Diagnostic accuracy and prognostic valued of plasmatic Cystatin-C in children undergoing pediatric cardiac surgery

Background Diagnosis and treatment of acute kidney injury (AKI) is often delayed in children after cardiac surgery due to the lack of an early biomarker of renal damage. Our aim was to evaluate the diagnostic accuracy of plasma cystatin-C as an early biomarker of AKI and its prognostic value in pediatric cardiac surgery. Methods Cystatin-C and creatinine were measured pre-operatively and at 2-6-12 h post-surgery. The primary outcome was: AKI (defined as an increase of >= 1.5 of plasma creatinine from baseline) and a composite marker, including major complications and/or extubation time > 15 days. Risk was evaluated using Cox proportional hazards regression analysis, considering some continuous predictors in the basal model (i.e., age, body surface area and Aristotle-score) to which cystatin-C peak values were added. Discrimination, calibration, and reclassification tests were also performed. Results 248 children (140 males) undergoing cardiac surgery (median age 6.5 months; IQR: 1.7-40.1 months; range 0-17 years) have been enrolled. Post operatory Cystatin-C values were found to be an early diagnostic marker of AKI showing the best area under the ROC curve value (AUC) at 12 h (0.746, CI 95% 0.674-0.818). In the multivariable analyses, peak cystatin-C values showed a significant hazard ratio (HR = 2.665, CI 95% 1.750-4.059, p < 0.001). Finally, post operatory cystatin-C at 12 h significantly improved the AUC (p = 0.017) compared to basal model, resulting a net gain in reclassification proportion (NRI = 0.417, p < 0.001). Conclusions Our data show that cystatin-C should be considered an early biomarker of AKI, improving the risk prediction for complicated outcome in pediatric cardiac surgery.