Elevation of creatine kinase is associated with acute kidney injury in hospitalized patients infected with seasonal influenza virus

Background Although acute kidney injury (AKI) is known as a potential complication of influenza infections, there is limited information concerning the association between influenza and AKI. The aim of this study is to evaluate the incidence, the mortality, and risk factors of AKI in hospitalized patients by seasonal influenza viral infections. Methods We performed a single center, retrospective observational study. 123 patients admitted to Iwata City Hospital due to influenza for 3 seasons were included. We examined the association between the incidence of AKI and clinical parameters using Spearman's correlation analyses, receiver-operating characteristic (ROC) curves, and multivariate logistic regression analyses. Results Of 123 patients, AKI developed in 46 patients (37.4%). Patients with AKI showed higher serum creatine kinase (CK, P < 0.001), higher creatinine (Cr, P < 0.001), and higher C-reactive protein (CRP) levels (P < 0.001) at admission and higher mortality rate (P < 0.05) compared with patients without AKI. The severity of kidney injuries was well correlated with serum CK levels (P < 0.001). By ROC curve analysis, 186 U/L was the most predictive value of CK levels for AKI (sensitivity, 0.674; specificity, 0.688; and area under the curve [AUC], 0.714). Multivariate logistic regression analyses revealed that elevated CK levels (> 186 U/L) were significantly associated with AKI (P < 0.01). Conclusions The incidence of AKI and the mortality were high in hospitalized patients infected with seasonal influenza. The slight elevation of CK levels (> 186 U/L) at admission was associated with the development of AKI.