Retrospective analysis of the risk factors for linezolid-induced thrombocytopenia in adult Japanese patients

Background Thrombocytopenia is a major side effect of linezolid therapy. However, there are few reports about the risk factors for linezolid-induced thrombocytopenia. Objective The aim of this study is to evaluate the risk factors for thrombocytopenia in patients who undergo linezolid therapy. Setting Aomori Prefectural Central Hospital in Japan, a tertiary 695 beds hospital. Method A retrospective review was performed using the hospital's medical records. From January 2010 to August 2012, 75 adult patients who received linezolid therapy were enrolled in this study. Main outcome measure Linezolid-induced thrombocytopenia was defined as a decrease in the patient's platelet count to < 10 x 10(4)/mu L or a reduction of a parts per thousand yen30 % from their baseline value. Odds ratios (OR) for thrombocytopenia were analyzed using multivariate stepwise logistic regression analysis. Results Thrombocytopenia occurred in 29 patients (38.6 %), seven of whom required platelet transfusions. The patients who developed thrombocytopenia were significantly older, displayed a significantly higher frequency of renal insufficiency, and received linezolid therapy for significantly longer than the patients without thrombocytopenia. Stepwise logistic regression analysis suggested that receiving linezolid therapy for a parts per thousand yen14 days was a significant risk factor for thrombocytopenia [OR 13.3, 95 % confidence interval (CI) 3.2-55.6, p < 0.01], whereas the creatinine clearance rate exhibited a significant negative correlation with the incidence of the condition [OR 0.98, 95 % CI 0.96-0.99, p = 0.037]. The incidence of thrombocytopenia among the patients who demonstrated creatinine clearance rates of < 30 mL/min was 60 % (12/20), which was significantly higher than that observed among the patients who displayed creatinine clearance rates of more than 60 mL/min (26.4 %, 9/34, p = 0.014). Conclusion Receiving linezolid therapy for a parts per thousand yen14 days and a low creatinine clearance rate were suggested to be risk factors for linezolid-induced thrombocytopenia. The platelet counts of patients with these risk factors should be closely monitored.