of the fractional fifth-order KdV equation are obtained. At last, by virtue of the sub-equation method, some exact solutions to the fractional fifth-order KdV equation are provided. PMID:24523885

Numerical solution of distributed order fractional differential equations

NASA Astrophysics Data System (ADS)

Katsikadelis, John T.

2014-02-01

In this paper a method for the numerical solution of distributed order FDEs (fractional differential equations) of a general form is presented. The method applies to both linear and nonlinear equations. The Caputo type fractional derivative is employed. The distributed order FDE is approximated with a multi-term FDE, which is then solved by adjusting appropriately the numerical method developed for multi-term FDEs by Katsikadelis. Several example equations are solved and the response of mechanical systems described by such equations is studied. The convergence and the accuracy of the method for linear and nonlinear equations are demonstrated through well corroborated numerical results.

Analytical Equations for Orbital Transfer Maneuvers of a Vehicle Using Constant Low Thrust

DTIC Science & Technology

1981-12-01

136auks" ,b , .. .. a. AFIT/GA/AA/81D -3 ANALITICAL EQUATIOIS FOR OR.BITAL TRASFER MANIUVRS OF A V 1CI, USING CONSTANT LOW THRUST THESIS AFIT/GA/AA...nondimensional radius ( )m - specified values vii. AFIT/GA/AA/81D -3 Abstract The object of this study is to derive a set of equations which predict the...study is to derive a set of equations which predict the results of orbital maneuvers of vehicles using constant low thrust. These equations are

Three-pattern decomposition of global atmospheric circulation: part II—dynamical equations of horizontal, meridional and zonal circulations

NASA Astrophysics Data System (ADS)

Hu, Shujuan; Cheng, Jianbo; Xu, Ming; Chou, Jifan

2018-04-01

The three-pattern decomposition of global atmospheric circulation (TPDGAC) partitions three-dimensional (3D) atmospheric circulation into horizontal, meridional and zonal components to study the 3D structures of global atmospheric circulation. This paper incorporates the three-pattern decomposition model (TPDM) into primitive equations of atmospheric dynamics and establishes a new set of dynamical equations of the horizontal, meridional and zonal circulations in which the operator properties are studied and energy conservation laws are preserved, as in the primitive equations. The physical significance of the newly established equations is demonstrated. Our findings reveal that the new equations are essentially the 3D vorticity equations of atmosphere and that the time evolution rules of the horizontal, meridional and zonal circulations can be described from the perspective of 3D vorticity evolution. The new set of dynamical equations includes decomposed expressions that can be used to explore the source terms of large-scale atmospheric circulation variations. A simplified model is presented to demonstrate the potential applications of the new equations for studying the dynamics of the Rossby, Hadley and Walker circulations. The model shows that the horizontal air temperature anomaly gradient (ATAG) induces changes in meridional and zonal circulations and promotes the baroclinic evolution of the horizontal circulation. The simplified model also indicates that the absolute vorticity of the horizontal circulation is not conserved, and its changes can be described by changes in the vertical vorticities of the meridional and zonal circulations. Moreover, the thermodynamic equation shows that the induced meridional and zonal circulations and advection transport by the horizontal circulation in turn cause a redistribution of the air temperature. The simplified model reveals the fundamental rules between the evolution of the air temperature and the horizontal, meridional and zonal components of global atmospheric circulation.

The What and Where of Adding Channel Noise to the Hodgkin-Huxley Equations

PubMed Central

Goldwyn, Joshua H.; Shea-Brown, Eric

2011-01-01

Conductance-based equations for electrically active cells form one of the most widely studied mathematical frameworks in computational biology. This framework, as expressed through a set of differential equations by Hodgkin and Huxley, synthesizes the impact of ionic currents on a cell's voltage—and the highly nonlinear impact of that voltage back on the currents themselves—into the rapid push and pull of the action potential. Later studies confirmed that these cellular dynamics are orchestrated by individual ion channels, whose conformational changes regulate the conductance of each ionic current. Thus, kinetic equations familiar from physical chemistry are the natural setting for describing conductances; for small-to-moderate numbers of channels, these will predict fluctuations in conductances and stochasticity in the resulting action potentials. At first glance, the kinetic equations provide a far more complex (and higher-dimensional) description than the original Hodgkin-Huxley equations or their counterparts. This has prompted more than a decade of efforts to capture channel fluctuations with noise terms added to the equations of Hodgkin-Huxley type. Many of these approaches, while intuitively appealing, produce quantitative errors when compared to kinetic equations; others, as only very recently demonstrated, are both accurate and relatively simple. We review what works, what doesn't, and why, seeking to build a bridge to well-established results for the deterministic equations of Hodgkin-Huxley type as well as to more modern models of ion channel dynamics. As such, we hope that this review will speed emerging studies of how channel noise modulates electrophysiological dynamics and function. We supply user-friendly MATLAB simulation code of these stochastic versions of the Hodgkin-Huxley equations on the ModelDB website (accession number 138950) and http://www.amath.washington.edu/~etsb/tutorials.html. PMID:22125479

Fokker-Planck Equations of Stochastic Acceleration: A Study of Numerical Methods

NASA Astrophysics Data System (ADS)

Park, Brian T.; Petrosian, Vahe

1996-03-01

Stochastic wave-particle acceleration may be responsible for producing suprathermal particles in many astrophysical situations. The process can be described as a diffusion process through the Fokker-Planck equation. If the acceleration region is homogeneous and the scattering mean free path is much smaller than both the energy change mean free path and the size of the acceleration region, then the Fokker-Planck equation reduces to a simple form involving only the time and energy variables. in an earlier paper (Park & Petrosian 1995, hereafter Paper 1), we studied the analytic properties of the Fokker-Planck equation and found analytic solutions for some simple cases. In this paper, we study the numerical methods which must be used to solve more general forms of the equation. Two classes of numerical methods are finite difference methods and Monte Carlo simulations. We examine six finite difference methods, three fully implicit and three semi-implicit, and a stochastic simulation method which uses the exact correspondence between the Fokker-Planck equation and the it5 stochastic differential equation. As discussed in Paper I, Fokker-Planck equations derived under the above approximations are singular, causing problems with boundary conditions and numerical overflow and underflow. We evaluate each method using three sample equations to test its stability, accuracy, efficiency, and robustness for both time-dependent and steady state solutions. We conclude that the most robust finite difference method is the fully implicit Chang-Cooper method, with minor extensions to account for the escape and injection terms. Other methods suffer from stability and accuracy problems when dealing with some Fokker-Planck equations. The stochastic simulation method, although simple to implement, is susceptible to Poisson noise when insufficient test particles are used and is computationally very expensive compared to the finite difference method.

Hidden symmetries of Eisenhart-Duval lift metrics and the Dirac equation with flux

NASA Astrophysics Data System (ADS)

Cariglia, Marco

2012-10-01

The Eisenhart-Duval lift allows embedding nonrelativistic theories into a Lorentzian geometrical setting. In this paper we study the lift from the point of view of the Dirac equation and its hidden symmetries. We show that dimensional reduction of the Dirac equation for the Eisenhart-Duval metric in general gives rise to the nonrelativistic Lévy-Leblond equation in lower dimension. We study in detail in which specific cases the lower dimensional limit is given by the Dirac equation, with scalar and vector flux, and the relation between lift, reduction, and the hidden symmetries of the Dirac equation. While there is a precise correspondence in the case of the lower dimensional massive Dirac equation with no flux, we find that for generic fluxes it is not possible to lift or reduce all solutions and hidden symmetries. As a by-product of this analysis, we construct new Lorentzian metrics with special tensors by lifting Killing-Yano and closed conformal Killing-Yano tensors and describe the general conformal Killing-Yano tensor of the Eisenhart-Duval lift metrics in terms of lower dimensional forms. Last, we show how, by dimensionally reducing the higher dimensional operators of the massless Dirac equation that are associated with shared hidden symmetries, it is possible to recover hidden symmetry operators for the Dirac equation with flux.

Dynamic analysis of a hollow cylinder subject to a dual traveling force imposed on its inner surface

NASA Astrophysics Data System (ADS)

Lee, Sooyoung; Seok, Jongwon

2015-03-01

The dynamic behavior of a hollow cylinder under a dual traveling force applied to the inner surface is investigated in this study. The cylinder is constrained at both the top and bottom surfaces not to move in the length direction but free in other directions. And a dual force travels at a constant velocity along the length direction on the inner surface of the hollow cylinder. The resulting governing field equations and the associated boundary conditions are ruled by the general Hooke's law. Due to the nature of the field equations, proper adjoint system of equations and biorthogonality conditions were derived in a precise and detailed manner. To solve these field equations in this study, the method of separation of variable is used and the method of Fro¨benius is employed for the differential equations in the radial direction. Using the field equations, the eigenanalyses on both the original and its adjoint system were performed with great care, which results in the eigenfunction sets of both systems. The biorthogonality conditions were applied to the field equations to obtain the discretized equation for each mode. Using the solutions of the discretized equations that account for the boundary forcing terms, the critical speed for a dual traveling force for each mode could be computed.

Are Predictive Equations for Estimating Resting Energy Expenditure Accurate in Asian Indian Male Weightlifters?

PubMed

Joseph, Mini; Gupta, Riddhi Das; Prema, L; Inbakumari, Mercy; Thomas, Nihal

2017-01-01

The accuracy of existing predictive equations to determine the resting energy expenditure (REE) of professional weightlifters remains scarcely studied. Our study aimed at assessing the REE of male Asian Indian weightlifters with indirect calorimetry and to compare the measured REE (mREE) with published equations. A new equation using potential anthropometric variables to predict REE was also evaluated. REE was measured on 30 male professional weightlifters aged between 17 and 28 years using indirect calorimetry and compared with the eight formulas predicted by Harris-Benedicts, Mifflin-St. Jeor, FAO/WHO/UNU, ICMR, Cunninghams, Owen, Katch-McArdle, and Nelson. Pearson correlation coefficient, intraclass correlation coefficient, and multiple linear regression analysis were carried out to study the agreement between the different methods, association with anthropometric variables, and to formulate a new prediction equation for this population. Pearson correlation coefficients between mREE and the anthropometric variables showed positive significance with suprailiac skinfold thickness, lean body mass (LBM), waist circumference, hip circumference, bone mineral mass, and body mass. All eight predictive equations underestimated the REE of the weightlifters when compared with the mREE. The highest mean difference was 636 kcal/day (Owen, 1986) and the lowest difference was 375 kcal/day (Cunninghams, 1980). Multiple linear regression done stepwise showed that LBM was the only significant determinant of REE in this group of sportspersons. A new equation using LBM as the independent variable for calculating REE was computed. REE for weightlifters = -164.065 + 0.039 (LBM) (confidence interval -1122.984, 794.854]. This new equation reduced the mean difference with mREE by 2.36 + 369.15 kcal/day (standard error = 67.40). The significant finding of this study was that all the prediction equations underestimated the REE. The LBM was the sole determinant of REE in this population. In the absence of indirect calorimetry, the REE equation developed by us using LBM is a better predictor for calculating REE of professional male weightlifters of this region.

Dynamical systems theory for nonlinear evolution equations.

PubMed

Choudhuri, Amitava; Talukdar, B; Das, Umapada

2010-09-01

We observe that the fully nonlinear evolution equations of Rosenau and Hymann, often abbreviated as K(n,m) equations, can be reduced to Hamiltonian form only on a zero-energy hypersurface belonging to some potential function associated with the equations. We treat the resulting Hamiltonian equations by the dynamical systems theory and present a phase-space analysis of their stable points. The results of our study demonstrate that the equations can, in general, support both compacton and soliton solutions. For the K(2,2) and K(3,3) cases one type of solutions can be obtained from the other by continuously varying a parameter of the equations. This is not true for the K(3,2) equation for which the parameter can take only negative values. The K(2,3) equation does not have any stable point and, in the language of mechanics, represents a particle moving with constant acceleration.

A Bivariate Chebyshev Spectral Collocation Quasilinearization Method for Nonlinear Evolution Parabolic Equations

PubMed Central

Motsa, S. S.; Magagula, V. M.; Sibanda, P.

2014-01-01

This paper presents a new method for solving higher order nonlinear evolution partial differential equations (NPDEs). The method combines quasilinearisation, the Chebyshev spectral collocation method, and bivariate Lagrange interpolation. In this paper, we use the method to solve several nonlinear evolution equations, such as the modified KdV-Burgers equation, highly nonlinear modified KdV equation, Fisher's equation, Burgers-Fisher equation, Burgers-Huxley equation, and the Fitzhugh-Nagumo equation. The results are compared with known exact analytical solutions from literature to confirm accuracy, convergence, and effectiveness of the method. There is congruence between the numerical results and the exact solutions to a high order of accuracy. Tables were generated to present the order of accuracy of the method; convergence graphs to verify convergence of the method and error graphs are presented to show the excellent agreement between the results from this study and the known results from literature. PMID:25254252

A bivariate Chebyshev spectral collocation quasilinearization method for nonlinear evolution parabolic equations.

PubMed

Motsa, S S; Magagula, V M; Sibanda, P

2014-01-01

This paper presents a new method for solving higher order nonlinear evolution partial differential equations (NPDEs). The method combines quasilinearisation, the Chebyshev spectral collocation method, and bivariate Lagrange interpolation. In this paper, we use the method to solve several nonlinear evolution equations, such as the modified KdV-Burgers equation, highly nonlinear modified KdV equation, Fisher's equation, Burgers-Fisher equation, Burgers-Huxley equation, and the Fitzhugh-Nagumo equation. The results are compared with known exact analytical solutions from literature to confirm accuracy, convergence, and effectiveness of the method. There is congruence between the numerical results and the exact solutions to a high order of accuracy. Tables were generated to present the order of accuracy of the method; convergence graphs to verify convergence of the method and error graphs are presented to show the excellent agreement between the results from this study and the known results from literature.

Optimal Control for Stochastic Delay Evolution Equations

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

Meng, Qingxin, E-mail: mqx@hutc.zj.cn; Shen, Yang, E-mail: skyshen87@gmail.com

2016-08-15

In this paper, we investigate a class of infinite-dimensional optimal control problems, where the state equation is given by a stochastic delay evolution equation with random coefficients, and the corresponding adjoint equation is given by an anticipated backward stochastic evolution equation. We first prove the continuous dependence theorems for stochastic delay evolution equations and anticipated backward stochastic evolution equations, and show the existence and uniqueness of solutions to anticipated backward stochastic evolution equations. Then we establish necessary and sufficient conditions for optimality of the control problem in the form of Pontryagin’s maximum principles. To illustrate the theoretical results, we applymore » stochastic maximum principles to study two examples, an infinite-dimensional linear-quadratic control problem with delay and an optimal control of a Dirichlet problem for a stochastic partial differential equation with delay. Further applications of the two examples to a Cauchy problem for a controlled linear stochastic partial differential equation and an optimal harvesting problem are also considered.« less

Wave equations in conformal gravity

NASA Astrophysics Data System (ADS)

Du, Juan-Juan; Wang, Xue-Jing; He, You-Biao; Yang, Si-Jiang; Li, Zhong-Heng

2018-05-01

We study the wave equation governing massless fields of all spins (s = 0, 1 2, 1, 3 2 and 2) in the most general spherical symmetric metric of conformal gravity. The equation is separable, the solution of the angular part is a spin-weighted spherical harmonic, and the radial wave function may be expressed in terms of solutions of the Heun equation which has four regular singular points. We also consider various special cases of the metric and find that the angular wave functions are the same for all cases, the actual shape of the metric functions affects only the radial wave function. It is interesting to note that each radial equation can be transformed into a known ordinary differential equation (i.e. Heun equation, or confluent Heun equation, or hypergeometric equation). The results show that there are analytic solutions for all the wave equations of massless spin fields in the spacetimes of conformal gravity. This is amazing because exact solutions are few and far between for other spacetimes.

Kinetic effects on Alfven wave nonlinearity. II - The modified nonlinear wave equation

NASA Technical Reports Server (NTRS)

Spangler, Steven R.

1990-01-01

A previously developed Vlasov theory is used here to study the role of resonant particle and other kinetic effects on Alfven wave nonlinearity. A hybrid fluid-Vlasov equation approach is used to obtain a modified version of the derivative nonlinear Schroedinger equation. The differences between a scalar model for the plasma pressure and a tensor model are discussed. The susceptibilty of the modified nonlinear wave equation to modulational instability is studied. The modulational instability normally associated with the derivative nonlinear Schroedinger equation will, under most circumstances, be restricted to left circularly polarized waves. The nonlocal term in the modified nonlinear wave equation engenders a new modulational instability that is independent of beta and the sense of circular polarization. This new instability may explain the occurrence of wave packet steepening for all values of the plasma beta in the vicinity of the earth's bow shock.

The Existence of the Solution to One Kind of Algebraic Riccati Equation

NASA Astrophysics Data System (ADS)

Liu, Jianming

2018-03-01

The matrix equation ATX + XA + XRX + Q = O is called algebraic Riccati equation, which is very important in the fields of automatic control and other engineering applications. Many researchers have studied the solutions to various algebraic Riccati equations and most of them mainly applied the matrix methods, while few used the functional analysis theories. This paper mainly studies the existence of the solution to the following kind of algebraic Riccati equation from the functional view point: ATX + XA + XRX ‑λX + Q = O Here, X, A, R, Q ∈ n×n , Q is a symmetric matrix, and R is a positive or negative semi-definite matrix, λ is arbitrary constants. This paper uses functional approach such as fixed point theorem and contraction mapping thinking so as to provide two sufficient conditions for the solvability about this kind of Riccati equation and to arrive at some relevant conclusions.

Novel asymmetric representation method for solving the higher-order Ginzburg-Landau equation

PubMed Central

Wong, Pring; Pang, Lihui; Wu, Ye; Lei, Ming; Liu, Wenjun

2016-01-01

In ultrafast optics, optical pulses are generated to be of shorter pulse duration, which has enormous significance to industrial applications and scientific research. The ultrashort pulse evolution in fiber lasers can be described by the higher-order Ginzburg-Landau (GL) equation. However, analytic soliton solutions for this equation have not been obtained by use of existing methods. In this paper, a novel method is proposed to deal with this equation. The analytic soliton solution is obtained for the first time, and is proved to be stable against amplitude perturbations. Through the split-step Fourier method, the bright soliton solution is studied numerically. The analytic results here may extend the integrable methods, and could be used to study soliton dynamics for some equations in other disciplines. It may also provide the other way to obtain two-soliton solutions for higher-order GL equations. PMID:27086841

From the nonlinear Fokker-Planck equation to the Vlasov description and back: Confined interacting particles with drag

NASA Astrophysics Data System (ADS)

Plastino, A. R.; Curado, E. M. F.; Nobre, F. D.; Tsallis, C.

2018-02-01

Nonlinear Fokker-Planck equations endowed with power-law diffusion terms have proven to be valuable tools for the study of diverse complex systems in physics, biology, and other fields. The nonlinearity appearing in these evolution equations can be interpreted as providing an effective description of a system of particles interacting via short-range forces while performing overdamped motion under the effect of an external confining potential. This point of view has been recently applied to the study of thermodynamical features of interacting vortices in type II superconductors. In the present work we explore an embedding of the nonlinear Fokker-Planck equation within a Vlasov equation, thus incorporating inertial effects to the concomitant particle dynamics. Exact time-dependent solutions of the q -Gaussian form (with compact support) are obtained for the Vlasov equation in the case of quadratic confining potentials.

Asymptotic expansions and solitons of the Camassa-Holm - nonlinear Schrödinger equation

NASA Astrophysics Data System (ADS)

Mylonas, I. K.; Ward, C. B.; Kevrekidis, P. G.; Rothos, V. M.; Frantzeskakis, D. J.

2017-12-01

We study a deformation of the defocusing nonlinear Schrödinger (NLS) equation, the defocusing Camassa-Holm NLS, hereafter referred to as CH-NLS equation. We use asymptotic multiscale expansion methods to reduce this model to a Boussinesq-like equation, which is then subsequently approximated by two Korteweg-de Vries (KdV) equations for left- and right-traveling waves. We use the soliton solution of the KdV equation to construct approximate solutions of the CH-NLS system. It is shown that these solutions may have the form of either dark or antidark solitons, namely dips or humps on top of a stable continuous-wave background. We also use numerical simulations to investigate the validity of the asymptotic solutions, study their evolution, and their head-on collisions. It is shown that small-amplitude dark and antidark solitons undergo quasi-elastic collisions.

Two-layer interfacial flows beyond the Boussinesq approximation: a Hamiltonian approach

NASA Astrophysics Data System (ADS)

Camassa, R.; Falqui, G.; Ortenzi, G.

2017-02-01

The theory of integrable systems of Hamiltonian PDEs and their near-integrable deformations is used to study evolution equations resulting from vertical-averages of the Euler system for two-layer stratified flows in an infinite two-dimensional channel. The Hamiltonian structure of the averaged equations is obtained directly from that of the Euler equations through the process of Hamiltonian reduction. Long-wave asymptotics together with the Boussinesq approximation of neglecting the fluids’ inertia is then applied to reduce the leading order vertically averaged equations to the shallow-water Airy system, albeit in a non-trivial way. The full non-Boussinesq system for the dispersionless limit can then be viewed as a deformation of this well known equation. In a perturbative study of this deformation, a family of approximate constants of the motion are explicitly constructed and used to find local solutions of the evolution equations by means of hodograph-like formulae.

