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The following is a summary of “Biphasic anaphylaxis in a Canadian tertiary care centre: an evaluation of incidence and risk factors from electronic health records and telephone interviews,” published in the February 2025 issue of Allergy, Asthma & Clinical Immunology by Ellis et al.
A 2007 study in Kingston, Ontario, reported a 19.4% biphasic anaphylaxis rate. Few updates exist on its etiology and risk factors.
Researchers conducted a retrospective study to evaluate the incidence and predictors of biphasic anaphylaxis in a single centre. They analyzed records of patients with diagnosed anaphylaxis.
They evaluated all patients diagnosed with “allergic reaction,” “anaphylaxis,” “drug allergy,” or “insect sting allergy” in 2 Kingston hospitals from November 2015 to August 2017. They contacted patients post-ED discharge for consent and symptom confirmation. A trained allergist assessed anaphylaxis criteria and classified reactions as uniphasic, biphasic, or non-anaphylactic biphasic. They conducted a full medical review and statistically compared each type of anaphylactic event.
The results showed that of 138 anaphylactic events, 15.94% were biphasic, 79.0% were uniphasic, and 5.07% were non-anaphylactic biphasic. The second reaction occurred at an average of 19.0 h. Biphasic reactions were less severe than initial reactions (P = 0.0002) but more severe than non-anaphylactic biphasic events (P < 0.0001). No management differences were found.
Investigators found a 15.94% incidence of biphasic reactions with a second-phase onset at 19.0 h. The second reaction was less severe than the first.
Source: aacijournal.biomedcentral.com/articles/10.1186/s13223-024-00919-2
