COMPARISON OF CYSTATIN-C-BASED FORMULAS FOR EVALUATION OF RESIDUAL RENAL FUNCTION IN PERITONEAL DIALYSIS PATIENTS

Suojian Zhang, Xu Zhang, Haitao Li, Juan Cao

Department of Nephrology, Taixing People’s Hospital, Taizhou 225400 China

Introduction: The present study aims to compare three cystatin-C (cys C)-based formulas which evaluate residual renal function (RRF) in peritoneal dialysis (PD) patients.

Materials and methods: 94 patients who were undergoing regular PD treatment were enrolled. The average clearance of 24-h urea and creatinine was taken as the gold standard, which was called measured RRF (mRRF). RRF was also estimated by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI), Hoek and Yang formulas. We compared the deviation and accuracy of estimated RRF (eRRF) calculated by the three formulas. 

Results: CysC was not correlated with demographic characteristics, albumin, prealbumin, blood glucose, glycosylated hemoglobin, intact parathyroid hormone or high-sensitivity C-reactive protein, and negatively correlated with mRRF. The mean bias and limit of agreement were -3.9 (-0.7 to -7.1) ml/min/1.73 m2 for the CKD-EPI formula, -0.3 (2.6 to -3.2) ml/min/1.73 m2 for the Hoek formula and 0.9 (3.6 to -1.9 )ml/min/1.73 m2 for the Yang formula. The Yang formula showed the smallest relative difference and the CKD-EPI formula showed the largest. Accuracy of the CKD-EPI formula was the worst and there was no difference in accuracy between the Hoek and Yang formulas within 30% and 50%.

Conclusion: The CKD-EPI formula showed the largest bias and the lowest accuracy. The Hoek formula showed the smallest mean bias and the Yang formula had the smallest relative differences. There was no difference between the Yang and Hoek formulas for accuracy within 30% and 50%. It may inappropriate to use the CKD-EPI formula to estimate RRF of PD patients.