Prevalence and predictors of initial oral antibiotic treatment failure in adult emergency department patients with cellulitis: a pilot study

INTRODUCTION Assessment of cellulitis severity in the emergency department (ED) setting is problematic. Given the lack of research performed to describe the epidemiology and management of cellulitis, it is unsurprising that heterogeneous antibiotic prescribing and poor adherence to guidelines is common. It has been shown that up to 20.5% of ED patients with cellulitis require either a change in route or dose of the initially prescribed antibiotic regimen. The current treatment failure rate for empirically prescribed oral antibiotic therapy in Irish EDs is unknown. The association of patient risk factors with treatment failure has not been described in our setting. Lower prevalence of community-acquired methicillin-resistant Staphylococcus aureus-associated infection, differing antibiotic prescribing preferences and varying availability of outpatient intravenous therapy programmes may result in different rates of empiric antibiotic treatment failure from those previously described. METHODS AND ANALYSIS Consecutive ED patients with cellulitis will be enrolled on a 24/7 basis from 3 Irish EDs. A prespecified set of clinical variables will be measured on each patient discharged on empiric oral antibiotic therapy. A second independent study recruiter will assess at least 10% of cases for each of the predictor variables. Follow-up by telephone call will occur at 14 days for all discharged patients where measurement of the primary outcome will occur. Our primary outcome is treatment failure, defined as a change in route of antibiotic administration from oral to intravenous antibiotic. Our secondary outcome is change in dose or type of prescribed antibiotic. A cohort of approximately 152 patients is required to estimate the proportion of patients failing oral antibiotic treatment with a margin of error of 0.05 around the estimate. ETHICS AND DISSEMINATION Full ethics approval has been granted. An integrated dissemination plan, involving diverse clinical specialties and enrolled patients, is described. TRIAL REGISTRATION NUMBER NCT 02230813.