Objective: To evaluate the perioperative course of urine levels of the renal damage biomarkers tissue inhibitor of metalloproteinase 2 (TIMP-2) and insulin-like growth factor-binding protein 7 (IGFBP7) and to evaluate the predictive value of elevated TIMP-2 × IGFBP7 concentrations to predict acute kidney injury (AKI) early after cardiac on-pump surgery.
Design: Prospective, observational cohort study.
Setting: University hospital.
Participants: The study comprised 110 consecutive patients undergoing elective cardiac surgery with cardiopulmonary bypass (CPB) between January and March 2014.
Interventions: None.
Measurements and main results: Urinary TIMP-2 × IGFBP7 levels were quantified using a commercially available kit at the following measurement points: before surgery, 1 hour after starting CPB, 4 hours after weaning from CPB, and 24 hours after weaning from CPB (time points 1-4). Postoperative AKI was defined according to Kidney Disease Improving Global Outcomes criteria. AKI after cardiac surgery was diagnosed in 9 patients (8%). The perioperative course of TIMP-2 × IGFBP7 was significantly different in patients with and without postoperative AKI (p < 0.001). TIMP-2 × IGFBP7 levels were significantly higher in patients with AKI 1 hour after CPB start and 24 hours after weaning from CPB (p < 0.05). TIMP-2 × IGFBP7 levels >0.40 (ng/mL)2/1,000 measured at 1 hour after starting CPB were found to be the optimal cut-off, with a sensitivity of 0.778 and a specificity of 0.641. The negative predictive value was 0.972.
Conclusions: Urine levels of TIMP-2 × IGFBP7 are predictive for AKI at an early time point (1 hour after starting CPB). Renal damage biomarkers such as TIMP-2 and IGFBP7 might be recommended as a supplement to traditionally used criteria of AKI prediction.
Keywords: acute kidney injury; cardiac surgery; urine biomarkers.
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