CDK-EPI equation may be the most proper formula based on creatinine in determining glomerular filtration rate in Chinese patients with chronic kidney disease

To compare the performance of the Chronic Kidney Disease Epidemiology Collaboration (CDK-EPI) equation, the 24-h creatinine clearance rate (24hCCr), Cockroft–Gault (C-G) formula, the abbreviated Modification of Diet in Renal Disease (aMDRD) equation, the modified Modification of Diet in Renal Disease (mMDRD) equation in determining glomerular filtration rate (GFR) in Chinese patients with chronic kidney disease (CKD) and detect the most proper method to measure GFR in clinical practice.

One hundred and fifty-four patients with CKD were enrolled in the present study. ^99mTc-diethylene triamine pentaacetic acid (^99mTc-DTPA) plasma clearance method measured by dual plasma sampling method (rGFR) was considered as the reference standard. GFR was estimated simultaneously using five methods: (1) CDK-EPI equation (eGFR1); (2) 24hCCr (eGFR2); (3) C-G formula (eGFR3); (4) abbreviated MDRD equation (eGFR4); (5) mMDRD equation (eGFR5). The comparison of correlation, regression, bias, precision, accuracy, limit of agreement, and receiver-operating characteristics (ROC) for detecting CKD (with a GFR cutoff of 60 mL min⁻¹ 1.73 m⁻²) among the methods was analyzed to identify the most suitable method.

All the equations correlated well with rGFR, and the correlation coefficient of CDK-EPI equation was the highest (r_eGFR1 = 0.922, P < 0.001). The Bland–Altman analysis showed that the limit of agreement for CDK-EPI equation was −25.5 to 30.3 mL min⁻¹ 1.73 m⁻², which was the least range among the tested equations. The CDK-EPI equation represented the best capability in precision (14.24 mL min⁻¹ 1.73 m⁻²). The ROC curve showed the best performance in detecting CKD. The accuracy within ±30 % of CDK-EPI equation, 24hCCr, and mMDRD equation was 72.08, 69.48, and 70.13 %, respectively, and no statistical significant difference was found (P > 0.05). However, CDK-EPI equation had the highest accuracy when compared with the other two equations (P < 0.05). And its performance on bias showed no statistically significant difference compared with other four equations.

Although its bias and accuracy did not overmatch the other four equations in our patient group, the CDK-EPI equation outperformed the other equations based on creatinine in correlation, precision, limit of agreement, and detecting CKD, and it is very simple, time-saving, and cost-effective. So we recommend intensely that the CDK-EPI equation is the most suitable method in determining GFR in Chinese patients with CKD and can be applied generally in clinical practice.