OBJECTIVES: The incidence of skin and skin structure infections (SSSIs) due to Staphylococcus aureus (SA) is increasing. There have been few published studies on the costs of outpatient treatment for SA-SSSIs.
METHODS: This retrospective analysis used a large managed-care database to assess the duration of SA-SSSI episodes treated with selected antibiotics (vancomycin, oral linezolid, and daptomycin, termed “study antibiotics”). Patients were included if they had a SA-SSSI between January 1, 2002 and December 31, 2005 based on ICD-9-CM codes. Treatment episodes began on the date of the first antibiotic and ended when the patient had fourteen consecutive days with no study antibiotic or SSSI hospitalization. Costs, represented by health plan payments, were updated to 2005 US dollars. A generalized linear model (GLM) was used to assess predictors of costs.
RESULTS: A total of 1,997 patients met the cohort selection criteria. Mean (SD) age was 46.3 (12.6) and 55.9% of patients were male. Average episode length was 24 days, and 95% of patients received vancomycin or oral linezolid as their initial study antibiotic. Patients remained on study antibiotics for approximately 16 days, and only 5% of patients were switched to another study antibiotic. Mean (SD) episode costs were $9,250 ($20,357) [median, $3,327 IQR: $1,643 to $8,128], represented primarily by pharmacy and outpatient medical services. Based on the GLM, we found that treatment failure (i.e., study antibiotic switching or hospitalization), bacteremia, osteomyelitis, multiple complications, Charlson comorbidity score, treatment with daptomycin, and episode duration were all significant positive predictors of costs. Alternatively, treatment with oral linezolid, hospitalization prior to receiving a study antibiotic, and receipt of a non-study antibiotic before the treatment episode were significant negative predictors of costs.
CONCLUSION: The costs of treating SA-SSSIs are substantial and vary by type of antibiotic therapy, comorbidities, and failure rates.
