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Evaluating the Laboratory Risk Indicator to Differentiate Cellulitis from Necrotizing Fasciitis in the Emergency
Michael M Neeki1,2, Fanglong Dong3, Christine Au3
1Arrowhead Regional Medical Center, Department of Emergency Medicine, Colton, California.
Introduction:
Necrotizing fasciitis (NF) is an uncommon but rapidly progressive infection that results in gross morbidity 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. This study analyzed the ability of the LRINEC score to accurately rule out NF in patients who were confirmed to have 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 from 0-13 for each patient with all pertinent laboratory values. Three categories were developed per the original LRINEC score guidelines denoting NF risk stratification: high risk (LRINEC score ≥8), moderate risk (LRINEC score 6-7), and low risk (LRINEC score ≤5). All cases missing laboratory values were due to the absence of a C-reactive protein (CRP) value. Since the score for a negative or positive CRP value for the LRINEC score was 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) were moderate or high risk for NF based on LRINEC score. Of the 135 ED patients with a diagnosis of NF, 22 patients had valid CRP laboratory values and LRINEC scores were calculated. Among the other 113 patients without CRP values, six patients had a LRINEC score ≥ 8, and 19 patients had a LRINEC score ≤ 1. Thus, a total of 47 patients were further classified based on LRINEC score without a CRP value. More than half of the NF group (63.8%, n=30 of 47) had a low risk based on LRINEC ≤5. Moreover, LRINEC appeared to perform better 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 differentiation between cellulitis and NF in the ED setting. This decision instrument demonstrated a high false positive rate when determining NF risk stratification in confirmed cases of cellulitis and a high false negative rate in cases of confirmed NF.
Insights
The Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score is not reliable for diagnosing necrotizing fasciitis (NF) in emergency departments. It shows high false positive and false negative rates, making it inaccurate for differentiating NF from cellulitis.
Area of Science:
- Emergency Medicine
- Infectious Diseases
- Surgical Infections
Background:
- Necrotizing fasciitis (NF) is a severe, rapidly progressing soft tissue infection with high morbidity and mortality.
- Accurate early diagnosis is critical for effective treatment.
- The Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score is a tool used to differentiate NF from other soft tissue infections.
Purpose of the Study:
- To evaluate the accuracy of the LRINEC score in ruling out NF in patients with confirmed cellulitis.
- To assess the LRINEC score's capability in differentiating between cellulitis and NF in the emergency department (ED) setting.
Main Methods:
- A 10-year retrospective chart review of ED patients (≥18 years) diagnosed with cellulitis or NF.
- Calculation of LRINEC scores (0-13) using laboratory values, including C-reactive protein (CRP).
- Stratification into high (≥8), moderate (6-7), and low (≤5) risk categories, with methods to handle missing CRP values.
Main Results:
- Over 10% of cellulitis patients had moderate or high LRINEC scores.
- Among confirmed NF patients, a significant proportion (63.8%) were classified as low risk (LRINEC ≤5), especially those with missing CRP values.
- The LRINEC score performed better in patients with diabetes compared to those without.
Conclusions:
- The LRINEC score demonstrates limited accuracy for NF risk stratification and differentiation from cellulitis in the ED.
- The tool exhibits a high false positive rate in cellulitis cases and a high false negative rate in confirmed NF cases.
- Clinical judgment alongside the LRINEC score is essential for accurate diagnosis and management of suspected NF.
