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Accuracy of a GFR estimating equation over time in people with a wide range of kidney function.

ABSTRACT: Change in glomerular filtration rate (GFR) is important for clinical decision making. GFR estimates from serum creatinine level provide an unbiased but imprecise estimate of GFR at single time points. However, the accuracy of estimated GFR over time is not well known.Longitudinal study of diagnostic test accuracy.4 clinical trials with longitudinal measurements of GFR and serum creatinine on the same day, including individuals with and without kidney disease with a wide range of kidney function, diverse racial backgrounds, and varied clinical characteristics.GFR estimated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation.GFR measured using urinary clearance of (125)I-iothalamate.Data included 19,735 GFR measurements in 3,531 participants during a mean follow-up of 2.6 years. Mean values at baseline for measured and estimated GFR and error (measured GFR - estimated GFR) were 73.1 (95% CI, 71.6 to 74.5), 72.7 (95% CI, 71.5 to 74.0), and 0.14 (95% CI, -0.35 to 0.63) mL/min/1.73 m(2), respectively. Mean rates of change in measured and estimated GFR and error were -2.3 (95% CI, -2.4 to -2.1), -2.2 (95% CI, -2.4 to -2.1), and -0.09 (95% CI, -0.24 to 0.05) mL/min/1.73 m(2) per year (P < 0.001, P < 0.001, and P = 0.2, respectively). Variability (ie, standard deviation) among participants in rate of change in measured GFR, estimated GFR, and error was 4.3, 3.4, and 3.3 mL/min/1.73 m(2) per year, respectively. Only 15% of participants had a rate of change in error >3 mL/min/1.73 m(2) per year, and only 2% had a rate of change in error >5% per year.Participants' characteristics were not available over time.The accuracy of GFR estimates did not change over time. Clinicians should interpret changes in estimated GFR over time as reflecting changes in measured GFR rather than changes in errors in the GFR estimates in most individuals.

SUBMITTER: Padala S

PROVIDER: S-EPMC3399947 | biostudies-literature | 2012 Aug

REPOSITORIES: biostudies-literature

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Accuracy of a GFR estimating equation over time in people with a wide range of kidney function.

Padala Smita S Tighiouart Hocine H Inker Lesley A LA Contreras Gabriel G Beck Gerald J GJ Lewis Julia J Steffes Michael M Rodby Roger A RA Schmid Christopher H CH Levey Andrew S AS

American journal of kidney diseases : the official journal of the National Kidney Foundation 20120410 2

<h4>Background</h4>Change in glomerular filtration rate (GFR) is important for clinical decision making. GFR estimates from serum creatinine level provide an unbiased but imprecise estimate of GFR at single time points. However, the accuracy of estimated GFR over time is not well known.<h4>Study design</h4>Longitudinal study of diagnostic test accuracy.<h4>Settings & participants</h4>4 clinical trials with longitudinal measurements of GFR and serum creatinine on the same day, including individua ...[more]

PMID: 22495467

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Project description:Background and objectiveseGFR equations have been evaluated in kidney transplant recipients with variable performance. We assessed the performance of the Modification of Diet in Renal Disease equation and the Chronic Kidney Disease Epidemiology Collaboration equations on the basis of creatinine, cystatin C, and both (eGFR creatinine-cystatin C) compared with measured GFR by iothalamate clearance and evaluated their non-GFR determinants and associations across 15 cardiovascular risk factors.Design, setting, participants, & measurementsA cross-sectional cohort of 1139 kidney transplant recipients >1 year after transplant was analyzed. eGFR bias, precision, and accuracy (percentage of estimates within 30% of measured GFR) were assessed. Interaction of each cardiovascular risk factor with eGFR relative to measured GFR was determined.ResultsMedian measured GFR was 55.0 ml/min per 1.73 m(2). eGFR creatinine overestimated measured GFR by 3.1% (percentage of estimates within 30% of measured GFR of 80.4%), and eGFR Modification of Diet in Renal Disease underestimated measured GFR by 2.2% (percentage of estimates within 30% of measured GFR of 80.4%). eGFR cystatin C underestimated measured GFR by -13.7% (percentage of estimates within 30% of measured GFR of 77.1%), and eGFR creatinine-cystatin C underestimated measured GFR by -8.1% (percentage of estimates within 30% of measured GFR of 86.5%). Lower measured GFR associated with older age, women, obesity, longer time after transplant, lower HDL, lower hemoglobin, lower albumin, higher triglycerides, higher proteinuria, and an elevated cardiac troponin T level but did not associate with diabetes, smoking, cardiovascular events, pretransplant dialysis, or hemoglobin A1c. These risk factor associations differed for five risk factors with eGFR creatinine, six risk factors for eGFR Modification of Diet in Renal Disease, ten risk factors for eGFR cystatin C, and four risk factors for eGFR creatinine-cystatin C.ConclusionsThus, eGFR creatinine and eGFR creatinine-cystatin C are preferred over eGFR cystatin C in kidney transplant recipients because they are less biased, more accurate, and more consistently reflect the same risk factor associations seen with measured GFR.

