Effect of Urine Output on the Predictive Precision of NephroCheck in On-Pump Cardiac Surgery With Crystalloid Cardioplegia: Insights from the PrevAKI Study

Abstract

Objectives: Previous studies in other settings suggested that urine output (UO) might affect NephroCheck predictive value. We investigated the correlation between NephroCheck and UO in cardiac surgery patients.

Design: Post hoc analysis of a multicenter study.

Setting: University hospital.

Participants: Patients who underwent cardiac surgery using cardiopulmonary bypass (CPB) and crystalloid cardioplegia.

Measurements and main results: All patients underwent NephroCheck testing 4 hours after CPB discontinuation. The primary outcome was the correlation between UO, NephroCheck results, and acute kidney injury (AKI, defined according to Kidney Disease: Improving Global Outcomes). Of 354 patients, 337 were included. Median NephroCheck values were 0.06 (ng/mL)²/1,000) for the overall population and 0.15 (ng/mL)²/1,000) for patients with moderate to severe AKI. NephroCheck showed a significant inverse correlation with UO (ρ = -0.17; p = 0.002) at the time of measurement. The area under the receiver characteristic curve (AUROC) for NephroCheck was 0.60 (95% confidence interval [CI], 0.54-0.65), whereas for serum creatinine was 0.82 (95% CI, 0.78-0.86; p < 0.001). When limiting the analysis to the prediction of moderate to severe AKI, NephroCheck had a AUROC of 0.82 (95% CI, 0.77 to 0.86; p<0.0001), while creatinine an AUROC of 0.83 (95% CI, 0.79-0.87; p = 0.001).

Conclusions: NephroCheck measured 4 hours after the discontinuation from the CPB predicts moderate to severe AKI. However, a lower threshold may be necessary in patients undergoing cardiac surgery with CPB. Creatinine measured at the same time of the test remains a reliable marker of subsequent development of renal failure.

Keywords: Nephrocheck; [TIMP-2]·[IGFBP7]; acute kidney injury; cardiac surgery; cell-cycle arrest marker; creatinine; renal biomarkers; urine output.