Evaluating the Laboratory Risk Indicator to Differentiate Cellulitis from Necrotizing Fasciitis in the Emergency Department
Abstract
Introduction: Necrotizing fasciitis (NF) is an uncommon but rapidly progressive infection that results in grossmorbidity and mortality if not treated in its early stages. The Laboratory Risk Indicator for Necrotizing Fasciitis(LRINEC) score is used to distinguish NF from other soft tissue infections such as cellulitis or abscess. Thisstudy analyzed the ability of the LRINEC score to accurately rule out NF in patients who were confirmed tohave cellulitis, as well as the capability to differentiate cellulitis from NF.
Methods: This was a 10-year retrospective chart-review study that included emergency department (ED)patients ≥18 years old with a diagnosis of cellulitis or NF. We calculated a LRINEC score ranging from0-13 for each patient with all pertinent laboratory values. Three categories were developed per the originalLRINEC score guidelines denoting NF risk stratification: high risk (LRINEC score ≥8), moderate risk (LRINECscore 6-7), and low risk (LRINEC score ≤5). All cases missing laboratory values were due to the absence ofa C-reactive protein (CRP) value. Since the score for a negative or positive CRP value for the LRINEC scorewas 0 or 4 respectively, a LRINEC score of 0 or 1 without a CRP value would have placed the patient in the“low risk” group and a LRINEC score of 8 or greater without CRP value would have placed the patient in the“high risk” group. These patients missing CRP values were added to these respective groups.
Results: Among the 948 ED patients with cellulitis, more than one-tenth (10.7%, n=102 of 948) weremoderate or high risk for NF based on LRINEC score. Of the 135 ED patients with a diagnosis of NF, 22patients had valid CRP laboratory values and LRINEC scores were calculated. Among the other 113 patientswithout CRP values, six patients had a LRINEC score ≥ 8, and 19 patients had a LRINEC score ≤ 1. Thus, atotal of 47 patients were further classified based on LRINEC score without a CRP value. More than half of theNF group (63.8%, n=30 of 47) had a low risk based on LRINEC ≤5. Moreover, LRINEC appeared to performbetter in the diabetes population than in the non-diabetes population.
Conclusion: The LRINEC score may not be an accurate tool for NF risk stratification and differentiationbetween cellulitis and NF in the ED setting. This decision instrument demonstrated a high false positive ratewhen determining NF risk stratification in confirmed cases of celulitis and a high false negative rate in casesof confirmed NF.