Validation of the Baseline Recurrence Risk in Cellulitis (BRRISC) score and the added impact of acute clinical response

Objectives The BRRISC score predicts hospital-attended recurrence of cellulitis using baseline clinical data. In practice, clinicians assess treatment response when deciding antibiotic duration. We investigated whether markers of acute clinical response improved prognostic score performance within an external validation cohort. Methods We recruited adults with lower limb cellulitis attending hospital. Outcomes included ‘hospital-attended recurrence’ (primary outcome for validation) and ‘any recurrence’. We assessed clinical response from days 0-3 of treatment. Using multivariate logistic regression with backwards elimination, we identified response variables independently associated with either outcome for an extended score. Results Of 202 patients, 8% (n=17) experienced ‘hospital-attended recurrence’ and 23% (n=46) ‘any recurrence’. In this validation dataset, the BRRISC score had a C-index=0.75 (95%CI, 0.64-0.86) for predicting ‘hospital-attended recurrence’. There was weak evidence that an extended score, incorporating day-2/3 severity of skin blistering, improved the C-index to 0.83 (0.75-0.92). No acute clinical response variables were independently associated with ‘any recurrence’ after adjusting for BRRISC score. Conclusion Our measures of early clinical response did not add useful prognostic information to BRRISC score baseline risk. Further research should consider whether responses after day-3 add helpful information, whether risk stratification can personalise antibiotic duration, and explore non-antibiotic approaches to prevent recurrence.