Integrable Equations in Multi-Dimensions (2+1) are Bi-Hamiltonian Systems,

DTIC Science & Technology

1987-02-01

equation [18]. It should be noted that the 80 equation has more similarities [19] with the Kadomtsev - Petviashvili (KP...Cimento, 39B, 1 (1977). [31] P. Caudrey, Discrete and Periodic Spectral Transforms Related to the Kadomtsev - Petviashvili Equation , preprint U.M.I.S.T. (1985). II ’AI D p-I 4, - -- - -- - - -w 4 ...TOM NONLINEAR STUDIES IDTIC I IELEC )// MAR 2 51988 I / \\ / Integrable Equations in Multi- dimensions (2+1) are Bi-Hamiltonian Systems by A.S.

Solitary waves, rogue waves and homoclinic breather waves for a (2 + 1)-dimensional generalized Kadomtsev-Petviashvili equation

NASA Astrophysics Data System (ADS)

Dong, Min-Jie; Tian, Shou-Fu; Yan, Xue-Wei; Zou, Li; Li, Jin

2017-10-01

We study a (2 + 1)-dimensional generalized Kadomtsev-Petviashvili (gKP) equation, which characterizes the formation of patterns in liquid drops. By using Bell’s polynomials, an effective way is employed to succinctly construct the bilinear form of the gKP equation. Based on the resulting bilinear equation, we derive its solitary waves, rogue waves and homoclinic breather waves, respectively. Our results can help enrich the dynamical behavior of the KP-type equations.

Bogomolny equations in certain generalized baby BPS Skyrme models

NASA Astrophysics Data System (ADS)

Stępień, Ł. T.

2018-01-01

By using the concept of strong necessary conditions (CSNCs), we derive Bogomolny equations and Bogomol’nyi-Prasad-Sommerfield (BPS) bounds for two certain modifications of the baby BPS Skyrme model: the nonminimal coupling to the gauge field and the k-deformed ungauged model. In particular, we study how the Bogomolny equations and the equation for the potential reflect these two modifications. In both examples, the CSNC method appears to be a very useful tool. We also find certain localized solutions of these Bogomolny equations.

The non-autonomous YdKN equation and generalized symmetries of Boll equations

NASA Astrophysics Data System (ADS)

Gubbiotti, G.; Scimiterna, C.; Levi, D.

2017-05-01

In this paper, we study the integrability of a class of nonlinear non-autonomous quad graph equations compatible around the cube introduced by Boll in the framework of the generalized Adler, Bobenko, and Suris (ABS) classification. We show that all these equations possess three-point generalized symmetries which are subcases of either the Yamilov discretization of the Krichever-Novikov equation or of its non-autonomous extension. We also prove that all those symmetries are integrable as they pass the algebraic entropy test.

Effective equations for the quantum pendulum from momentous quantum mechanics

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

Hernandez, Hector H.; Chacon-Acosta, Guillermo; Departamento de Matematicas Aplicadas y Sistemas, Universidad Autonoma Metropolitana-Cuajimalpa, Artificios 40, Mexico D. F. 01120

In this work we study the quantum pendulum within the framework of momentous quantum mechanics. This description replaces the Schroedinger equation for the quantum evolution of the system with an infinite set of classical equations for expectation values of configuration variables, and quantum dispersions. We solve numerically the effective equations up to the second order, and describe its evolution.

Nonlinear Waves and Inverse Scattering

DTIC Science & Technology

1992-01-29

equations include the Kadomtsev - Petviashvili (K-P), Davey-Stewartson (D-S), 2+1 Toda, and Self-Dual Yang-Mills (SDYM) equations . We have uncovered a... Petviashvili Equation and Associated Constraints, M.J. Ablowitz and Javier Villaroel, Studies in Appl. Math. 85, (1991), 195-213. 12. On the Hamiltonian...nonlinear wave equations of physical significance, multidimensional inverse scattering, numer- ically induced instabilities and chaos, and forced

Biomass equations for major tree species of the Northeast

Treesearch

Louise M. Tritton; James W. Hornbeck

1982-01-01

Regression equations are used in both forestry and ecosystem studies to estimate tree biomass from field measurements of dbh (diameter at breast height) or a combination of dbh and height. Literature on biomass is reviewed, and 178 sets of publish equation for 25 species common to the Northeastern Unites States are listed. On the basis of these equations, estimates of...

Inverse Scattering Problem For The Schrödinger Equation With An Additional Quadratic Potential On The Entire Axis

NASA Astrophysics Data System (ADS)

Guseinov, I. M.; Khanmamedov, A. Kh.; Mamedova, A. F.

2018-04-01

We consider the Schrödinger equation with an additional quadratic potential on the entire axis and use the transformation operator method to study the direct and inverse problems of the scattering theory. We obtain the main integral equations of the inverse problem and prove that the basic equations are uniquely solvable.

Differential Equations Models to Study Quorum Sensing.

PubMed

Pérez-Velázquez, Judith; Hense, Burkhard A

2018-01-01

Mathematical models to study quorum sensing (QS) have become an important tool to explore all aspects of this type of bacterial communication. A wide spectrum of mathematical tools and methods such as dynamical systems, stochastics, and spatial models can be employed. In this chapter, we focus on giving an overview of models consisting of differential equations (DE), which can be used to describe changing quantities, for example, the dynamics of one or more signaling molecule in time and space, often in conjunction with bacterial growth dynamics. The chapter is divided into two sections: ordinary differential equations (ODE) and partial differential equations (PDE) models of QS. Rates of change are represented mathematically by derivatives, i.e., in terms of DE. ODE models allow describing changes in one independent variable, for example, time. PDE models can be used to follow changes in more than one independent variable, for example, time and space. Both types of models often consist of systems (i.e., more than one equation) of equations, such as equations for bacterial growth and autoinducer concentration dynamics. Almost from the onset, mathematical modeling of QS using differential equations has been an interdisciplinary endeavor and many of the works we revised here will be placed into their biological context.

Numerical solutions of Navier-Stokes equations for a Butler wing

NASA Technical Reports Server (NTRS)

Abolhassani, J. S.; Tiwari, S. N.

1985-01-01

The flow field is simulated on the surface of a given delta wing (Butler wing) at zero incident in a uniform stream. The simulation is done by integrating a set of flow field equations. This set of equations governs the unsteady, viscous, compressible, heat conducting flow of an ideal gas. The equations are written in curvilinear coordinates so that the wing surface is represented accurately. These equations are solved by the finite difference method, and results obtained for high-speed freestream conditions are compared with theoretical and experimental results. In this study, the Navier-Stokes equations are solved numerically. These equations are unsteady, compressible, viscous, and three-dimensional without neglecting any terms. The time dependency of the governing equations allows the solution to progress naturally for an arbitrary initial initial guess to an asymptotic steady state, if one exists. The equations are transformed from physical coordinates to the computational coordinates, allowing the solution of the governing equations in a rectangular parallel-piped domain. The equations are solved by the MacCormack time-split technique which is vectorized and programmed to run on the CDC VPS 32 computer.

Accuracy of Bioelectrical Impedance Analysis in Estimated Longitudinal Fat-Free Mass Changes in Male Army Cadets.

PubMed

Langer, Raquel D; Matias, Catarina N; Borges, Juliano H; Cirolini, Vagner X; Páscoa, Mauro A; Guerra-Júnior, Gil; Gonçalves, Ezequiel M

2018-03-26

Bioelectrical impedance analysis (BIA) is a practical and rapid method for making a longitudinal analysis of changes in body composition. However, most BIA validation studies have been performed in a clinical population and only at one moment, or point in time (cross-sectional study). The aim of this study is to investigate the accuracy of predictive equations based on BIA with regard to the changes in fat-free mass (FFM) in Brazilian male army cadets after 7 mo of military training. The values used were determined using dual-energy X-ray absorptiometry (DXA) as a reference method. The study included 310 male Brazilian Army cadets (aged 17-24 yr). FFM was measured using eight general predictive BIA equations, with one equation specifically applied to this population sample, and the values were compared with results obtained using DXA. The student's t-test, adjusted coefficient of determination (R2), standard error of estimation (SEE), Lin's approach, and the Bland-Altman test were used to determine the accuracy of the predictive BIA equations used to estimate FFM in this population and between the two moments (pre- and post-moment). The FFM measured using the nine predictive BIA equations, and determined using DXA at the post-moment, showed a significant increase when compared with the pre-moment (p < 0.05). All nine predictive BIA equations were able to detect FFM changes in the army cadets between the two moments in a very similar way to the reference method (DXA). However, only the one BIA equation specific to this population showed no significant differences in the FFM estimation between DXA at pre- and post-moment of military routine. All predictive BIA equations showed large limits of agreement using the Bland-Altman approach. The eight general predictive BIA equations used in this study were not found to be valid for analyzing the FFM changes in the Brazilian male army cadets, after a period of approximately 7 mo of military training. Although the BIA equation specific to this population is dependent on the amount of FFM, it appears to be a good alternative to DXA for assessing FFM in Brazilian male army cadets.

The Analysis of the Problems the Pre-Service Teachers Experience in Posing Problems about Equations

ERIC Educational Resources Information Center

Isik, Cemalettin; Kar, Tugrul

2012-01-01

The present study aimed to analyse the potential difficulties in the problems posed by pre-service teachers about first degree equations with one unknown and equation pairs with two unknowns. It was carried out with 20 pre-service teachers studying in the Department of Elementary Mathematics Educations at a university in Eastern Turkey. The…

Impact of Inclusion or Exclusion of Repeaters on Test Equating

ERIC Educational Resources Information Center

Puhan, Gautam

2011-01-01

This study examined the effect of including or excluding repeaters on the equating process and results. New forms of two tests were equated to their respective old forms using either all examinees or only the first timer examinees in the new form sample. Results showed that for both tests used in this study, including or excluding repeaters in the…

Cycle-time equations for five small tractors operating in low-volume small-diameter hardwood stands

Treesearch

Chris B. LeDoux; Neil K. Huyler; Neil K. Huyler

1992-01-01

Prediction equations for estimating cycle time were developed for five small tractors studied under various silvicultural treatments and operating conditions. The tractors studied included the Pasquali 933, a Holder A60F, a Forest Ant Forwarder (Skogsman), a Massey-Ferguson, and a Sam4 Minitarus. Skidding costs were estimated based on the cycle-time equations. Using...

Improving Teaching Quality and Problem Solving Ability through Contextual Teaching and Learning in Differential Equations: A Lesson Study Approach

ERIC Educational Resources Information Center

Khotimah, Rita Pramujiyanti; Masduki

2016-01-01

Differential equations is a branch of mathematics which is closely related to mathematical modeling that arises in real-world problems. Problem solving ability is an essential component to solve contextual problem of differential equations properly. The purposes of this study are to describe contextual teaching and learning (CTL) model in…

Central role of the observable electric potential in transport equations.

PubMed

Garrido, J; Compañ, V; López, M L

2001-07-01

Nonequilibrium systems are usually studied in the framework of transport equations that involve the true electric potential (TEP), a nonobservable variable. Nevertheless another electric potential, the observable electric potential (OEP), may be defined to construct a useful set of transport equations. In this paper several basic characteristics of the OEP are deduced and emphasized: (i) the OEP distribution depends on thermodynamic state of the solution, (ii) the observable equations have a reference value for all other transport equations, (iii) the bridge that connects the OEP with a certain TEP is usually defined by the ion activity coefficient, (iv) the electric charge density is a nonobservable variable, and (v) the OEP formulation constitutes a natural model for studying the fluxes in membrane systems.

A reference equation for maximal aerobic power for treadmill and cycle ergometer exercise testing: Analysis from the FRIEND registry.

PubMed

de Souza E Silva, Christina G; Kaminsky, Leonard A; Arena, Ross; Christle, Jeffrey W; Araújo, Claudio Gil S; Lima, Ricardo M; Ashley, Euan A; Myers, Jonathan

2018-05-01

Background Maximal oxygen uptake (VO 2 max) is a powerful predictor of health outcomes. Valid and portable reference values are integral to interpreting measured VO 2 max; however, available reference standards lack validation and are specific to exercise mode. This study was undertaken to develop and validate a single equation for normal standards for VO 2 max for the treadmill or cycle ergometer in men and women. Methods Healthy individuals ( N = 10,881; 67.8% men, 20-85 years) who performed a maximal cardiopulmonary exercise test on either a treadmill or a cycle ergometer were studied. Of these, 7617 and 3264 individuals were randomly selected for development and validation of the equation, respectively. A Brazilian sample (1619 individuals) constituted a second validation cohort. The prediction equation was determined using multiple regression analysis, and comparisons were made with the widely-used Wasserman and European equations. Results Age, sex, weight, height and exercise mode were significant predictors of VO 2 max. The regression equation was: VO 2 max (ml kg -1  min -1 ) = 45.2 - 0.35*Age - 10.9*Sex (male = 1; female = 2) - 0.15*Weight (pounds) + 0.68*Height (inches) - 0.46*Exercise Mode (treadmill = 1; bike = 2) ( R = 0.79, R 2  = 0.62, standard error of the estimate = 6.6 ml kg -1  min -1 ). Percentage predicted VO 2 max for the US and Brazilian validation cohorts were 102.8% and 95.8%, respectively. The new equation performed better than traditional equations, particularly among women and individuals ≥60 years old. Conclusion A combined equation was developed for normal standards for VO 2 max for different exercise modes derived from a US national registry. The equation provided a lower average error between measured and predicted VO 2 max than traditional equations even when applied to an independent cohort. Additional studies are needed to determine its portability.

Asymptotic analysis of the local potential approximation to the Wetterich equation

NASA Astrophysics Data System (ADS)

Bender, Carl M.; Sarkar, Sarben

2018-06-01

This paper reports a study of the nonlinear partial differential equation that arises in the local potential approximation to the Wetterich formulation of the functional renormalization group equation. A cut-off-dependent shift of the potential in this partial differential equation is performed. This shift allows a perturbative asymptotic treatment of the differential equation for large values of the infrared cut-off. To leading order in perturbation theory the differential equation becomes a heat equation, where the sign of the diffusion constant changes as the space-time dimension D passes through 2. When D  <  2, one obtains a forward heat equation whose initial-value problem is well-posed. However, for D  >  2 one obtains a backward heat equation whose initial-value problem is ill-posed. For the special case D  =  1 the asymptotic series for cubic and quartic models is extrapolated to the small infrared-cut-off limit by using Padé techniques. The effective potential thus obtained from the partial differential equation is then used in a Schrödinger-equation setting to study the stability of the ground state. For cubic potentials it is found that this Padé procedure distinguishes between a -symmetric theory and a conventional Hermitian theory (g real). For an theory the effective potential is nonsingular and has a stable ground state but for a conventional theory the effective potential is singular. For a conventional Hermitian theory and a -symmetric theory (g  >  0) the results are similar; the effective potentials in both cases are nonsingular and possess stable ground states.

Prediction equations of forced oscillation technique: the insidious role of collinearity.

PubMed

Narchi, Hassib; AlBlooshi, Afaf

2018-03-27

Many studies have reported reference data for forced oscillation technique (FOT) in healthy children. The prediction equation of FOT parameters were derived from a multivariable regression model examining the effect of age, gender, weight and height on each parameter. As many of these variables are likely to be correlated, collinearity might have affected the accuracy of the model, potentially resulting in misleading, erroneous or difficult to interpret conclusions.The aim of this work was: To review all FOT publications in children since 2005 to analyze whether collinearity was considered in the construction of the published prediction equations. Then to compare these prediction equations with our own study. And to analyse, in our study, how collinearity between the explanatory variables might affect the predicted equations if it was not considered in the model. The results showed that none of the ten reviewed studies had stated whether collinearity was checked for. Half of the reports had also included in their equations variables which are physiologically correlated, such as age, weight and height. The predicted resistance varied by up to 28% amongst these studies. And in our study, multicollinearity was identified between the explanatory variables initially considered for the regression model (age, weight and height). Ignoring it would have resulted in inaccuracies in the coefficients of the equation, their signs (positive or negative), their 95% confidence intervals, their significance level and the model goodness of fit. In Conclusion with inaccurately constructed and improperly reported models, understanding the results and reproducing the models for future research might be compromised.

Dispersive shock waves in the Kadomtsev-Petviashvili and two dimensional Benjamin-Ono equations

NASA Astrophysics Data System (ADS)

Ablowitz, Mark J.; Demirci, Ali; Ma, Yi-Ping

2016-10-01

Dispersive shock waves (DSWs) in the Kadomtsev-Petviashvili (KP) equation and two dimensional Benjamin-Ono (2DBO) equation are considered using step like initial data along a parabolic front. Employing a parabolic similarity reduction exactly reduces the study of such DSWs in two space one time (2 + 1) dimensions to finding DSW solutions of (1 + 1) dimensional equations. With this ansatz, the KP and 2DBO equations can be exactly reduced to the cylindrical Korteweg-de Vries (cKdV) and cylindrical Benjamin-Ono (cBO) equations, respectively. Whitham modulation equations which describe DSW evolution in the cKdV and cBO equations are derived and Riemann type variables are introduced. DSWs obtained from the numerical solutions of the corresponding Whitham systems and direct numerical simulations of the cKdV and cBO equations are compared with very good agreement obtained. In turn, DSWs obtained from direct numerical simulations of the KP and 2DBO equations are compared with the cKdV and cBO equations, again with good agreement. It is concluded that the (2 + 1) DSW behavior along self similar parabolic fronts can be effectively described by the DSW solutions of the reduced (1 + 1) dimensional equations.

Investigation of two and three parameter equations of state for cryogenic fluids

NASA Technical Reports Server (NTRS)

Jenkins, Susan L.; Majumdar, Alok K.; Hendricks, Robert C.

1990-01-01

Two-phase flows are a common occurrence in cryogenic engines and an accurate evaluation of the heat-transfer coefficient in two-phase flow is of significant importance in their analysis and design. The thermodynamic equation of state plays a key role in calculating the heat transfer coefficient which is a function of thermodynamic and thermophysical properties. An investigation has been performed to study the performance of two- and three-parameter equations of state to calculate the compressibility factor of cryogenic fluids along the saturation loci. The two-parameter equations considered here are van der Waals and Redlich-Kwong equations of state. The three-parameter equation represented here is the generalized Benedict-Webb-Rubin (BWR) equation of Lee and Kesler. Results have been compared with the modified BWR equation of Bender and the extended BWR equations of Stewart. Seven cryogenic fluids have been tested; oxygen, hydrogen, helium, nitrogen, argon, neon, and air. The performance of the generalized BWR equation is poor for hydrogen and helium. The van der Waals equation is found to be inaccurate for air near the critical point. For helium, all three equations of state become inaccurate near the critical point.

Boundary states at reflective moving boundaries

NASA Astrophysics Data System (ADS)

Acosta Minoli, Cesar A.; Kopriva, David A.

2012-06-01

We derive and evaluate boundary states for Maxwell's equations, the linear, and the nonlinear Euler gas-dynamics equations to compute wave reflection from moving boundaries. In this study we use a Discontinuous Galerkin Spectral Element method (DGSEM) with Arbitrary Lagrangian-Eulerian (ALE) mapping for the spatial approximation, but the boundary states can be used with other methods, like finite volume schemes. We present four studies using Maxwell's equations, one for the linear Euler equations, and one more for the nonlinear Euler equations. These are: reflection of light from a plane mirror moving at constant velocity, reflection of light from a moving cylinder, reflection of light from a vibrating mirror, reflection of sound from a plane wall and dipole sound generation by an oscillating cylinder in an inviscid flow. The studies show that the boundary states preserve spectral convergence in the solution and in derived quantities like divergence and vorticity.

Global-in-time solutions for the isothermal Matovich-Pearson equations

NASA Astrophysics Data System (ADS)

Feireisl, Eduard; Laurençot, Philippe; Mikelić, Andro

2011-01-01

In this paper we study the Matovich-Pearson equations describing the process of glass fibre drawing. These equations may be viewed as a 1D-reduction of the incompressible Navier-Stokes equations including free boundary, valid for the drawing of a long and thin glass fibre. We concentrate on the isothermal case without surface tension. Then the Matovich-Pearson equations represent a nonlinearly coupled system of an elliptic equation for the axial velocity and a hyperbolic transport equation for the fluid cross-sectional area. We first prove existence of a local solution, and, after constructing appropriate barrier functions, we deduce that the fluid radius is always strictly positive and that the local solution remains in the same regularity class. This estimate leads to the global existence and uniqueness result for this important system of equations.

Parallels between control PDE's (Partial Differential Equations) and systems of ODE's (Ordinary Differential Equations)

NASA Technical Reports Server (NTRS)

Hunt, L. R.; Villarreal, Ramiro

1987-01-01

System theorists understand that the same mathematical objects which determine controllability for nonlinear control systems of ordinary differential equations (ODEs) also determine hypoellipticity for linear partial differentail equations (PDEs). Moreover, almost any study of ODE systems begins with linear systems. It is remarkable that Hormander's paper on hypoellipticity of second order linear p.d.e.'s starts with equations due to Kolmogorov, which are shown to be analogous to the linear PDEs. Eigenvalue placement by state feedback for a controllable linear system can be paralleled for a Kolmogorov equation if an appropriate type of feedback is introduced. Results concerning transformations of nonlinear systems to linear systems are similar to results for transforming a linear PDE to a Kolmogorov equation.

