Risk factors for anaemia in patients on prolonged linezolid therapy for chronic osteomyelitis: a case-control study

Objectives: The intrinsic properties of the new antibiotic linezolid make it an attractive candidate for the treatment of chronic osteomyelitis. However, data regarding the tolerance of long-term linezolid administration are still lacking. Methods: The medical charts of patients given linezolid for >4 weeks were retrospectively analysed, especially their haematology. In a case-control study, we compared the respective characteristics of patients who developed anaemia during linezolid therapy and those who did not. Results: Forty-five adults with chronic osteomyelitis received 600 mg linezolid intravenously twice daily for 7 days, and then orally, for a mean total duration of 15.9 weeks (range, 6-36). Anaemia episodes requiring blood transfusion occurred in 13/45 patients (28.9%). Median time from treatment initiation to anaemia onset was 7.4 weeks (range, 4-16). Anaemia was significantly associated with premature linezolid therapy cessation (P=0.0012). No linezolid-related thrombocytopenia was observed. By univariate analysis, four variables were associated with the occurrence of anaemia: age >58 years, alcohol abuse, diabetes mellitus and low haemoglobin before linezolid treatment. Logistic regression analysis revealed two independent risk factors for anaemia: age >58 years (OR = 20.5, 95% CI 0.69-599; P=0.0001) and pre-treatment haemoglobin <10.5 g/dL (OR = 16.49, 95% CI 1.06-255; P=0.04). Conclusions: Profound anaemia may occur in adult patients with chronic osteomyelitis on prolonged linezolid therapy, and often necessitates linezolid cessation. These patients are likely to be aged >58 years and to have low pre-treatment haemoglobin. The results for the present series might help physicians to identify patients who should not be given long-term linezolid treatment for chronic osteomyelitis.