Early detection of cardiac surgery‑associated acute kidney injury by microRNA-21.

We tested the hypothesis whether microRNA-21 (miR-21) can detect CSA-AKI earlier than serum creatinine (sCr). A total of 103 patients scheduled to undergo cardiac surgery. CSA-AKI was defined as sCr > 0.3 mg/dl 24 h after surgery. The patients were divided into two groups according to whether or not developing AKI after surgery. Serum and urinary miR-21 were measured prior to, and 6, 12 and 24 h after surgery. Baseline serum and urinary levels of miR-21 in AKI group were lower than in non-AKI group. Moreover, the levels of miR-21 were significantly lower 6 h after surgery for serum, and 6 and 12 h after surgery for urine samples than those before surgery in AKI group. Area under the curve (AUC) of the receiver operating characteristic (ROC) values were 0.81 (95% CI: 0.65-0.97) for serum miR-21 (6 h after surgery), 0.90 (95% CI: 0.79-0.99) for urine (6 h after surgery), and 0.86 (95% CI: 0.71-0.98) for urine (12 h after surgery). While both postoperative serum and urinary miR-21 levels can predict AKI development, urinary miR-21 especially 6 h after surgery is a more reliable marker than serum miR-21 for detection of established CSA-AKI (Tab. 1, Fig. 3, Ref. 43).