In Reply We thank Delanaye and Pottel for their comments on our Research Letter,1 and we acknowledge their contributions in developing and validating the full age spectrum (FAS) equation for glomerular filtration rate (GFR) estimation using creatinine.2 The 2012 Kidney Disease Improving Global Outcomes guideline states that the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine equation should be used as the first step in GFR evaluation unless another equation has been proven to be more accurate (A.S.L. and L.A.I. were lead researchers on CKD-EPI, and A.S.L. was a member of the guideline work group). The rationale for using a single GFR estimating equation whenever possible is to facilitate communication in clinical practice, research, and public health. We reported previously that the FAS creatinine equation, which does not include race, did not perform better than the CKD-EPI creatinine equation in the CKD-EPI validation data set.3 We also reported previously that the FAS creatinine equation showed significant differential bias between African American and non–African American individuals in the CKD-EPI development and internal validation data set (the same data set analyzed in our Research Letter1); the median difference between estimated and measured GFR was –3.72 mL/min/1.73 m2 (95% CI, −4.28 to −3.11) (underestimation) in 2601 African Americans and 1.76 mL/min/1.73 m2 (95% CI, 1.45 to 2.17) (overestimation) in 5653 non–African American individuals.3 Further analyses show the relationship of the magnitude of the underestimation in African Americans by level of GFR is similar to that of the CKD-EPI creatinine equation without using race, as shown in our Research Letter.1 Thus we conclude that using the FAS creatinine equation would not be helpful in estimating GFR without using race.
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Levey AS, Titan SM, Inker LA. Estimating Glomerular Filtration Rate in African American Individuals—Reply. JAMA Intern Med. Published online July 20, 2020. doi:10.1001/jamainternmed.2020.2377
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