Diagnostic Differentiation of Necrotising Fasciitis from Severe Cellulitis and Erysipelas: A Prospective Study of Clinical, Laboratory and Intraoperative Predictors

Abstract

Background: Necrotising fasciitis (NF) is a rapidly progressive and potentially fatal soft-tissue infection in which early diagnosis remains challenging because its initial clinical appearance may resemble severe cellulitis or erysipelas. Delay in surgical intervention is associated with increased morbidity and mortality. Clinical examination, inflammatory biomarkers and scoring systems such as the Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) may assist diagnosis, although none should replace clinical judgement and urgent surgical assessment. Methods: This prospective observational study included 50 consecutive adult patients presenting with severe soft-tissue infection and clinical suspicion of either NF, severe cellulitis or erysipelas. Patients were evaluated clinically and underwent complete blood count, C-reactive protein (CRP), serum sodium, creatinine, glucose and other routine biochemical investigations. LRINEC scores were calculated at admission. Patients with suspected NF underwent urgent surgical exploration, with intraoperative findings considered the reference standard. Patients were categorized into a necrotising infection group and a non-necrotising group. Clinical, laboratory and operative variables were compared using chi-square/Fisher's exact test and independent-samples t-test. A p value <0.05 was considered statistically significant. Results: Of 50 patients, 21 (42.0%) had surgically confirmed NF and 29 (58.0%) had non-necrotising infection, including severe cellulitis and erysipelas. Severe pain disproportionate to the visible skin findings, edema extending beyond erythema, bullae/skin discoloration, hypotension and altered sensorium were significantly more frequent in NF. Mean CRP, total leukocyte count, serum creatinine and LRINEC score were significantly higher, while serum sodium was significantly lower, in the NF group. A LRINEC score ≥6 was present in 16 (76.2%) patients with NF compared with 5 (17.2%) non-NF patients (p<0.001). Intraoperative fascial edema, grayish necrotic fascia, thin brownish fluid and easy blunt dissection were strongly associated with NF. Early surgical exploration within 12 hours was associated with lower postoperative complication rates. Conclusion: NF should be suspected in patients with severe pain out of proportion, rapidly progressive edema, systemic toxicity, bullous or necrotic skin changes and characteristic laboratory abnormalities. LRINEC may support clinical assessment but should not be used alone to exclude NF. In patients with significant clinical suspicion, prompt surgical exploration remains the most reliable method of confirming the diagnosis. The practical approach should therefore combine high clinical suspicion, appropriate laboratory assessment and immediate surgical evaluation. When NF is clinically suspected, definitive surgical exploration should not be delayed for laboratory scoring or imaging.

Keywords: necrotising fasciitis; cellulitis; erysipelas; LRINEC; C-reactive protein; surgical exploration; soft-tissue infection.