Biphasic reactions in patients with anaphylaxis treated with corticosteroids

Although the incidence of anaphylaxis is rapidly increasing, the clinical characteristics and associated factors of a biphasic reaction are unclear.

To determine the incidence and clinical characteristics of biphasic reactions in patients with anaphylaxis treated with corticosteroids.

A total of 655 patients with anaphylaxis visiting the emergency department of a tertiary teaching hospital from January 2007 through December 2014 were analyzed. Patient characteristics, triggers, symptoms and signs, in-hospital management, and disposition were recorded. A biphasic reaction was defined as the development of anaphylaxis after complete resolution of the initial reaction without further exposure to the offending agent within 7 days. Univariate and multivariate analyses on the predictors of the biphasic reaction were performed.

Of the 415 patients with anaphylaxis treated with corticosteroids, 9 patients (2.2%) developed a biphasic reaction. The mean age was 48.4 years, and 221 patients (54.4%) were women. The median time from complete resolution of initial clinical symptoms to occurrence of the biphasic reaction was 15 hours (range 1-45). History of drug anaphylaxis (odds ratio 14.3, 95% confidence interval 2.4-85.8) was a contributing factor to the development of the biphasic reaction.

The incidence of biphasic reactions was 2.2% in patients treated with corticosteroids and those with a history of drug anaphylaxis were at greater risk.