Evaluation of near-fatal reactions to allergen immunotherapy injections

Background: The overall incidence of near-fatal reactions (NFRs) after immunotherapy injections is unknown. Investigation of NFRs might identify preventive strategies that could avert fatal immunotherapy reactions. Objective: We sought to determine the incidence and characteristics of NFRs to allergen immunotherapy. Methods: In a brief survey of fatal reactions (FRs) and NFRs administered to practicing allergists, 273 of 646 respondents reported NFRs after immunotherapy injections; a NFR was defined as respiratory compromise, hypotension, or both requiring emergency epinephrine. Respondents were mailed a 105-item questionnaire regarding the details of NFRs and circumstances of these events. Results: During the period from 1990 through 2001, the incidence of unconfirmed NFRs was estimated at 23 per year (5.4 events per million injections). There were 68 confirmed NFRs on the basis of responses to the long survey, with a mean case incidence of 4.7 per year or I NFR per million injections. Asthma was present in 46% of near-fatal reactors and in 88% of fatal reactors identified in this study. Hypotension was reported in 80% and respiratory failure occurred in 10% of NFRs and exclusively in asthmatic subjects. Epinephrine was delayed or not administered in 6% of NFRs versus 30% of reported FRs (OR, 7.3; 95% Cl, 1.4-39.8; P = .01). Conclusions: Confirmed NFRs were 2.5 times more frequent than FRs. Favorable outcomes of NFRs when compared with FRs could be related to lower asthma prevalence and appropriate management of life-threatening anaphylaxis.