Birch pollen is a prevalent aeroallergen during the springtime allergy season. In field studies, variable allergen exposure and environmental factors can impact data quality while environmental exposure units (EEUs) deliver controlled, standardized, reproducible allergen exposures.
To inform study design for EEU trials evaluating anti-allergic therapies.
In this prospective study, 76 birch-allergic participants experienced 3 exposures to birch pollen: an out-of-season EEU challenge (two 3-hour sessions on consecutive days); a natural seasonal exposure; and an in-season EEU challenge (3hour exposure 2-weeks post birch pollen season initiation).
Total nasal symptom score (TNSS), total ocular symptom score (TOSS), and total symptom score (TSS = TNSS + TOSS) were assessed every 30 minutes and daily during EEU and natural exposures, respectively. TSSs were highly associated between day 2 of the out-of-season and the in-season EEU challenges, with a good association between maximum TSS during the natural and in-season EEU challenges, and natural season and day 2 of the out-of-season EEU challenge (P < .001 for all). Participants had higher maximum change from baseline TSS during day 2 of the out-of-season EEU challenge (12.4) vs the: first day (9.8); in-season EEU challenge (8.4); and natural seasonal exposure (7.6; P < .001 for all).
Allergic symptoms are highly associated between participants exposed to birch pollen in the EEU (maximum change in symptom scores during day 2) and in the field. A hybrid trial design may be useful to demonstrate the clinical efficacy of novel anti-allergic therapies requiring fewer participants and shorter timelines, and expediting treatment availability.

Copyright © 2021. Published by Elsevier Inc.

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