Stability analysis solutions and optical solitons in extended nonlinear Schrödinger equation with higher-order odd and even terms

NASA Astrophysics Data System (ADS)

Peng, Wei-Qi; Tian, Shou-Fu; Zou, Li; Zhang, Tian-Tian

2018-01-01

In this paper, the extended nonlinear Schrödinger equation with higher-order odd (third order) and even (fourth order) terms is investigated, whose particular cases are the Hirota equation, the Sasa-Satsuma equation and Lakshmanan-Porsezian-Daniel equation by selecting some specific values on the parameters of higher-order terms. We first study the stability analysis of the equation. Then, using the ansatz method, we derive its bright, dark solitons and some constraint conditions which can guarantee the existence of solitons. Moreover, the Ricatti equation extension method is employed to derive some exact singular solutions. The outstanding characteristics of these solitons are analyzed via several diverting graphics.

Field equations from Killing spinors

NASA Astrophysics Data System (ADS)

Açık, Özgür

2018-02-01

From the Killing spinor equation and the equations satisfied by their bilinears, we deduce some well-known bosonic and fermionic field equations of mathematical physics. Aside from the trivially satisfied Dirac equation, these relativistic wave equations in curved spacetimes, respectively, are Klein-Gordon, Maxwell, Proca, Duffin-Kemmer-Petiau, Kähler, twistor, and Rarita-Schwinger equations. This result shows that, besides being special kinds of Dirac fermions, Killing fermions can be regarded as physically fundamental. For the Maxwell case, the problem of motion is analysed in a reverse manner with respect to the studies of Einstein-Groemer-Infeld-Hoffmann and Jean Marie Souriau. In the analysis of the gravitino field, a generalised 3-ψ rule is found which is termed the vanishing trace constraint.

Operator Approach to the Master Equation for the One-Step Process

NASA Astrophysics Data System (ADS)

Hnatič, M.; Eferina, E. G.; Korolkova, A. V.; Kulyabov, D. S.; Sevastyanov, L. A.

2016-02-01

Background. Presentation of the probability as an intrinsic property of the nature leads researchers to switch from deterministic to stochastic description of the phenomena. The kinetics of the interaction has recently attracted attention because it often occurs in the physical, chemical, technical, biological, environmental, economic, and sociological systems. However, there are no general methods for the direct study of this equation. The expansion of the equation in a formal Taylor series (the so called Kramers-Moyal's expansion) is used in the procedure of stochastization of one-step processes. Purpose. However, this does not eliminate the need for the study of the master equation. Method. It is proposed to use quantum field perturbation theory for the statistical systems (the so-called Doi method). Results: This work is a methodological material that describes the principles of master equation solution based on quantum field perturbation theory methods. The characteristic property of the work is that it is intelligible for non-specialists in quantum field theory. Conclusions: We show the full equivalence of the operator and combinatorial methods of obtaining and study of the one-step process master equation.

In vitro dissolution kinetic study of theophylline from hydrophilic and hydrophobic matrices.

PubMed

Maswadeh, Hamzah M; Semreen, Mohammad H; Abdulhalim, Abdulatif A

2006-01-01

Oral dosage forms containing 300 mg theophylline in matrix type tablets, were prepared by direct compression method using two kinds of matrices, glycerylbehenate (hydrophobic), and (hydroxypropyl)methyl cellulose (hydrophilic). The in vitro release kinetics of these formulations were studied at pH 6.8 using the USP dissolution apparatus with the paddle assemble. The kinetics of the dissolution process were studied by analyzing the dissolution data using four kinetic equations, the zero-order equation, the first-order equation, the Higuchi square root equation and the Hixson-Crowell cube root law. The analysis of the dissolution kinetic data for the theophylline preparations in this study shows that it follows the first order kinetics and the release process involves erosion / diffusion and an alteration in the surface area and diameter of the matrix system, as well as in the diffusion path length from the matrix drug load during the dissolution process. This relation is best described by the use of both the first-order equation and the Hixson-Crowell cube root law.

Green's function solution to heat transfer of a transparent gas through a tube

NASA Technical Reports Server (NTRS)

Frankel, J. I.

1989-01-01

A heat transfer analysis of a transparent gas flowing through a circular tube of finite thickness is presented. This study includes the effects of wall conduction, internal radiative exchange, and convective heat transfer. The natural mathematical formulation produces a nonlinear, integrodifferential equation governing the wall temperature and an ordinary differential equation describing the gas temperature. This investigation proposes to convert the original system of equations into an equivalent system of integral equations. The Green's function method permits the conversion of an integrodifferential equation into a pure integral equation. The proposed integral formulation and subsequent computational procedure are shown to be stable and accurate.

Exact solutions and conservation laws of the system of two-dimensional viscous Burgers equations

NASA Astrophysics Data System (ADS)

Abdulwahhab, Muhammad Alim

2016-10-01

Fluid turbulence is one of the phenomena that has been studied extensively for many decades. Due to its huge practical importance in fluid dynamics, various models have been developed to capture both the indispensable physical quality and the mathematical structure of turbulent fluid flow. Among the prominent equations used for gaining in-depth insight of fluid turbulence is the two-dimensional Burgers equations. Its solutions have been studied by researchers through various methods, most of which are numerical. Being a simplified form of the two-dimensional Navier-Stokes equations and its wide range of applicability in various fields of science and engineering, development of computationally efficient methods for the solution of the two-dimensional Burgers equations is still an active field of research. In this study, Lie symmetry method is used to perform detailed analysis on the system of two-dimensional Burgers equations. Optimal system of one-dimensional subalgebras up to conjugacy is derived and used to obtain distinct exact solutions. These solutions not only help in understanding the physical effects of the model problem but also, can serve as benchmarks for constructing algorithms and validation of numerical solutions of the system of Burgers equations under consideration at finite Reynolds numbers. Independent and nontrivial conserved vectors are also constructed.

Validation of Accelerometer Prediction Equations in Children with Chronic Disease.

PubMed

Stephens, Samantha; Takken, Tim; Esliger, Dale W; Pullenayegum, Eleanor; Beyene, Joseph; Tremblay, Mark; Schneiderman, Jane; Biggar, Doug; Longmuir, Pat; McCrindle, Brian; Abad, Audrey; Ignas, Dan; Van Der Net, Janjaap; Feldman, Brian

2016-02-01

The purpose of this study was to assess the criterion validity of existing accelerometer-based energy expenditure (EE) prediction equations among children with chronic conditions, and to develop new prediction equations. Children with congenital heart disease (CHD), cystic fibrosis (CF), dermatomyositis (JDM), juvenile arthritis (JA), inherited muscle disease (IMD), and hemophilia (HE) completed 7 tasks while EE was measured using indirect calorimetry with counts determined by accelerometer. Agreement between predicted EE and measured EE was assessed. Disease-specific equations and cut points were developed and cross-validated. In total, 196 subjects participated. One participant dropped out before testing due to time constraints, while 15 CHD, 32 CF, 31 JDM, 31 JA, 30 IMD, 28 HE, and 29 healthy controls completed the study. Agreement between predicted and measured EE varied across disease group and ranged from (ICC) .13-.46. Disease-specific prediction equations exhibited a range of results (ICC .62-.88) (SE 0.45-0.78). In conclusion, poor agreement was demonstrated using current prediction equations in children with chronic conditions. Disease-specific equations and cut points were developed.

Outcomes of a service teaching module on ODEs for physics students

NASA Astrophysics Data System (ADS)

Hyland, Diarmaid; van Kampen, Paul; Nolan, Brien C.

2018-07-01

This paper reports on the first part of a multiphase research project that seeks to identify and address the difficulties encountered by physics students when studying differential equations. Differential equations are used extensively by undergraduate physics students, particularly in the advanced modules of their degree. It is, therefore, necessary that students develop conceptual understanding of differential equations in addition to procedural skills. We have investigated the difficulties encountered by third-year students at Dublin City University in an introductory differential equations module. We developed a survey to identify these difficulties and administered it to students who had recently completed the module. We found that students' mathematical ability in relation to procedural competence is an issue in their study of differential equations, but not as severe an issue as their conceptual understanding. Mathematical competence alone is insufficient if we expect our students to be able to recognize the need for differential equations in a physical context and to be able to set up, solve and interpret the solutions of such equations. We discuss the implications of these results for the next stages of the research project.

On the conservation laws of Derrida-Lebowitz-Speer-Spohn equation

NASA Astrophysics Data System (ADS)

San, Sait; Yaşar, Emrullah

2015-05-01

In this study, the nonlocal conservation theorem and multiplier approach are performed on the 1 + 1 dimensional Derrida-Lebowitz-Speer-Spohn (DLSS) equation which arises in quantum semi conductor theory. We obtain local conservation laws by using the both methods. Furthermore by utilizing the relationship between conservation laws and Lie point symmetries, the DLSS equation is reduced to third order ordinary differential equation.

Nonlinear Waves

DTIC Science & Technology

1989-06-15

Hamiltonian Formulation of the Kadomtsev - Petviashvili and Benjamin-Ono Equations , A.S. Fokas and P.M. Santini, J. Math. Phys. 29 (3) 604-617 (1988...Prototypes are the so-called Kadomtsev -Petviashvilli and Davey-Stewartson equations . These equations arise in a variety of physical instances such as water...plasma physics. Moreover the study of solutions to some of the underlying nonlinear evolution equations has led naturally to the investigation and new

The Impact of Test Dimensionality, Common-Item Set Format, and Scale Linking Methods on Mixed-Format Test Equating

ERIC Educational Resources Information Center

Öztürk-Gübes, Nese; Kelecioglu, Hülya

2016-01-01

The purpose of this study was to examine the impact of dimensionality, common-item set format, and different scale linking methods on preserving equity property with mixed-format test equating. Item response theory (IRT) true-score equating (TSE) and IRT observed-score equating (OSE) methods were used under common-item nonequivalent groups design.…

Study of analytical method to seek for exact solutions of variant Boussinesq equations.

PubMed

Khan, Kamruzzaman; Akbar, M Ali

2014-01-01

In this paper, we have been acquired the soliton solutions of the Variant Boussinesq equations. Primarily, we have used the enhanced (G'/G)-expansion method to find exact solutions of Variant Boussinesq equations. Then, we attain some exact solutions including soliton solutions, hyperbolic and trigonometric function solutions of this equation. 35 K99; 35P05; 35P99.

Improving North American forest biomass estimates from literature synthesis and meta-analysis of existing biomass equations

Treesearch

David C. Chojnacky; Jennifer C. Jenkins; Amanda K. Holland

2009-01-01

Thousands of published equations purport to estimate biomass of individual trees. These equations are often based on very small samples, however, and can provide widely different estimates for trees of the same species. We addressed this issue in a previous study by devising 10 new equations that estimated total aboveground biomass for all species in North America (...

Approximating a nonlinear advanced-delayed equation from acoustics

NASA Astrophysics Data System (ADS)

Teodoro, M. Filomena

2016-10-01

We approximate the solution of a particular non-linear mixed type functional differential equation from physiology, the mucosal wave model of the vocal oscillation during phonation. The mathematical equation models a superficial wave propagating through the tissues. The numerical scheme is adapted from the work presented in [1, 2, 3], using homotopy analysis method (HAM) to solve the non linear mixed type equation under study.

Utility of Equations to Estimate Peak Oxygen Uptake and Work Rate From a 6-Minute Walk Test in Patients With COPD in a Clinical Setting.

PubMed

Kirkham, Amy A; Pauhl, Katherine E; Elliott, Robyn M; Scott, Jen A; Doria, Silvana C; Davidson, Hanan K; Neil-Sztramko, Sarah E; Campbell, Kristin L; Camp, Pat G

2015-01-01

To determine the utility of equations that use the 6-minute walk test (6MWT) results to estimate peak oxygen uptake ((Equation is included in full-text article.)o2) and peak work rate with chronic obstructive pulmonary disease (COPD) patients in a clinical setting. This study included a systematic review to identify published equations estimating peak (Equation is included in full-text article.)o2 and peak work rate in watts in COPD patients and a retrospective chart review of data from a hospital-based pulmonary rehabilitation program. The following variables were abstracted from the records of 42 consecutively enrolled COPD patients: measured peak (Equation is included in full-text article.)o2 and peak work rate achieved during a cycle ergometer cardiopulmonary exercise test, 6MWT distance, age, sex, weight, height, forced expiratory volume in 1 second, forced vital capacity, and lung diffusion capacity. Estimated peak (Equation is included in full-text article.)o2 and peak work rate were estimated from 6MWT distance using published equations. The error associated with using estimated peak (Equation is included in full-text article.)o2 or peak work to prescribe aerobic exercise intensities of 60% and 80% was calculated. Eleven equations from 6 studies were identified. Agreement between estimated and measured values was poor to moderate (intraclass correlation coefficients = 0.11-0.63). The error associated with using estimated peak (Equation is included in full-text article.)o2 or peak work rate to prescribe exercise intensities of 60% and 80% of measured values ranged from mean differences of 12 to 35 and 16 to 47 percentage points, respectively. There is poor to moderate agreement between measured peak (Equation is included in full-text article.)o2 and peak work rate and estimations from equations that use 6MWT distance, and the use of the estimated values for prescription of aerobic exercise intensity would result in large error. Equations estimating peak (Equation is included in full-text article.)o2 and peak work rate are of low utility for prescribing exercise intensity in pulmonary rehabilitation programs.

Community pharmacist intervention in patients with renal impairment.

PubMed

Pourrat, Xavier; Sipert, Anne-Sophie; Gatault, Philippe; Sautenet, Bénédicte; Hay, Nicolas; Guinard, Francis; Guegan, Françoise; Halimi, Jean-Michel

2015-12-01

In France, community pharmacists do not have free access to patients' lab results, and it is therefore impossible for them to identify patients with renal impairment. (1) to evaluate the ability of community pharmacists (CPs) to identify drug related problems (DRP) in patients at risk for or suffering from renal impairment; (2) to evaluate the proportions of recommendations by CPs that lead to a modification by GP. A prospective and observational study involving 24 community pharmacists in France. Following special training, community pharmacists were asked to select 52 patients with the following characteristics: ≥65 years of age; prescribed at least two diabetic and/or antihypertensive drugs. Serum creatinine value was obtained for each patient and glomerular filtration rate estimated (eGFR) with the aMDRD formula. Those with a eGFR 60 ml/min/1.73 m² were considered having chronic kidney disease (CKD). Data was collected concerning whether the community pharmacists identified drug related problems and tried to inform the GP who prescribed the medications. Identified DRP were reviewed by a team of nephrologists and hospital clinical pharmacists. The proportion of CKD patients and those without serum creatinine monitoring, the number of drug related problems identified by community pharmacists, and the proportion of drug related problems resolved by the community pharmacists intervention to the GP. Of the total 791 patients identified, 180 (22.8 %) exhibited CKD, and 57 (7.2 %) had not undergone serum creatinine monitoring. Among the 1297 drugs prescribed, 260 had to be adapted to eGFR. The proportion of DRP was 21.5 % (56/260), of which 40 % (20) were identified by community pharmacists. Once the GP was informed, 33.3 % (6/18) of DRP were resolved. Community pharmacists identified 40 % of DRP related to CKD prescriptions, leading to prescription modification by GPs in a third of the cases. These interventions are likely to decrease drug-related morbidity and mortality.

The effect of some medications given to CKD patients on vitamin D levels.

PubMed

Yuste, Claudia; Quiroga, Borja; de Vinuesa, Soledad García; Goicoechea, Maria Angeles; Barraca, Daniel; Verdalles, Ursula; Luño, Jose

2015-01-01

Vitamin D deficiency and polypharmacy is a common problem over chronic kidney disease (CKD) population. To assess the clinical and analytical characteristics of CKD patients with 25-OH-D3 deficiency (<15 ng/mL), including the possible role of associated drugs. A single center observational review of 137 incident patients referred to our outpatient clinic with different stages of CKD and 25-OH-D3<15ng/mL (male gender 53.3%, mean age 70.8 [±16.1] years, mean GFR (MDRD-4) 43.6 [±25.5] ml/min/1.73 m²). 25-OH-D3 levels were collected in spring. Clinical and biochemical data and associated medications were recorded. Mean 25-OH-D3 levels were 8.23 [±4.03] ng/ml. Eighty-eight patients (64.7%) had 3 or more concomitant drugs. Only 7 patients (5.1%) were not receiving any medication. Patients were divided in three groups according the therapies into none (n=26), RAS inhibitors or allopurinol (n=81), and RAS inhibitors plus allopurinol (n=30); with the aim to study the influence of statin therapy. Patients under renin angiotensin (RAS) inhibitors or Allopurinol treatment presented significantly higher 25-OH-D3 levels (p=0.001 and p=0.01 respectively), however patients with Statins treatment had lower 25-OH-D3 level (p=0.039). Personal history of diabetes, cardiovascular events or other therapies did not modify 25-OH-D3 levels, adjusted by age and eGFR. CKD patients with vitamin D deficiency who received RAS inhibitors or Allopurinol treatment had higher 25-OH-D3 levels, however those with statins treatment had lower vitamin D levels. Randomized controlled trials are required to confirm these findings. Copyright © 2015. Published by Elsevier España, S.L.U.

Renal outcomes of simultaneous liver-kidney transplantation compared to liver transplant alone for candidates with renal dysfunction.

PubMed

Brennan, Todd V; Lunsford, Keri E; Vagefi, Parsia A; Bostrom, Alan; Ma, Michael; Feng, Sandy

2015-01-01

It is unclear whether a concomitant kidney transplant grants survival benefit to liver transplant (LT) candidates with renal dysfunction (RD). We retrospectively studied LT candidates without RD (n = 714) and LT candidates with RD who underwent either liver transplant alone (RD-LTA; n = 103) or simultaneous liver-kidney transplant (RD-SLKT; n = 68). RD was defined as renal replacement therapy (RRT) requirement or modification of diet in renal disease (MDRD)-glomerular filtration rate (GFR) <25 mL/min/1.73 m(2) . RD-LTAs had worse one-yr post-transplant survival compared to RD-SLKTs (79.6% vs. 91.2%, p = 0.05). However, RD-LTA recipients more often had hepatitis C (60.2% vs. 41.2%, p = 0.004) and more severe liver disease (MELD 37.9 ± 8.1 vs. 32.7 ± 9.1, p = 0.0001). Twenty RD-LTA recipients died in the first post-transplant year. Evaluation of the cause and timing of death relative to native renal recovery revealed that only four RD-LTA recipients might have derived survival benefit from RD-SLKT. Overall, 87% of RD-LTA patients recovered renal function within one month of transplant. One yr after RD-LTA or RD-SLKT, serum creatinine (1.5 ± 1.2 mg/dL vs. 1.4 ± 0.5 mg/dL, p = 0.63) and prevalence of stage 4 or 5 chronic kidney disease (CKD; 5.9% vs. 6.8%, p = 0.11) were comparable. Our series provides little evidence that RD-SLKT would have yielded substantial short-term survival benefit to RD-LTA recipients. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Gender, renal function, and outcomes on the liver transplant waiting list: assessment of revised MELD including estimated glomerular filtration rate.

PubMed

Myers, Robert P; Shaheen, Abdel Aziz M; Aspinall, Alexander I; Quinn, Robert R; Burak, Kelly W

2011-03-01

The Model for End-Stage Liver Disease (MELD) allocation system for liver transplantation (LT) may present a disadvantage for women by including serum creatinine, which is typically lower in females. Our objectives were to investigate gender disparities in outcomes among LT candidates and to assess a revised MELD, including estimated glomerular filtration rate (eGFR), for predicting waiting list mortality. Adults registered for LT between 2002 and 2007 were identified using the UNOS database. We compared components of MELD, MDRD-derived eGFR, and the 3-month probability of LT and death between genders. Discrimination of MELD, MELDNa, and revised models including eGFR for mortality were compared using c-statistics. A total of 40,393 patients (36% female) met the inclusion criteria; 9% died and 24% underwent LT within 3 months of listing. Compared with men, women had lower median serum creatinine (0.9 vs. 1.0 mg/dl), eGFR (72 vs. 83 ml/min/1.73 m(2)), and mean MELD (16.5 vs. 17.2; all p <0.0005), but within most MELD strata, had higher bilirubin and INR. After adjusting for relevant covariates including creatinine and body weight, women were less likely than men to receive a LT (hazard ratio [HR] 0.85; 95% CI 0.79-0.87) and had greater 3-month mortality (HR 1.13; 95% CI 1.05-1.21). Revision of MELD and MELDNa to include eGFR did not improve discrimination for 3-month mortality (c-statistics: MELD 0.896, MELD-eGFR 0.894, MELDNa 0.911, MELDNa-eGFR 0.905). Women are disadvantaged under MELD potentially due to its inclusion of creatinine. However, since including eGFR in MELD does not improve mortality prediction, alternative refinements are necessary. Copyright © 2010 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

Cumulative Effects of Several Target Organ Damages in Risk Assessment in Hypertension.

