Incidence of anaphylaxis with circulatory symptoms: a study over a 3-year period comprising 940 000 inhabitants of the Swiss Canton Bern

Background Diagnosis of anaphylaxis is clinically based and usually straightforward. However, data on the epidemiology of anaphylaxis, particularly the most profound and life-threatening form such as anaphylactic shock are limited and thought to be under-reported. Objective The primary aim of this study was to investigate the incidence and the causes of severe anaphylaxis with circulatory signs in the Canton Bern, which comprises about 940 000 inhabitants or approximately one-seventh of the population of Switzerland. Methods During a 3-year period, 1 January 1996 to 31 December 1998, all medical records (7739 documents) from the two allergy clinics of the Canton Bern have been reviewed. In addition, all seven board-certified specialists of the Foederatio Medicorum Helveticorum (FMH) in Allergology and Clinical Immunology of this Canton as well as all 17 hospitals with emergency units of this area have been contacted for cases with an anaphylactic event not referred to the allergy clinics. Results Overall, 226 individuals, 106 females (47%) with a mean age of 41 years (range, 5-74 years) and 120 males (53%) with a mean age of 38 years (8 months-83 years) were diagnosed as having presented generalized, life-threatening anaphylaxis with circulatory symptoms. Altogether, these patients experienced 246 episodes of severe systemic reactions. In addition, death due to anaphylaxis occurred in three subjects. The annual incidence of anaphylaxis per 100 000 inhabitants per year ranged between 7.9 and 9.6 cases. Hymenoptera stings (58.8%), drugs (18.1%), and foods (10.1%) were the most commonly identified culprits for anaphylaxis. In 5.3% of all anaphylactic events, the cause could not be identified. Conclusion The incidence rate of severe life-threatening anaphylaxis with circulatory signs in the Canton Bern, Switzerland, with 7.9-9.6 per 100 000 inhabitants per year is comparable to the findings of other epidemiological investigations. In most events, a causal agent or allergen could be identified by a careful allergological examination.