Cystatin C and Kidney Function Recovery in Patients Requiring Continuous KRT for Acute Kidney Injury

Abstract

Background Plasma cystatin C is a reliable marker to estimate kidney function; however, it is unknown whether this remains true in patients receiving continuous KRT (CKRT). In this study, we tested the hypothesis that lower concentrations of plasma cystatin C during the first 3 days of CKRT would predict kidney function recovery. Methods We performed a retrospective observational study of 72 patients from a 126-patient, single-center CKRT study. We studied two a priori defined cohorts of patients without advanced CKD who had AKI requiring CKRT: (1) with early kidney function recovery defined as liberation from KRT within 7 days of CKRT initiation versus (2) with delayed kidney function recovery defined as receipt of KRT for .21 days or death while on KRT. Subsequent analysis included patients with advanced CKD and intermediate kidney function recovery (liberation between 8 and 21 days). Cystatin C was then measured on stored plasma, urine, and dialysis effluent collected before CKRT initiation and on days 1, 2, and 3 of CKRT. Results Plasma cystatin C was significantly lower in patients with early kidney function recovery in comparison with patients with delayed kidney function recovery on days 1 (1.79 versus 2.39 mg/L), 2 (1.91 versus 2.38 mg/L), and 3 (2.04 versus 2.67 mg/L) of CKRT. Sieving coefficient and CKRT clearance of cystatin C were similar for patients with early and delayed kidney function recovery. The lowest plasma cystatin C concentration on days 1–3 of CKRT predicted early kidney function recovery with an area under the receiver operating curve of 0.77 (P50.002), positive likelihood ratio of 5.60 for plasma cystatin C,1.30 mg/L, and negative likelihood ratio of 0.17 for plasma cystatin C $1.88 mg/L. Conclusions Lower plasma cystatin C concentrations during the first 3 days of CKRT are associated with early kidney function recovery.