title: Treatment failure in emergency department patients with cellulitis.
abstract: OBJECTIVE
  To identify the rate of treatment failure in emergency department patients with cellulitis.
  
  
  METHODS
  This prospective observational convenience study enrolled adult patients with uncomplicated cellulitis. Physicians performed a standardized assessment prior to treatment. To calculate the interrater reliability of the assessment, duplicate data collection forms were completed on a small subsample of patients. Treatment failure was defined as the occurrence of any one of the following events after the initial emergency department visit: incision and drainage of abscess; change in antibiotics (not due to allergy/intolerance); specialist consultation; or, hospital admission. Comparison of means and proportions between the 2 groups was performed with univariate associations, using parametric or non-parametric tests where appropriate.
  
  
  RESULTS
  Seventy-five patients were enrolled; 57% were male, the mean age was 48 (standard deviation 19), 71 (95%) patients had extremity cellulitis and 10 (13%) had abscess with cellulitis. Fourteen episodes (18.7%, 95% confidence interval [CI] 11%-28%) were classified as treatment failures, with an oral antibiotic failure rate of 6.8% (95% CI 2%-22%) and an emergency department-based intravenous antibiotic failure rate of 26.1% (95% CI 16%-40%). Patients with treatment failure were older (mean age 59 yr v. 46 yr, p = 0.02) and more likely to have been taking oral antibiotics at enrollment (50% v. 16.4%, p = 0.01). Patients with a larger surface area of infection were also more likely to fail treatment (465.1 cm2 v. 101.5 cm2, p < 0.01). Interrater agreement was high for the presence of fever (kappa 1.0) and the size of surface area of infection (intraclass correlation coefficient 0.98), but low for assessments of both severity (kappa 0.35) and need for admission (kappa 0.46).
  
  
  CONCLUSIONS
  The treatment of cellulitis with daily emergency department-based intravenous antibiotics has a failure rate of more than 25% in our centre. Cellulitis patients with a larger surface area of infection and previous (failed) oral therapy are more likely to fail treatment. Further research should focus on defining eligibility for treatment with emergency department-based intravenous antibiotics.
authors.affiliation: Department of Emergency Medicine, Queen's University, Kingston, Ontario, Canada. hm9@post.queensu.ca
authors.forename: Heather
authors.initials: H
authors.lastname: Murray
authors.forename: Ian
authors.initials: I
authors.lastname: Stiell
authors.forename: George
authors.initials: G
authors.lastname: Wells