PubMed

Harbaoui, Brahim; Courand, Pierre-Yves; Defforges, Alice; Khettab, Fouad; Milon, Hugues; Girerd, Nicolas; Lantelme, Pierre

2016-02-01

The prognostic value of screening multiple target organ damages (TODs) in hypertensive subjects has not been extensively studied. We estimated the prognostic value of considering 3 TODs in estimating the 10-year survival in hypertensive subjects. At baseline 1,848 out of a cohort of 1,963 hypertensive patients had a previous cardiovascular disease (CVD) or assessments of 3 TODs: Modification in Diet in Renal Disease (MDRD) <60ml/min or albuminuria >300mg/day, Sokolow index >3.5 mV, and advanced hypertensive retinopathy (grades 3 and 4 of Keith-Wagener-Barker classification). The cohort was divided into 5 groups: 0 TOD (N = 978), 1 TOD (N = 308), 2 TODs (N = 94), 3 TODs (N = 30), and previous CVD (N = 438). After 10 years of follow-up, we observed 418 deaths of which 254 from cardiovascular cause. The adjusted hazard ratios for the major cardiovascular risk factors showed a progressive risk associated with the number of TODs. For all-cause death, the hazard ratios [95% confidence intervals] vs. 0 TOD of the other 4 groups were 1.91 [1.39-2.63], 1.99 [1.28-3.10], 4.33 [2.42-7.72], and 3.09 [2.35-4.05], respectively. For cardiovascular death, the hazard ratios [95% confidence intervals] were of the same order of magnitude: 2.14 [1.38-3.32], 2.12 [1.15-3.89], 4.22 [1.83-9.72], and 4.24 [2.95-6.11], respectively. Our results indicate that hypertensive patients with several TODs had a worst outcome. Thus, it seems important to screen for multiple TODs in hypertension; especially check for severe hypertensive retinopathy in patients with left ventricular hypertrophy (LVH) and renal damage. © American Journal of Hypertension, Ltd 2015. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Methods for estimating selected spring and fall low-flow frequency statistics for ungaged stream sites in Iowa, based on data through June 2014

USGS Publications Warehouse

Eash, David A.; Barnes, Kimberlee K.; O'Shea, Padraic S.

2016-09-19

A statewide study was led to develop regression equations for estimating three selected spring and three selected fall low-flow frequency statistics for ungaged stream sites in Iowa. The estimation equations developed for the six low-flow frequency statistics include spring (April through June) 1-, 7-, and 30-day mean low flows for a recurrence interval of 10 years and fall (October through December) 1-, 7-, and 30-day mean low flows for a recurrence interval of 10 years. Estimates of the three selected spring statistics are provided for 241 U.S. Geological Survey continuous-record streamgages, and estimates of the three selected fall statistics are provided for 238 of these streamgages, using data through June 2014. Because only 9 years of fall streamflow record were available, three streamgages included in the development of the spring regression equations were not included in the development of the fall regression equations. Because of regulation, diversion, or urbanization, 30 of the 241 streamgages were not included in the development of the regression equations. The study area includes Iowa and adjacent areas within 50 miles of the Iowa border. Because trend analyses indicated statistically significant positive trends when considering the period of record for most of the streamgages, the longest, most recent period of record without a significant trend was determined for each streamgage for use in the study. Geographic information system software was used to measure 63 selected basin characteristics for each of the 211streamgages used to develop the regional regression equations. The study area was divided into three low-flow regions that were defined in a previous study for the development of regional regression equations.Because several streamgages included in the development of regional regression equations have estimates of zero flow calculated from observed streamflow for selected spring and fall low-flow frequency statistics, the final equations for the three low-flow regions were developed using two types of regression analyses—left-censored and generalized-least-squares regression analyses. A total of 211 streamgages were included in the development of nine spring regression equations—three equations for each of the three low-flow regions. A total of 208 streamgages were included in the development of nine fall regression equations—three equations for each of the three low-flow regions. A censoring threshold was used to develop 15 left-censored regression equations to estimate the three fall low-flow frequency statistics for each of the three low-flow regions and to estimate the three spring low-flow frequency statistics for the southern and northwest regions. For the northeast region, generalized-least-squares regression was used to develop three equations to estimate the three spring low-flow frequency statistics. For the northeast region, average standard errors of prediction range from 32.4 to 48.4 percent for the spring equations and average standard errors of estimate range from 56.4 to 73.8 percent for the fall equations. For the northwest region, average standard errors of estimate range from 58.9 to 62.1 percent for the spring equations and from 83.2 to 109.4 percent for the fall equations. For the southern region, average standard errors of estimate range from 43.2 to 64.0 percent for the spring equations and from 78.1 to 78.7 percent for the fall equations.The regression equations are applicable only to stream sites in Iowa with low flows not substantially affected by regulation, diversion, or urbanization and with basin characteristics within the range of those used to develop the equations. The regression equations will be implemented within the U.S. Geological Survey StreamStats Web-based geographic information system application. StreamStats allows users to click on any ungaged stream site and compute estimates of the six selected spring and fall low-flow statistics; in addition, 90-percent prediction intervals and the measured basin characteristics for the ungaged site are provided. StreamStats also allows users to click on any Iowa streamgage to obtain computed estimates for the six selected spring and fall low-flow statistics.

Solving Fuzzy Fractional Differential Equations Using Zadeh's Extension Principle

PubMed Central

Ahmad, M. Z.; Hasan, M. K.; Abbasbandy, S.

2013-01-01

We study a fuzzy fractional differential equation (FFDE) and present its solution using Zadeh's extension principle. The proposed study extends the case of fuzzy differential equations of integer order. We also propose a numerical method to approximate the solution of FFDEs. To solve nonlinear problems, the proposed numerical method is then incorporated into an unconstrained optimisation technique. Several numerical examples are provided. PMID:24082853

On the three dimensional structure of stratospheric material transport associated with various types of waves

NASA Astrophysics Data System (ADS)

Kinoshita, T.; Sato, K.

2016-12-01

The Transformed Eulerian-Mean (TEM) equations were derived by Andrews and McIntyre (1976, 1978) and have been widely used to examine wave-mean flow interaction in the meridional cross section. According to previous studies, the Brewer-Dobson circulation in the stratosphere is driven by planetary waves, baroclinic waves, and inertia-gravity waves, and that the meridional circulation from the summer hemisphere to the winter hemisphere in the mesosphere is mainly driven by gravity waves (e.g., Garcia and Boville 1994; Plumb and Semeniuk 2003; Watanabe et al. 2008; Okamoto et al. 2011). However, the TEM equations do not provide the three-dimensional view of the transport, so that the three dimensional TEM equations have been formulated (Hoskins et al. 1983, Trenberth 1986, Plumb 1985, 1986, Takaya and Nakamura 1997, 2001, Miyahara 2006, Kinoshita et al. 2010, Noda 2010, Kinoshita and Sato 2013a, b, and Noda 2014). On the other hand, the TEM equations cannot properly treat the lower boundary and unstable waves. The Mass-weighted Isentropic Mean (MIM) equations derived by Iwasaki (1989, 1990) are the equations that overcome those problems and the formulation of three-dimensional MIM equations have been studied. The present study applies the three-dimensional TEM and MIM equations to the ERA-Interim reanalysis data and examines the climatological character of three-dimensional structure of Stratospheric Brewer-Dobson circulation. Next, we will discuss how to treat the flow associated with spatial structure of stationary waves.

Dynamic of solitary wave solutions in some nonlinear pseudoparabolic models and Dodd-Bullough-Mikhailov equation

NASA Astrophysics Data System (ADS)

Ilhan, O. A.; Bulut, H.; Sulaiman, T. A.; Baskonus, H. M.

2018-02-01

In this study, the modified exp ( - Φ (η )) -expansion function method is used in constructing some solitary wave solutions to the Oskolkov-Benjamin-Bona-Mahony-Burgers, one-dimensional Oskolkov equations and the Dodd-Bullough-Mikhailov equation. We successfully construct some singular solitons and singular periodic waves solutions with the hyperbolic, trigonometric and exponential function structures to these three nonlinear models. Under the choice of some suitable values of the parameters involved, we plot the 2D and 3D graphics to some of the obtained solutions in this study. All the obtained solutions in this study verify their corresponding equation. We perform all the computations in this study with the help of the Wolfram Mathematica software. The obtained solutions in this study may be helpful in explaining some practical physical problems.

Dynamical property analysis of fractionally damped van der pol oscillator and its application

NASA Astrophysics Data System (ADS)

Zhong, Qiuhui; Zhang, Chunrui

2012-01-01

In this paper, the fractionally damped van der pol equation was studied. Firstly, the fractionally damped van der pol equation was transformed into a set of integer order equations. Then the Lyapunov exponents diagram was given. Secondly, it was transformed into a set of fractional integral equations and solved by a predictor-corrector method. The time domain diagrams and phase trajectory were used to describe the dynamic behavior. Finally, the fractionally damped van der pol equation was used to detect a weak signal.

Analytical solutions of the space-time fractional Telegraph and advection-diffusion equations

NASA Astrophysics Data System (ADS)

Tawfik, Ashraf M.; Fichtner, Horst; Schlickeiser, Reinhard; Elhanbaly, A.

2018-02-01

The aim of this paper is to develop a fractional derivative model of energetic particle transport for both uniform and non-uniform large-scale magnetic field by studying the fractional Telegraph equation and the fractional advection-diffusion equation. Analytical solutions of the space-time fractional Telegraph equation and space-time fractional advection-diffusion equation are obtained by use of the Caputo fractional derivative and the Laplace-Fourier technique. The solutions are given in terms of Fox's H function. As an illustration they are applied to the case of solar energetic particles.

A semi-discrete Kadomtsev-Petviashvili equation and its coupled integrable system

NASA Astrophysics Data System (ADS)

Li, Chun-Xia; Lafortune, Stéphane; Shen, Shou-Feng

2016-05-01

We establish connections between two cascades of integrable systems generated from the continuum limits of the Hirota-Miwa equation and its remarkable nonlinear counterpart under the Miwa transformation, respectively. Among these equations, we are mainly concerned with the semi-discrete bilinear Kadomtsev-Petviashvili (KP) equation which is seldomly studied in literature. We present both of its Casorati and Grammian determinant solutions. Through the Pfaffianization procedure proposed by Hirota and Ohta, we are able to derive the coupled integrable system for the semi-discrete KP equation.

Symmetry Reductions of Fourth-Order Nonlinear Diffusion Equations: Lubrication Model and Some Generalizations

NASA Astrophysics Data System (ADS)

Gandarias, M. L.; Medina, E.

Fourth-order nonlinear diffusion equations appear frequently in the description of physical processes, among these, the lubrication equation ut = (unuxxxx)x or the corresponding modified version ut = unuxxxx play an important role in the study of the interface movements. In this work we analyze the generalizations of the above equations given by ut = (f(u)uxxxx)x, ut = (f(u)uxxxx, and we find that if f(u) = un or f(u) = e-u the equations admit extra classical symmetries. The corresponding reductions are performed and some solutions are characterized.

The discrete Toda equation revisited: dual β-Grothendieck polynomials, ultradiscretization, and static solitons

NASA Astrophysics Data System (ADS)

Iwao, Shinsuke; Nagai, Hidetomo

2018-04-01

This paper presents a study of the discrete Toda equation that was introduced in 1977. In this paper, it is proved that the determinantal solution of the discrete Toda equation, obtained via the Lax formalism, is naturally related to the dual Grothendieck polynomials, a K-theoretic generalization of the Schur polynomials. A tropical permanent solution to the ultradiscrete Toda equation is also derived. The proposed method gives a tropical algebraic representation of the static solitons. Lastly, a new cellular automaton realization of the ultradiscrete Toda equation is proposed.

Measurement Uncertainty Budget of the PMV Thermal Comfort Equation

NASA Astrophysics Data System (ADS)

Ekici, Can

2016-05-01

Fanger's predicted mean vote (PMV) equation is the result of the combined quantitative effects of the air temperature, mean radiant temperature, air velocity, humidity activity level and clothing thermal resistance. PMV is a mathematical model of thermal comfort which was developed by Fanger. The uncertainty budget of the PMV equation was developed according to GUM in this study. An example is given for the uncertainty model of PMV in the exemplification section of the study. Sensitivity coefficients were derived from the PMV equation. Uncertainty budgets can be seen in the tables. A mathematical model of the sensitivity coefficients of Ta, hc, T_{mrt}, T_{cl}, and Pa is given in this study. And the uncertainty budgets for hc, T_{cl}, and Pa are given in this study.

Dynamics of nonautonomous discrete rogue wave solutions for an Ablowitz-Musslimani equation with PT-symmetric potential.

PubMed

Yu, Fajun

2017-02-01

Starting from a discrete spectral problem, we derive a hierarchy of nonlinear discrete equations which include the Ablowitz-Ladik (AL) equation. We analytically study the discrete rogue-wave (DRW) solutions of AL equation with three free parameters. The trajectories of peaks and depressions of profiles for the first- and second-order DRWs are produced by means of analytical and numerical methods. In particular, we study the solutions with dispersion in parity-time ( PT) symmetric potential for Ablowitz-Musslimani equation. And we consider the non-autonomous DRW solutions, parameters controlling and their interactions with variable coefficients, and predict the long-living rogue wave solutions. Our results might provide useful information for potential applications of synthetic PT symmetric systems in nonlinear optics and condensed matter physics.

The fifth-order partial differential equation for the description of the α + β Fermi-Pasta-Ulam model

NASA Astrophysics Data System (ADS)

Kudryashov, Nikolay A.; Volkov, Alexandr K.

2017-01-01

We study a new nonlinear partial differential equation of the fifth order for the description of perturbations in the Fermi-Pasta-Ulam mass chain. This fifth-order equation is an expansion of the Gardner equation for the description of the Fermi-Pasta-Ulam model. We use the potential of interaction between neighbouring masses with both quadratic and cubic terms. The equation is derived using the continuous limit. Unlike the previous works, we take into account higher order terms in the Taylor series expansions. We investigate the equation using the Painlevé approach. We show that the equation does not pass the Painlevé test and can not be integrated by the inverse scattering transform. We use the logistic function method and the Laurent expansion method to find travelling wave solutions of the fifth-order equation. We use the pseudospectral method for the numerical simulation of wave processes, described by the equation.

A Variational Formalism for the Radiative Transfer Equation and a Geostrophic, Hydrostatic Atmosphere: Prelude to Model 3

NASA Technical Reports Server (NTRS)

Achtemeier, Gary L.

1991-01-01

The second step in development of MODEL III is summarized. It combines the four radiative transfer equations of the first step with the equations for a geostrophic and hydrostatic atmosphere. This step is intended to bring radiance into a three dimensional balance with wind, height, and temperature. The use of the geostrophic approximation in place of the full set of primitive equations allows for an easier evaluation of how the inclusion of the radiative transfer equation increases the complexity of the variational equations. Seven different variational formulations were developed for geostrophic, hydrostatic, and radiative transfer equations. The first derivation was too complex to yield solutions that were physically meaningful. For the remaining six derivations, the variational method gave the same physical interpretation (the observed brightness temperatures could provide no meaningful input to a geostrophic, hydrostatic balance) at least through the problem solving methodology used in these studies. The variational method is presented and the Euler-Lagrange equations rederived for the geostrophic, hydrostatic, and radiative transfer equations.

High-order rogue waves of the Benjamin-Ono equation and the nonlocal nonlinear Schrödinger equation

NASA Astrophysics Data System (ADS)

Liu, Wei

2017-10-01

High-order rogue wave solutions of the Benjamin-Ono equation and the nonlocal nonlinear Schrödinger equation are derived by employing the bilinear method, which are expressed by simple polynomials. Typical dynamics of these high-order rogue waves are studied by analytical and graphical ways. For the Benjamin-Ono equation, there are two types of rogue waves, namely, bright rogue waves and dark rogue waves. In particular, the fundamental rogue wave pattern is different from the usual fundamental rogue wave patterns in other soliton equations. For the nonlocal nonlinear Schrödinger equation, the exact explicit rogue wave solutions up to the second order are presented. Typical rogue wave patterns such as Peregrine-type, triple and fundamental rogue waves are put forward. These high-order rogue wave patterns have not been shown before in the nonlocal Schrödinger equation.

Solving the interval type-2 fuzzy polynomial equation using the ranking method

NASA Astrophysics Data System (ADS)

Rahman, Nurhakimah Ab.; Abdullah, Lazim

2014-07-01

Polynomial equations with trapezoidal and triangular fuzzy numbers have attracted some interest among researchers in mathematics, engineering and social sciences. There are some methods that have been developed in order to solve these equations. In this study we are interested in introducing the interval type-2 fuzzy polynomial equation and solving it using the ranking method of fuzzy numbers. The ranking method concept was firstly proposed to find real roots of fuzzy polynomial equation. Therefore, the ranking method is applied to find real roots of the interval type-2 fuzzy polynomial equation. We transform the interval type-2 fuzzy polynomial equation to a system of crisp interval type-2 fuzzy polynomial equation. This transformation is performed using the ranking method of fuzzy numbers based on three parameters, namely value, ambiguity and fuzziness. Finally, we illustrate our approach by numerical example.

Multi criteria evaluation for universal soil loss equation based on geographic information system

NASA Astrophysics Data System (ADS)

Purwaamijaya, I. M.

2018-05-01

The purpose of this research were to produce(l) a conceptual, functional model designed and implementation for universal soil loss equation (usle), (2) standard operational procedure for multi criteria evaluation of universal soil loss equation (usle) using geographic information system, (3) overlay land cover, slope, soil and rain fall layers to gain universal soil loss equation (usle) using multi criteria evaluation, (4) thematic map of universal soil loss equation (usle) in watershed, (5) attribute table of universal soil loss equation (usle) in watershed. Descriptive and formal correlation methods are used for this research. Cikapundung Watershed, Bandung, West Java, Indonesia was study location. This research was conducted on January 2016 to May 2016. A spatial analysis is used to superimposed land cover, slope, soil and rain layers become universal soil loss equation (usle). Multi criteria evaluation for universal soil loss equation (usle) using geographic information system could be used for conservation program.

Propagation of nonlinear shock waves for the generalised Oskolkov equation and its dynamic motions in the presence of an external periodic perturbation

NASA Astrophysics Data System (ADS)

Ak, Turgut; Aydemir, Tugba; Saha, Asit; Kara, Abdul Hamid

2018-06-01

Propagation of nonlinear shock waves for the generalised Oskolkov equation and dynamic motions of the perturbed Oskolkov equation are investigated. Employing the unified method, a collection of exact shock wave solutions for the generalised Oskolkov equations is presented. Collocation finite element method is applied to the generalised Oskolkov equation for checking the accuracy of the proposed method by two test problems including the motion of shock wave and evolution of waves with Gaussian and undular bore initial conditions. Considering an external periodic perturbation, the dynamic motions of the perturbed generalised Oskolkov equation are studied depending on the system parameters with the help of phase portrait and time series plot. The perturbed generalised Oskolkov equation exhibits period-3, quasiperiodic and chaotic motions for some special values of the system parameters, whereas the generalised Oskolkov equation presents shock waves in the absence of external periodic perturbation.

Fifth-order complex Korteweg-de Vries-type equations

NASA Astrophysics Data System (ADS)

Khanal, Netra; Wu, Jiahong; Yuan, Juan-Ming

2012-05-01

This paper studies spatially periodic complex-valued solutions of the fifth-order Korteweg-de Vries (KdV)-type equations. The aim is at several fundamental issues including the existence, uniqueness and finite-time blowup problems. Special attention is paid to the Kawahara equation, a fifth-order KdV-type equation. When a Burgers dissipation is attached to the Kawahara equation, we establish the existence and uniqueness of the Fourier series solution with the Fourier modes decaying algebraically in terms of the wave numbers. We also examine a special series solution to the Kawahara equation and prove the convergence and global regularity of such solutions associated with a single mode initial data. In addition, finite-time blowup results are discussed for the special series solution of the Kawahara equation.

The accuracy of the compressible Reynolds equation for predicting the local pressure in gas-lubricated textured parallel slider bearings

PubMed Central

Qiu, Mingfeng; Bailey, Brian N.; Stoll, Rob

2014-01-01

The validity of the compressible Reynolds equation to predict the local pressure in a gas-lubricated, textured parallel slider bearing is investigated. The local bearing pressure is numerically simulated using the Reynolds equation and the Navier-Stokes equations for different texture geometries and operating conditions. The respective results are compared and the simplifying assumptions inherent in the application of the Reynolds equation are quantitatively evaluated. The deviation between the local bearing pressure obtained with the Reynolds equation and the Navier-Stokes equations increases with increasing texture aspect ratio, because a significant cross-film pressure gradient and a large velocity gradient in the sliding direction develop in the lubricant film. Inertia is found to be negligible throughout this study. PMID:25049440

Continuous properties of the data-to-solution map for a generalized μ-Camassa-Holm integrable equation

NASA Astrophysics Data System (ADS)

Yu, Shengqi

2018-05-01

This work studies a generalized μ-type integrable equation with both quadratic and cubic nonlinearities; the μ-Camassa-Holm and modified μ-Camassa-Holm equations are members of this family of equations. It has been shown that the Cauchy problem for this generalized μ-Camassa-Holm integrable equation is locally well-posed for initial data u0 ∈ Hs, s > 5/2. In this work, we further investigate the continuity properties to this equation. It is proved in this work that the data-to-solution map of the proposed equation is not uniformly continuous. It is also found that the solution map is Hölder continuous in the Hr-topology when 0 ≤ r < s with Hölder exponent α depending on both s and r.

