Serum creatinine as marker of kidney function in South Asians: a study of reduced GFR in adults in Pakistan.

Migrant populations of South Asian origin have a higher risk for chronic kidney disease than the native whites. Several formulas have been developed to estimate kidney function from serum creatinine concentration. However, none of these has been validated in the South Asian population, which generally has different muscle mass composition than whites. A population-based cross-sectional study was performed on 262 individuals who were aged > or = 40 yr in Karachi, Pakistan. Reduced GFR was defined as creatinine clearance (Ccr) measured in 24-h urine collection of <60 ml/min per 1.73 m2. Creatinine excretion was compared with age- and gender-matched white individuals by comparison of observed versus expected results on the basis of a formula using t test. The agreement among Cockcroft Gault (CG) Ccr and Modification of Diet in Renal Disease (MDRD) Study GFR equations was assessed by regression analyses, and the degree of accuracy of estimated versus measured GFR was determined. Mean (95% confidence interval) creatinine excretion was 1.7 (1.0 to 2.4) mg/kg per d lower than expected for age- and gender-matched white individuals (P < 0.001). The coefficient of determination for measured Ccr on the logarithmic scale was 66.7 and 55.6% for the CG and MDRD Study equations, respectively. The proportion of estimates within 20, 30, and 50% of measured Ccr values was 47.7 versus 32.8% (P < 0.001), 64.9 versus 49.6% (P < 0.001), and 79.4 versus 72.9 (P = 0.07) for CG versus MDRD Study equations, respectively. Lower mean creatinine excretion in these individuals may explain, in part, suboptimal agreement between estimated versus measured GFR. Inclusion of terms for ethnic and racial groups other than white and black might improve the performance of GFR estimating equations.