Laboratory findings consistent with the diagnosis of necrotizing fasciitis include positive blood and tissue culture, elevated inflammatory markers, leukocytosis and elevated serum creatinine.

Laboratory tests consistent with diagnosis of necrotizing fasciitis include:^[1]

The following are the tests used to diagnose the causative organism:

• Gram stain and culture of tissues and aspirates
• Blood culture
• Culture of throat and vaginal swabs
• Fungal culture (immunocompromised or trauma patients)
• Enrichment cultures (patients with recent antibiotic use)

The biochemistry findings consistent with diagnosis of necrotizing fasciitis include:

• Elevated C-reactive protein
• Elevated serum creatine kinase
• Hypocalcemia (sign of severity in synergistic NF)
• Hypoalbuminemia
• Hyponatremia (<135mmol/L)
• Elevated serum lactate levels (high serum lactate combined with low sodium levels may be predictive of mortality)
• Arterial blood gas (ABG) analysis
• Urine analysis
• Elevated blood urea nitrogen (BUN)

The following are complete blood count with differential findings:

• Rapidly falling hemoglobin
• Leukocytosis (>14,000/µL)
• Leukopenia (if associated with STSS)
• Lymphopenia
• Thrombocytopenia

Other diagnostic studies of necrotizing fasciitis include:^[2]

• Tissue oxygen saturation monitoring:

• Occurs at the bedside.
• Is a noninvasive method to continuously monitor extremities at risk and avoid delayed diagnosis
  • Tissue oxygen saturation is measured using near-infrared spectroscopy.
• In patients with necrotizing faciitis, oxygen saturation are often diminished in the lower extremities and return to normal after fasciotomy.