Monocyte to Lymphocyte Ratio, A Novel Predictor of Acute Kidney Injury After Cardiac Valve Surgery

Background: Although inflammation contributes to the development of acute kidney injury (AKI), the role of monocyte to lymphocyte ratio (MLR) in predicting the risk of postoperative AKI in patients underwent cardiac surgery is not completely clear yet. This study aimed to investigate whether elevated MLR predicts postoperative AKI.
Materials and methods: In this retrospective study, a total of 331 adult patients who underwent heart valve replacement were included. These patients are not distinguished between single valve replacement or double valve replacement. AKI was diagnosed, according to the KDIGO classification criteria. The associations between monocyte to lymphocyte ratio (MLR), neutrophil to lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR) and the occurrence of AKI were investigated.
Results: Postoperative AKI was detected in 37 (11.2%) patients. In the early period after surgery, the patients who developed AKI had a significant higher preoperative MLR than those who did not (0.38(0.33-0.44) vs. 0.26(0.20-0.34), = 0.02). The receiver operating characteristics (ROC) curve showed that the area under the curve (AUC) of the MLR for predicting AKI was 0.772 (P = 0.01), and the cut-off value was 0.47. Multivariate logistic regression analysis suggested that the higher preoperative MLR (≥0.47) was independent predictor of AKI (OR: 2.951, 95% CI: 1.412-6.167, P = 0.004). According to the cut-off value group verification, patients in the higher preoperative MLR group are more likely to have low cardiac output syndrome (LCOS), renal replacement therapy, and hospital death after surgery.
Conclusion: These results showed that MLR could be used as a cost-effective predictor of postoperative AKI in patients who undergo heart valve replacement surgery.