Who is at-risk for severe anaphylaxis in France?

Background: The understanding of risk factors related to severe anaphylaxis is key to implementing prevention strategies. We present the first French population-based nine-year anaphylaxis hospitalization study evaluating specific trends and factors related to severe anaphylaxis (SA), to support identification of phenotypes at-risk. Methods: This study used descriptive data from the French hospitalization database for the years 2012–2021, and included all patients hospitalized with anaphylaxis using International Classification of Diseases (ICD)-10 codes listed as a primary diagnosis. SA were cases that either required a hospitalization in intensive care units or resulted in death. Potential risk factors were identified according to corresponding ICD codes, available as secondary data during the patient's hospitalization. Results: The average hospitalization rate of all cases of anaphylaxis (SA and non-SA) was 1.34/100,000/year, and rate of admissions for SA was 0.08/100,000/year. Among the 5463 SA, 37.7% had unspecified coding label, when trigger was not identified. For SA cases in which trigger was identified, most were related to drugs (45.6%), followed by food (9.3%) and insect sting (7.2%). Overall, admissions due to anaphylaxis (SA and non-SA) were more frequent in males (57%). However, when the trigger was drugs, the proportion was significantly higher in females. For children aged 5–9 years, the most common trigger for SA was food. Patients for which SA was triggered by insect stings were identified exclusively in the 10–14 years age group. Chronic spontaneous urticaria was associated with insect sting-induced anaphylaxis, regardless of the severity. Angioedema was associated with all causes of SA. Cases of anaphylaxis presenting with urticaria and angioedema included cases with identified and unidentified triggers. Asthma and a personal history of allergy were associated with drug- and food-induced anaphylaxis. Conclusion: This is the first study to provide data on severe phenotypes of anaphylaxis in France. Data presented is key to the implementation of public health actions and preventive strategies to improve quality care.