Self-reported symptoms of grass allergic subjects correlate positively with symptom scores recorded in a controlled environment

Abstract

The environmental exposure chamber (EEC) model mimics naturalistic airborne allergen exposure that patients would encounter in their everyday lives. It allows for the exposure of subjects to a steady and consistent levels of allergen in a controlled environment for repeated exposure days, allowing for reproducibility of data over successive studies. [1 & 2] The aim of this study was to examine the correlation between Total Symptom Scores (TSS) recorded by grass-allergic subjects in the field and their TSS evoked by allergen exposure in the EEC. A total of 149 subjects were screened for grass allergy using skin prick test and serum IgE. Eligible subjects were exposed to airborne grass pollen in the EEC for 3-hours, and recorded their TSS every 30 minutes. The same subjects reported their daily at-home TSS for 6-days prior to peak pollen day, their perception of pollen exposure, and their estimated time spent outdoors using an e-diary. Correlation analysis was performed to investigate the relationship between data gathered in the EEC and in the field diaries. Average TSS for the same subjects who reported no exposure in the field was 9.04 compared to 19.74 in the EEC and showed no correlation (r=0.218, p=0.274). Whereas subjects who reported daily outdoor exposure of 0-3 hours had the strongest correlation (r=0.616, p<0.0001) between field and EEC. Higher TSS was reported by those exposed ≥8 hours daily (18.50 field vs 20.37 EEC). A significant positive correlation (r= 0.5726, p<0.0001) was also observed in subjects who spent 4-7 hours outside. The EEC represents a promising tool to enhance the reliability and comparability of clinical data by controlling confounding variables that are inherent to traditional field-based trials. Many factors should be considered when evaluating the relationship between allergy symptoms in EEC versus field. Specifically, the amount of time subjects spend outdoors and their perceptions of allergen exposure are important considerations that show the EEC can be used to approximate everyday pollen exposures in clinical trials.