The discrepancy between serum creatinine and cystatin C can predict renal function after treatment for postrenal acute kidney injury: multicenter study and pooled data analysis.

Background: Although serum cystatin C and creatinine are used as practical markers of renal function, the discrepancy between them in postrenal acute kidney injury (AKI) cases was reported. The aim of this study was to determine whether the preoperative serum cystatin C (pre-CysC) level could predict clinical outcomes after treatment in patients with postrenal AKI.
Methods: Patients who underwent urological interventions with postrenal AKI were enrolled in this prospective observational study. Associations among preoperative serum creatinine (pre-sCr), pre-CysC, and nadir postoperative serum creatinine (post-sCr) were evaluated. In addition, based on our results in combination with detailed data from the literature, a predictive equation for postoperative serum creatinine (post-sCr) was developed by simple regression analysis and validated using Bland-Altman plots.
Results: Finally, 19 patients were eligible for analysis in this study. The value calculated by subtracting pre-CysC (mg/L) from pre-sCr (mg/dl) had a strong correlation to the decrement of serum creatinine (r = 0.9508, p < 0.0001). We added the data of 16 patients obtained from the literature to our series, which were totally randomized into 2 groups, training set and validation set in a 2:1 ratio (n = 23 and 12, respectively) to develop and validate a predictive equation for post-sCr. The mean difference between the predictive and actual post-sCr, -0.68 mg/dl (95% CI -1.62 to 0.26) in the validation set was within the limits of agreement.
Conclusion: We showed that the discrepancy between pre-sCr and pre-CysC could predict improvement of renal function after intervention in patients with postrenal AKI.