Symbolic generation of elastic rotor blade equations using a FORTRAN processor and numerical study on dynamic inflow effects on the stability of helicopter rotors

NASA Technical Reports Server (NTRS)

Reddy, T. S. R.

1986-01-01

The process of performing an automated stability analysis for an elastic-bladed helicopter rotor is discussed. A symbolic manipulation program, written in FORTRAN, is used to aid in the derivation of the governing equations of motion for the rotor. The blades undergo coupled bending and torsional deformations. Two-dimensional quasi-steady aerodynamics below stall are used. Although reversed flow effects are neglected, unsteady effects, modeled as dynamic inflow are included. Using a Lagrangian approach, the governing equations are derived in generalized coordinates using the symbolic program. The program generates the steady and perturbed equations and writes into subroutines to be called by numerical routines. The symbolic program can operate on both expressions and matrices. For the case of hovering flight, the blade and dynamic inflow equations are converted to equations in a multiblade coordinate system by rearranging the coefficients of the equations. For the case of forward flight, the multiblade equations are obtained through the symbolic program. The final multiblade equations are capable of accommodating any number of elastic blade modes. The computer implementation of this procedure consists of three stages: (1) the symbolic derivation of equations; (2) the coding of the equations into subroutines; and (3) the numerical study after identifying mass, damping, and stiffness coefficients. Damping results are presented in hover and in forward flight with and without dynamic inflow effects for various rotor blade models, including rigid blade lag-flap, elastic flap-lag, flap-lag-torsion, and quasi-static torsion. Results from dynamic inflow effects which are obtained from a lift deficiency function for a quasi-static inflow model in hover are also presented.

Assessing Glomerular Filtration Rate in Hospitalized Patients: A Comparison Between CKD-EPI and Four Cystatin C-Based Equations

PubMed Central

de la Torre, Judith; Ramos, Natalia; Quiroz, Augusto; Garjau, Maria; Torres, Irina; Azancot, M. Antonia; López, Montserrat; Sobrado, Ana

2011-01-01

Summary Background and objectives A specific method is required for estimating glomerular filtration rate GFR in hospitalized patients. Our objective was to validate the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation and four cystatin C (CysC)–based equations in this setting. Design, setting, participants, & measurements This was an epidemiologic, cross-sectional study in a random sample of hospitalized patients (n = 3114). We studied the accuracy of the CKD-EPI and four CysC-based equations—based on (1) CysC alone or (2) adjusted by gender; (3) age, gender, and race; and (4) age, gender, race, and creatinine, respectively—compared with GFR measured by iohexol clearance (mGFR). Clinical, biochemical, and nutritional data were also collected. Results The CysC equation 3 significantly overestimated the GFR (bias of 7.4 ml/min per 1.73 m2). Most of the error in creatinine-based equations was attributable to calculated muscle mass, which depended on patient's nutritional status. In patients without malnutrition or reduced body surface area, the CKD-EPI equation adequately estimated GFR. Equations based on CysC gave more precise mGFR estimates when malnutrition, extensive reduction of body surface area, or loss of muscle mass were present (biases of 1 and 1.3 ml/min per 1.73 m2 for equations 2 and 4, respectively, versus 5.9 ml/min per 1.73 m2 for CKD-EPI). Conclusions These results suggest that the use of equations based on CysC and gender, or CysC, age, gender, and race, is more appropriate in hospitalized patients to estimate GFR, since these equations are much less dependent on patient's nutritional status or muscle mass than the CKD-EPI equation. PMID:21852668

Predictive Equations Are Inaccurate in the Estimation of the Resting Energy Expenditure of Children With End-Stage Liver Disease.

PubMed

Carpenter, Andrea; Ng, Vicky Lee; Chapman, Karen; Ling, Simon C; Mouzaki, Marialena

2017-03-01

Malnutrition is common in children with end-stage liver disease (ESLD) and is associated with increased morbidity and mortality. The inability to accurately estimate energy needs of these patients may contribute to their poor nutrition status. In clinical practice, predictive equations are used to calculate resting energy expenditure (cREE). The objective of this study is to assess the accuracy of commonly used equations in pediatric patients with ESLD. Retrospective study performed at the Hospital for Sick Children. Clinical, laboratory, and indirect calorimetry data from children listed for liver transplant between February 2013 and December 2014 were reviewed. Calorimetry results were compared with cREE estimated using the Food and Agriculture Organization/World Health Organization/United Nations University (FAO/WHO/UNU), Schofield [weight], and Schofield [weight and height] equations. Forty-five patients were included in this study. The median age was 9 months, and the most common indication for transplantation was biliary atresia (64%). The Schofield [weight and height], FAO/WHO/UNU, and Schofield [weight] equations were compared with indirect calorimetry and found to have a mean (SD) difference of 48.8 (344.0), 59.3 (229.8), and 206.5 (502.6) kcal/d, respectively. The FAO/WHO/UNU, Schofield [weight], and Schofield [weight and height] equations introduced a mean error of 21%, 38%, and 76%, respectively. The FAO/WHO/UNU equation tended to underestimate, whereas the Schofield equations overestimated the REE. Commonly used predictive equations perform poorly in infants and young children with ESLD. Indirect calorimetry should be used when available to guide energy provision, particularly in children who are already malnourished.

Assessing the Reliability of Regional Depth-Duration-Frequency Equations for Gauged and Ungauged Sites

NASA Astrophysics Data System (ADS)

Castellarin, A.; Montanari, A.; Brath, A.

2002-12-01

The study derives Regional Depth-Duration-Frequency (RDDF) equations for a wide region of northern-central Italy (37,200 km 2) by following an adaptation of the approach originally proposed by Alila [WRR, 36(7), 2000]. The proposed RDDF equations have a rather simple structure and allow an estimation of the design storm, defined as the rainfall depth expected for a given storm duration and recurrence interval, in any location of the study area for storm durations from 1 to 24 hours and for recurrence intervals up to 100 years. The reliability of the proposed RDDF equations represents the main concern of the study and it is assessed at two different levels. The first level considers the gauged sites and compares estimates of the design storm obtained with the RDDF equations with at-site estimates based upon the observed annual maximum series of rainfall depth and with design storm estimates resulting from a regional estimator recently developed for the study area through a Hierarchical Regional Approach (HRA) [Gabriele and Arnell, WRR, 27(6), 1991]. The second level performs a reliability assessment of the RDDF equations for ungauged sites by means of a jack-knife procedure. Using the HRA estimator as a reference term, the jack-knife procedure assesses the reliability of design storm estimates provided by the RDDF equations for a given location when dealing with the complete absence of pluviometric information. The results of the analysis show that the proposed RDDF equations represent practical and effective computational means for producing a first guess of the design storm at the available raingauges and reliable design storm estimates for ungauged locations. The first author gratefully acknowledges D.H. Burn for sponsoring the submission of the present abstract.

FEV1/FVC and FEV1 for the assessment of chronic airflow obstruction in prevalence studies: do prediction equations need revision?

PubMed

Roche, Nicolas; Dalmay, François; Perez, Thierry; Kuntz, Claude; Vergnenègre, Alain; Neukirch, Françoise; Giordanella, Jean-Pierre; Huchon, Gérard

2008-11-01

Little is known on the long-term validity of reference equations used in the calculation of FEV(1) and FEV(1)/FVC predicted values. This survey assessed the prevalence of chronic airflow obstruction in a population-based sample and how it is influenced by: (i) the definition of airflow obstruction; and (ii) equations used to calculate predicted values. Subjects aged 45 or more were recruited in health prevention centers, performed spirometry and fulfilled a standardized ECRHS-derived questionnaire. Previously diagnosed cases and risk factors were identified. Prevalence of airflow obstruction was calculated using: (i) ATS-GOLD definition (FEV(1)/FVC<0.70); and (ii) ERS definition (FEV(1)/FVC

Geometry, Heat Equation and Path Integrals on the Poincaré Upper Half-Plane

NASA Astrophysics Data System (ADS)

Kubo, R.

1988-01-01

Geometry, heat equation and Feynman's path integrals are studied on the Poincaré upper half-plane. The fundamental solution to the heat equation partial f/partial t = Delta_{H} f is expressed in terms of a path integral defined on the upper half-plane. It is shown that Kac's statement that Feynman's path integral satisfies the Schrödinger equation is also valid for our case.

Detecting and Correcting Scale Drift in Test Equating: An Illustration from a Large Scale Testing Program

ERIC Educational Resources Information Center

Puhan, Gautam

2009-01-01

The purpose of this study is to determine the extent of scale drift on a test that employs cut scores. It was essential to examine scale drift for this testing program because new forms in this testing program are often put on scale through a series of intermediate equatings (known as equating chains). This process may cause equating error to…

Scale Drift in Equating on a Test That Employs Cut Scores. Research Report. ETS RR-07-34

ERIC Educational Resources Information Center

Puhan, Gautam

2007-01-01

The purpose of this study is to determine the extent of scale drift on a test that employs cut scores. It is essential to examine scale drift in a testing program using new forms that are often put on scale through a series of intermediate equatings (known as equating chains). This may cause equating error to accumulate to a point where scale…

Preliminary bioelectrical impedance analysis (BIA) equation for body composition assessment in young females from Colombia

NASA Astrophysics Data System (ADS)

Caicedo-Eraso, J. C.; González-Correa, C. H.; González-Correa, C. A.

2013-04-01

A previous study showed that reported BIA equations for body composition are not suitable for Colombian population. The purpose of this study was to develop and validate a preliminary BIA equation for body composition assessment in young females from Colombia, using hydrodensitometry as reference method. A sample of 30 young females was evaluated. Inclusion and exclusion criteria were defined to minimize the variability of BIA. Height, weight, BIA, residual lung volume (RV) and underwater weight (UWW) were measured. A preliminary BIA equation was developed (r2 = 0.72, SEE = 2.48 kg) by stepwise multiple regression with fat-free mass (FFM) as dependent variable and weight, height and impedance measurements as independent variables. The quality of regression was evaluated and a cross-validation against 50% of sample confirmed that results obtained with the preliminary BIA equation is interchangeable with results obtained with hydrodensitometry (r2 = 0.84, SEE = 2.62 kg). The preliminary BIA equation can be used for body composition assessment in young females from Colombia until a definitive equation is developed. The next step will be increasing the sample, including a second reference method, as deuterium oxide dilution (D2O), and using multi-frequency BIA (MF-BIA). It would also be desirable to develop equations for males and other ethnic groups in Colombia.

Assessments of a Turbulence Model Based on Menter's Modification to Rotta's Two-Equation Model

NASA Technical Reports Server (NTRS)

Abdol-Hamid, Khaled S.

2013-01-01

The main objective of this paper is to construct a turbulence model with a more reliable second equation simulating length scale. In the present paper, we assess the length scale equation based on Menter s modification to Rotta s two-equation model. Rotta shows that a reliable second equation can be formed in an exact transport equation from the turbulent length scale L and kinetic energy. Rotta s equation is well suited for a term-by-term modeling and shows some interesting features compared to other approaches. The most important difference is that the formulation leads to a natural inclusion of higher order velocity derivatives into the source terms of the scale equation, which has the potential to enhance the capability of Reynolds-averaged Navier-Stokes (RANS) to simulate unsteady flows. The model is implemented in the PAB3D solver with complete formulation, usage methodology, and validation examples to demonstrate its capabilities. The detailed studies include grid convergence. Near-wall and shear flows cases are documented and compared with experimental and Large Eddy Simulation (LES) data. The results from this formulation are as good or better than the well-known SST turbulence model and much better than k-epsilon results. Overall, the study provides useful insights into the model capability in predicting attached and separated flows.

The Fourier transforms for the spatially homogeneous Boltzmann equation and Landau equation

NASA Astrophysics Data System (ADS)

Meng, Fei; Liu, Fang

2018-03-01

In this paper, we study the Fourier transforms for two equations arising in the kinetic theory. The first equation is the spatially homogeneous Boltzmann equation. The Fourier transform of the spatially homogeneous Boltzmann equation has been first addressed by Bobylev (Sov Sci Rev C Math Phys 7:111-233, 1988) in the Maxwellian case. Alexandre et al. (Arch Ration Mech Anal 152(4):327-355, 2000) investigated the Fourier transform of the gain operator for the Boltzmann operator in the cut-off case. Recently, the Fourier transform of the Boltzmann equation is extended to hard or soft potential with cut-off by Kirsch and Rjasanow (J Stat Phys 129:483-492, 2007). We shall first establish the relation between the results in Alexandre et al. (2000) and Kirsch and Rjasanow (2007) for the Fourier transform of the Boltzmann operator in the cut-off case. Then we give the Fourier transform of the spatially homogeneous Boltzmann equation in the non cut-off case. It is shown that our results cover previous works (Bobylev 1988; Kirsch and Rjasanow 2007). The second equation is the spatially homogeneous Landau equation, which can be obtained as a limit of the Boltzmann equation when grazing collisions prevail. Following the method in Kirsch and Rjasanow (2007), we can also derive the Fourier transform for Landau equation.

Impact of a proposed revision of the IESTI equation on the acute risk assessment conducted when setting maximum residue levels (MRLs) in the European Union (EU): A case study.

PubMed

Breysse, Nicolas; Vial, Gaelle; Pattingre, Lauriane; Ossendorp, Bernadette C; Mahieu, Karin; Reich, Hermine; Rietveld, Anton; Sieke, Christian; van der Velde-Koerts, Trijntje; Sarda, Xavier

2018-06-03

Proposals to update the methodology for the international estimated short-term intake (IESTI) equations were made during an international workshop held in Geneva in 2015. Changes to several parameters of the current four IESTI equations (cases 1, 2a, 2b, and 3) were proposed. In this study, the overall impact of these proposed changes on estimates of short-term exposure was studied using the large portion data available in the European Food Safety Authority PRIMo model and the residue data submitted in the framework of the European Maximum Residue Levels (MRL) review under Article 12 of Regulation (EC) No 396/2005. Evaluation of consumer exposure using the current and proposed equations resulted in substantial differences in the exposure estimates; however, there were no significant changes regarding the number of accepted MRLs. For the different IESTI cases, the median ratio of the new versus the current equation is 1.1 for case 1, 1.4 for case 2a, 0.75 for case 2b, and 1 for case 3. The impact, expressed as a shift in the IESTI distribution profile, indicated that the 95th percentile IESTI shifted from 50% of the acute reference dose (ARfD) with the current equations to 65% of the ARfD with the proposed equations. This IESTI increase resulted in the loss of 1.2% of the MRLs (37 out of 3110) tested within this study. At the same time, the proposed equations would have allowed 0.4% of the MRLs (14 out of 3110) that were rejected with the current equations to be accepted. The commodity groups that were most impacted by these modifications are solanacea (e.g., potato, eggplant), lettuces, pulses (dry), leafy brassica (e.g., kale, Chinese cabbage), and pome fruits. The active substances that were most affected were fluazifop-p-butyl, deltamethrin, and lambda-cyhalothrin.

Deep circulations under simple classes of stratification

NASA Technical Reports Server (NTRS)

Salby, Murry L.

1989-01-01

Deep circulations where the motion field is vertically aligned over one or more scale heights are studied under barotropic and equivalent barotropic stratifications. The study uses two-dimensional equations reduced from the three-dimensional primitive equations in spherical geometry. A mapping is established between the full primitive equations and general shallow water behavior and the correspondence between variables describing deep atmospheric motion and those of shallow water behavior is established.

FANS Simulation of Propeller Wash at Navy Harbors (ESTEP Project ER-201031)

DTIC Science & Technology

2016-08-01

this study, the Finite-Analytic Navier–Stokes code was employed to solve the Reynolds-Averaged Navier–Stokes equations in conjunction with advanced...site-specific harbor configurations, it is desirable to perform propeller wash study by solving the Navier–Stokes equations directly in conjunction ...Analytic Navier–Stokes code was employed to solve the Reynolds-Averaged Navier–Stokes equations in conjunction with advanced near-wall turbulence

A nonlinear ordinary differential equation associated with the quantum sojourn time

NASA Astrophysics Data System (ADS)

Benguria, Rafael D.; Duclos, Pierre; Fernández, Claudio; Sing-Long, Carlos

2010-11-01

We study a nonlinear ordinary differential equation on the half-line, with the Dirichlet boundary condition at the origin. This equation arises when studying the local maxima of the sojourn time for a free quantum particle whose states belong to an adequate subspace of the unit sphere of the corresponding Hilbert space. We establish several results concerning the existence and asymptotic behavior of the solutions.

Exact traveling wave solutions of modified KdV-Zakharov-Kuznetsov equation and viscous Burgers equation.

PubMed

Islam, Md Hamidul; Khan, Kamruzzaman; Akbar, M Ali; Salam, Md Abdus

2014-01-01

Mathematical modeling of many physical systems leads to nonlinear evolution equations because most physical systems are inherently nonlinear in nature. The investigation of traveling wave solutions of nonlinear partial differential equations (NPDEs) plays a significant role in the study of nonlinear physical phenomena. In this article, we construct the traveling wave solutions of modified KDV-ZK equation and viscous Burgers equation by using an enhanced (G '/G) -expansion method. A number of traveling wave solutions in terms of unknown parameters are obtained. Derived traveling wave solutions exhibit solitary waves when special values are given to its unknown parameters. 35C07; 35C08; 35P99.

Linear stability analysis of the Vlasov-Poisson equations in high density plasmas in the presence of crossed fields and density gradients

NASA Technical Reports Server (NTRS)

Kaup, D. J.; Hansen, P. J.; Choudhury, S. Roy; Thomas, Gary E.

1986-01-01

The equations for the single-particle orbits in a nonneutral high density plasma in the presence of inhomogeneous crossed fields are obtained. Using these orbits, the linearized Vlasov equation is solved as an expansion in the orbital radii in the presence of inhomogeneities and density gradients. A model distribution function is introduced whose cold-fluid limit is exactly the same as that used in many previous studies of the cold-fluid equations. This model function is used to reduce the linearized Vlasov-Poisson equations to a second-order ordinary differential equation for the linearized electrostatic potential whose eigenvalue is the perturbation frequency.

Rainfall Threshold for Flash Flood Early Warning Based on Rational Equation: A Case Study of Zuojiao Watershed in Yunnan Province

NASA Astrophysics Data System (ADS)

Li, Q.; Wang, Y. L.; Li, H. C.; Zhang, M.; Li, C. Z.; Chen, X.

2017-12-01

Rainfall threshold plays an important role in flash flood warning. A simple and easy method, using Rational Equation to calculate rainfall threshold, was proposed in this study. The critical rainfall equation was deduced from the Rational Equation. On the basis of the Manning equation and the results of Chinese Flash Flood Survey and Evaluation (CFFSE) Project, the critical flow was obtained, and the net rainfall was calculated. Three aspects of the rainfall losses, i.e. depression storage, vegetation interception, and soil infiltration were considered. The critical rainfall was the sum of the net rainfall and the rainfall losses. Rainfall threshold was estimated after considering the watershed soil moisture using the critical rainfall. In order to demonstrate this method, Zuojiao watershed in Yunnan Province was chosen as study area. The results showed the rainfall thresholds calculated by the Rational Equation method were approximated to the rainfall thresholds obtained from CFFSE, and were in accordance with the observed rainfall during flash flood events. Thus the calculated results are reasonable and the method is effective. This study provided a quick and convenient way to calculated rainfall threshold of flash flood warning for the grass root staffs and offered technical support for estimating rainfall threshold.

Explicit expressions for meromorphic solutions of autonomous nonlinear ordinary differential equations

NASA Astrophysics Data System (ADS)

Demina, Maria V.; Kudryashov, Nikolay A.

2011-03-01

Meromorphic solutions of autonomous nonlinear ordinary differential equations are studied. An algorithm for constructing meromorphic solutions in explicit form is presented. General expressions for meromorphic solutions (including rational, periodic, elliptic) are found for a wide class of autonomous nonlinear ordinary differential equations.

Local algebraic analysis of differential systems

NASA Astrophysics Data System (ADS)

Kaptsov, O. V.

2015-06-01

We propose a new approach for studying the compatibility of partial differential equations. This approach is a synthesis of the Riquier method, Gröbner basis theory, and elements of algebraic geometry. As applications, we consider systems including the wave equation and the sine-Gordon equation.

Students' Understanding of Quadratic Equations

ERIC Educational Resources Information Center

López, Jonathan; Robles, Izraim; Martínez-Planell, Rafael

2016-01-01

Action-Process-Object-Schema theory (APOS) was applied to study student understanding of quadratic equations in one variable. This required proposing a detailed conjecture (called a genetic decomposition) of mental constructions students may do to understand quadratic equations. The genetic decomposition which was proposed can contribute to help…

A comparative study of turbulence models in predicting hypersonic inlet flows

NASA Technical Reports Server (NTRS)

Kapoor, Kamlesh

1993-01-01

A computational study has been conducted to evaluate the performance of various turbulence models. The NASA P8 inlet, which represents cruise condition of a typical hypersonic air-breathing vehicle, was selected as a test case for the study; the PARC2D code, which solves the full two dimensional Reynolds-averaged Navier-Stokes equations, was used. Results are presented for a total of six versions of zero- and two-equation turbulence models. Zero-equation models tested are the Baldwin-Lomax model, the Thomas model, and a combination of the two. Two-equation models tested are low-Reynolds number models (the Chien model and the Speziale model) and a high-Reynolds number model (the Launder and Spalding model).

