Anaphylaxis is a potentially life-threatening allergic reaction, but even when appropriately treated, there is a strong risk of recurrence, according to a new study.

The report in the Annals of Allergy, Asthma and Immunology looked at risk factors associated with recurrent anaphylaxis-related emergency department (ED) visits within a year of a previous visit with the same presentation.

For the large observational cohort study, Mayo Clinic researchers used an administrative claims database to identify patients seeking emergency care for anaphylaxis from 2008 through 2012, based on an International Classification of Diseases, Ninth Revision,

Clinical Modification diagnosis code algorithm. Patients with at least 2 years of continuous enrollment in a health plan were included. During the 5-year study period, 7,367 patients with a median age of 42 years—adults making up about 77% of the total—met the inclusion criteria.

The researchers reported the following as the most common anaphylaxis triggers:
• Unspecified (56.2%)
• Food (25.3%)
• Medication (14.6%)
• Venom (3.9%)

Results indicated that, overall, 3.0% of patients had an additional anaphylaxis-related ED visit within 1 year (3.61 episodes per 100 patient-years). Using multivariable analysis, the study team determined that risk factors associated with anaphylaxis recurrence were food trigger (odds ratio [OR], 2.31; 95% confidence interval [CI], 1.34-3.99), history of asthma (OR, 1.30; 95% CI, 1.13-1.51), and intensive care unit admission at the index anaphylaxis event (OR, 1.95; 95% CI, 1.41-2.69).

“In this contemporary cohort study, history of asthma, food trigger, and greater index anaphylaxis severity, as measured by intensive care unit admission, were associated with a higher likelihood of a recurrent anaphylaxis-related ED visit within one year,” the study authors concluded.

Another study focusing on a pediatric cohort found similar results. Based on a telephone survey of 166 children who had been hospitalized in an intensive care unit for anaphylaxis, the report in Pediatric Allergy and Immunology found that the main index triggers were drugs (45%) and foods (37%). Over nearly 8 years of follow-up, 36% of the children experienced 399 new allergic reactions, and 12 of them required intensive care unit readmission.

“Food was the trigger for 79% of recurrent reactions and drugs for 8%. The food trigger was previously known in 83%, the same as the index trigger in 69%,” noted the researchers from Children’s Hospital, Roubaix, France.

Overall, 1.5% of the recurrent reactions were treated with adrenaline injection and 8% required an emergency hospital admission. Recurrence appeared to be linked to history of food allergy (P <10-4), asthma (P <.005), and atopic dermatitis (P <.05).

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