Comparison of biphasic and monophasic anaphylaxis
Patients with monophasic anaphylaxis (n = 224) and biphasic anaphylaxis (n = 13), did not differ by sex, mean age or age distribution (Supplemental Figure), cardiovascular disease, diabetes, dysthyroidism, chronic urticaria, renal failure, beta-blocker treatment, inhaled corticosteroids use, proton pump inhibitor use or smoking habits (Table 2). However, asthma was more frequent with biphasic than monophasic anaphylaxis (n=6/13, 46.1%; vs 38/224, 16.9%; odds ratio = 4 [95% confidence interval 1.05-14.81], p = 0.02). In the monophasic group, 19 patients had mild asthma, 16 moderate asthma and 3 severe asthma. In the biphasic group, 4 patients had mild asthma and 2 moderate asthma. The proportion of patients with atopic disease was similar in both groups (34/38, 89%; and 5/6, 83%). The two groups did not differ in the use of inhaled corticosteroids (n=19/38, 50%; and 2/6, 33%, odds ratio= 0.341 [95% confidence interval 0.03-2.23], p = 0.26).
The two groups did not differ in history of allergic rhino-conjunctivitis, atopic dermatitis, contact eczema, history of Hymenoptera venom allergy, food allergy or drug hypersensitivity (Table 2) or severity grade of anaphylaxis, skin involvement, respiratory symptoms, digestive symptoms and use of epinephrine (Table 3). However, loss of consciousness during the first phase was more frequent with biphasic than monophasic anaphylaxis (100% of biphasic patients vs 58.9% of monophasic patients, p= 0.008) (Table 3). The distribution of culprit allergens was similar in both groups, with Hymenoptera venom and NMBAs the most frequently reported in our allergy center (Table 4).
Basal tryptase levels were significantly higher with biphasic than monophasic anaphylaxis (median: 6.1 µg/l, n = 13 vs 4.2 µg/l, n = 224, p=0.009) (Figure 2). For asthma patients, basal tryptase level was significantly higher for those with biphasic than monophasic anaphylaxis (median: 5.3 µg/l, n = 6 vs 3.7 µg/l, n = 38, p=0.015). Of note, although with Hymenoptera venom allergy, basal tryptase level was similar with biphasic and monophasic anaphylaxis (median 4.9 vs 4.5 µg/l, p=0.46), for drug allergy, the level was significantly higher with biphasic than monophasic anaphylaxis (median 11.2 vs 4.2 µg/L, p=0.0004).