Urinary [TIMP-2]*[IGFBP7] for early prediction of acute kidney injury after coronary artery bypass surgery

Background: Acute kidney injury (AKI) is a common complication after cardiac surgery. Currently, prediction of AKI with classical tools remains uncertain. Therefore, it was the aim of the present study to evaluate two new urinary biomarkers-insulin-like growth factor-binding protein 7 (IGFBP7) and tissue inhibitor of metalloproteinases-2 (TIMP-2) in patients after coronary artery bypass surgery (CABG). Methods: In a prospective cohort study, 60 consecutive patients undergoing isolated on-pump CABG were enrolled. Urine samples collected every 12 h in the postoperative course were analyzed for the product of TIMP-2 and IGFBP7. Urinary output, serum creatinine and estimated glomerular filtration rate (eGFR) were recorded simultaneously. Primary clinical endpoint was the development of AKI stage 2 or 3 according to the classification of the KDIGO within 48 h after surgery. Results: 48 male and 12 female patients with a mean age of 69.61 +/- 8.4 years were included. 19 patients developed an AKI (31.6 %), six patients met the endpoint with AKI 2 or 3 (10 %). Urinary [TIMP-2]*[IGFBP7] increased significantly as early as 4 h after CABG in patients with AKI 2/3 (1.83 +/- 2.15 vs. 0.23 +/- 0.45, p < 0.05) whereas serum creatinine did not increase until 48 h after surgery. The diagnostic accuracy of [TIMP 2]*[IGFBP7] on day one after surgery for the prediction of AKI 2/3 was significantly better (sensitivity 0.89, specificity 0.81, AUC 0.817, 95 % CI 0.622-1.0 SE 0.099, p = 0.022, cut-off 0.817) than for serum creatinine (AUC 0.359, sensitivity 0.50, specificity of 0.52, cut-off value 1.17 mg/dl) and eGFR. Conclusion: Urinary [TIMP-2]*[IGFBP7] represents a sensitive and specific biomarker to predict moderate to severe AKI very early after CABG. Analyses from our ongoing larger study are necessary to confirm these findings and probably increase sensitivity and specificity.