Necrotizing Fasciitis: Sensitivity and Specificity

Introduction: An extremely deadly soft tissue infection involving the deep fascia. This may be caused by Group A Streptococcus or gas-forming organisms such as Clostridium perfringens.

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Tags: Infection Musculoskeletal Tag this Diagnosis.

The sensitivity and specificity of findings for Necrotizing Fasciitis are listed below. See the left navigation bar to change the display.

Sensitive and Specific Findings

MRI

100%

86%

But based on a more recent paper, sensitivity and specificity are likely lower. Exact values will depend on which imaging findings are considered.

Study: AJR Am J Roentgenol. 1998 Mar;170(3):615-20. PMID: 9490940

Radiology. 2011 Jun;259(3):816-24. PMID: 21406630

Sensitive Findings

CT Scan

100%

81%

Versus non-necrotizing soft tissue infections. (Gold standard - surgery and pathology.)

From the article: Four elements consistent with NSTI were sought in particular: (1) asymmetrical and diffuse areas of soft tissue inflammation and ischemia, (2) muscle necrosis, (3) gas across tissue planes, and (4) fluid collections. The test (CT) result was considered positive for NSTI if it identified inflamed and ischemic or necrotic soft tissues with or without gas and fluid collections. It was considered negative if no such findings were reported.

Study: Arch Surg. 2010 May;145(5):452-5. PMID: 20479343

Leukocytosis or Hyponatremia

90%

76%

admission WBC > 15.4 x 10(9)/L or serum sodium [Na] < 135 mmol/L

Study: J Am Coll Surg. 2000 Sep;191(3):227-31. PMID: 10989895

Poorly Diagnostic Findings

Laboratory Risk Indicator in Necrotising Fasciitis

80%

67%

LRINEC >= 6

http://www.mdcalc.com/lrinec-score-for-necrotizing-soft-tissue-infection/