From the Guidelines
Necrotizing fasciitis, not "necrotizing Tacitus," is diagnosed through laboratory tests including complete blood count (CBC), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), comprehensive metabolic panel, creatine kinase (CK), and blood cultures, with the Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score being a helpful tool. The LRINEC score, as proposed by Sartelli et al. 1, assigns points for abnormalities in six independent variables: serum C-reactive protein level (> 150 mg/L), white blood cell (WBC) count (> 15,000/μL), hemoglobin level (< 13.5 g/dL), serum sodium level (< 135 mmol/L), serum creatinine level (> 1.6 mg/dL [142 mmol/l]), and serum glucose level (> 180 mg/dL [10 mmol/l]). With a score of 8 or higher, there is a 75% risk of a necrotizing soft tissue infection (NSTI).
Key Laboratory Tests
- Complete blood count (CBC) showing elevated white blood cell count with left shift
- C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) showing inflammation
- Comprehensive metabolic panel revealing electrolyte abnormalities
- Creatine kinase (CK) showing muscle damage
- Blood cultures to identify causative organisms
Importance of Early Diagnosis
Early diagnosis of necrotizing fasciitis is crucial, as it is a rapidly progressing infection requiring immediate surgical intervention and broad-spectrum antibiotics to prevent severe complications including sepsis and death, as emphasized by the Infectious Diseases Society of America 1. Imaging studies like MRI, CT scan, or ultrasound may complement laboratory findings but are not laboratory tests themselves. The most important diagnostic feature of necrotizing fasciitis is the appearance of the subcutaneous tissues or fascial planes at operation, with clinical judgment being the most important element in diagnosis.
From the Research
Laboratory Findings for Necrotizing Fasciitis
The following laboratory findings may indicate necrotizing fasciitis:
- Elevated white blood cell count (WBC) >14 x 10(9)/L 2
- Serum sodium <135 mmol/L 2
- Blood urea nitrogen (BUN) >15 mg/dL 2
- Lactic acid of 8.2 mg/dL or higher 3
- Presence of gas within the necrotized fasciae (characteristic but may be lacking) 4
Diagnostic Challenges
- No single laboratory value can diagnose necrotizing fasciitis; ultimately, necrotizing fasciitis is a clinical diagnosis 3
- Imaging studies can help to differentiate necrotizing fasciitis from infections located more superficially, but findings lack specificity 4
- The gold standard for diagnosis remains intraoperative tissue culture 5