Use of the LRINEC Score in Diabetic Patients

Abstract

Background: The LRINEC (laboratory risk indicators for necrotizing fasciitis) score was developed in 2004 to help distinguish necrotizing fasciitis from severe soft tissue infections. Some of the laboratory tests, however, may be elevated at baseline in diabetic patients. Aim: To evaluate the use of the LRINEC score in diabetic patients. Patients and methods: A retrospective study was performed on all patients admitted with either a primary diagnosis of cellulitis or necrotizing fasciitis between April 2010 and June 2014. Patients were excluded if they did not have the appropriate presenting lab values to calculate a LRINEC score. Presenting lab values were used to calculate each patient’s LRINEC score and diabetic status was evaluated using International Classification of Diseases (ICD)-9 coding. All cases of necrotizing fasciitis were confirmed surgically. Results: A total of 670 patients met our inclusion criteria with 415 non-diabetic patients and 255 diabetic patients. Twenty-four of the non-diabetic patients (6.1%) and 11 of the diabetic patients (4.3%) had surgically confirmed necrotizing fasciitis. The average presenting LRINEC score in non-diabetic patients with and without necrotizing fasciitis was 6.9 ± 2.4 and 2.5 ± 2.4, respectively. The average presenting LRINEC score in diabetic patients with and without necrotizing fasciitis was 9.8 ± 2.1 and 4.1 ± 2.9, respectively. These scores were significantly higher (p < 0.01) than their non-diabetic counterparts. The sensitivity and specificity of a LRINEC score of 6 in non-diabetic patients was 0.79 (95% CI 0.57-0.99) and 0.86 (95% CI 0.82-0.89), respectively. In diabetic patients, the sensitivity and specificity were 0.91 (95% CI 0.57-0.99) and 0.72 (95% CI 0.67-0.78). Discussion: The LRINEC score is significantly higher in diabetic patients when compared with non-diabetic patients. Using a cutoff score of 6 produces a test with a poor specificity in diabetic patients. Introduction Necrotizing fasciitis is a serious, life threatening soft tissue infection that can spread rapidly along fascial planes. This rapid spread often leads to hemodynamic instability, systemic sepsis and can eventually lead to multi-organ failure and death. Given the severity of this infection, early diagnosis and treatment, including surgical debridement, are vital. Diagnosis of necrotizing fasciitis is a clinical diagnosis, and given the consequences in delayed treatment, it should be managed with a high index of suspicion. Unfortunately, the common presenting features of swelling, pain and erythema [1] are non-specific and early necrotizing fasciitis can easily be mistaken for cellulitis [2], which is largely treated non-operatively. There are “hard signs” of necrotizing fasciitis that are more specific including pain out of proportion, rapidly spreading infection, bullae, skin ecchymosis/sloughing, gas in tissue, skin anesthesia, edema beyond erythema and sepsis, but these are only present in 43% of cases [3]. Various adjunct tests have been described to help with this challenging clinical problem including advanced imaging, the finger test, tissue oxygen monitoring, and early histological analysis [4,5]. Another diagnostic aid is the laboratory risk indicators for necrotizing fasciitis (LRINEC score). This test was introduced by Wong, et al. in 2004 as a diagnostic aid using common laboratory test to distinguish necrotizing fasciitis from other severe soft tissue infections [6]. The LRINEC score is a weighted score from 0-13, using C-reactive protein, glucose, sodium, white blood cell count, hemoglobin and creatinine. Table 1 shows the variables and weighted scoring system used to calculate the LRINEC score. As originally described, a score of at least 6 had a positive *Corresponding author: Timothy Cheng, MD, Department of Orthopaedic Surgery, University of California San Diego, 200 West Arbor Drive, San Diego, CA 92103, USA, Tel: +858-336-0453, E-mail: ttc003@ucsd.edu OriginAl reSeArCh ArTiCle