Best Fitting Prediction Equations for Basal Metabolic Rate: Informing Obesity Interventions in Diverse Populations

PubMed Central

Sabounchi, Nasim S.; Rahmandad, Hazhir; Ammerman, Alice

2014-01-01

Basal Metabolic Rate (BMR) represents the largest component of total energy expenditure and is a major contributor to energy balance. Therefore, accurately estimating BMR is critical for developing rigorous obesity prevention and control strategies. Over the past several decades, numerous BMR formulas have been developed targeted to different population groups. A comprehensive literature search revealed 248 BMR estimation equations developed using diverse ranges of age, gender, race, fat free mass, fat mass, height, waist-to-hip ratio, body mass index, and weight. A subset of 47 studies included enough detail to allow for development of meta-regression equations. Utilizing these studies, meta-equations were developed targeted to twenty specific population groups. This review provides a comprehensive summary of available BMR equations and an estimate of their accuracy. An accompanying online BMR prediction tool (available at http://www.sdl.ise.vt.edu/tutorials.html) was developed to automatically estimate BMR based on the most appropriate equation after user-entry of individual age, race, gender, and weight. PMID:23318720

Prediction of Skin Temperature Distribution in Cosmetic Laser Surgery

NASA Astrophysics Data System (ADS)

Ting, Kuen; Chen, Kuen-Tasnn; Cheng, Shih-Feng; Lin, Wen-Shiung; Chang, Cheng-Ren

2008-01-01

The use of lasers in cosmetic surgery has increased dramatically in the past decade. To achieve minimal damage to tissues, the study of the temperature distribution of skin in laser irradiation is very important. The phenomenon of the thermal wave effect is significant due to the highly focused light energy of lasers in very a short time period. The conventional Pennes equation does not take the thermal wave effect into account, which the thermal relaxation time (τ) is neglected, so it is not sufficient to solve instantaneous heating and cooling problem. The purpose of this study is to solve the thermal wave equation to determine the realistic temperature distribution during laser surgery. The analytic solutions of the thermal wave equation are compared with those of the Pennes equation. Moreover, comparisons are made between the results of the above equations and the results of temperature measurement using an infrared thermal image instrument. The thermal wave equation could likely to predict the skin temperature distribution in cosmetic laser surgery.

Lie-Hamilton systems on the plane: Properties, classification and applications

NASA Astrophysics Data System (ADS)

Ballesteros, A.; Blasco, A.; Herranz, F. J.; de Lucas, J.; Sardón, C.

2015-04-01

We study Lie-Hamilton systems on the plane, i.e. systems of first-order differential equations describing the integral curves of a t-dependent vector field taking values in a finite-dimensional real Lie algebra of planar Hamiltonian vector fields with respect to a Poisson structure. We start with the local classification of finite-dimensional real Lie algebras of vector fields on the plane obtained in González-López, Kamran, and Olver (1992) [23] and we interpret their results as a local classification of Lie systems. By determining which of these real Lie algebras consist of Hamiltonian vector fields relative to a Poisson structure, we provide the complete local classification of Lie-Hamilton systems on the plane. We present and study through our results new Lie-Hamilton systems of interest which are used to investigate relevant non-autonomous differential equations, e.g. we get explicit local diffeomorphisms between such systems. We also analyse biomathematical models, the Milne-Pinney equations, second-order Kummer-Schwarz equations, complex Riccati equations and Buchdahl equations.

Quadratically Convergent Method for Simultaneously Approaching the Roots of Polynomial Solutions of a Class of Differential Equations

NASA Astrophysics Data System (ADS)

Recchioni, Maria Cristina

2001-12-01

This paper investigates the application of the method introduced by L. Pasquini (1989) for simultaneously approaching the zeros of polynomial solutions to a class of second-order linear homogeneous ordinary differential equations with polynomial coefficients to a particular case in which these polynomial solutions have zeros symmetrically arranged with respect to the origin. The method is based on a family of nonlinear equations which is associated with a given class of differential equations. The roots of the nonlinear equations are related to the roots of the polynomial solutions of differential equations considered. Newton's method is applied to find the roots of these nonlinear equations. In (Pasquini, 1994) the nonsingularity of the roots of these nonlinear equations is studied. In this paper, following the lines in (Pasquini, 1994), the nonsingularity of the roots of these nonlinear equations is studied. More favourable results than the ones in (Pasquini, 1994) are proven in the particular case of polynomial solutions with symmetrical zeros. The method is applied to approximate the roots of Hermite-Sobolev type polynomials and Freud polynomials. A lower bound for the smallest positive root of Hermite-Sobolev type polynomials is given via the nonlinear equation. The quadratic convergence of the method is proven. A comparison with a classical method that uses the Jacobi matrices is carried out. We show that the algorithm derived by the proposed method is sometimes preferable to the classical QR type algorithms for computing the eigenvalues of the Jacobi matrices even if these matrices are real and symmetric.

A local equation for differential diagnosis of β-thalassemia trait and iron deficiency anemia by logistic regression analysis in Southeast Iran.

PubMed

Sargolzaie, Narjes; Miri-Moghaddam, Ebrahim

2014-01-01

The most common differential diagnosis of β-thalassemia (β-thal) trait is iron deficiency anemia. Several red blood cell equations were introduced during different studies for differential diagnosis between β-thal trait and iron deficiency anemia. Due to genetic variations in different regions, these equations cannot be useful in all population. The aim of this study was to determine a native equation with high accuracy for differential diagnosis of β-thal trait and iron deficiency anemia for the Sistan and Baluchestan population by logistic regression analysis. We selected 77 iron deficiency anemia and 100 β-thal trait cases. We used binary logistic regression analysis and determined best equations for probability prediction of β-thal trait against iron deficiency anemia in our population. We compared diagnostic values and receiver operative characteristic (ROC) curve related to this equation and another 10 published equations in discriminating β-thal trait and iron deficiency anemia. The binary logistic regression analysis determined the best equation for best probability prediction of β-thal trait against iron deficiency anemia with area under curve (AUC) 0.998. Based on ROC curves and AUC, Green & King, England & Frazer, and then Sirdah indices, respectively, had the most accuracy after our equation. We suggest that to get the best equation and cut-off in each region, one needs to evaluate specific information of each region, specifically in areas where populations are homogeneous, to provide a specific formula for differentiating between β-thal trait and iron deficiency anemia.

Solution Methods for Certain Evolution Equations

NASA Astrophysics Data System (ADS)

Vega-Guzman, Jose Manuel

Solution methods for certain linear and nonlinear evolution equations are presented in this dissertation. Emphasis is placed mainly on the analytical treatment of nonautonomous differential equations, which are challenging to solve despite the existent numerical and symbolic computational software programs available. Ideas from the transformation theory are adopted allowing one to solve the problems under consideration from a non-traditional perspective. First, the Cauchy initial value problem is considered for a class of nonautonomous and inhomogeneous linear diffusion-type equation on the entire real line. Explicit transformations are used to reduce the equations under study to their corresponding standard forms emphasizing on natural relations with certain Riccati(and/or Ermakov)-type systems. These relations give solvability results for the Cauchy problem of the parabolic equation considered. The superposition principle allows to solve formally this problem from an unconventional point of view. An eigenfunction expansion approach is also considered for this general evolution equation. Examples considered to corroborate the efficacy of the proposed solution methods include the Fokker-Planck equation, the Black-Scholes model and the one-factor Gaussian Hull-White model. The results obtained in the first part are used to solve the Cauchy initial value problem for certain inhomogeneous Burgers-type equation. The connection between linear (the Diffusion-type) and nonlinear (Burgers-type) parabolic equations is stress in order to establish a strong commutative relation. Traveling wave solutions of a nonautonomous Burgers equation are also investigated. Finally, it is constructed explicitly the minimum-uncertainty squeezed states for quantum harmonic oscillators. They are derived by the action of corresponding maximal kinematical invariance group on the standard ground state solution. It is shown that the product of the variances attains the required minimum value only at the instances that one variance is a minimum and the other is a maximum, when the squeezing of one of the variances occurs. Such explicit construction is possible due to the relation between the diffusion-type equation studied in the first part and the time-dependent Schrodinger equation. A modication of the radiation field operators for squeezed photons in a perfect cavity is also suggested with the help of a nonstandard solution of Heisenberg's equation of motion.

Development of 1RM Prediction Equations for Bench Press in Moderately Trained Men.

PubMed

Macht, Jordan W; Abel, Mark G; Mullineaux, David R; Yates, James W

2016-10-01

Macht, JW, Abel, MG, Mullineaux, DR, and Yates, JW. Development of 1RM prediction equations for bench press in moderately trained men. J Strength Cond Res 30(10): 2901-2906, 2016-There are a variety of established 1 repetition maximum (1RM) prediction equations, however, very few prediction equations use anthropometric characteristics exclusively or in part, to estimate 1RM strength. Therefore, the purpose of this study was to develop an original 1RM prediction equation for bench press using anthropometric and performance characteristics in moderately trained male subjects. Sixty male subjects (21.2 ± 2.4 years) completed a 1RM bench press and were randomly assigned a load to complete as many repetitions as possible. In addition, body composition, upper-body anthropometric characteristics, and handgrip strength were assessed. Regression analysis was used to develop a performance-based 1RM prediction equation: 1RM = 1.20 repetition weight + 2.19 repetitions to fatigue - 0.56 biacromial width (cm) + 9.6 (R = 0.99, standard error of estimate [SEE] = 3.5 kg). Regression analysis to develop a nonperformance-based 1RM prediction equation yielded: 1RM (kg) = 0.997 cross-sectional area (CSA) (cm) + 0.401 chest circumference (cm) - 0.385%fat - 0.185 arm length (cm) + 36.7 (R = 0.81, SEE = 13.0 kg). The performance prediction equations developed in this study had high validity coefficients, minimal mean bias, and small limits of agreement. The anthropometric equations had moderately high validity coefficient but larger limits of agreement. The practical applications of this study indicate that the inclusion of anthropometric characteristics and performance variables produce a valid prediction equation for 1RM strength. In addition, the CSA of the arm uses a simple nonperformance method of estimating the lifter's 1RM. This information may be used to predict the starting load for a lifter performing a 1RM prediction protocol or a 1RM testing protocol.

Autologous hematopoietic cell transplantation for multiple myeloma patients with renal insufficiency: A Center for International Blood and Marrow Transplant Research Analysis

PubMed Central

Mahindra, Anuj; Hari, Parameswaran; Fraser, Raphael; Fei, Mingwei; Huang, Jiaxing; Berdeja, Jesus; Callander, Natalie; Costa, Luciano; Diaz, Miguel Angel; Freytes, Cesar; Gale, Robert Peter; Girnius, Saulius; Holmberg, Leona; Kharfan-Dabaja, Mohamad; Kumar, Shaji; Kyle, Robert; Lazarus, Hillard; Lee, Cindy; Maiolino, Angelo; Moreb, Jan; Nishihori, Taiga; Pawarode, Attaphol; Saad, Ayman; Savani, Bipin N.; Schriber, Jeffrey; William, Basem; Wirk, Baldeep M.; Krishnan, Amrita; Nieto, Yago; D’Souza, Anita

2017-01-01

Autologous hematopoietic cell transplantation (AHCT) in multiple myeloma (MM) patients with renal insufficiency (RI) is controversial. Patients who underwent AHCT for MM between 2008-2013 were identified (N =1492) and grouped as normal/mild (≥60 ml/min), N=1240, moderate (30-59), N=185 and severe RI (<30), N=67 based on MDRD. Multivariate analysis of non-relapse mortality (NRM), relapse, progression-free survival (PFS) and overall survival (OS) was performed. Of the 67 patients with severe RI, 35 were on dialysis prior to AHCT. Patients received melphalan 200 mg/m2 (Mel200) in 92% (normal/mild), 75% (moderate) and 33% (severe) RI; remainder received 140 mg/m2 (Mel140). Thirty four of 35 patients with severe RI achieved post-AHCT dialysis independence. The 5-year PFS for normal, moderate and severe RI was 35 (95% CI, 31-38)%, 40 (31-49)% and 27 (15-40)% respectively, (p=0·42); 5-year OS for normal, mod and severe RI was 68 (65-71)%, 68 (60-76)% and 60 (46-74)% respectively, (p=0·69). With moderate RI, 5-year PFS for HDM 140 mg/m2 was 18 (6-35)% and for Mel200 was 46 (36-57)% (p=0·009). With severe RI, 5-year PFS Mel140 was 25 (11-41) % and for Mel200 was 32 (11-58)% (p=0·37). We conclude that AHCT is safe and effective in patients with MM with RI. PMID:28920949

Renal Function in Type 2 Diabetes with Rosiglitazone, Metformin, and Glyburide Monotherapy

PubMed Central

Viberti, Giancarlo; Zinman, Bernard; Haffner, Steven M.; Aftring, R. Paul; Paul, Gitanjali; Kravitz, Barbara G.; Herman, William H.; Holman, Rury R.; Kahn, Steven E.

2011-01-01

Summary Background and objectives In ADOPT (A Diabetes Outcomes Prevention Trial), initial monotherapy with rosiglitazone provided more durable glycemic control than metformin or glyburide in patients with recently diagnosed type 2 diabetes. Herein, we examine differences in albumin excretion, renal function (estimated GFR), and BP over 5 years between treatment groups. Design, setting, participants, & measurements A total of 4351 recently diagnosed, drug-naïve patients with type 2 diabetes were treated and followed for up to 5 years with rosiglitazone, metformin, or glyburide and were examined with periodic assessments of albumin/creatinine ratio (ACR), modification of diet in renal disease (MDRD)-estimated GFR, and BP. Results The ACR rose slowly with metformin. It fell with rosiglitazone and less so with glyburide over the first 2 years, and then rose slowly over time. Estimated GFR (eGFR) with all therapies rose into the high normal range over the first 3 to 4 years, more so with rosiglitazone, and then declined, more so with glyburide. Systolic BP was stable over time, values with rosiglitazone being lower, and diastolic BP declined over time, more so with rosiglitazone than with metformin or glyburide. There was no difference among groups in the incidence of emergent albuminuria (ACR ≥30 mg/g), hypertension, or impaired eGFR (<60 ml/min per 1.73 m2). Conclusions Over a 5-year period, initial monotherapy with rosiglitazone retards the rise of ACR compared with metformin, preserves eGFR compared with glyburide, and lowers BP relative to both comparators. PMID:21454723

Properties of the two-dimensional heterogeneous Lennard-Jones dimers: An integral equation study

PubMed Central

Urbic, Tomaz

2016-01-01

Structural and thermodynamic properties of a planar heterogeneous soft dumbbell fluid are examined using Monte Carlo simulations and integral equation theory. Lennard-Jones particles of different sizes are the building blocks of the dimers. The site-site integral equation theory in two dimensions is used to calculate the site-site radial distribution functions and the thermodynamic properties. Obtained results are compared to Monte Carlo simulation data. The critical parameters for selected types of dimers were also estimated and the influence of the Lennard-Jones parameters was studied. We have also tested the correctness of the site-site integral equation theory using different closures. PMID:27875894

Equivalence transformations and conservation laws for a generalized variable-coefficient Gardner equation

NASA Astrophysics Data System (ADS)

de la Rosa, R.; Gandarias, M. L.; Bruzón, M. S.

2016-11-01

In this paper we study the generalized variable-coefficient Gardner equations of the form ut + A(t) unux + C(t) u2nux + B(t) uxxx + Q(t) u = 0 . This class broadens out many other equations previously considered: Johnpillai and Khalique (2010), Molati and Ramollo (2012) and Vaneeva et al. (2015). The use of the equivalence group of this class allows us to perform an exhaustive study and a simple and clear formulation of the results. Some conservation laws are derived for the nonlinearly self-adjoint equations by using a general theorem on conservation laws. We also construct conservation laws by applying the multipliers method.

On Critical Behaviour in Systems of Hamiltonian Partial Differential Equations.

PubMed

Dubrovin, Boris; Grava, Tamara; Klein, Christian; Moro, Antonio

2015-01-01

We study the critical behaviour of solutions to weakly dispersive Hamiltonian systems considered as perturbations of elliptic and hyperbolic systems of hydrodynamic type with two components. We argue that near the critical point of gradient catastrophe of the dispersionless system, the solutions to a suitable initial value problem for the perturbed equations are approximately described by particular solutions to the Painlevé-I (P[Formula: see text]) equation or its fourth-order analogue P[Formula: see text]. As concrete examples, we discuss nonlinear Schrödinger equations in the semiclassical limit. A numerical study of these cases provides strong evidence in support of the conjecture.

Sex-specific lean body mass predictive equations are accurate in the obese paediatric population

PubMed Central

Jackson, Lanier B.; Henshaw, Melissa H.; Carter, Janet; Chowdhury, Shahryar M.

2015-01-01

Background The clinical assessment of lean body mass (LBM) is challenging in obese children. A sex-specific predictive equation for LBM derived from anthropometric data was recently validated in children. Aim The purpose of this study was to independently validate these predictive equations in the obese paediatric population. Subjects and methods Obese subjects aged 4–21 were analysed retrospectively. Predicted LBM (LBMp) was calculated using equations previously developed in children. Measured LBM (LBMm) was derived from dual-energy x-ray absorptiometry. Agreement was expressed as [(LBMm-LBMp)/LBMm] with 95% limits of agreement. Results Of 310 enrolled patients, 195 (63%) were females. The mean age was 11.8 ± 3.4 years and mean BMI Z-score was 2.3 ± 0.4. The average difference between LBMm and LBMp was −0.6% (−17.0%, 15.8%). Pearson’s correlation revealed a strong linear relationship between LBMm and LBMp (r=0.97, p<0.01). Conclusion This study validates the use of these clinically-derived sex-specific LBM predictive equations in the obese paediatric population. Future studies should use these equations to improve the ability to accurately classify LBM in obese children. PMID:26287383

A critical review and database of biomass and volume allometric equation for trees and shrubs of Bangladesh

NASA Astrophysics Data System (ADS)

Mahmood, H.; Siddique, M. R. H.; Akhter, M.

2016-08-01

Estimations of biomass, volume and carbon stock are important in the decision making process for the sustainable management of a forest. These estimations can be conducted by using available allometric equations of biomass and volume. Present study aims to: i. develop a compilation with verified allometric equations of biomass, volume, and carbon for trees and shrubs of Bangladesh, ii. find out the gaps and scope for further development of allometric equations for different trees and shrubs of Bangladesh. Key stakeholders (government departments, research organizations, academic institutions, and potential individual researchers) were identified considering their involvement in use and development of allometric equations. A list of documents containing allometric equations was prepared from secondary sources. The documents were collected, examined, and sorted to avoid repetition, yielding 50 documents. These equations were tested through a quality control scheme involving operational verification, conceptual verification, applicability, and statistical credibility. A total of 517 allometric equations for 80 species of trees, shrubs, palm, and bamboo were recorded. In addition, 222 allometric equations for 39 species were validated through the quality control scheme. Among the verified equations, 20%, 12% and 62% of equations were for green-biomass, oven-dried biomass, and volume respectively and 4 tree species contributed 37% of the total verified equations. Five gaps have been pinpointed for the existing allometric equations of Bangladesh: a. little work on allometric equation of common tree and shrub species, b. most of the works were concentrated on certain species, c. very little proportion of allometric equations for biomass estimation, d. no allometric equation for belowground biomass and carbon estimation, and d. lower proportion of valid allometric equations. It is recommended that site and species specific allometric equations should be developed and consistency in field sampling, sample processing, data recording and selection of allometric equations should be maintained to ensure accuracy in estimation of biomass, volume, and carbon stock in different forest types of Bangladesh.

Theoretical study of the incompressible Navier-Stokes equations by the least-squares method

NASA Technical Reports Server (NTRS)

Jiang, Bo-Nan; Loh, Ching Y.; Povinelli, Louis A.

1994-01-01

Usually the theoretical analysis of the Navier-Stokes equations is conducted via the Galerkin method which leads to difficult saddle-point problems. This paper demonstrates that the least-squares method is a useful alternative tool for the theoretical study of partial differential equations since it leads to minimization problems which can often be treated by an elementary technique. The principal part of the Navier-Stokes equations in the first-order velocity-pressure-vorticity formulation consists of two div-curl systems, so the three-dimensional div-curl system is thoroughly studied at first. By introducing a dummy variable and by using the least-squares method, this paper shows that the div-curl system is properly determined and elliptic, and has a unique solution. The same technique then is employed to prove that the Stokes equations are properly determined and elliptic, and that four boundary conditions on a fixed boundary are required for three-dimensional problems. This paper also shows that under four combinations of non-standard boundary conditions the solution of the Stokes equations is unique. This paper emphasizes the application of the least-squares method and the div-curl method to derive a high-order version of differential equations and additional boundary conditions. In this paper, an elementary method (integration by parts) is used to prove Friedrichs' inequalities related to the div and curl operators which play an essential role in the analysis.

Charge and energy migration in molecular clusters: A stochastic Schrödinger equation approach.

