[Factors Resulting Correlation and Differences in Renal Function Evaluation Index Using the Serum Cystatin C and...

We previously reported the association of the estimated glomerular filtration rate (eGFR_creat) calculated from the serum creatinine level (S-Cr) measured using the Jaffe method with the GFR (eGFR_cys) estimated from the serum cystatin C level (CysC). However, few studies have compared the eGFR_creat using the enzymatic method with the eGFR_cys. It is unclear whether there are differences in the results of renal function assessment. The purpose of this study was to compare the eGFR_creat calculated from the S-Cr with the eGFR_cys 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 differences 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 eGFR_creat was 67.0 mL/min/1.73 m², being significantly higher than the mean eGFR_cys (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 eGFR_creat in comparison with the eGFR_cys included the serum albumin and BUN/S-Cr. The differences between the eGFR_creat calculated from the S-Cr and eGFR_cys were less marked than when adopting the Jaffe method in our previous study. However, the eGFR_creat were higher than the eGFR_cys in patients with malnutrition or dehydration.