Predictors of failure of empiric outpatient antibiotic therapy in emergency department patients with uncomplicated cellulitis.

BACKGROUND: Despite several expert panel recommendations and cellulitis treatment guidelines, there are currently no clinical decision rules to assist clinicians in deciding which emergency department (ED) patients should be treated with oral antibiotics and which patients require intravenous (IV) therapy at first presentation of cellulitis amenable to outpatient treatment.

OBJECTIVES: The objective was to determine risk factors associated with adult patients presenting to the ED with cellulitis who fail initial antibiotic therapy as outpatients and require a change of antibiotics or admission to hospital.

METHODS: This was a prospective cohort study of patients 18 years of age or older presenting with cellulitis to one of two tertiary care EDs (combined annual census 140,000). Patients were excluded if they had been treated with antibiotics for the cellulitis before presenting to the ED, if they were admitted to the hospital, or if they had an abscess only. Trained research personnel administered a questionnaire at the initial ED visit with telephone follow-up 2 weeks later. Multivariable logistic regression models determined predictor variables independently associated with treatment failure (failed initial antibiotic therapy and required a change of antibiotics or admission to hospital).

RESULTS: A total of 598 patients were enrolled, 52 were excluded, and 49 were lost to follow-up. The mean (±standard deviation [SD]) age was 53.1 (±18.4) years and 56.4% were male. A total of 185 patients (37.2%) were given oral antibiotics, 231 (46.5%) were given IV antibiotics, and 81 patients (16.3%) received both oral and IV antibiotics in the ED. A total of 102 (20.5%, 95% confidence [CI] = 17.2% to 24.2%) patients had treatment failures. Fever (temperature > 38°C) at triage (odds ratio [OR] = 4.3, 95% CI = 1.6 to 11.7), chronic leg ulcers (OR = 2.5, 95% CI = 1.1 to 5.2), chronic edema or lymphedema (OR = 2.5, 95% CI = 1.5 to 4.2), prior cellulitis in the same area (OR = 2.1, 95% CI = 1.3 to 3.5), and cellulitis at a wound site (OR = 1.9, 95% CI = 1.2 to 3.0) were independently associated with treatment failure.

CONCLUSIONS: These risk factors should be considered when initiating empiric antibiotic therapy for ED patients with cellulitis amenable to outpatient treatment.