Background:

• Necrotizing soft tissue infections (NSTIs), such as necrotizing fasciitis (NF), are rapidly progressive diseases associated with significant morbidity and mortality, and outcomes rely on prompt diagnosis, early initiation of antibiotics and surgical debridement.
• NSTIs can be difficult to diagnose early as their classic features of erythema, edema and pain out of proportion are relatively nonspecific and the more definitive visible signs, such as hemorrhagic bullae, crepitus, ecchymotic discoloration or superficial necrosis, are late manifestations.

The LRINEC Score:

• The Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score was developed as a clinical decision tool to establish earlier NF diagnosis by helping distinguish it from other severe but non-necrotizing soft tissue infections, such as cellulitis or abscess.

Pitfalls:

#1 – Poor sensitivity

• Recent meta-analytical data has shown significant variability in the LRINEC score’s sensitivity (ranging from 36% to 77%) which does not allow for clinicians to confidently identify and rule out NF.

#2 – Poor external validation

• Subsequent trials attempting to validate the LRINEC score have failed to produce similar results. A summary comparing results is as follows:

#3 – Not validated in the ED

The original study used admitted patients and their admission bloodwork to derive their criteria.  These were patients who could have therefore had more time to develop systemic derangement, and NOT who the ED clinician would be trying to screen for early disease.

#4 – Trying to detect early disease with late-stage markers

• The LRINEC score’s ability to differentiate it from other non-necrotizing infections is based on the ability to generate points, BUT it uses markers (WBC, HgB, sodium, creatinine and glucose) that elevate in response to severe systemic derangement to detect early disease. Therefore, it makes sense that early cases (which have not had time to develop systemic derangement) could go undetected.

• The LRINEC score may be used as an adjunct to assist with the clinical diagnosis. While it’s good specificity allows it to help differentiate NF from other non-necrotizing infections, its poor sensitivity and weak PPV render it a sub-optimal screening tool and incapable of confidently identifying early NF.
• Scores >6 are NOT diagnostic of NF.
• Scores of <6 DO NOT rule out NF.
• Recent literature has suggested that the LRINEC score’s strong NPV may have a future role as a rule out tool, but further studies are required.

1. Hill J. Necrotizing Fasciitis and the Spectrum of Soft Tissue Infections. 2018. Available at: https://www.tamingthesru.com/blog/2018/9/3/necrotizing-fasciitis-and-the-spectrum-of-soft-tissue-infections. Accessed Dec 5, 2023.

   
   

2. Hwang C. LRINEC Score for Necrotizing Soft-Tissue Infection. 2018. Available at: https://www.ebmedicine.net/media_library/files/Calculated%20Decisions%20E0112%20LRINEC.pdf. Accessed Dec 5, 2023.

   
   

3. El-Menyar A, Asim M, Mudali IN, Mekkodathil A, Latifi R, Al-Thani H. The laboratory risk indicator for necrotizing fasciitis (LRINEC) scoring: the diagnostic and potential prognostic role. Scand J Trauma Resusc Emerg Med. 2017;25(1):28. Published 2017 Mar 7. doi:10.1186/s13049-017-0359-z

   
   

4. Wong CH, Khin LW, Heng KS, Tan KC, Low CO. The LRINEC (Laboratory Risk Indicator for Necrotizing Fasciitis) score: a tool for distinguishing necrotizing fasciitis from other soft tissue infections. Crit Care Med. 2004;32(7):1535-1541. doi:10.1097/01.ccm.0000129486.35458.7d

   
   

5. April MD, Long B. What Is the Accuracy of Physical Examination, Imaging, and the LRINEC Score for the Diagnosis of Necrotizing Soft Tissue Infection?. Ann Emerg Med. 2019;73(1):22-24. doi:10.1016/j.annemergmed.2018.06.029

   
   

6. Kim DH, Kim SW, Hwang SH. Application of the laboratory risk indicator for necrotizing fasciitis score to the head and neck: a systematic review and meta-analysis. ANZ J Surg. 2022;92(7-8):1631-1637. doi:10.1111/ans.17459

   
   

7. Tarricone A, Mata K, Gee A, et al. A Systematic Review and Meta-Analysis of the Effectiveness of LRINEC Score for Predicting Upper and Lower Extremity Necrotizing Fasciitis. J Foot Ankle Surg. 2022;61(2):384-389. doi:10.1053/j.jfas.2021.09.015

   
   

8. Johnson LJ, Crisologo PA, Sivaganesan S, Caldwell CC, Henning J. Evaluation of the Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score for detecting necrotizing soft tissue infections in patients with diabetes and lower extremity infection. Diabetes Res Clin Pract. 2021;171:108520. doi:10.1016/j.diabres.2020.108520

   
   

9. Bechar J, Sepehripour S, Hardwicke J, Filobbos G. Laboratory risk indicator for necrotising fasciitis (LRINEC) score for the assessment of early necrotising fasciitis: a systematic review of the literature. Ann R Coll Surg Engl. 2017 May;99(5):341-346. doi: 10.1308/rcsann.2017.0053. PMID: 28462647; PMCID: PMC5449710.