DETERMINING TRUE GLOMERULAR-FILTRATION STATUS IN NEWLY PRESENTING TYPE-2 DIABETIC SUBJECTS USING AGE AND SEX ADJUSTMENT

OBJECTIVE - To determine age- and sex-adjusted reference ranges (ASARR s) for glomerular filtration status using data from nondiabetic subjec ts and to apply these to newly presenting type 2 diabetic subjects. RE SEARCH DESIGN AND METHODS - Glomerular filtration rate corrected for b ody surface area (cGFR) was determined using a radionuclide (Cr-51-EDT A) method in 75 nondiabetic subjects (37 men, 38 women) and 219 type 2 diabetic subjects (157 men, 62 women). The 95% constant reference ran ges (CRRs) were calculated as mean nondiabetic cGFR +/- 1.96 SD. The 9 5% ASARRs were calculated by Altman's method from the nondiabetic cGFR versus age regression residuals for both male and female subjects. RE SULTS - Using Altman's method, the intercepts, but not the gradients, of the cGFR versus age regressions were significantly different betwee n male and female subjects (intercept difference [95% CI] 8.2 [1.3-15. 1], gradient difference -0.4 [-1.1 to 0.3]). Fitting a common gradient , 95% ASARRs for normofiltration were found to be from 123.9 - (0.89 x age) to 181.7 - (0.89 x age) for male subjects, and from 116.0 - (0.8 9 x age) to 173.2 - (0.89 x age) for female subjects. The 95% CRR for normofiltration was 70.2-138.1 ml . min(-1) . (1.73 m)(-2). When appli ed to the diabetic cGFRs, the CRRs and ASARRs gave, respectively, 17% (37/219) versus 21% (46/219) hyperfiltrators and 83% (181/219) versus 79% (172/219) normofiltrators. Using the ASARRs, 14 normofiltrators (6 men, 8 women) were reclassified as hyperfiltrators (change [n/total n ] [95% CI] 8% [14/181] [4-12]), and 5 hyperfiltrators (5 men, 0 women) were reclassified as normofiltrators (change 14% [5/37] [5-30]). CONC LUSIONS - We conclude that age and sex adjustment are essential to ass ess glomerular filtration status.