Reference values for glomerular filtration rate in healthy Brazilian adults

Background: Glomerular filtration rate (GFR) is the best index of renal function, but age, gender and ethnicity can putatively affect its values. The aim of this study was to establish reference values for GFR in healthy Brazilian subjects while taking these factors into account. Methods: In this cross-sectional study, GFR was measured by the Cr-51-EDTA single-injection method. GFR reference values were developed according to CLSI Guidelines for Defining, Establishing, and Verifying Reference Intervals in the Clinical Laboratory (CLSI C28 protocol). Results: The age range of the 285 healthy individuals was 19 to 70 years, 57% were females, and GFR was 106 +/- 18 mL/min/1.73 m(2). There was no difference between male and female GFRs (108 +/- 18 vs. 104 +/- 18 mL/min/1.73 m(2) respectively, P = 0.134), and reference values were therefore developed from the pooled sample. GFR values were lower in subjects aged >= 45 years as compared with those younger than 45 years (98 +/- 15 vs. 112 +/- 18 mL/min/1.73 m(2), P < 0.001). Based on mean +/- 2 SD, GFR reference values were 76 to 148 mL/min/1.73 m(2) for subjects younger than 45 years and 68 to 128 mL/min/1.73 m(2) for individuals older than 45 years, irrespective of gender. Conclusion: The age-adjusted reference intervals reported may be reliably adopted to evaluate kidney function, since they are based on recommended standards.