Patients with urticaria are at a higher risk of anaphylaxis: A nationwide population-based retrospective cohort study in Taiwan.

The clinical features of urticaria and anaphylaxis are similar, and they share common causal immune-mediated pathways. We aimed to investigate the risk of anaphylaxis among patients with urticaria. A 12-year population-based retrospective cohort study was conducted. Investigated subjects were identified from the Taiwan National Health Insurance Research Database by the International Classification of Disease, Ninth Revision, Clinical Modification. We included 126 031 subjects with newly diagnosed urticaria and 252 062 matched controls between 2000 and 2013. Risk of anaphylaxis among patients with urticaria was calculated by calculating adjusted hazards ratios (HR) after matching for confounding comorbidities. Urticaria was more common in women than it was in men (58% vs 42%), with a peak onset age of 20-40 years. The number of comorbidities including asthma, allergic rhinitis, herpes zoster, hepatitis B and C, rheumatoid arthritis and gout were higher in patients with urticaria than that in age- and sex-matched controls. The crude HR for anaphylaxis among urticaria subjects was 2.883 (95% confidence interval [CI], 2.787-2.982; P < 0.001). After adjustment for potential confounders which have been proposed to increase the risk of anaphylaxis, patients with urticaria were found to be at a significantly high risk of anaphylaxis with an adjusted HR of 2.529 (95% CI, 2.442-2.619; P < 0.001). We conclude that the incidence rate of anaphylaxis is significantly high in patients with urticaria in Taiwan.