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- Is it possible to develop a diagnostic scoring system to distinguish necrotizing fasciitis (NF) from other soft tissue infections based on laboratory tests routinely performed for the evaluation of severe soft tissue infections?
- Developed the Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score to aid in the to risk stratification of patients presenting with signs of cellulitis in order determine likelihoood of NF.
- The LRINEC score may help in detecting cases of necrotizing fasciitis, even early in the disease course. The variables used in the score are routinely measured to assess severe soft tissue infections. Patients with LRINEC score ≥ 6 should be careful evaluated for the presence of necrotizing fasciitis.
Using six laboratory measurements a Score greater than or equal to 6 indicates that necrotizing fasciitis (NF) should be considered high on the differential diagnosis. The LRINEC Scoring system is:
Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) Score
Has not been prospectively validated, index of suspicion is key and 10% of the patients with a score < 6 had Necrotizing Fasciitis. A score > 6 has PPV of 92% and NPV of 96% for necrotizing fasciitis.
- CRP (mg/L) ≥150: 4 points
- WBC count (×103/mm3)
- <15: 0 points
- 15–25: 1 point
- >25: 2 points
- Hemoglobin (g/dL)
- >13.5: 0 points
- 11–13.5: 1 point
- <11: 2 points
- Sodium (mmol/L) <135: 2 points
- Creatinine (umol/L) >141: 2 points
- Glucose >180 mg/dL (10 mmol/L): 1 point
Grouping by Scores
- Low Risk: score 5 (10% of pts with score < 6 still had nec fasc)
- Moderate Risk: score 6– 7
- High Risk: score >8
A LRINEC score, a score ≥ 6 is a reasonable cut-off to rule in necrotizing fasciitis, but a LRINEC < 6 does not completely rule out the diagnosis.
- Retrospective observational study, two teaching tertiary care hospitals from 1997-2002
- Patients divided into a developmental cohort (N=314) and a validation cohort (N=140)
- 145 with NF (study patients)
- 309 with severe cellulitis or abscesses (controls)
- Mean Age: 51.5 yo
- Male Gender: 63%
- Diabetes: 61%
- PVD: 19%
- Patients were identified through a computer-generated search through the Medical Records Department for all patients diagnosed with NF.
- Control patients were randomly selected (SAS statistical software) from 2555 patients admitted with the diagnosis of cellulitis or abscesses during the same period. Control patients were randomly selected from this patient pool.
- Severe soft tissue infections: based on documentation in the patients’ charts, the use of parenteral antibiotics for >48 hrs, and abscesses (when present) needing surgical debridement.
Internal validation of the data set was done by bootstrap resampling technique. External validation: performed in a separate cohort of 56 consecutive patients with necrotizing fasciitis seen at a separate hospital (Singapore General Hospital) be- tween June 1999 and December 2002.
- Eighty-four patients were randomly selected from patients admitted to that hospital for severe cellulitis or abscesses during the same period and used as controls.
- Controls were excluded from the retrospective controls. Patients with a length of stay of <48 hrs and the use of oral antibiotics only were excluded as these patients were considered
to have minor soft tissue infections.
Since this was a derivation with a internal validation in a retrospective fashion there were no interventions
- In the developmental cohort of 89 patients, only 13 (14.6%) patients had a diagnosis or suspicion of necrotizing fasciitis on admission. A majority were therefore initially missed, resulting in delayed operative debridement. In contrast, 80 (89.9%) of these patients had a LRINEC score of >6.
- A score of >8 is strongly predictive of necrotizing fasciitis (positive predictive value, 93.4%; 95% CI, 85.5–97.2).
Criticisms & Further Discussion
- Prior to derivation of the LRINEC score, the admission WBC > 15.4 x 10(9)/L or serum sodium [Na] < 135 mmol/L) was suggested as a method for distinguishing between patients with NF and nonnecrotizing soft tissue infection (non-NF). These two criteria had a PPV 26% and NPV 99%
- Other cases have shown than necrotizing fasciitis can exist in LRINEC cases of score 0 giving further support to clinical judgment overriding any scoring system for NF.
- This score was retrospectively derived and retrospectively validated and caution should be applied when relying on this rule since there has not been a prospective derivation. Clinical judgement should be used as the ultimate guide for escalating care for operative managment.
- ↑ Wong C. "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):1535-41.
- ↑ Wall DB et al. A simple model to help distinguish necrotizing fasciitis from nonnecrotizing soft tissue infection. J Am Coll Surg. 2000 Sep;191(3):227-31.