Interest of Urinary [TIMP-2] × [IGFBP-7] for Predicting the Occurrence of Acute Kidney Injury After Cardiac Surgery: A Gray Zone Approach.

Background: This study assessed the ability of 3-hour postoperative urinary tissue inhibitor of metalloproteinases-2 × insulin-like growth factor binding protein-7 ([TIMP-2] × [IGFBP-7]) to predict postoperative acute kidney injury (AKI) in patients undergoing cardiopulmonary bypass during cardiac surgery.
Methods: Patients undergoing cardiac surgery with cardiopulmonary bypass were eligible for this study. Patients with initial chronic renal insufficiency requiring renal replacement therapy, patients <18 years of age, and parturients were not included. Anesthesia and hemodynamic management followed current practices. Urinary [TIMP2] × [IGFBP-7] was measured in 3-hour postoperative period. The primary objective was the occurrence of AKI (Kidney Disease: Improving Global Outcome [KDIGO] stage >0) within the first 48 hours postoperatively. The ability of urinary [TIMP-2] × [IGFBP-7] to predict postoperative AKI was assessed by building a receiver operating characteristic curve (with 95% confidence interval [CI] and by a gray zone approach that allowed either the prediction or the exclusion of postoperative AKI with a sensitivity >0.90 and a specificity >0.90).
Results: AKI occurred in 34 of 93 patients included (37%). The area under the receiver operating characteristic curve of urinary [TIMP-2] × [IGFBP-7] was 0.73 (95% CI, 0.62-0.83). The best cutoff value for urinary [TIMP-2] × [IGFBP-7] in predicting AKI was 0.3 ng/mL/1000 [0.09-1.40] (sensitivity = 76%; 95% CI, 73-97, specificity = 64%; 95% CI, 42-69). Urinary [TIMP-2] × [IGFBP-7] of <0.09 ng/mL/1000 and >1.40 ng/mL/1000 had a sensitivity and specificity >90% in predicting postoperative AKI. Fifty-nine patients (63%) were within the gray zone.
Conclusions: In patients undergoing cardiopulmonary bypass during cardiac surgery, urinary [TIMP-2] × [IGFBP-7] could not accurately predict the occurrence of postoperative AKI.