The association between L1 skeletal muscle index derived from routine CT and in-hospital mortality in CAP patients in the ED

Introduction: Low muscle mass is associated with an increased mortality risk due to medical comorbidities such as chronic obstructive pulmonary disease, cardiovascular disease, and cerebrovascular disease. Computed tomography (CT) has been identified as the gold standard for measuring body composition. We evaluated the relationship between the L1 SMI measured from CT and in-hospital mortality in patients with community-acquired pneumonia (CAP). Methods: From January 2015 to June 2015, 311 patients who were diagnosed with CAP and underwent CT in the ED were retrospectively analyzed. Multivariate binary logistic regression analysis was used to assess independent predictors of in-hospital mortality. All variables with a significance level < 0.1 by univariate analysis were included in a multivariate logistic regression model. The primary outcome was all-cause in-hospital mortality. Results: Among the 311 patients, 33 (10.6%) died. We divided the patients into two groups based on the optimal sex-specific cut-off value of the L1 SMI (45 cm2/m2 in males and 40 cm2/m2 in females). A low L1 SMI was present in 90 (28.9%) of the 311 patients. In multivariate analysis, low L1 SMI, diabetes mellitus, albumin and APACHE II score were significantly associated with in-hospital mortality (aOR 3.39, 3.73, 0.09 and 1.10, respectively). Conclusion: SMI assessment at L1 is achievable in patients with CAP receiving routine chest CT, and the L1 SMI is associated with high in-hospital mortality, more hospitalizations and ventilator application in patients with CAP in the ED. This could help establish an early strategy for critical care of patients with L1 SMI obtained by chest CT for diagnosis in CAP patients in the ED. •Community-acquired pneumonia is the leading cause of death from infection worldwide.•Low muscle mass is associated with an increased mortality risk in critically ill.•SMI assessment at L1 is achievable in patients with CAP receiving routine chest CT.•Low L1 SMI is associated with higher mortality, more hospitalization and ventilator application in CAP.•L1 SMI could help establish early strategies for critical care in patients with CAP in the ED.