Usefulness of dermoscopy in the evaluation of patch test reactions

Abstract

Background: Despite being widely used in different areas of dermatology, there have been fewstudies evaluating the benefit of dermoscopy in the interpretation of patch tests, especially inweak and doubtful reactions.Objectives: To evaluate the role of dermoscopy in the interpretation of patch tests and describethe main findings of the reactions.Method: Prospective study, carried out in dermatology reference centers in southern Brazil,which evaluated the final results of patch tests analyzed with the aid of dermoscopy.Results: 77 patients and 160 reactions were included. The most prevalent substances werenickel sulphate (23.8%), kathon CG (9.4%), and perfume mix (8.8%). The main dermoscopicfindings were reaction area greater than half of the chamber site (90%), homogeneous erythema(86.9%), vesicles (30%), crusts (21.3%), perifollicular erythema (35%), pore reaction (19.4%) andpustules (8.8%). Dermoscopy was found to facilitate the definition of erythema in reactions onblack skin and when due to substances with deposition of pigment. Of the 64 weak or doubtfulreactions, 36 (56.25%) showed a change in the final result after dermoscopy evaluation; of the 36doubtful reactions, 33 (91.6%) showed a change in the final result after dermoscopy evaluation(p < 0.001).Study limitations: The probable limitation of the study is its sample size. Though certain sig-nificance levels have been reached, other possible relationships may not have been observed.Conclusion: Dermoscopy improves significantly the interpretation of patch tests, especially inweak and doubtful reactions.