Food was the principal trigger for 91% of recurrent episodes. Interestingly, children with recurrent anaphylaxis were 71% less likely to have peanut as a trigger, most likely because of extra vigilance regarding this notorious allergen, according to Dr. O’Keefe.
He noted a couple of significant study limitations. One is the small sample size. However, the study is being expanded to other academic medical centers across Canada, which will strengthen the findings.
The other limitation is the potential for bias introduced because parents whose child had severe anaphylaxis as the first episode were more than threefold more likely to participate in the prospective study. Still, the finding of a 29% annual recurrence rate among children in the Canadian study is not far afield from the results of some retrospective studies. For example, investigators at the Mayo Clinic reported as part of the Rochester Epidemiology Project a 21% incidence of a second anaphylactic event occurring at a median of 395 days after the first event in both child and adult residents of Olmsted County, Minn. (J. Allergy Clin. Immunol. 2008;122:1161-5).
That study and others also suggest that the incidence of anaphylaxis is increasing. In Olmsted County, the rate rose from 46.9 cases/100,000 persons in 1990 to 58.9 cases/100,000 in 2000.
Asked why the prehospital use of injectable epinephrine was so low in the Montreal children, Dr. O’Keefe said there are several possible reasons.
“We know that the rates among physicians as well as parents and children are lower than what they should be. Some of the reasons include failure to identify anaphylaxis, not having the device with you, and, finally, patients have to know how to use it and be willing to. There’s a psychological hurdle involving fear of misusing the device or hurting their child or using it inappropriately that prevents people from using it,” he said.
The study was supported by research grants from AllerGen, Health Canada, and Sanofi.