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The LRINEC score for Nec Fasc

The LRINEC score for Nec Fasc

Study: The LRINEC (Laboratory Risk Indicator for Necrotizing Fasciitis) score: A tool for distinguishing

necrotizing fasciitis from other soft tissue infections. Chin-Ho et al. Crit Care Med 2004 Vol. 32, No. 7

Purpose: It is difficult to distinguish necrotizing fasciitis (nec fasc) from abscess/cellulitis by clinical signs

early in the disease process. Nec fasc is a time sensitive disease which would benefit from earlier

recognition. The goal of the study was to find laboratory values that would raise a concern for Nec Fasc.

The Work

The study came out of Singapore in 2004. Through two hospitals they ran a development and validation

cohorts concurrently (a flaw, which we will discuss).

Development Cohort- Took all nec fasc patients from 1997-2002. Used OR defined nesc fasc, which is a

great standard, and were able to find 89 nesc fasc patients for analysis. They concurrently assessed the

lab values of 225 severe cellulitis or abscess patients. With these two groups outlined, the investigators

compared the available laboratory values of each group to assess for statistically significant differences

between groups.

Thirteen labs were reviewed for difference, and 6 were found to be statistically significantly different.

These are the components of the LRINEC score, outlined in Table 2.

Validation Cohort- In a hospital down the street they ran a concurrent (1997-2002) validation group.

They obtained 56 OR confirmed nec fasc cases and 84 randomly selected cellulitis/abscess patients.

They did an analysis of the LRINEC score for these two groups.

Results- Tables 3 and 4 show the statistical analysis of the initial variables with the univariate and

multivariate analyses. It is worth noting CRP was only available in ~85% of the patients. From these

analyses, the LRINEC score (table 2) was derived. In looking at the ORs of Table 4 and the points in the

final LRINEC score of Table 2, we see that a large association and weight is put in an elevated CRP.

In assessing the negative and positive predictive values of the score, the investigators found strong

numbers in a score ≥ 6, with a PPV 92% and a NPV of 96%.

Value of the Work

Initially I was concerned in the value of this paper and it representing a “data mining” project. While

there certainly are flaws in the study, the authors are very aware of them and discuss these limitations

in their discussion.

For me, the idea of a concurrently run “validation cohorot” in a hospital within the same city doesn’t

quite pass the litmus test. That said, other studies have come forward as true validation studies with

mixed results, but seeming to show some value in the NPV of the score

(http://hqmeded.com/necrotizing-fasciitis/).

The investigators did a fanstatic job in their wording of the value of their score. They state a score ≥6

“should raise suspicion for” nec fasc. Stronger language I think would have been inappropriate.

Secondly, they address the lack of clinical components to their score well. Again, nec fasc is a rapidly

progressive disease and the reliance on obvious clinical findings such as frank crepitus, hemorrhagic

bullae, etc would miss early disease and raise morbidity for patients. The hope is to find early nec fasc

and treat it quickly. Finally, the authors are very insightful in stating that the LRINEC score measures the

probability of nec fasc based on the severity of sepsis. They recognize the limitations of the score in

patients with multiple possible sources for laboratory derangements.

Take home

While at first I was hard on this paper for its data mining and pseudo-validation cohort, the discussion

and conclusion sections brought it back for me. The CRP is very heavily weighted in the score and while I

do not intend to follow the hard and fast cut offs of the LRINEC score itself, derangements in the

component laboratory values will increase my concern and aggressiveness in these patients.

#infectiousdisease #Musculoskeletal