Clinical Communications: Adults
A Case of Necrotizing Fasciitis with a LRINEC Score of Zero: Clinical Suspicion Should Trump Scoring Systems

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Abstract

Background

Necrotizing fasciitis (NF) is a potentially lethal infection involving the skin, subcutaneous tissue, and fascia. The Laboratory Risk Indicator for Necrotizing fasciitis (LRINEC) score has been proposed as a way of using abnormal laboratory values to distinguish between severe cellulitis and necrotizing fasciitis.

Objectives

The utility of the LRINEC system, including a review of current literature on this scoring system, is discussed.

Case Report

A case of a 37-year-old man is presented. As part of the diagnostic work-up, appropriate laboratory tests necessary to calculate a LRINEC score were obtained. Despite a LRINEC score of 0, NF was later confirmed at surgery.

Conclusions

Although the LRINEC score has been proposed as a robust way of identifying patients with early NF, it failed to detect NF in the patient reported here. NF should thus remain primarily a disease of clinical suspicion, and this suspicion should trump the LRINEC score.

Introduction

Necrotizing fasciitis (NF) is a potentially lethal infection involving the skin, subcutaneous tissue, and fascia. Although first described by Hippocrates, the term “necrotizing fasciitis” was coined by Wilson in 1951 (1). Although more than 2000 years have passed since the discovery of the disease, the mortality rate remains high, with approximately 25–35% of patients eventually succumbing despite modern surgical techniques and antibiotics (2). The prevalence, however, remains low at approximately 0.4 cases per 100,000 (2). The key to reducing mortality is early recognition and prompt treatment. This is often difficult, because the classic signs of NF, including fever, erythema, and bullae are frequently absent in early disease, and the frequency of NF is low enough to prevent any one provider from having extensive experience with NF (3). Thus, early disease is often mistaken for cellulitis or abscess, sometimes with disastrous consequences.

Several authors have noted that laboratory examinations in NF patients are often abnormal, unlike those same values in patients with severe cellulitis 4, 5, 6, 7. In 2004, Wong and colleagues proposed a way of using these abnormal laboratory values to differentiate cases of NF (6). The resulting scoring system, termed the Laboratory Risk Indicator for Necrotizing fasciitis (LRINEC) score, uses a combination of abnormal laboratory variables to calculate the risk of NF (Table 1). On this scoring system, scores ≥6 are highly predictive of NF, with an area under the curve (ie, accuracy) of approximately .98 and a negative predictive value of .96 6, 7.

Some authors have argued that because even such a robust score will incorrectly identify 4 out of 100 patients with NF, the diagnosis of NF should thus remain a clinical one 8, 9. Subsequent reports have shown, however, that cases of NF that are “missed” by LRINEC still have a positive score, even if it does not initially reach a cutoff of 6 on this scale. For instance, Holland (2009) noted that, in a tropical tertiary care referral center in Australia, the LRINEC score had only a negative predictive value of 86% (10). However, in this series of patients, all confirmed NF cases had a LRINEC score of at least 5; the negative predictive value of the LRINEC score in this population would have been 100% if the cutoff was lowered to this value. Indeed, in Wong's (2004) validation cohort of 56 patients with NF and 84 controls with severe cellulitis or abscess, the probability of NF was noted to approach zero as the LRINEC score approached zero (6).

Despite such studies showing the robustness of the LRINEC score, the score may nonetheless not be applicable to all patients. Here, for example, we report a case of surgically confirmed NF in which the LRINEC score was initially 0 in the Emergency Department (ED). This suggests that the LRINEC scoring system may poorly assess some patients and thus, may not be as valuable as clinical suspicion.

Section snippets

Case Report

A 37-year-old Spanish-speaking man presented to our mixed urban-suburban ED with a chief complaint of “left knee pain.” The triage nurse noted that the patient indicated similar symptoms when his knee was last infected, and that he had surgery “a few times.” No past medical history was available in the electronic medical record, as this was his first visit to our facility. Triage vitals noted a temperature of 36.6°C (97.8°F), a blood pressure of 121/94 mm Hg, a heart rate of 111 beats/min, a

Discussion

Early NF is often mistaken as cellulitis, especially if no crepitance or bullae are noted. The LRINEC score has been proposed by Wong and colleagues as a way of evaluating early NF, as a LRINEC score above 6 has an accuracy of approximately 98% in distinguishing NF from non-NF cases (6). Indeed, Wong and colleagues note in their 2004 paper that the LRINEC score “is a robust score capable of detecting even clinically early cases of NF” (6). Data reported in their original paper suggest that the

Conclusions

Although the LRINEC score has been proposed as a robust way of identifying patients with early NF, it failed to detect NF in the patient reported here. NF should thus remain primarily a disease of clinical suspicion. If the history or physical examination findings are suggestive of NF, this clinical suspicion should trump the LRINEC score.

Acknowledgments

The authors would like to thank Travis Gault, ba, who assisted in the preparation of this report.

References (11)

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    This notion is supported by a recent study in which 70% of patients admitted to the intensive care unit with NF had an LRINEC score of greater than 6 and the mortality was 29.3%66; patients with less severe disease were excluded. Subsequent studies have demonstrated the tool’s limited sensitivity when scores are less than 6 and therefore it should not be used to rule out a necrotizing soft tissue infection.64,67,68 In summary, for suspected necrotizing infections, no single clinical laboratory test or group of tests adequately replaces timely surgical inspection.

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