Klotho: a novel and early biomarker of acute kidney injury after cardiac valve replacement surgery in adults.

Klotho is a potential biomarker and therapeutic target in a model of acute kidney injury (AKI) induced in rats by ischemia-reperfusion injury. However, the sensitivity and specificity of serum Klotho for early detecting clinical AKI are unknown. This prospective study evaluated the significance of serum Klotho for early detection of postoperative AKI among adult patients undergoing cardiac valve replacement surgery. Moreover, we also compared the utilities of serum Klotho, serum creatinine and cystatin C in early detection of AKI. There was no marked difference between AKI and non-AKI groups in preoperative serum Klotho levels. Immediately after the operation, serum Klotho decreased significantly in patients with AKl. In spite of the poor specificity, its diagnostic sensitivity was excellent. On postoperative 1 d, with the rapid recovery toward the preoperative level, the ability of serum Klotho for early detecting AKI declined. Changes in serum Klotho levels at every time point among patients without AKI did not reveal any statistical significance. We showed that AKI is a state of transient Klotho deficiency in patients undergoing cardiac valve replacement surgery. Serum Klotho levels were drastically decreased beginning at 0h with ideal ROC-AUC, sensitivity but poor specificity, which didn't exceed 4 h after operation, suggesting that serum Klotho could serve as a potential biomarker for CSA-AKI, especially during the short period after cardiac surgery. A larger multicentre cohort study of population in different ages undergoing on-pump cardiac surgery is required to identify the optimal timing of serum Klotho measurement and the optimal cut-off points for clinical use to further refine the optimal timing for early detection of AKI.