Prospective derivation and validation of a NECROtizing Soft tissue InfectionS (NECROSIS) score: An EAST multicenter trial

BACKGROUND Although several risk indices have been developed to aid in the diagnosis of necrotizing soft tissue infections (NSTIs), these instruments suffer from varying levels of reproducibility and failure to incorporate key clinical variables in model development. The objective of this study was to derive and validate a clinical risk index score, NECROSIS, for identifying NSTIs in emergency general surgery (EGS) patients being evaluated for severe skin and soft tissue infections. METHODS We performed a prospective study across 16 sites in the United States of adult EGS patients with suspected NSTIs over a 30-month period. Variables analyzed included demographics, admission vitals and laboratories, physical examination, radiographic, and operative findings. The main outcome measure was the presence of NSTI diagnosed clinically at the time of surgery. Multivariate analysis was performed to identify independent predictors for the presence of NSTI using the Hosmer-Lemeshow test and the Akaike information criteria. RESULTS Of 362 patients, 297 (82%) were diagnosed with an NSTI. Overall mortality was 12.3%. Multivariate analysis identified three independent predictors for NSTI: systolic blood pressure of ≤120 mm Hg, violaceous skin, and white blood cell count of ≥15 × 10 3 /μL. Multivariate modeling demonstrated Hosmer-Lemeshow goodness of fit ( p = 0.9) with a c statistic for the prediction curve of 0.75. Test characteristics of the NECROSIS score were similar between the derivation and validation cohorts. CONCLUSION NECROSIS is a simple and potentially useful clinical index score for identifying at-risk EGS patients with NSTIs. Future validation studies are warranted. LEVEL OF EVIDENCE Diagnostic Tests or Criteria; Level III.