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

Objectives: 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.
Methods: 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.
Results: 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).
Conclusion: 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.