Recurrent anaphylaxis in the United States: time of onset and risk factors

Background: Studies have not yet examined the trends and risk factors of biphasic and recurrent anaphylaxis in the United States using International Classification of Diseases, tenth revision (ICD-10) CM codes. The goal of this study is to examine the trends of biphasic and recurrent anaphylaxis in all patient care settings (inpatient, outpatient, emergency department, and observation). Methods: We used the Clinformatics database from 2015 to 2017. Our main outcome measure was recurrent anaphylactic events occurring within 1 year after the initial event. We used Cox proportional hazards modeling to assess the factors associated with recurrent anaphylaxis and the Kaplan-Meier method to estimate time to recurrence. Results: There were a total of 19,039 patients with incident anaphylaxis in 2016 and, of these, 2017 had a recurrent anaphylaxis event in the 12-month period after the index date (10.6%). The most common trigger for recurrent anaphylaxis is venom followed by food allergens. Pediatric patients aged <18 years were more likely to develop recurrent anaphylaxis compared with patients aged 18 to 64 years (hazard ratio [HR], 1.53). Patients with allergic rhinitis and asthma were more likely to develop recurrent anaphylaxis compared to those without these comorbidities (HR, 1.15 and 1.27, respectively). Conclusion: This is the first national study using ICD-10 CM codes looking at rates of biphasic and recurrent anaphylaxis in all patient care settings. Recurrent anaphylaxis is more common in the first 3 days after the initial event, in younger patients (<18 years), and in patients with allergic rhinitis and/or asthma. Physicians need to prescribe epinephrine auto-injectors and educate their patients about the risk of recurrence.