PRS6 QUANTIFYING THE DEGREE OF OVERLAP BETWEEN ALLERGIC AND EOSINOPHILIC SUBTYPES IN PATIENTS WITH MODERATE-TO-SEVERE ASTHMA

Abstract

Asthma is increasingly recognized as a highly heterogeneous disease, with various asthma subtypes proposed, such as allergic or eosinophilic. It is unclear what proportion of asthma patients have overlapping allergic and eosinophilic subtypes. Our study aimed to characterize this proportion in the moderate-to-severe asthma population. Two post-hoc analyses of adult (≥18 years) asthma populations were conducted. The first analysis was conducted in a study population not selected for any subtype (non-subtype, N=1044), and the second analysis was conducted in a population selected for allergic asthma (N=1546). The percentage of overlapping/non-overlapping asthma subtypes in each study population was assessed using the following definitions: allergic asthma - a positive skin test or in vitro reactivity to an aeroallergen; and eosinophilic asthma - a blood eosinophil count ≥300 cells/μL. Baseline characteristics for the subtypes were also summarized. In the non-subtype selected population, 78.0% had allergic asthma and 39.3% had eosinophilic asthma. Among patients with allergic asthma, only 39.5% also had eosinophilic asthma, while 76.0% of patients with eosinophilic asthma also had allergic asthma. In the population selected for allergic asthma, 40.2% had eosinophilic asthma. Baseline demographics were similar between allergic and eosinophilic subtypes with respect to age, sex, smoking status, body mass index, and exacerbation history. Total IgE levels were similar between allergic and eosinophilic asthma. Predictably, eosinophil levels were higher in the eosinophilic asthma subtype compared with the allergic asthma subtype. In these large post-hoc analyses, allergic asthma was more prevalent than eosinophilic asthma. Although an overlap was observed between subtypes, a minority of patients with allergic asthma had concomitant eosinophilic asthma. The consistency of findings across populations provided robustness to the overlaps identified. This study quantified the degree of overlap between subtypes and may help payors to better understand patient populations and assist in formulary development.