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Background: Anaphylaxis due to unknown trigger (AUT) is anaphylaxis not explained by a proved or presumptive cause or stimulus at the time of the reaction. Research describing the management and follow-up of AUT is limited., Objective: To assess and compare the demographic and clinical characteristics and the management of adult and pediatric AUT cases across Canada., Methods: Participants were identified between 2011 and 2018 in emergency departments at 8 centers across Canada as part of the Cross-Canada Anaphylaxis Registry. A standardized form documenting the reaction and management in children and adults was completed. Patients were contacted for follow-up to determine assessment by an allergist., Results: A total of 295 AUT cases (7.5%) were recruited among 3,922 cases of anaphylaxis. In the prehospital setting, children (adjusted odds ratio [aOR], 1.20; 95% CI, 1.05-1.37) and those with a known food allergy (aOR, 1.14; 95% CI, 1.02-1.28) were more likely to receive treatment with epinephrine. Children were also more likely to be assessed by an allergist after their reaction (aOR, 1.43; 95% CI, 1.13-1.81) and were more likely to have an identified trigger for their reaction (aOR, 1.35; 95% CI, 1.07-1.70). Among patients contacted for follow-up, food was identified as the cause of reaction in 11 of 76 patients. A new food allergy was diagnosed in 4 patients (2 children and 2 adults)., Conclusions: Our findings highlight important differences between management and follow-up of adult and pediatric AUT cases. It is crucial to follow up all cases of AUT and establish appropriate treatment and management guidelines., (Copyright © 2018 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Background: Studies suggest knowledge gaps about epinephrine use and vaccination of persons with egg allergy., Objective: We compared the perception of Canadian allergists and nonallergists on issues related to epinephrine use and vaccination of persons with egg allergy., Methods: Canadian allergists, pediatricians, general practitioners/family physicians and emergency room physicians were recruited through medical associations and surveyed on these issues. Multivariate logistic regression models were used to identify determinants of specific responses., Results: One-hundred fourteen allergists and 613 nonallergists participated. For most issues with accepted best practices, allergists were more likely to adhere to recommendations. Allergists versus nonallergists were more likely to recommend intramuscular epinephrine for anaphylaxis (odds ratio [OR] = 3.8; 95% CI, 1.43-10.11). Older physicians (OR = 0.98; 95% CI, 0.97-0.99), Canadian-Paediatric-Surveillance-Program participants (OR = 0.48; 95% CI, 0.24-0.96), family physicians (OR = 0.39; 95% CI, 0.16-0.96), and general practitioners (OR = 0.14; 95% CI, 0.04-0.52) were less likely to recommend intramuscular use. However, in severe anaphylaxis, >25% of both groups would not give epinephrine for patients presenting with breathing difficulties or hypotension. Use of epinephrine for severe anaphylaxis was less likely in older physicians (OR = 0.97; 95% CI, 0.95-0.99), female physicians (OR = 0.60; 95% CI, 0.39-0.89), and those practicing in Ontario (OR = 0.56; 95% CI, 0.36-0.86), Manitoba (OR = 0.42; 95% CI, 0.19-0.90), or Nova-Scotia (OR = 0.31; 95% CI, 0.12-0.78). Allergists (OR = 6.22; 95% CI, 3.60-10.72) and physicians treating mainly children (OR = 3.41; 95% CI, 1.87-6.25), or practicing in Quebec (OR = 1.68; 95% CI, 1.12-2.55) were more likely to recommend measles-mumps-rubella vaccination in a community facility., Conclusion: Knowledge gaps about mode and indications for epinephrine administration and vaccination policies need to be addressed in future education programs to ensure prompt epinephrine use and to avoid unnecessary restriction of vaccines., (Copyright © 2013 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)