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

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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.


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).


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/mL2/1000 [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/mL2/1000 and >1.40 ng/mL2/1000 had a sensitivity and specificity >90% in predicting postoperative AKI. Fifty-nine patients (63%) were within the gray zone.


In patients undergoing cardiopulmonary bypass during cardiac surgery, urinary [TIMP-2] × [IGFBP-7] could not accurately predict the occurrence of postoperative AKI.

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