Initial Serum C-reactive Protein Level as a Predictor of Increasing Serum Vancomycin Concentration During Treatment

Background: Vancomycin has a narrow therapeutic window, and an increase in its serum concentration-to-dose ratio during treatment can cause renal toxicity. Therefore, this study was aimed at finding a marker to identify patients at risk of increasing serum vancomycin during treatment. Methods: This was a retrospective cohort study of patients treated with vancomycin at Kanazawa University Hospital, Japan, from April 2012 to May 2015. Spearman correlation coefficients were calculated to determine the correlations between changes in vancomycin concentration-to-dose ratio and initial values or changes in laboratory data and other parameters. In addition, a multiple regression analysis was conducted. Results: One hundred ninety-nine patients for whom 2 or more points of data on therapeutic drug monitoring (TDM) of intravenous vancomycin treatment were available and did not undergo dialysis were included in the study. Changes in vancomycin concentration-to-dose ratio were associated with C-reactive protein (CRP) and sodium (Na) levels on the initial day of TDM and with changes in white blood cell count, Na, and estimated glomerular filtration rates (eGFRs). Multiple regression analysis helped identify CRP and Na levels on the initial day of TDM and change in eGFR as independent influencing variables. Conclusions: A high serum CRP level on the initial day of TDM is an independent predictor of increasing vancomycin concentration-to-dose ratio in patients receiving intravenous vancomycin treatment, even if eGFR remains unchanged.