GFR Estimating Equations in a Multiethnic Asian Population

Background: Clinical practice guidelines recommend using equations for estimating glomerular filtration rate (GFR) in chronic kidney disease (CKD) management and research. The MDRD (Modification of Diet in Renal Disease) Study and CKD-EPI (CKD Epidemiology Collaboration) equations originally were derived from a North American population and had an ethnic coefficient adjustment for African Americans. A Chinese coefficient for the MDRD Study equation subsequently was determined, but this has not been externally validated. We compared the accuracy of the equations, evaluated the ethnic coefficients, and assessed the equations for disease staging in a multiethnic Asian population with CKD. Study Design: A diagnostic test study comparing the Asian coefficient (and subgroups)-modified MDRD Study and CKD-EPI equations and a cross-sectional study assessing disease staging. Setting & Participants: 232 outpatients (52% men; 40.5% Chinese, 32% Malay, and 27.5% Indian/other) with stable CKD. Index Test: Asian and ethnicity-based modifications of the MDRD Study and CKD-EPI equations. Reference Test: Measured GFR using 3-sample plasma clearance of technetium-99m diethylenetriaminepentaacetic acid (Tc-99m-DTPA), calculated using the slope-intercept method, with body surface area normalization (du Bois) and Brochner-Mortensen correction. Results: Overall, the CKD-EPI equation is more accurate than the MDRD Study equation throughout the GFR range, with improved bias (median difference of estimated GFR - measured GFR) and root mean square error (P < 0.001). CKD-EPI versus MDRD Study equation: bias, 1.1 +/- 13.8 vs -1.0 +/- 15.2 mL/min/1.73 m(2); precision, 12.1 vs 12.2 mL/min/1.73 m(2). Ethnic coefficients did not improve estimates of GFR significantly. The correctness of staging was improved using the CKD-EPI equation. Limitations: All participants had CKD, but few were of European descent. The reference GFR technique was different from the original studies. Conclusions: The CKD-EPI is more accurate than the MDRD Study equation, particularly at higher GFRs. Therefore, we recommend adopting the CKD-EPI equation without ethnic adjustment for estimating GFR in multiethnic Asian patients with CKD. Am J Kidney Dis. 58(1):56-63. (C) 2011 by the National Kidney Foundation, Inc.