Relationship between serum total IgE and disease severity in patients with allergic asthma in Spain

To evaluate the association between serum total IgE levels and disease severity in adult patients with persistent allergic asthma and to explore the main predictors of IgE levels. We performed a multicenter, retrospective, observational study including adult patients diagnosed ≥ 1 year previously with persistent allergic asthma who were positive to ≥ 1 allergen. Patients also had serum total IgE and spirometry results available from the previous 12 months. Inclusion was stratified by asthma severity according to the GEMA 2009 criteria. We included 383 patients with allergic asthma (129 mild, 82 moderate, and 172 severe). Mean (SD) age was 38 (15), 46 (16), and 45 (15) years, respectively (P < 0.001). Serum total IgE levels varied markedly (coefficient of variation, 147%). No association was observed with forced expiratory volume in 1 second (FEV1) or asthma severity: mean (SD)/median (IQR) of 403 (616)/214 (108-409), 361 (516)/204 (126-361), and 473 (676)/211 (98-545) IU/mL in the mild, moderate, and severe subgroups, respectively (P = .951). The severe subgroup had a higher percentage of patients with > 400 IU/mL (36% vs 26.4% [mild] and 18.3% [moderate], P = .010). In a multivariate multiple regression model, the independent predictors of higher IgE were younger age (P = .004), sensitization to ≥ 2 allergens (P = .009), male gender (P = .025), and family history of asthma (P = .122). Serum total IgE levels in adult patients with persistent allergic asthma were high (two-thirds with levels > 150 IU/mL) and extremely variable. We did not find a significant association between serum total IgE levels and asthma severity or airflow limitation, except for a higher percentage of patients with IgE > 400 IU/mL in the severe subgroup.