PubMed

Plehn, Thomas; May, Volkhard

2017-01-21

The performance of stochastic Schrödinger equations for simulating dynamic phenomena in large scale open quantum systems is studied. Going beyond small system sizes, commonly used master equation approaches become inadequate. In this regime, wave function based methods profit from their inherent scaling benefit and present a promising tool to study, for example, exciton and charge carrier dynamics in huge and complex molecular structures. In the first part of this work, a strict analytic derivation is presented. It starts with the finite temperature reduced density operator expanded in coherent reservoir states and ends up with two linear stochastic Schrödinger equations. Both equations are valid in the weak and intermediate coupling limit and can be properly related to two existing approaches in literature. In the second part, we focus on the numerical solution of these equations. The main issue is the missing norm conservation of the wave function propagation which may lead to numerical discrepancies. To illustrate this, we simulate the exciton dynamics in the Fenna-Matthews-Olson complex in direct comparison with the data from literature. Subsequently a strategy for the proper computational handling of the linear stochastic Schrödinger equation is exposed particularly with regard to large systems. Here, we study charge carrier transfer kinetics in realistic hybrid organic/inorganic para-sexiphenyl/ZnO systems of different extension.

Determination of body composition using air displacement plethysmography, anthropometry and bio-electrical impedance in rural elderly Mexican men and women.

PubMed

Aleman-Mateo, H; Esparza Romero, J; Macias Morales, N; Salazar, G; Wyatt, J; Valencia, M E

2004-01-01

Air displacement plethysmography with the BOD-POD is a new densitometry technique, and has been found to be an accurate method to measure body composition. The aim of this study was to assess body composition in a group of free living healthy subjects 60 years of age or older from a rural area of Northwest Mexico, and to evaluate body composition by anthropometry and bioelectrical impedance (BIA) using equations reported for other elderly populations. Body composition was evaluated in 21 women and 26 men with the BOD-POD, by anthropometry, and BIA and compared to different equations using the Bland- Altman procedure. Body fat in elderly women and men was 42.7 and 30.2 % respectively. In women, Segal's equation using BIA 1, based on standing height, showed no significant differences with the BOD-POD. There was satisfactory agreement between Segal's equation and BOD-POD. In men similar results was found with Deurenberg's equation using B1A 2 based on recumbent length. Segal's and Deurenberg's equations were accurate and precise for the estimation of body fat in the elderly of this study. The use of these equations could improve the estimation of body composition for similar elderly subjects. Further studies are recommended with a larger size samples to include elderly subjects from other Latin American countries.

Charge and energy migration in molecular clusters: A stochastic Schrödinger equation approach

NASA Astrophysics Data System (ADS)

Plehn, Thomas; May, Volkhard

2017-01-01

The performance of stochastic Schrödinger equations for simulating dynamic phenomena in large scale open quantum systems is studied. Going beyond small system sizes, commonly used master equation approaches become inadequate. In this regime, wave function based methods profit from their inherent scaling benefit and present a promising tool to study, for example, exciton and charge carrier dynamics in huge and complex molecular structures. In the first part of this work, a strict analytic derivation is presented. It starts with the finite temperature reduced density operator expanded in coherent reservoir states and ends up with two linear stochastic Schrödinger equations. Both equations are valid in the weak and intermediate coupling limit and can be properly related to two existing approaches in literature. In the second part, we focus on the numerical solution of these equations. The main issue is the missing norm conservation of the wave function propagation which may lead to numerical discrepancies. To illustrate this, we simulate the exciton dynamics in the Fenna-Matthews-Olson complex in direct comparison with the data from literature. Subsequently a strategy for the proper computational handling of the linear stochastic Schrödinger equation is exposed particularly with regard to large systems. Here, we study charge carrier transfer kinetics in realistic hybrid organic/inorganic para-sexiphenyl/ZnO systems of different extension.

More than just "plug-and-chug": Exploring how physics students make sense with equations

NASA Astrophysics Data System (ADS)

Kuo, Eric

Although a large part the Physics Education Research (PER) literature investigates students' conceptual understanding in physics, these investigations focus on qualitative, conceptual reasoning. Even in modeling expert problem solving, attention to conceptual understanding means a focus on initial qualitative analysis of the problem; the equations are typically conceived of as tools for "plug-and-chug" calculations. In this dissertation, I explore the ways that undergraduate physics students make conceptual sense of physics equations and the factors that support this type of reasoning through three separate studies. In the first study, I investigate how students' can understand physics equations intuitively through use of a particular class of cognitive elements, symbolic forms (Sherin, 2001). Additionally, I show how students leverage this intuitive, conceptual meaning of equations in problem solving. By doing so, these students avoid algorithmic manipulations, instead using a heuristic approach that leverages the equation in a conceptual argument. The second study asks the question why some students use symbolic forms and others don't. Although it is possible that students simply lack the knowledge required, I argue that this is not the only explanation. Rather, symbolic forms use is connected to particular epistemological stances, in-the-moment views on what kinds of knowledge and reasoning are appropriate in physics. Specifically, stances that value coherence between formal, mathematical knowledge and intuitive, conceptual knowledge are likely to support symbolic forms use. Through the case study of one student, I argue that both reasoning with equations and epistemological stances are dynamic, and that shifts in epistemological stance can produce shifts in whether symbolic forms are used to reason with equations. The third study expands the focus to what influences how students reason with equations across disciplinary problem contexts. In seeking to understand differences in how the same student reasons on two similar problems in calculus and physics, I show two factors, beyond the content or structure of the problems, that can help explain why reasoning on these two problems would be so different. This contributes to an understanding of what can support or impede transfer of content knowledge across disciplinary boundaries.

Spot urine sodium measurements do not accurately estimate dietary sodium intake in chronic kidney disease12

PubMed Central

Dougher, Carly E; Rifkin, Dena E; Anderson, Cheryl AM; Smits, Gerard; Persky, Martha S; Block, Geoffrey A; Ix, Joachim H

2016-01-01

Background: Sodium intake influences blood pressure and proteinuria, yet the impact on long-term outcomes is uncertain in chronic kidney disease (CKD). Accurate assessment is essential for clinical and public policy recommendations, but few large-scale studies use 24-h urine collections. Recent studies that used spot urine sodium and associated estimating equations suggest that they may provide a suitable alternative, but their accuracy in patients with CKD is unknown. Objective: We compared the accuracy of 4 equations [the Nerbass, INTERSALT (International Cooperative Study on Salt, Other Factors, and Blood Pressure), Tanaka, and Kawasaki equations] that use spot urine sodium to estimate 24-h sodium excretion in patients with moderate to advanced CKD. Design: We evaluated the accuracy of spot urine sodium to predict mean 24-h urine sodium excretion over 9 mo in 129 participants with stage 3–4 CKD. Spot morning urine sodium was used in 4 estimating equations. Bias, precision, and accuracy were assessed and compared across each equation. Results: The mean age of the participants was 67 y, 52% were female, and the mean estimated glomerular filtration rate was 31 ± 9 mL · min–1 · 1.73 m–2. The mean ± SD number of 24-h urine collections was 3.5 ± 0.8/participant, and the mean 24-h sodium excretion was 168.2 ± 67.5 mmol/d. Although the Tanaka equation demonstrated the least bias (mean: −8.2 mmol/d), all 4 equations had poor precision and accuracy. The INTERSALT equation demonstrated the highest accuracy but derived an estimate only within 30% of mean measured sodium excretion in only 57% of observations. Bland-Altman plots revealed systematic bias with the Nerbass, INTERSALT, and Tanaka equations, underestimating sodium excretion when intake was high. Conclusion: These findings do not support the use of spot urine specimens to estimate dietary sodium intake in patients with CKD and research studies enriched with patients with CKD. The parent data for this study come from a clinical trial that was registered at clinicaltrials.gov as NCT00785629. PMID:27357090

Spot urine sodium measurements do not accurately estimate dietary sodium intake in chronic kidney disease.

PubMed

Dougher, Carly E; Rifkin, Dena E; Anderson, Cheryl Am; Smits, Gerard; Persky, Martha S; Block, Geoffrey A; Ix, Joachim H

2016-08-01

Sodium intake influences blood pressure and proteinuria, yet the impact on long-term outcomes is uncertain in chronic kidney disease (CKD). Accurate assessment is essential for clinical and public policy recommendations, but few large-scale studies use 24-h urine collections. Recent studies that used spot urine sodium and associated estimating equations suggest that they may provide a suitable alternative, but their accuracy in patients with CKD is unknown. We compared the accuracy of 4 equations [the Nerbass, INTERSALT (International Cooperative Study on Salt, Other Factors, and Blood Pressure), Tanaka, and Kawasaki equations] that use spot urine sodium to estimate 24-h sodium excretion in patients with moderate to advanced CKD. We evaluated the accuracy of spot urine sodium to predict mean 24-h urine sodium excretion over 9 mo in 129 participants with stage 3-4 CKD. Spot morning urine sodium was used in 4 estimating equations. Bias, precision, and accuracy were assessed and compared across each equation. The mean age of the participants was 67 y, 52% were female, and the mean estimated glomerular filtration rate was 31 ± 9 mL · min(-1) · 1.73 m(-2) The mean ± SD number of 24-h urine collections was 3.5 ± 0.8/participant, and the mean 24-h sodium excretion was 168.2 ± 67.5 mmol/d. Although the Tanaka equation demonstrated the least bias (mean: -8.2 mmol/d), all 4 equations had poor precision and accuracy. The INTERSALT equation demonstrated the highest accuracy but derived an estimate only within 30% of mean measured sodium excretion in only 57% of observations. Bland-Altman plots revealed systematic bias with the Nerbass, INTERSALT, and Tanaka equations, underestimating sodium excretion when intake was high. These findings do not support the use of spot urine specimens to estimate dietary sodium intake in patients with CKD and research studies enriched with patients with CKD. The parent data for this study come from a clinical trial that was registered at clinicaltrials.gov as NCT00785629. © 2016 American Society for Nutrition.

Meta-Analytic Structural Equation Modeling (MASEM): Comparison of the Multivariate Methods

ERIC Educational Resources Information Center

Zhang, Ying

2011-01-01

Meta-analytic Structural Equation Modeling (MASEM) has drawn interest from many researchers recently. In doing MASEM, researchers usually first synthesize correlation matrices across studies using meta-analysis techniques and then analyze the pooled correlation matrix using structural equation modeling techniques. Several multivariate methods of…

A lower bound on the solutions of Kapustin-Witten equations

NASA Astrophysics Data System (ADS)

Huang, Teng

2016-11-01

In this article, we consider the Kapustin-Witten equations on a closed four-manifold. We study certain analytic properties of solutions to the equations on a closed manifold. The main result is that there exists an L2 -lower bound on the extra fields over a closed four-manifold satisfying certain conditions if the connections are not ASD connections. Furthermore, we also obtain a similar result about the Vafa-Witten equations.

Use of Jackknifing to Evaluate Effects of Anchor Item Selection on Equating with the Nonequivalent Groups with Anchor Test (NEAT) Design. Research Report. ETS RR-15-10

ERIC Educational Resources Information Center

Lu, Ru; Haberman, Shelby; Guo, Hongwen; Liu, Jinghua

2015-01-01

In this study, we apply jackknifing to anchor items to evaluate the impact of anchor selection on equating stability. In an ideal world, the choice of anchor items should have little impact on equating results. When this ideal does not correspond to reality, selection of anchor items can strongly influence equating results. This influence does not…

Study of coupled nonlinear partial differential equations for finding exact analytical solutions.

PubMed

Khan, Kamruzzaman; Akbar, M Ali; Koppelaar, H

2015-07-01

Exact solutions of nonlinear partial differential equations (NPDEs) are obtained via the enhanced (G'/G)-expansion method. The method is subsequently applied to find exact solutions of the Drinfel'd-Sokolov-Wilson (DSW) equation and the (2+1)-dimensional Painlevé integrable Burgers (PIB) equation. The efficiency of this method for finding these exact solutions is demonstrated. The method is effective and applicable for many other NPDEs in mathematical physics.

Cystatin C-based glomerular filtration rate associates more closely with mortality than creatinine-based or combined glomerular filtration rate equations in unselected patients.

PubMed

Helmersson-Karlqvist, Johanna; Ärnlöv, Johan; Larsson, Anders

2016-10-01

Decreased glomerular filtration rate (GFR) is an important cardiovascular risk factor, but estimated GFR (eGFR) may differ depending on whether it is based on creatinine or cystatin C. A combined creatinine/cystatin C equation has recently been shown to best estimate GFR; however, the benefits of using the combined equation for risk prediction in routine clinical care have been less studied. This study compares mortality risk prediction by eGFR using the combined creatinine/cystatin C equation (CKD-EPI), a sole creatinine equation (CKD-EPI) and a sole cystatin C equation (CAPA), respectively, using assays that are traceable to international calibrators. All patients analysed for both creatinine and cystatin C from the same blood sample tube (n = 13,054) during 2005-2007 in Uppsala University Hospital Laboratory were divided into eGFR risk categories>60, 30-60 and <30 mL/min/1.73 m(2) by each eGFR equation. During follow-up (median 4.6 years), 4398 participants died, of which 1396 deaths were due to cardiovascular causes. Reduced eGFR was significantly associated with death as assessed by all eGFR equations. The net reclassification improvement (NRI) for the combination equation compared with the sole creatinine equation was 0.10 (p < 0.001) for all-cause mortality and 0.08 (p < 0.001) for cardiovascular mortality, indicating improved reclassification. In contrast, NRI for the combination equation, compared with the sole cystatin C equation, was -0.06 (p < 0.001) for all-cause mortality and -0.02 (p = 0.032) for cardiovascular mortality, indicating a worsened reclassification. In routine clinical care, cystatin C-based eGFR was more closely associated with mortality compared with both creatinine-based eGFR and creatinine/cystatin C-based eGFR. © The European Society of Cardiology 2016.

Long-time behavior for suspension bridge equations with time delay

NASA Astrophysics Data System (ADS)

Park, Sun-Hye

2018-04-01

In this paper, we consider suspension bridge equations with time delay of the form u_{tt}(x,t) + Δ ^2 u (x,t) + k u^+ (x,t) + a_0 u_t (x,t) + a_1 u_t (x, t- τ ) + f(u(x,t)) = g(x). Many researchers have studied well-posedness, decay rates of energy, and existence of attractors for suspension bridge equations without delay effects. But, as far as we know, there is no work about suspension equations with time delay. In addition, there are not many studies on attractors for other delayed systems. Thus we first provide well-posedness for suspension equations with time delay. And then show the existence of global attractors and the finite dimensionality of the attractors by establishing energy functionals which are related to the norm of the phase space to our problem.

Maximum Likelihood and Restricted Likelihood Solutions in Multiple-Method Studies

PubMed Central

Rukhin, Andrew L.

2011-01-01

A formulation of the problem of combining data from several sources is discussed in terms of random effects models. The unknown measurement precision is assumed not to be the same for all methods. We investigate maximum likelihood solutions in this model. By representing the likelihood equations as simultaneous polynomial equations, the exact form of the Groebner basis for their stationary points is derived when there are two methods. A parametrization of these solutions which allows their comparison is suggested. A numerical method for solving likelihood equations is outlined, and an alternative to the maximum likelihood method, the restricted maximum likelihood, is studied. In the situation when methods variances are considered to be known an upper bound on the between-method variance is obtained. The relationship between likelihood equations and moment-type equations is also discussed. PMID:26989583

Maximum Likelihood and Restricted Likelihood Solutions in Multiple-Method Studies.

PubMed

Rukhin, Andrew L

2011-01-01

A formulation of the problem of combining data from several sources is discussed in terms of random effects models. The unknown measurement precision is assumed not to be the same for all methods. We investigate maximum likelihood solutions in this model. By representing the likelihood equations as simultaneous polynomial equations, the exact form of the Groebner basis for their stationary points is derived when there are two methods. A parametrization of these solutions which allows their comparison is suggested. A numerical method for solving likelihood equations is outlined, and an alternative to the maximum likelihood method, the restricted maximum likelihood, is studied. In the situation when methods variances are considered to be known an upper bound on the between-method variance is obtained. The relationship between likelihood equations and moment-type equations is also discussed.

A comparative study of two codes with an improved two-equation turbulence model for predicting jet plumes

NASA Technical Reports Server (NTRS)

Balakrishnan, L.; Abdol-Hamid, Khaled S.

1992-01-01

Compressible jet plumes were studied using a two-equation turbulence model. A space marching procedure based on an upwind numerical scheme was used to solve the governing equations and turbulence transport equations. The computed results indicate that extending the space marching procedure for solving supersonic/subsonic mixing problems can be stable, efficient and accurate. Moreover, a newly developed correction for compressible dissipation has been verified in fully expanded and underexpanded jet plumes. For a sonic jet plume, no improvement in results over the standard two-equation model was seen. However for a supersonic jet plume, the correction due to compressible dissipation successfully predicted the reduced spreading rate of the jet compared to the sonic case. The computed results were generally in good agreement with the experimental data.

Studies of Coherent Synchrotron Radiation with the Discontinuous Galerkin Method

NASA Astrophysics Data System (ADS)

Bizzozero, David A.

In this thesis, we present methods for integrating Maxwell's equations in Frenet-Serret coordinates in several settings using discontinuous Galerkin (DG) finite element method codes in 1D, 2D, and 3D. We apply these routines to the study of coherent synchrotron radiation, an important topic in accelerator physics. We build upon the published computational work of T. Agoh and D. Zhou in solving Maxwell's equations in the frequency-domain using a paraxial approximation which reduces Maxwell's equations to a Schrodinger-like system. We also evolve Maxwell's equations in the time-domain using a Fourier series decomposition with 2D DG motivated by an experiment performed at the Canadian Light Source. A comparison between theory and experiment has been published (Phys. Rev. Lett. 114, 204801 (2015)). Lastly, we devise a novel approach to integrating Maxwell's equations with 3D DG using a Galilean transformation and demonstrate proof-of-concept. In the above studies, we examine the accuracy, efficiency, and convergence of DG.

On the transition from the Ginzburg-Landau equation to the extended Fisher-Kolmogorov equation

NASA Astrophysics Data System (ADS)

Rottschäfer, Vivi; Doelman, Arjen

1998-07-01

The Ginzburg-Landau (GL) equation ‘generically’ describes the behaviour of small perturbations of a marginally unstable basic state in systems on unbounded domains. In this paper we consider the transition from this generic situation to a degenerate (co-dimension 2) case in which the GL approach is no longer valid. Instead of studying a general underlying model problem, we consider a two-dimensional system of coupled reaction-diffusion equations in one spatial dimension. We show that near the degeneration the behaviour of small perturbations is governed by the extended Fisher-Kolmogorov (eFK) equation (at leading order). The relation between the GL-equation and the eFK-equation is quite subtle, but can be analysed in detail. The main goal of this paper is to study this relation, which we do asymptotically. The asymptotic analysis is compared to numerical simulations of the full reaction-diffusion system. As one approaches the co-dimension 2 point, we observe that the stable stationary periodic patterns predicted by the GL-equation evolve towards various different families of stable, stationary (but not necessarily periodic) so-called ‘multi-bump’ solutions. In the literature, these multi-bump patterns are shown to exist as solutions of the eFK-equation, but there is no proof of the asymptotic stability of these solutions. Our results suggest that these multi-bump patterns can also be asymptotically stable in large classes of model problems.

A three-dimensional, finite element model for coastal and estuarine circulation

USGS Publications Warehouse

Walters, R.A.

1992-01-01

This paper describes the development and application of a three-dimensional model for coastal and estuarine circulation. The model uses a harmonic expansion in time and a finite element discretization in space. All nonlinear terms are retained, including quadratic bottom stress, advection and wave transport (continuity nonlinearity). The equations are solved as a global and a local problem, where the global problem is the solution of the wave equation formulation of the shallow water equations, and the local problem is the solution of the momentum equation for the vertical velocity profile. These equations are coupled to the advection-diffusion equation for salt so that density gradient forcing is included in the momentum equations. The model is applied to a study of Delaware Bay, U.S.A., where salinity intrusion is the primary focus. ?? 1991.

Dirac and Klein-Gordon-Fock equations in Grumiller’s spacetime

NASA Astrophysics Data System (ADS)

Al-Badawi, A.; Sakalli, I.

We study the Dirac and the chargeless Klein-Gordon-Fock equations in the geometry of Grumiller’s spacetime that describes a model for gravity of a central object at large distances. The Dirac equation is separated into radial and angular equations by adopting the Newman-Penrose formalism. The angular part of the both wave equations are analytically solved. For the radial equations, we managed to reduce them to one dimensional Schrödinger-type wave equations with their corresponding effective potentials. Fermions’s potentials are numerically analyzed by serving their some characteristic plots. We also compute the quasinormal frequencies of the chargeless and massive scalar waves. With the aid of those quasinormal frequencies, Bekenstein’s area conjecture is tested for the Grumiller black hole. Thus, the effects of the Rindler acceleration on the waves of fermions and scalars are thoroughly analyzed.

Symmetry classification of time-fractional diffusion equation

NASA Astrophysics Data System (ADS)

Naeem, I.; Khan, M. D.

