Determination of reference intervals for creatinine and evaluation of creatinine-based estimating equation for Chinese patients with chronic kidney disease

BackgroundSeveral equations have been developed to estimate glomerular filtration rate (GFR). The aim of this study was to evaluate the performance of the three equations derived from Modification of Diet in Renal Disease (MDRD) formula: a-MDRD (original simplified), c-MDRD (modified with the Chinese coefficient), and j-MDRD (modified with the Japanese coefficient) in Chinese patients with chronic kidney disease (CKD). We also established the serum creatinine (Scr) reference intervals for Chinese healthy population.MethodA total of 1132 healthy individuals and 283 CKD patients were enrolled in this study. Scr was measured by Jaffe kinetic method.ResultsThe sex-related Scr reference intervals were 71–104 µmol/l for males and 59–85 µmol/l for females. The c-MDRD equation overestimated reference GFR (rGFR) in CKD at stages 2, 3 and 4, but yielded lower bias over wide range of GFR. However, j-MDRD and a-MDRD resulted in a considerable bias. The j-MDRD equation was significantly lower than rGFR over wide range of GFR. a-MDRD and c-MDRD revealed similar accuracy, whereas j-MDRD produced lower accuracy than a-MDRD.ConclusionNo racial differences in the Scr reference intervals were observed. The modified MDRD formulas based on data from Asian population do not significantly improve the accuracy and bias, as compared those of the original MDRD. Therefore, whether the original MDRD for GFR estimation needs to be modified by an ethnic factor requires further investigation and validation.