Risk factors for severe anaphylaxis in the United States

Background Anaphylaxis is an acute systemic allergic reaction and may be life-threatening. Objective To assess risk factors associated with severe and near-fatal anaphylaxis in a large observational cohort study. Methods We analyzed administrative claims data from Medicare Advantage and privately insured enrollees in the United States from 2005 to 2014. Severe anaphylaxis was defined as anaphylaxis resulting in hospital or intensive care unit (ICU) admission, requiring endotracheal intubation, or meeting criteria for near-fatal anaphylaxis. Results Of 38,695 patients seen in the emergency department for anaphylaxis during the study period, 4,431 (11.5%) required hospitalization, 2,057 (5.3%) were admitted to the ICU, 567 (1.5%) required endotracheal intubation, and 174 (0.45%) were classified as having a near-fatal episode. Multivariable analysis revealed that medication-related anaphylaxis (odds ratio [OR], 1.50; 95% confidence interval [CI], 1.38–1.63; P <.001), age of 65 years or older (OR, 3.15; 95% CI, 2.88–3.44; P <.001), and the presence of cardiac disease (OR, 1.56; 95% CI, 1.50–1.63; P <.001) or lung disease (OR, 1.23; 95% CI, 1.16–1.30; P <.001) were associated with increased odds of severe anaphylaxis requiring any hospital admission, ICU admission, or intubation or being a near-fatal reaction. Conclusion In this large contemporary cohort study, 11.6% of patients had severe anaphylaxis. Age of 65 years or older, medication as a trigger, and presence of comorbid conditions (specifically cardiac and lung disease) were associated with significantly higher odds of severe anaphylaxis. Additional studies examining risk factors for severe anaphylaxis are needed to define risk assessment strategies and establish a framework for management.