Don't Count on the LRINEC Score for Necrotizing Fasciitis

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Don't rely on the LRINEC score to distinguish which patients do or do not have necrotizing fasciitis (NF).  It fails as a reliable diagnostic screening test.  NF remains a clinical diagnosis.  For a free, awesome morsel of FOAM, emDocs has a list of cellulitis mimics that is, quite simply, a fantastic bit of scholarship.  If you're new to EM, this is must-read.

Why does this matter?
You may get push back from colleagues who tell you the patient "can't have NF" because their LRINEC score is low.  Remember, don't trust this score.  NF is a clinical diagnosis.  If you suspect it, call in the surgeons.

Can you tell nec fasc from cellulitis? Neither can the LRINEC score.
The LRINEC score (worst mnemonic ever...) was designed to help distinguish routine cellulitis from necrotizing fasciitis (NF).  See the score here on MDCalc.  This ten year retrospective chart review sampled 948 patients with cellulitis and 135 patients with NF.  The LRINEC score categorized 10.7% of the cellulitis patients as at risk for NF - false positives.  Of the 135 actual NF patients, only 47 could be scored (lacked CRP) and 30/47 (64%) were categorized as low risk - false negative.  Scary.  The LRINEC score as originally derived was highly accurate, but subsequent external validation studies have shown it to be pretty awful.  See our previous post on the original landmark LRINEC article

Source
Evaluating the Laboratory Risk Indicator to Differentiate Cellulitis from Necrotizing Fasciitis in the Emergency Department.  West J Emerg Med. 2017 Jun;18(4):684-689. doi: 10.5811/westjem.2017.3.33607. Epub 2017 May 12.

Peer reviewed by Thomas Davis, MD.