Biological variation of estimated glomerular filtrations rate in apparently healthy individuals within 24 h calculated using new CKD-EPI equations

Abstract Background Glomerular filtrations rate (GFR) estimated based on serum creatinine (S-Crea) and/or serum cystatin C (S-Cys-C) levels is often used to assess renal function. The commonly used equations are the Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI), However, short-term studies of the corresponding GFR biological variation(BV) are scarce, and all have included race coefficients. In this study, We aimed to use the MDRD and without race coefficients of CKD-EPI new equations (CKD-EPI Crea , CKD-EPI Cys-C , and CKD-EPI Crea+Cys-C ) to estimate the BV of eGFR within 24 h. Methods 30 apparently healthy subjects blood samples were collected once at 4-h intervals for 24h, Measuring S-Crea and S-Cys-C, using MDRD and CKD-EPI new equations to estimated GFR(eGFR). Results Based on the MDRD, CKD-EPI Crea , CKD-EPI Cys-C , and CKD-EPI Crea+Cys-C equations, the within-subject CV I (95% confidence interval (CI)) of eGFR for the 30 apparently healthy subjects were 8.39%(7.50–9.51),3.90%(3.49–4.42),6.58%(5.88–7.46)and5.03%(4.50–5.71), respectively. Further, the corresponding individual index(II) values were 0.69, 0.48, 0.51, and 0.31, respectively,and the corresponding positive and negative reference change values (RCV pos/neg ) were (29.30%,-22.66%), (12.69%,-11.26%), (20.97%,-17.33%), and (15.88%,-13.70%), respectively. Additionally, the RCV pos/neg values of the individual apparently healthy subjects were significantly different,indicating obvious individual characteristics.The largest corresponding individual RCVpos/neg values were (56.51%,-36.11%), (20.99%,-17.35%), (44.93%,-31.00%),and (28.83%, -22.38%), respectively, while the smallest values were (12.36%,-11.00%), (5.32%, -5.05%), (5.76%,-5.45%), and (5.01%,-4.77%),respectively. Conclusions The presence of BV has impact on the interpretation of GFR results, in turn affecting the CKD stage,so when using eGFRs based on MDRD and CKD-EPI equations,it is necessary to combine RCV pos/neg values before interpreting the results.