The relationship between Nephrocheck® test values, outcomes, and urinary output in critically ill patients at risk of acute kidney injury

Abstract

Background: Nephrocheck® was approved for acute kidney injury (AKI) risk assessment in critically illness. However, new studies suggest that urinary concentration affects Nephrocheck® and previous studies did not provide data on urinary output (UO) at the time of measurement. Methods: We performed a prospective cohort study of the Nephrocheck® in intensive care unit patients fulfilling standard inclusion criteria. The primary outcome was Stage 2 or 3 AKI defined by both UO and creatinine Kidney Disease Improving Global Outcomes (KDIGO) criteria in the subsequent 12 h. The secondary outcome was the relationship of UO with Nephrocheck® measurement. Results: Among 98 patients, the primary outcome occurred in 53 (54.1%) overall, but in 23 (23.5%) by creatinine criteria alone. The median (interquartile range) Nephrocheck® in patients with subsequent Stage 2 or 3 AKI was greater than in Stage 1 or no-AKI patients (0.97 [0.48–1.99] vs. 0.46 [0.22–1.17]; p =.005). However, its area under the receiver characteristic curve was 0.66 (95% confidence interval [CI], 0.56–0.77). Moreover, Nephrocheck® was significantly and inversely correlated with UO (ρ = −.46, p <.001) at the time of measurement and, on a multivariable logistic regression, Nephrocheck® was not associated with subsequent Stage 2 or 3 AKI (OR 1.06 [95% CI, 0.74–1.53], p =.73). In contrast, the UO had an OR of 0.98 for each ml/h increase (95% CI, 0.97–1.00, p =.007). Conclusion: Nephrocheck®'s predictive performance was limited and its value was inversely correlated with UO. Nephrocheck® had no independent relationship with outcome once UO at measurement was considered.