Impact of switching from the 2009 to the 2021 CKD-EPI Equation for eGFR

Abstract Recent national and international guidelines have recommended implementing the 2021 CKD-EPI equation for estimating glomerular filtration rate (eGFR). Relative to the 2009 CKD-EPI equation, the 2021 equation eliminates race-based modifiers in the calculation of eGFR based on a remodeling of the original CKD-EPI dataset. Further, updated guidelines now recommend integrating Cystatin C as a confirmatory test in all patients with an eGFR between 45-59 mL/min/1.73m2. Here we assess the impact of switching from the 2009 CKD-EPI creatinine-based equation to the 2021 CKD-EPI creatinine-based equation on both non-black and black populations and assess the feasibility of implementing a reflex for Cystatin C on all patients with an eGFR between 45-59 mL/min/1.73m2. The laboratory information system was queried retrospectively from 11/01/2021 to 12/31/2021 for age, sex, self-identified ethnicity, and serum creatinine concentrations from basic/comprehensive metabolic panels and renal panels. Slope and linearity of the reported eGFR with the 2009 and 2021 equations were compared using Deming regression and Fisher’s exact test was used to assess the proportion of eGFR results