Skin prick tests (SPT) are a useful initial diagnostic tool for assessing allergic response. The Environmental Exposure chamber (EEC) is used to expose subjects to controlled, natural levels of allergen in order to evaluate their allergic response. We wanted to determine if the SPT could predict patient’s symptom severity in the EEC.
A study involving 152 patients was analyzed to determine correlations between SPT and maximum TSS. Subjects underwent a screening visit where a panel of SPT were performed including three different grass allergen extracts (5-grass mix, Meadow fescue grass, and Rye grass and were exposed to grass pollen in the EEC at a concentration of 3500 ± 500 grains/m3 for 6 hours, over 3 consecutive days. Total symptom scores (TSS) were obtained at scheduled intervals.
Correlation analysis revealed a weak correlation between the 5-grass mix SPT and the symptom severity (r2=0.31). A correlation of r2=0.34 was identified when comparing the Meadow Fescue grass SPT to the maximum TSS. This also shows a weak correlation between the SPT and TSS. Finally, the rye grass showed the weakest correlation of r2=0.29 between the SPT and maximum TSS.
This analysis demonstrates that the SPT is correlated with symptom response. The value is less than 0.5, indicating SPT alone cannot be used as a predictor of allergic response when exposed to allergen. Overall, enrolling subjects in allergic rhinitis clinical trials based on SPT alone may not be suitable and additional clinical response assessment such as EEC exposure should be done for eligibility.