Utilizing Longitudinal Within-Individual Changes of Serum Creatinine, Cystatin C, and/or eGFR to Optimize Clinical Sensitivity and Eliminate Race and Gender Corrections.

Abstract

The recent recommendation by the American Society of Nephrology/National Kidney Foundation task force to immediately eliminate the “race” factor in the estimated glomerular filtration rate (eGFR) equation (1) is a much-needed and long-overdue correction of the original Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) eGFR equations. While the primary and continual goal of the MDRD, CKD-EPI, and other eGFR equations has been to agree with measured GFR (mGFR), we believe this was misguided as shown by the necessity of updating to the CKD-EPI (2021) equation to improve its clinical ability to detect and monitor changes in kidney function for all persons. This new emphasis will enhance the role of the eGFR as a clinical guide for determining chronic kidney disease (CKD) stage and possible referral to nephrology. Because eGFR is calculated from serum creatinine (sCr) and/or cystatin C (sCysC), which are reliable measurements, we propose that these measurements and eGFRs calculated from them are actually more clinically useful, more reliable, and far more used than mGFRs, which have much greater analytical and physiological variation (2–5). Indeed, it was the variability of the mGFR, not the more reliable sCr, that required both the MDRD and CKD-EPI equations to accept wide error tolerances of ±30%, with 81% of the MDRD eGFRs and 84% of CKD-EPI eGFRs within the 30% error tolerance.