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

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Finding	Sensitivity	Specificity	Comments, Study
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
Laboratory Risk Indicator in Necrotising Fasciitis	80%	67%	LRINEC >= 6 http://www.mdcalc.com/lrinec-score-for-necrotizing-soft-tissue-infection/ Study: Anaesth Intensive Care. 2009 Jul;37(4):588-92. PMID: 19681416 Crit Care Med. 2004 Jul;32(7):1535-41. PMID: 15241098
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
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