Urinary TIMP-2 and IGFBP-7 protein levels as early predictors of acute kidney injury after cardiac surgery.

BACKGROUND: Acute kidney injury (AKI) is a frequent complication associated with on-pump cardiac surgery. Early recognition may alter their prognosis. Therefore, the urinary concentrations of TIMP-2 (tissue inhibitor of metalloproteinases-2) and IGFBP7 (insulin-like growth factor-binding protein) as predictors for AKI were studied.

METHODS: Repetitive blood and urine samples were collected consecutively from 50 patients. Demographic, intra-, and postoperative data were recorded prospectively. To calculate the production of the TIMP-2 and IGFBP-7 protein concentrations, urinary samples were taken preoperatively, intraoperatively at 30 and 60 min after aortic clamping and at 0, 6, 12, and 24 h after admission to the intensive care unit (ICU).

RESULTS: AKI occurred in 14 patients (28%), all of them at Kidney Disease: Improving Global Outcomes stage 1. Predictive value for [TIMP-2] × [IGFBP7] was shown at 0 and 24 h after admission to ICU. At 0 h, the sensitivity was 84.6% and the specificity 55.6% for an ideal calculated cutoff at 0.07. After 24 h, the ideal cutoff amounted to 0.35 with a sensitivity of 53.8% and a specificity of 88.2%. The receiver operating characteristic curves demonstrated areas under the curve of 0.725 and 0.718. The suggested cutoffs of 0.3 and 2.0 could not be confirmed. The serum creatinine was reached to the peak median within 48 h after admission to ICU.

CONCLUSION: Postoperative risk assessment for the development of AKI can be established by [ TIMP - 2 ] × [ IGFBP 7 ] . Previously suggested cutoff values could not be confirmed. A correlation with urinary dilution parameters may enable the identification of more universal cutoffs.