Glomerular filtration rate (GFR) estimates facilitate detection of chronic kidney disease. Performance of the Modification of Diet in Renal Disease (MDRD) Study equation varies substantially among populations. To describe the performance of the equation in a large, diverse population, estimated GFR (eGFR) was compared to measured GFR (mGFR) in a cross-sectional analysis of 5504 participants in 10 studies that included measurements of standardized serum creatinine and urinary clearance of iothalamate. At eGFR <60 ml/min per 1.73 m2, the MDRD Study equation had lower bias and higher precision than at eGFR ≥60 ml/min per 1.73 m2. The accuracy of the equation, measured by the percent of estimates that fell within 30% of mGFR, was similar for eGFR values above or below 60 ml/min per 1.73 m2 (82% and 84%, respectively). Differences in performance among subgroups defined by age, sex, race, diabetes, transplant status, and body mass index were small when eGFR was <60 ml/min per 1.73 m2. The MDRD Study equation therefore provides unbiased and reasonably accurate estimates across a wide range of subgroups when eGFR is <60 ml/min per 1.73 m2. In individual patients, interpretation of GFR estimates near 60 ml/min per 1.73 m2 should be interpreted with caution to avoid misclassification of chronic kidney disease in the context of the clinical setting.
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