GFR Estimation in Adolescents and Young Adults (original) (raw)
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GFR Prediction From Cystatin C and Creatinine in Children: Effect of Including Body Cell Mass
American Journal of Kidney Diseases, 2012
Background: Aiming to develop a more accurate cystatin C-based model for estimation of glomerular filtration rate (GFR) in children, we hypothesized that inclusion of body cell mass (BCM) would increase the accuracy of the GFR estimate in comparison to a well-established GFR reference method. Study Design: Diagnostic test accuracy study. Settings & Participants: 119 children (mean age, 8.8; range, 2.3-14.9 years) referred for GFR measurement by chromium 51 ethylenediaminetetraacetic acid ( 51 Cr-EDTA) clearance (mean GFR, 98; range, 13.7-147.4 mL/min/1.73 m 2 ).
American Journal of Kidney Diseases, 2013
Background: Glomerular filtration rate (GFR) is a measure of kidney function, commonly estimated using equations that adjust serum creatinine concentration for age, race, and sex. The Modification of Diet in Renal Disease (MDRD) Study equation is widely used, but underestimates GFR at higher levels. The serum creatinine-based Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI cr) equation generally provides more accurate estimation at GFR Ͼ60 mL/min/1.73 m 2. Newer equations have been reported using cystatin C concentration either alone (CKD-EPI cys) or in combination with creatinine concentration (CKD-EPI cr-cys). None of these equations has been well validated in older people. We tested the accuracy of these equations in people 74 years or older compared with GFR measured by a reference method. Study Design: Diagnostic test evaluation in a prospective cohort. Setting & Participants: Participants (n ϭ 394; median age, 80 [range, 74-97] years) recruited from nephrology clinics and the community. Index Test: GFR estimated using the MDRD Study, CKD-EPI cr , CKD-EPI cys and CKD-EPI cr-cys equations. Reference Test: GFR measured using an iohexol clearance method. Results: Median measured GFR was 53.4 (range, 7.2-100.9) mL/min/1.73 m 2. MDRD Study-, CKD-EPI cr-, and CKD-EPI cr-cys-estimated GFRs overestimated GFR (median differences of 3.5 [PϽ 0.001], 1.7 [P Ͻ 0.001], and 0.8 [P ϭ 0.02] mL/min/1.73 m 2 , respectively); the CKD-EPI cys equation was unbiased. Accuracy (percentage of estimates within 30% of measured GFR [P 30 ]) was 81%, 83%, 86%, and 86% for the MDRD Study, CKD-EPI cr , CKD-EPI cys , and CKD-EPI cr-cys equations, respectively. Accuracy of the MDRD Study equation was inferior (P ϭ 0.004) to the CKD-EPI cr equation at GFR Ͼ60 mL/min/1.73 m 2. Limitations: Those of non-European ancestry were not included. For practical reasons, only a 4-hour sampling protocol was used for iohexol clearance. Conclusions: The CKD-EPI cr equation appeared less biased and was more accurate than the MDRD Study equation. No equation achieved an ideal P 30 in the overall population. Our data suggest that GFR estimation is as satisfactory in older people of European ancestry as it has been reported to be in younger individuals.
Journal of The American Society of Nephrology, 2006
Whereas much research has investigated equations for obtaining estimated GFR (eGFR) from serum creatinine in crosssectional settings, little attention has been given to validating these equations as outcomes in longitudinal studies of chronic kidney disease. A common objective of chronic kidney disease studies is to identify risk factors for progression, characterized by slope (rate of change over time) or time to event (time until a designated decline in kidney function or ESRD). The relationships of 35 baseline factors with eGFR-based outcomes were compared with the relationships of the same factors with iothalamate GFR (iGFR)-based outcomes in the African American Study of Kidney Disease and Hypertension (AASK; n ؍ 1094). With the use of the AASK equation to calculate eGFR, results were compared between time to halving of eGFR or ESRD and time to halving of iGFR or ESRD (with effect sizes expressed per 1 SD) and between eGFR and iGFR slopes starting 3 mo after randomization. The effects of the baseline factors were similar between the eGFR-and iGFR-based time-to-event outcomes (Pearson R ؍ 0.99, concordance R ؍ 0.98). Small but statistically significant differences (P < 0.05, without adjustment for multiple analyses) were observed for seven of the 35 factors. Agreement between eGFR and iGFR was somewhat weaker, although still relatively high for slope-based outcomes (Pearson R ؍ 0.93, concordance R ؍ 0.92). Effects of covariate adjustment for age, gender, baseline GFR, and urine proteinuria also were similar between the eGFR and iGFR outcomes. Sensitivity analyses including death in the composite time-to-event outcomes or using the Modification of Diet in Renal Disease equation instead of the AASK equation provided similar results. In conclusion, the data from the AASK provide tentative support for use of outcomes that are based on an established eGFR formula using serum creatinine as a surrogate for measured iGFR-based outcomes in analyses of risk factors for the progression of kidney disease.