Project description:BackgroundBeta-2 microglobulin (B2M) and cystatin C are novel glomerular filtration markers that have a stronger association with adverse outcomes than creatinine. The B2M-based glomerular filtration rate (GFR) estimating equation was built in 2016. Several new creatinine and cystatin C equations were developed in 2019 in China. However, external validation of these new equations remains to be seen.MethodsThis is a prospective cohort study. The equations were validated in a population totaling 830 participants (median age 62 years). These equations include the B2M-based equation (built in 2016), three CKD-EPI equations (built in 2009 and 2012), three Yang-Du equations (C-CKD-EPIscr, C-CKD-EPIcys, and C-CKD-EPIscr-cys equations, all of which were Chinese-modified CKD-EPI equations developed by Yang et al. in 2019), and a Xiangya equation (a creatinine-based equation built in the Third Xiangya Hospital in 2019). The estimated GFR (eGFR) calculated separately by 8 equations (B2M GFR, CKD-EPIscr, CKD-EPIcys, CKD-EPIscr-cys, C-CKD-EPIscr, C-CKD-EPIcys, C-CKD-EPIscr-cys, and Xiangya equations) was compared with the reference GFR (rGFR) measured by the 99mTc-DTPA renal dynamic imaging method. Participants were divided into CKD stage 1-5 specific subgroups. The primary outcomes of this study were bias, precision (interquartile range of difference, IQR), and accuracy (the proportion of eGFR within 30% of rGFR [P30] and root mean square error [RMSE]) of eGFR versus rGFR.ResultsThe B2M-based equation was worse than CKD-EPI equations and Yang-Du equations in most outcomes. CKD-EPIscr and C-CKD-EPIscr equations had a larger area under the receiver operating characteristic curve (ROCAUC). The CKD-EPIscr equation had the highest sensitivity (83.3%) and the Xiangya equation the highest specificity (89.5%) to diagnose CKD. The bias was the lowest in CKD-EPIcys and C-CKD-EPIscr-cys equations by median and mean difference (1.23 and -1.42, respectively). The Xiangya equation yielded the highest bias by both median and mean difference (8.29 and 6.52, respectively). The C-CKD-EPIscr equation was the most accurate with the highest P30 value (68.1%) and most precise with the lowest IQR (19). The Xiangya equation had the best RMSE (lowest RMSE, 0.56), and gave the best performance in the CKD stage 2 subgroup. The C-CKD-EPIscr-cys equation achieved the lowest bias in CKD stage 3-5 (p = 0.663, 0.104, and 0.130, respectively, compared with rGFR).ConclusionThe B2M-based equation was worse than CKD-EPI and Yang-Du equations on the whole. CKD-EPIcys and C-CKD-EPIscr-cys equations had the lowest bias, whereas the Xiangya equation yielded the highest bias. The Xiangya equation gave the best performance in the CKD stage 2 subgroup, while the C-CKD-EPIscr-cys equation achieved the lowest bias in CKD stage 3-5. Further work to improve the performance of the GFR estimating equation is needed.

Project description: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.

Project description:Assessment of GFR is central to clinical practice, research, and public health. Current Kidney Disease Improving Global Outcomes guidelines recommend measurement of serum creatinine to estimate GFR as the initial step in GFR evaluation. Serum creatinine is influenced by creatinine metabolism as well as GFR; hence, all equations to estimate GFR from serum creatinine include surrogates for muscle mass, such as age, sex, race, height, or weight. The guideline-recommended equation in adults (the 2009 Chronic Kidney Disease Epidemiology Collaboration creatinine equation) includes a term for race (specified as black versus nonblack), which improves the accuracy of GFR estimation by accounting for differences in non-GFR determinants of serum creatinine by race in the study populations used to develop the equation. In that study, blacks had a 16% higher average measured GFR compared with nonblacks with the same age, sex, and serum creatinine. The reasons for this difference are only partly understood, and the use of race in GFR estimation has limitations. Some have proposed eliminating the race coefficient, but this would induce a systematic underestimation of measured GFR in blacks, with potential unintended consequences at the individual and population levels. We propose a more cautious approach that maintains and improves accuracy of GFR estimates and avoids disadvantaging any racial group. We suggest full disclosure of use of race in GFR estimation, accommodation of those who decline to identify their race, and shared decision making between health care providers and patients. We also suggest mindful use of cystatin C as a confirmatory test as well as clearance measurements. It would be preferable to avoid specification of race in GFR estimation if there was a superior, evidence-based substitute. The goal of future research should be to develop more accurate methods for GFR estimation that do not require use of race or other demographic characteristics.

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Accuracy of a GFR estimating equation over time in people with a wide range of kidney function.

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Accuracy of a GFR estimating equation over time in people with a wide range of kidney function.

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