A simple model to help distinguish necrotizing fasciitis from nonnecrotizing soft tissue infection.

Abstract

Necrotizing fasciitis (NF) has been associated with certain "hard" clinical signs (hypotension, crepitance, skin necrosis, bullae, and gas on x-ray), but these may not always be present. Using results of a previous study, we developed a simple model to serve as an adjunctive tool in diagnosing NF (admission WBC > 15.4 x 10(9)/L or serum sodium [Na] < 135 mmol/L) and determined its ability to distinguish between patients with NF and nonnecrotizing soft tissue infection (non-NF). A retrospective review was conducted of consecutive NF (n=31) and non-NF patients (n= 328) treated at a single institution during an 11-month period. Comparison of admission vital signs, physical examination findings, radiology results, and number of patients meeting model criteria was performed. Ninety percent of NF patients and 24% of non-NF patients met model criteria (p < 0.0001). The model had a sensitivity of 90%, a specificity of 76%, a positive predictive value of 26%, and a negative predictive value of 99% for diagnosing NF. Nineteen (61%) NF patients had no "hard" signs of NF; the model correctly classified 18 (95%) of these patients. Admission WBC greater than 15.4 x 10(9)/L and serum Na less than 135mmol/L are useful parameters that may help to distinguish NF from non-NF infection, particularly when classic "hard" signs of NF are absent.