Beyond the LRINEC Score: A stratified diagnostic algorithm for subacute and atypical necrotizing fasciitis

While typical Necrotizing Soft Tissue Infections (NSTI) are clinically overt, atypical and subacute presentations pose a complex diagnostic challenge. These forms-characterized by subacute evolution, deceptive local signs, or atypical pathogens-often defy standard recognition patterns. The Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score is frequently utilized for emergency risk stratification; however, its sensitivity remains contested in contemporary literature.

We conducted a retrospective observational study (2007-2025) of 37 confirmed NSTI patients at a regional tertiary Plastic Surgery referral center. We analyzed admission physiology, microbiological profiles, and calculated retrospective LRINEC and SIARI (Site, Immuno, Age, Renal, Inflam) scores. To validate findings against potential data handling bias, a sensitivity analysis comparing zero-imputation versus complete case analysis was performed.

Despite high clinical severity (43.2% septic shock), the LRINEC score yielded a false negative rate of 18.9% (7/37 patients classified as "Low Risk"). These failures correlated with atypical profiles: head and neck localization, prior administration of non-steroidal anti-inflammatory drugs (NSAID), and subacute pathogens (Cutibacterium acnes, Actinomyces). Sensitivity analysis confirmed the statistical stability of these findings (P=0.66). Conversely, the SIARI score correctly reclassified all LRINEC false negative cases as high risk (Score ≥ 3).

The LRINEC score exhibits insufficient negative predictive value to safely exclude atypical and subacute NSTIs, potentially causing hazardous delays in surgical intervention. We propose a stratified clinical algorithm designed to enhance surgical vigilance and reduce the risk of missed diagnosis.