Development and Validation of a Cellulitis Risk Score: The Melbourne ASSET Score

BACKGROUND: The evidence is unclear about the optimal route of treatment for children with cellulitis, specifically how to assess the risk of moderate-to-severe cellulitis requiring intravenous (IV) antibiotics. We aimed to derive and validate a cellulitis risk assessment scoring system to guide providers as to which patients require IV antibiotics. METHODS: This was a prospective cohort study of children presenting to the emergency department aged 6 months to 18 years diagnosed with cellulitis from January 2014 to August 2017. Patients were divided into 2 groups based on route of antibiotics at 24 hours (the predetermined gold standard). Demographics and clinical features were compared. Clinicians were surveyed about which features they used to decide whether to start IV antibiotics. Combinations of differentiating features were plotted on receiver operating characteristic curves. RESULTS: There were 285 children in the derivation cohort used to create the Melbourne Area, Systemic features, Swelling, Eye, Tenderness (ASSET) Score, which has a maximum score of 7. The area under the curve was 0.86 (95% confidence interval 0.83-0.91). Using a cutoff score of 4 to start IV antibiotics yielded the highest correct classification of 80% of patients (sensitivity 60%; specificity 93%). This score was validated in 251 children and maintained a robust area under the curve of 0.83 (95% confidence interval 0.78-0.89). CONCLUSIONS: The Melbourne ASSET Score was derived and validated for cellulitis in children to guide clinicians regarding when to start IV antibiotics. Although intended for widespread use, if limitations exist in other settings, it is designed to allow for refinement and is amenable to local impact analysis.