2017-01-01

In this article, a new approach is proposed to construct the symmetry groups for a class of fractional differential equations which are expressed in the modified Riemann-Liouville fractional derivative. We perform a complete group classification of a nonlinear fractional diffusion equation which arises in fractals, acoustics, control theory, signal processing and many other applications. Introducing the suitable transformations, the fractional derivatives are converted to integer order derivatives and in consequence the nonlinear fractional diffusion equation transforms to a partial differential equation (PDE). Then the Lie symmetries are computed for resulting PDE and using inverse transformations, we derive the symmetries for fractional diffusion equation. All cases are discussed in detail and results for symmetry properties are compared for different values of α. This study provides a new way of computing symmetries for a class of fractional differential equations.

General existence principles for Stieltjes differential equations with applications to mathematical biology

NASA Astrophysics Data System (ADS)

López Pouso, Rodrigo; Márquez Albés, Ignacio

2018-04-01

Stieltjes differential equations, which contain equations with impulses and equations on time scales as particular cases, simply consist on replacing usual derivatives by derivatives with respect to a nondecreasing function. In this paper we prove new existence results for functional and discontinuous Stieltjes differential equations and we show that such general results have real world applications. Specifically, we show that Stieltjes differential equations are specially suitable to study populations which exhibit dormant states and/or very short (impulsive) periods of reproduction. In particular, we construct two mathematical models for the evolution of a silkworm population. Our first model can be explicitly solved, as it consists on a linear Stieltjes equation. Our second model, more realistic, is nonlinear, discontinuous and functional, and we deduce the existence of solutions by means of a result proven in this paper.

Receptor binding kinetics equations: Derivation using the Laplace transform method.

PubMed

Hoare, Sam R J

Measuring unlabeled ligand receptor binding kinetics is valuable in optimizing and understanding drug action. Unfortunately, deriving equations for estimating kinetic parameters is challenging because it involves calculus; integration can be a frustrating barrier to the pharmacologist seeking to measure simple rate parameters. Here, a well-known tool for simplifying the derivation, the Laplace transform, is applied to models of receptor-ligand interaction. The method transforms differential equations to a form in which simple algebra can be applied to solve for the variable of interest, for example the concentration of ligand-bound receptor. The goal is to provide instruction using familiar examples, to enable investigators familiar with handling equilibrium binding equations to derive kinetic equations for receptor-ligand interaction. First, the Laplace transform is used to derive the equations for association and dissociation of labeled ligand binding. Next, its use for unlabeled ligand kinetic equations is exemplified by a full derivation of the kinetics of competitive binding equation. Finally, new unlabeled ligand equations are derived using the Laplace transform. These equations incorporate a pre-incubation step with unlabeled or labeled ligand. Four equations for measuring unlabeled ligand kinetics were compared and the two new equations verified by comparison with numerical solution. Importantly, the equations have not been verified with experimental data because no such experiments are evident in the literature. Equations were formatted for use in the curve-fitting program GraphPad Prism 6.0 and fitted to simulated data. This description of the Laplace transform method will enable pharmacologists to derive kinetic equations for their model or experimental paradigm under study. Application of the transform will expand the set of equations available for the pharmacologist to measure unlabeled ligand binding kinetics, and for other time-dependent pharmacological activities. Copyright © 2017 Elsevier Inc. All rights reserved.

Emergence and analysis of Kuramoto-Sakaguchi-like models as an effective description for the dynamics of coupled Wien-bridge oscillators.

PubMed

English, L Q; Mertens, David; Abdoulkary, Saidou; Fritz, C B; Skowronski, K; Kevrekidis, P G

2016-12-01

We derive the Kuramoto-Sakaguchi model from the basic circuit equations governing two coupled Wien-bridge oscillators. A Wien-bridge oscillator is a particular realization of a tunable autonomous oscillator that makes use of frequency filtering (via an RC bandpass filter) and positive feedback (via an operational amplifier). In the past few years, such oscillators have started to be utilized in synchronization studies. We first show that the Wien-bridge circuit equations can be cast in the form of a coupled pair of van der Pol equations. Subsequently, by applying the method of multiple time scales, we derive the differential equations that govern the slow evolution of the oscillator phases and amplitudes. These equations are directly reminiscent of the Kuramoto-Sakaguchi-type models for the study of synchronization. We analyze the resulting system in terms of the existence and stability of various coupled oscillator solutions and explain on that basis how their synchronization emerges. The phase-amplitude equations are also compared numerically to the original circuit equations and good agreement is found. Finally, we report on experimental measurements of two coupled Wien-bridge oscillators and relate the results to the theoretical predictions.

Measurement and correlation of the solubility of gossypol acetic acid and gossypol acetic acid of optical activity in different solvents

NASA Astrophysics Data System (ADS)

Zhang, B.; Tang, H.; Liu, X. Y.; Zhai, X.; Yao, X. C.

2018-01-01

The equilibrium method was used to measure the solubility of gossypol acetic acid and gossypol acetic acid of optical activity in isopropyl alcohol, ethanol, acetic acid and ethyl acetate at temperature from 288.15 to 315.15. The Empirical equation and the Apelblat equation model were adopted to correlate the experimental data. For gossypol acetic acid, the root-mean-square deviations (RMSD) were observed in the range of 0.023-4.979 and 0.0112-0.614 for the Empirical equation and the Apelblat equation, respectively. For gossypol acetic acid of optical activity, the RMSD were observed in the range of 0.021-2.211 and 0.021-2.243 for the Empirical equation and the Apelblat equation, individually. And the maximum relative average deviation was 7.5%. Both equations offered an accurate mathematical expression of the experimental results. The calculated solubility showed a good relationship with the experimental solubility for most of solvents. This study provided valuable datas not only for optimizing the process of purification of gossypol acetic acid of optical activity in industry but also for further theoretical studies.

The construction of partner potential from the general potential Rosen-Morse and Manning Rosen in 4 dimensional Schrodinger system

NASA Astrophysics Data System (ADS)

Nathalia Wea, Kristiana; Suparmi, A.; Cari, C.; Wahyulianti

2017-11-01

The solution of the Schrodinger equation with physical potential is the important part in quantum physics. Many methods have been developed to resolve the Schrodinger equation. The Nikiforov-Uvarov method and supersymmetric method are the most methods that interesting to be explored. The supersymmetric method not only used to solve the Schrodinger equation but also used to construct the partner potential from a general potential. In this study, the Nikiforov-Uvarov method was used to solve the Schrodinger equation while the supersymmetric method was used to construction partner potential. The study about the construction of the partner potential from general potential Rosen-Morse and Manning Rosen in D-dimensional Schrodinger system has been done. The partner potential was obtained are solvable. By using the Nikiforov-Uvarov method the eigenfunction of the Schrodinger equation in D-dimensional system with general potential Rosen-Morse and Manning Rosen and the Schrodinger equation in D-dimensional system with partner potential Rosen-Morse and Manning Rosen are determined. The eigenfunctions are different between the Schrodinger equation with general potential and the Schrodinger potential with the partner potential.

Measurement of testicular volume in smaller testes: how accurate is the conventional orchidometer?

PubMed

Lin, Chih-Chieh; Huang, William J S; Chen, Kuang-Kuo

2009-01-01

The aim of this study was to evaluate the accuracy of different methods, including the Seager orchidometer (SO) and ultrasonography (US), for assessing testicular volume of smaller testes (testes volume less than 18 mL). Moreover, the equations used for the calculations--the Hansen formula (length [L] x width [W](2) x 0.52, equation A), the prolate ellipsoid formula (L x W x height [H] x 0.52, equation B), and the Lambert equation (L x W x H x 0.71, equation C)--were also examined and compared with the gold standard testicular volume obtained by water displacement (Archimedes principle). In this study, 30 testes from 15 men, mean age 75.3 (+/-8.3) years, were included. They all had advanced prostate cancer and were admitted for orchiectomy. Before the procedure, all the testes were assessed using SO and US. The dimensions were then input into each equation to obtain the volume estimates. The testicular volume by water displacement was 8.1 +/- 3.5 mL. Correlation coefficients (R(2)) of the 2 different methods (SO, US) to the gold standard were 0.70 and 0.85, respectively. The calculated testicular volumes were 9.2 +/- 3.9 mL (measured by SO, equation A), 11.9 +/- 5.2 mL (measured by SO, equation C), 7.3 +/- 4.2 mL (measured by US, equation A), 6.5 +/- 3.3 mL (measured by US, equation B) and 8.9 +/- 4.5 mL (measured by US, equation C). Only the mean size measured by US and volume calculated with the Hansen equation (equation A) and the mean size measured by US and volume calculated with the Lambert equation (equation C) showed no significant differences when compared with the volumes estimated by water displacement (mean difference 0.81 mL, P = .053, and 0.81 mL, P = .056, respectively). Based on our measurements, we categorized testicular volume by different cutoff values (7.0 mL, 7.5 mL, 8.0 mL, and 8.5 mL) to calculate a new constant for use in the Hansen equation. The new constant was 0.59. We then reexamined the equations using the new 0.59 constant, and found that the equation Volume (V) = L x W(2) x 0.59 was the best for describing testicular volume among our subjects (difference between the new equation and the gold standard of water displacement = 0.19 mL, P = .726). We also found that US was more precise in measuring testicular dimensions. We propose a new formula, V = L x W(2) x 0.59, to assess the volumes of smaller testes.

Predictive equations for total lung capacity and residual volume calculated from radiographs in a random sample of the Michigan population.

PubMed Central

Kilburn, K H; Warshaw, R H; Thornton, J C; Thornton, K; Miller, A

1992-01-01

BACKGROUND: Published predicted values for total lung capacity and residual volume are often based on a small number of subjects and derive from different populations from predicted spirometric values. Equations from the only two large studies gave smaller predicted values for total lung capacity than the smaller studies. A large number of subjects have been studied from a population which has already provided predicted values for spirometry and transfer factor for carbon monoxide. METHODS: Total lung capacity was measured from standard posteroanterior and lateral chest radiographs and forced vital capacity by spirometry in a population sample of 771 subjects. Prediction equations were developed for total lung capacity (TLC), residual volume (RV) and RV/TLC in two groups--normal and total. Subjects with signs or symptoms of cardiopulmonary disease were combined with the normal subjects and equations for all subjects were also modelled. RESULTS: Prediction equations for TLC and RV in non-smoking normal men and women were square root transformations which included height and weight but not age. They included a coefficient for duration of smoking in current smokers. The predictive equation for RV/TLC included weight, age, age and duration of smoking for current smokers and ex-smokers of both sexes. For the total population the equations took the same form but the height coefficients and constants were slightly different. CONCLUSION: These population based prediction equations for TLC, RV and RV/TLC provide reference standards in a population that has provided reference standards for spirometry and single breath transfer factor for carbon monoxide. PMID:1412094

U(1)-invariant membranes: The geometric formulation, Abel, and pendulum differential equations

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

Zheltukhin, A. A.; Fysikum, AlbaNova, Stockholm University, 106 91 Stockholm; NORDITA, Roslagstullsbacken 23, 106 91 Stockholm

The geometric approach to study the dynamics of U(1)-invariant membranes is developed. The approach reveals an important role of the Abel nonlinear differential equation of the first type with variable coefficients depending on time and one of the membrane extendedness parameters. The general solution of the Abel equation is constructed. Exact solutions of the whole system of membrane equations in the D=5 Minkowski space-time are found and classified. It is shown that if the radial component of the membrane world vector is only time dependent, then the dynamics is described by the pendulum equation.

The KP Approximation Under a Weak Coriolis Forcing

NASA Astrophysics Data System (ADS)

Melinand, Benjamin

2018-02-01

In this paper, we study the asymptotic behavior of weakly transverse water-waves under a weak Coriolis forcing in the long wave regime. We derive the Boussinesq-Coriolis equations in this setting and we provide a rigorous justification of this model. Then, from these equations, we derive two other asymptotic models. When the Coriolis forcing is weak, we fully justify the rotation-modified Kadomtsev-Petviashvili equation (also called Grimshaw-Melville equation). When the Coriolis forcing is very weak, we rigorously justify the Kadomtsev-Petviashvili equation. This work provides the first mathematical justification of the KP approximation under a Coriolis forcing.

A note on the solutions of some nonlinear equations arising in third-grade fluid flows: an exact approach.

PubMed

Aziz, Taha; Mahomed, F M

2014-01-01

In this communication, we utilize some basic symmetry reductions to transform the governing nonlinear partial differential equations arising in the study of third-grade fluid flows into ordinary differential equations. We obtain some simple closed-form steady-state solutions of these reduced equations. Our solutions are valid for the whole domain [0,∞) and also satisfy the physical boundary conditions. We also present the numerical solutions for some of the underlying equations. The graphs corresponding to the essential physical parameters of the flow are presented and discussed.

An algorithm for solving an arbitrary triangular fully fuzzy Sylvester matrix equations

NASA Astrophysics Data System (ADS)

Daud, Wan Suhana Wan; Ahmad, Nazihah; Malkawi, Ghassan

2017-11-01

Sylvester matrix equations played a prominent role in various areas including control theory. Considering to any un-certainty problems that can be occurred at any time, the Sylvester matrix equation has to be adapted to the fuzzy environment. Therefore, in this study, an algorithm for solving an arbitrary triangular fully fuzzy Sylvester matrix equation is constructed. The construction of the algorithm is based on the max-min arithmetic multiplication operation. Besides that, an associated arbitrary matrix equation is modified in obtaining the final solution. Finally, some numerical examples are presented to illustrate the proposed algorithm.

Integrability and structural stability of solutions to the Ginzburg-Landau equation

NASA Technical Reports Server (NTRS)

Keefe, Laurence R.

1986-01-01

The integrability of the Ginzburg-Landau equation is studied to investigate if the existence of chaotic solutions found numerically could have been predicted a priori. The equation is shown not to possess the Painleveproperty, except for a special case of the coefficients that corresponds to the integrable, nonlinear Schroedinger (NLS) equation. Regarding the Ginzburg-Landau equation as a dissipative perturbation of the NLS, numerical experiments show all but one of a family of two-tori solutions, possessed by the NLS under particular conditions, to disappear under real perturbations to the NLS coefficients of O(10 to the -6th).

On solutions of the fifth-order dispersive equations with porous medium type non-linearity

NASA Astrophysics Data System (ADS)

Kocak, Huseyin; Pinar, Zehra

2018-07-01

In this work, we focus on obtaining the exact solutions of the fifth-order semi-linear and non-linear dispersive partial differential equations, which have the second-order diffusion-like (porous-type) non-linearity. The proposed equations were not studied in the literature in the sense of the exact solutions. We reveal solutions of the proposed equations using the classical Riccati equations method. The obtained exact solutions, which can play a key role to simulate non-linear waves in the medium with dispersion and diffusion, are illustrated and discussed in details.

A Note on the Solutions of Some Nonlinear Equations Arising in Third-Grade Fluid Flows: An Exact Approach

PubMed Central

Mahomed, F. M.

2014-01-01

In this communication, we utilize some basic symmetry reductions to transform the governing nonlinear partial differential equations arising in the study of third-grade fluid flows into ordinary differential equations. We obtain some simple closed-form steady-state solutions of these reduced equations. Our solutions are valid for the whole domain [0,∞) and also satisfy the physical boundary conditions. We also present the numerical solutions for some of the underlying equations. The graphs corresponding to the essential physical parameters of the flow are presented and discussed. PMID:25143962

Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review.

PubMed

Frankenfield, David; Roth-Yousey, Lori; Compher, Charlene

2005-05-01

An assessment of energy needs is a necessary component in the development and evaluation of a nutrition care plan. The metabolic rate can be measured or estimated by equations, but estimation is by far the more common method. However, predictive equations might generate errors large enough to impact outcome. Therefore, a systematic review of the literature was undertaken to document the accuracy of predictive equations preliminary to deciding on the imperative to measure metabolic rate. As part of a larger project to determine the role of indirect calorimetry in clinical practice, an evidence team identified published articles that examined the validity of various predictive equations for resting metabolic rate (RMR) in nonobese and obese people and also in individuals of various ethnic and age groups. Articles were accepted based on defined criteria and abstracted using evidence analysis tools developed by the American Dietetic Association. Because these equations are applied by dietetics practitioners to individuals, a key inclusion criterion was research reports of individual data. The evidence was systematically evaluated, and a conclusion statement and grade were developed. Four prediction equations were identified as the most commonly used in clinical practice (Harris-Benedict, Mifflin-St Jeor, Owen, and World Health Organization/Food and Agriculture Organization/United Nations University [WHO/FAO/UNU]). Of these equations, the Mifflin-St Jeor equation was the most reliable, predicting RMR within 10% of measured in more nonobese and obese individuals than any other equation, and it also had the narrowest error range. No validation work concentrating on individual errors was found for the WHO/FAO/UNU equation. Older adults and US-residing ethnic minorities were underrepresented both in the development of predictive equations and in validation studies. The Mifflin-St Jeor equation is more likely than the other equations tested to estimate RMR to within 10% of that measured, but noteworthy errors and limitations exist when it is applied to individuals and possibly when it is generalized to certain age and ethnic groups. RMR estimation errors would be eliminated by valid measurement of RMR with indirect calorimetry, using an evidence-based protocol to minimize measurement error. The Expert Panel advises clinical judgment regarding when to accept estimated RMR using predictive equations in any given individual. Indirect calorimetry may be an important tool when, in the judgment of the clinician, the predictive methods fail an individual in a clinically relevant way. For members of groups that are greatly underrepresented by existing validation studies of predictive equations, a high level of suspicion regarding the accuracy of the equations is warranted.

Development of control systems for space shuttle vehicles. Volume 2: Appendixes

NASA Technical Reports Server (NTRS)

Stone, C. R.; Chase, T. W.; Kiziloz, B. M.; Ward, M. D.

1971-01-01

A launch phase random normal wind model is presented for delta wing, two-stage, space shuttle control system studies. Equations, data, and simulations for conventional launch studies are given as well as pitch and lateral equations and data for covariance analyses of the launch phase of MSFC vehicle B. Lateral equations and data for North American 130G and 134D are also included along with a high-altitude abort simulation.

Numerical study of radiometric forces via the direct solution of the Boltzmann kinetic equation

NASA Astrophysics Data System (ADS)

Anikin, Yu. A.

2011-07-01

The two-dimensional rarefied gas motion in a Crookes radiometer and the resulting radiometric forces are studied by numerically solving the Boltzmann kinetic equation. The collision integral is directly evaluated using a projection method, and second-order accurate TVD schemes are used to solve the advection equation. The radiometric forces are found as functions of the Knudsen number and the temperatures, and their spatial distribution is analyzed.

The Accuracy of Anthropometric Equations to Assess Body Fat in Adults with Down Syndrome

ERIC Educational Resources Information Center

Rossato, Mateus; Dellagrana, Rodolfo André; da Costa, Rafael Martins; de Souza Bezerra, Ewertton; dos Santos, João Otacílio Libardoni; Rech, Cassiano Ricardo

2018-01-01

Background: The aim of this study was to verify the accuracy of anthropometric equations to estimate the body density (BD) of adults with Down syndrome (DS), and propose new regression equations. Materials and methods: Twenty-one males (30.5 ± 9.4 years) and 17 females (27.3 ± 7.7 years) with DS participated in this study. The reference method for…

Observed Score Equating Using a Mini-Version Anchor and an Anchor with Less Spread of Difficulty: A Comparison Study

ERIC Educational Resources Information Center

Liu, Jinghua; Sinharay, Sandip; Holland, Paul; Feigenbaum, Miriam; Curley, Edward

2011-01-01

Two different types of anchors are investigated in this study: a mini-version anchor and an anchor that has a less spread of difficulty than the tests to be equated. The latter is referred to as a midi anchor. The impact of these two different types of anchors on observed score equating are evaluated and compared with respect to systematic error…

Non-Abelian Berry phase, instantons, and N=(0,4) supersymmetry

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

Laia, Joao N.

2010-12-15

In supersymmetric quantum mechanics, the non-Abelian Berry phase is known to obey certain differential equations. Here we study N=(0,4) systems and show that the non-Abelian Berry connection over R{sup 4n} satisfies a generalization of the self-dual Yang-Mills equations. Upon dimensional reduction, these become the tt* equations. We further study the Berry connection in N=(4,4) theories and show that the curvature is covariantly constant.

The Effect of Tutoring with Nonstandard Equations for Students with Mathematics Difficulty

ERIC Educational Resources Information Center

Powell, Sarah R.; Driver, Melissa K.; Julian, Tyler E.

2015-01-01

Students often misinterpret the equal sign (=) as operational instead of relational. Research indicates misinterpretation of the equal sign occurs because students receive relatively little exposure to equations that promote relational understanding of the equal sign. No study, however, has examined effects of nonstandard equations on the equation…

Effect of Differential Item Functioning on Test Equating

ERIC Educational Resources Information Center

Kabasakal, Kübra Atalay; Kelecioglu, Hülya

2015-01-01

This study examines the effect of differential item functioning (DIF) items on test equating through multilevel item response models (MIRMs) and traditional IRMs. The performances of three different equating models were investigated under 24 different simulation conditions, and the variables whose effects were examined included sample size, test…

IRT Equating of the MCAT. MCAT Monograph.

ERIC Educational Resources Information Center

Hendrickson, Amy B.; Kolen, Michael J.

This study compared various equating models and procedures for a sample of data from the Medical College Admission Test(MCAT), considering how item response theory (IRT) equating results compare with classical equipercentile results and how the results based on use of various IRT models, observed score versus true score, direct versus linked…