The Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score is useful as a negative predictor of necrotizing soft tissue infection in patients with diabetes and a lower extremity infection, according to study findings published in Diabetes Research and Clinical Practice.
Researchers evaluated 69 patients with type 2 diabetes who presented to the emergency department from September 2017 to October 2018 with a lower extremity infection that required surgical intervention. Investigators measured laboratory values for C-reactive protein, white blood cells, hemoglobin, sodium, creatinine, and glucose at presentation and calculated the LRINEC.
Of the participants, 4 were diagnosed with a necrotizing soft tissue infection (5.8%), 3 patients had a polymicrobial infection; 1 patient had a monomicrobial group A beta-hemolytic streptococcal infection. Half of the necrotizing soft tissue infection cases had overt necrosis noted on pathologic examination. In addition, 2 of these patients had subcutaneous emphysema noted on plain film radiographs, and 1 patient had a computed tomography scan that also demonstrated soft tissue emphysema.
The researchers found that the LRINEC was associated with a diagnosis of necrotizing soft tissue infection (P = .01). The sensitivity, specificity, positive predictive value, and negative predictive value were 100%, 69%, 16.6%, and 100%, respectively. In addition, increased C-reactive protein (odds ratio [OR] 1.01, P =.02, 95% CI 1.002-1.23) and white blood cell count (OR 1.34, P <.01, 95% CI 1.1-1.7) were associated with necrotizing soft tissue infection.
“The LRINEC was useful as a negative predictor of NSTI, while C-reactive protein and WBC count may have value as individual predictors,” stated the study authors. “We recommend high clinical suspicion of NSTIs in diabetics as laboratory evaluation may be nonspecific.”
Study limitations included the small number of patients with necrotizing soft tissue infection.
“Absence of emphysema on plain film radiography cannot rule out a diagnosis of NSTI,” the researchers commented. “Advanced imaging has high sensitivities, but these tests are time consuming and delay to surgical debridement in NTSIs increases rates of morbidity and mortality…. In this study, LRINEC may be useful in ruling out NSTIs in this patient population, especially in the setting of a normal [C-reactive protein] and [white blood cell count].”
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. org/10.1016/j.diabres.2020.108520