Comparison of Skin Test Reactivity of Sublingual Immunotherapy Tablets to Commercial Extracts
Monday, March 7, 2016
South Exhibit Hall H (Convention Center)
Marc F. Goldstein, MD FAAAAI, Gregory J. Hilditch, Ina F. Frankel, Alex L. Goldstein, PhD, Donald J. Dvorin, MD FAAAAI, George A. Belecanech, MD
Rationale: To evaluate and compare skin test reactivity of sublingual immunotherapy tablets (SLIT) based solutions to commercial grass and ragweed extracts (CE).

Methods: Sixteen subjects with allergic rhinitis consented to allergy skin testing with aqueous preparations of Grastek® and Ragwitek®; Timothy grass and short ragweed extract from three commercial suppliers, fish extract and SLIT excipients. Grastek® and Ragwitek® were diluted to similar concentrations found in CE for prick and intradermal testing. Intradermal testing was performed only when prick tests were negative. Intradermal test results were combined with prick test results. Results from CEs were compiled into a composite index via majority classification. Fleiss' Kappa and non-parametric bootstrap confidence intervals were computed for CE and SLIT versus the CE composite index, yielding measures of agreement between CEs themselves and the CE composite index and SLIT, respectively.

Results: Though the number of subjects is small, Kappa suggests strong agreement amongst the three CEs as well as between the CE composite index result and the analogous SLIT (Grass CEs: κ=0.92[0.71–1.0]; Grass index vs Grastek®: κ=0.87[0.58–1.0]; Ragweed CEs: κ=0.92[0.63–1.0]; Ragweed index vs Ragwitek®: κ=1.0[N/A]). The bootstrap confidence intervals do not include 0 in all but one case, suggesting that Kappas are significantly different from 0.

Conclusions: This study shows statistically significant skin test reactivity to aqueous solutions of Grastek® and Ragwitek® comparable to CE. Skin test reactions of each CE were consistent with each other; the skin test reaction of Grastek® and Ragwitek® were consistent with each CE.