Clinical Characteristics and Histopathology in Suspected Necrotizing Soft Tissue Infections.

Background: Necrotizing soft tissue infections (NSTIs) are severe diseases with high morbidity and mortality. The diagnosis is challenging. Several guidelines recommend tissue biopsies as an adjunct diagnostic in routine management, but neither biopsy sampling nor classification is standardized or validated. We studied the quality of tissue biopsy examination as part of routine diagnostics in NSTIs.

Methods: This was a retrospective cohort study of adult patients undergoing surgery due to suspected NSTIs in which tissue biopsy was taken as part of routine management. Clinical data were reviewed. The biopsies were evaluated according to a proposed histopathologic classification system and independently assessed by 2 pathologists. Interrater reliability and diagnostic accuracy were determined.

Results: Tissue biopsies from 75 patients were examined, 55 NSTIs and 20 non-NSTIs cases. The cohorts were similar in clinical characteristics. Interrater reliability for histopathologic staging was moderate (0.53) and fair (0.37) for diagnosis. The sensitivity of histologic diagnosis was 75% and the specificity 80%. The positive predictive value was 91% and the negative predictive value 53%. Necrotizing Infection Clinical Composite Endpoint (NICCE) success was associated with a more severe histological stage, achieved by 42% and 71% of the cases in stage 1 and 2, respectively ( = .046).

Conclusions: Our findings suggest that tissue biopsies have low clinical accuracy. The interrater reliability among experienced pathologists is only fair to moderate. A histopathologically more severe stage was associated with favorable outcome. These findings discourage the use of histopathologic evaluation as part of contemporary management of patients with suspected NSTI.