Intradermal positivity after negative prick testing for inhalants

Abstract

Objective Examine the incidence of positive intradermal tests after a negative skin prick test for 24 inhalant antigens. Study Design and Setting Retrospective study. Charts from patients who underwent modified quantitative testing over a 3-year period were reviewed. Patients were initially tested with Multi-Test II. Subjects with negative wheals to a specific allergen were then tested with a 1:500 weight:volume intradermal injection of that allergen. Results One hundred thirty-three patients underwent MQT for 24 antigens. Allergens with the highest incidence of positive intradermal wheals after negative prick testing were Dermatophagoides pteronyssinus and Dermatophagoides farinae at 26.67%. Allergens with elevated incidence of positive intradermals included fusarium, cockroach, cocklebur, rough marsh elder, and ragweed, all with incidences of 16% to 19%. Conclusion Positive intradermal responses after negative prick testing occur commonly. Future study is needed to determine the generalizability and clinical significance of these findings. EBM rating: C-4