(TIMP2) x (IGFBP7) as early renal biomarker for the prediction of acute kidney injury in aortic surgery (TIGER). A single center observational study.

OBJECTIVE: Postoperative acute kidney injury (po-AKI) is frequently observed after major vascular surgery and impacts on mortality rates. Early identification of po-AKI patients using the novel urinary biomarkers insulin-like growth factor-binding-protein 7 (IGFBP7) and tissue inhibitor of metalloproteinases-2 (TIMP-2) might help in early identification of individuals at risk of AKI and enable timely introduction of preventative or therapeutic interventions with the aim of reducing the incidence of po-AKI. We investigated whether biomarker-based monitoring would allow for early detection of po-AKI in patients undergoing abdominal aortic interventions. METHODS: In an investigator-initiated prospective single-center observational study in a tertiary care academic center, adult patients with emergency/ elective abdominal aortic repair were included. Patients were tested for concentrations of urinary (TIMP-2) x (IGFBP7) at baseline, after surgical interventions (PO), and in the mornings of the first postoperative day (POD1). The primary endpoint was a difference in urinary (TIMP-2) x (IGFBP7) levels at POD1 in patients with/ without po-AKI (all KDIGO stages, po-AKI until seven days after surgery). Secondary endpoints included sensitivity/ specificity analyses of previously proposed cut-off levels and clinical outcome measures (e.g. need for renal replacement therapy). RESULTS: 93 patients (n = 71 open surgery) were included. Po-AKI was observed in 33% (31/93) of patients. Urinary (TIMP-2) x (IGFBP7) levels at POD1 did not differ between patients with/ without AKI (median 0.39, interquartile range [IQR] 0.13-1.05 and median 0.23, IQR 0.14-0.53, p = .11, respectively) and PO (median 0.2, IQR 0.08-0.42, 0.18, IQR 0.09-0.46; p = .79). Higher median (TIMP-2) x (IGFBP7) levels were noted in KDIGO stage 3 pAKI patients at POD1 (3.75, IQR 1.97-6.92; p = .003). Previously proposed cutoff levels (0.3, 2) showed moderate sensitivity/ specificity (0.58/0.58 and 0.16/0.98, respectively). CONCLUSION: In a prospective monocentric observational study in patients after abdominal aortic repair, early assessment of urinary (TIMP-2) x (IGFBP7) did not appear to have adequate sensitivity/ specificity to identify patients that later developed postoperative AKI. CLINICALTRIALS.GOV: NCT03469765, registered March 19, 2018.