Patch testing with a combination of unrelated allergens: a new strategy

Abstract

A simplified method of patch testing was designed, in which several totally unrelated allergens were combined in each patch. The method was evaluated by double blind comparison of responses to 17 standard allergens applied individually as 17 conventional patch tests, and as two different sets of five patches each containing combinations of three of four allergens per patch, in 137 patients under investigation for contact allergic dermatitis. There were 89 positive responses to conventional patch testing with separate allergens and 94 and 86 positives to the two different combinations of the same allergens. Concordance of positive reactions to the two combinations was 80% and there were no irritant reactions. Conventional testing detected 70 and 74% of reactions to combination patches 1 and 2 and combination patches 1 and 2 detected 80 and 79% of the reactions to conventional testing. The combinations detected clinically relevant sensitivities not found by conventional testing. Thus, combination patch testing appears to give consistent and reliable results; its use would reduce the number of patches and increase the diagnostic yield for the specialist and permit preliminary screening by the general practitioner.