Validation of child serum creatinine-based prediction equations for glomerular filtration rate
Pediatric Nephrology, 2007
Equations for estimating glomerular filtration rate (GFR) are vital in caring for patients with renal disease and the current standard, the Schwartz formula, lacks precision. We evaluated several child serum creatinine-based GFR prediction equations. Subjects aged 2–21 years who underwent iothalamate GFR (IoGFR) testing between 1999 and 2004 were studied retrospectively. GFR was estimated using: (1) Schwartz formula (SchwartzGFR), using a local k value; (2) Schwartz model (SchwartzMod) using regression-derived coefficients; (3) Leger GFR (LegerGFR) using original coefficients; and (4) Leger model (LegerMod) using regression-derived coefficients. Bias, precision, and diagnostic characteristics were evaluated. There were 195 subjects [61% male; mean (SD) age 12.4 (4.5) years; mean (SD) IoGFR 78.9 (33.4) ml/min per 1.73 m2]. Only the LegerGFR overestimated IoGFR (5.5 ml/min per 1.73 m2). Precision for all formulae was poor (95% limits of agreement approximately −40 to 40 ml/min per 1.73 m2), but ≥72% of estimates were within 30% of IoGFR. Sensitivities for detecting IoGFR <30 and 90 ml/min per 1.73 m2 were highest using the SchwartzGFR (80%) and SchwartzMod (90%), respectively. The LegerGFR was most specific. Using local coefficients, the Schwartz and Leger models were imprecise estimates of GFR, but the Schwartz model was most unbiased and sensitive. Future research should derive more precise equations for GFR in children.
Journal of the American Society of Nephrology, 2005
Chronic kidney disease is currently on the rise and not only leads to ESRD necessitating dialysis or transplantation but also increases cardiovascular disease risk. Measurement of the GFR, the gold standard for assessing kidney function, is expensive and cumbersome. Several prediction formulas that are based on serum creatinine are currently used to estimate the GFR, but none has been validated in a large cohort of individuals with diabetes. The performance of two commonly used formulas, the abbreviated Modification of Diet in Renal Disease (MDRD) study formula for the GFR and the Cockcroft-Gault estimate of creatinine clearance, were examined against GFR measured by the renal clearance of iothalamate in 1286 individuals with type 1 diabetes from the Diabetes Control and Complications Trial (DCCT). The performance of these formulas was assessed by computing bias, precision, and accuracy. The DCCT participants had normal serum creatinine, unlike the MDRD patients, and somewhat lower creatinine excretion than subjects in the original cohort Cockcroft Gault, which led to biased and highly variable estimates of GFR when these formulas were applied to the DCCT subjects. The MDRD substantially underestimated iothalamate GFR, whereas the Cockcroft Gault formula underestimated it when it was <120 ml/min per 1.73 m 2 and overestimated it when iothalamate GFR was >130 ml/min per 1.73 m 2. Overall, only one third of the formula's estimates were within ؎10% of iothalamate GFR. By underestimating GFR, these formulas were likely to flag early declines in kidney function. Refitting the MDRD formula to the DCCT data gave a more accurate and unbiased prediction of GFR from serum creatinine; percentage of estimate within 10% of measured GFR increased to 56%. A substantial variability in the estimates, however, remained.
Clinical Kidney Journal
Background Differences in the performance of estimated glomerular filtration rate (eGFR) equations have been attributed to the mathematical form of the equations and to differences between patient demographics and measurement methods. We evaluated differences in serum creatinine (SCr) and eGFR in cohorts matched for age, sex, body mass index (BMI) and measured GFR (mGFR). Methods White North Americans from Minnesota (n = 1093) and the Chronic Renal Insufficiency Cohort (CRIC) (n = 1548) and White subjects from the European Kidney Function Consortium (EKFC) cohort (n = 7727) were matched for demographic patient characteristics (sex, age ± 3 years, BMI ± 2.5 kg/m2) and renal function (mGFR ± 3 ml/min/1.73 m2). SCr was measured with isotope dilution mass spectrometry (IDMS)-traceable assays in the Minnesota and EKFC cohorts and with non-standardized SCr assays recalculated to IDMS in the CRIC. The Minnesota cohort and CRIC shared a common method to measure GFR (renal clearance of iotha...
Kidney International, 2007
The Nijmegen Biomedical Study is a population-based cross-sectional study conducted in the eastern part of the Netherlands. As part of the overall study, we provide reference values of estimated glomerular filtration rate (GFR) for this Caucasian population without expressed risk. Age-stratified, randomly selected inhabitants received a postal questionnaire on lifestyle and medical history. In a large subset of the responders, serum creatinine was measured. The GFR was then measured using the abbreviated Modification of Diet in Renal Disease (MDRD) formula. To limit possible bias, serum creatinine was calibrated against measurements performed in the original MDRD laboratory. The study cohort included 2823 male and 3274 female Caucasian persons aged 18-90 years. A reference population of apparently healthy subjects was selected by excluding persons with known hypertension, diabetes, cardiovascular-or renal diseases. This healthy study cohort included 1660 male subjects and 2072 female subjects, of which 869 of both genders were 65 years or older. The median GFR was 85 ml/min/1.73 m 2 in 30-to 34-year-old men and 83 ml/min/1.73 m 2 in similar aged women. In these healthy persons, GFR declined approximately 0.4 ml/min/year. Our study provides age-and gender-specific reference values of GFR in a population of Caucasian persons without identifiable risk.
American journal of kidney diseases : the official journal of the National Kidney Foundation, 2004
The Modification of Diet in Renal Disease (MDRD) formula is recommended by European and American guidelines for estimating glomerular filtration rate (GFR). However, the accuracy of the formula has been questioned in several studies. Our objective is to evaluate the performance of the MDRD formula with special emphasis on the possibility that interlaboratory calibration differences for serum creatinine reduce the accuracy of the formula. The MDRD and 7 other commonly used formulae were evaluated regarding bias, precision, and accuracy. The 215 adults included were patients with chronic kidney disease, potential kidney donors, and patients referred before nephrotoxic chemotherapy. Serum creatinine was measured by means of a kinetic Jaffé method (Hitachi 917, Hitachi, Tokyo, Japan; reagents from Roche Diagnostics, Mannheim, Germany). GFR, measured as plasma clearance of chromium 51-labeled EDTA (Cr-EDTA), ranged from 3 to 162 mL/min/1.73 m2. The MDRD formula was heavily biased, but it...