Estimation of glomerular filtration rate using serum cystatin C in overweight and obese subjects.

BACKGROUND Obesity and overweight are strong independent risk factors for chronic kidney disease (CKD). Using serum creatinine-based estimated glomerular filtration rate (eGFR) equations in these subjects may be inaccurate. On the other hand, cystatin C-based eGFR equations may overestimate CKD prevalence as recent findings suggest an association of cystatin C with obesity. The objective of this study was to assess the accuracy of a cystatin C-based eGFR equation compared to two creatinine -based eGFR equations in overweight and obese subjects. METHODS This was a prospective cross-sectional study which recruited healthy volunteers aged 18-55 years with a body mass index (BMI) > or = 23kg/m(2) (Asia Pacific Guidelines). Their renal profiles, serum cystatin C and 99m technetium diethylene triamine pentacetic acid (99)mTc-DTPA) scans were performed on the same day. The correlations and accuracy of the creatinine-based and cystatin C-based eGFR equations with the (99)mTc-DTPA GFR were determined. RESULTS One hundred and one subjects with a median age of 30.0 (27.0-43.5) years and mean BMI of 28.7 +/- 4.5 kg/m(2) were recruited. The cystatin C-based eGFR equation showed the best correlation with the (99)mTc-DTPA GFR (r = 0.526, p = 0.001) and was more accurate in measuring abnormal GFR compared to the creatinine-based eGFR equations. CONCLUSION Our study showed that the cystatin C-based eGFR equation was more accurate, sensitive and specific in overweight and obese subjects compared to the creatinine-based eGFR equations.