Overlap of atopic, eosinophilic, and TH2-high asthma phenotypes in a general population with current asthma

Abstract

BackgroundAtopic, eosinophilic, and TH2-high asthma phenotypes may overlap, but the extent is unknown. Understanding the overlap across these phenotypes may be useful in guiding asthma patient care. ObjectiveTo examine the frequency and overlap of atopic, eosinophilic, and TH2-high asthma phenotypes. MethodsWe analyzed 2005 to 2006 data from the National Health and Nutrition Examination Survey. Patients with asthma were identified based on the participant self-report. Eosinophilic asthma was defined as a blood eosinophil cutoff point of ≥150, 300, or 400/μL. Atopic asthma was defined as having an allergen-specific IgE level of ≥0.35 IU/mL for any of the 9 perennial allergens tested. TH2-high asthma was defined as a total serum IgE of ≥100 IU/mL and a blood eosinophil count of ≥140/μL. ResultsThe study included 269 children and 310 adults. Depending on the eosinophil cutoff used, 31% to 78% of children and 21% to 69% of adults with asthma were classified as having eosinophilic asthma. In addition, 63% of children and 61% of adults were classified as having atopic disease and 48% of children and 37% of adults as having TH2-high asthma. At a higher eosinophil cutoff point, a greater proportion of eosinophilic asthma can be classified as atopic or TH2 high, but a lower proportion of atopic or TH2-high asthma can be classified as eosinophilic. Approximately 70% or more of children and adults with asthma were 1 of these 3 phenotypes. ConclusionA considerable overlap among eosinophilic, atopic, and TH2-high asthma phenotypes exists in a general asthma population.