Factors resulting correlation and differences in renal function evaluation index using the serum cystatin C and creatinine as measured by an enzymatic method

Abstract

We previously reported the association of the estimated glomerular filtration rate (eGFRcreat) calculated from the serum creatinine level (S-Cr) measured using the Jaffe method with the GFR (eGFRcys) estimated from the serum cystatin C level (CysC). However, few studies have compared the eGFRcreat using the enzymatic method with the eGFRcys. It is unclear whether there are differences in the results of renal function assessment. The purpose of this study was to compare the eGFRcreat calculated from the S-Cr with the eGFRcys calculated from the CysC in patients in whom the S-Cr and CysC were simultaneously measured using the enzymatic method, examine the correlations of respective parameters, and clarify physiological factors involved in diffierences among the parameters. The subjects were 1334 patients treated in 5 institutions. The mean values and correlation coefficient were statistically analyzed using Student's t-test and Pearson's test, respectively. Influential factors between formulae were analyzed using multiple regression analysis. The mean eGFRcreat was 67.0 mL/min/1.73 m2, being significantly higher than the mean eGFRcys (63.2). Multiple regression analysis showed that factors influencing differences in the S-Cr and CysC included the sex, age, serum albumin, and blood urea nitrogen BUN/S-Cr. Furthermore, factors involved in the overestimation of the eGFRcreat in comparison with the eGFRcys included the serum albumin and BUN/S-Cr. The differences between the eGFRcreat calculated from the S-Cr and eGFRcys were less marked than when adopting the Jaffe method in our previous study. However, the eGFRcreat were higher than the eGFRcys in patients with malnutrition or dehydration.