Strip patch testing does not affect reaction profiles of standard allergens

Abstract

Background: It has been hypothesized that positive reactions in the strip patch test are irritant rather than allergic.

Objective: To study reaction profiles of the baseline series patch test substances applied routinely on tape-stripped skin according to the reaction index (RI) and the positivity ratio (PR).

Patients and methods: One thousand two hundred and twenty-eight consecutive patients were routinely strip patch tested with the baseline series between January 2011 and June 2013 (intervention group). On the basis of test reactions at D3/D4, the RI, and the PR, 25 standard allergens were analysed, and the results were compared with those obtained in 1161 patients patch tested conventionally from July 2008 to December 2010 (historical control group).

Results: Nickel sulfate, fragrance mix I, cobalt chloride, Myroxylon pereirae (balsam of Peru) and colophonium showed the highest frequencies of positive reactions in both groups, without any significant differences. Of 25 patch test substances of the baseline series, 18 showed good reaction profiles in the intervention group, and 16 in the historical control group.

Conclusions: Reaction profiles of baseline series patch test substances remained largely unaffected by tape stripping the skin prior to patch testing. Thus, if conventional patch test results are presumed to be false-negative, performance of the strip patch test can be recommended independently of the standard allergen.

Keywords: contact allergens; patch test; positivity ratio; reaction index; strip patch test.