New Equations for Estimating Glomerular Filtration Rate

The Chronic Kidney Disease Epidemiology (CKD-EPI) Collaboration has recently published new equations for calculating estimated glomerular filtration rate (eGFR) based on serum creatinine and cystatin C (1). Implementation of these new equations for routine reporting of eGFR in adults is strongly recommended (2). For approximately 15 years, US clinical laboratories have been encouraged to report eGFR with creatinine measurements in adults (3). This recommendation was based on the relatively high prevalence of chronic kidney disease, which affects approximately 14% of the US adult population, and which often goes undetected in its early stages. Changes in serum creatinine concentration may not appear significant (e.g., 0.80 mg/dL vs 1.00 mg/dL) and may even be within the typical population-based reference interval and therefore not flagged on laboratory reports. But that change represents a nearly 25% difference in eGFR (in a 65-year-old female, 78 vs 59 mL/min/1.73m2) using the current CKD-EPI creatinine eGFR equation.