Abstract
BackgroundPatch testing with a baseline series is a common tool employed when the sensitizing agent in contact dermatitis is unclear. However, for Asian countries, there are no locally validated baseline series to utilize in screening.MethodsWe completed a retrospective analysis of all patients that had undergone patch testing with the European Baseline series, Shoe Series or Comprehensive International Baseline series, over 7 years from 2012 to 2018 in a tertiary care reference dermatology clinic in Sri Lanka to evaluate the suitability of these investigations to identify causes for contact dermatitis in the local study population.ResultsOut of 438 patients tested, 239 (54.8%) reacted to at least one substance in the series. The Shoe Series was significantly more likely to yield a positive result than the European Baseline Series (70.2% vs 46.9%, p < 0.05). The top three sensitizers identified by all series were nickel sulfate (16%, 70/438), p-phenylenediamine (12.3%, 54/438) and 2-mercaptobenzothiazole or mercapto mix (10.5%, 46/438).ConclusionShoe series has a comparatively high yield in the local population compared to European Baseline series. Since little less than half of the study population did not have any reactivity to any of the allergens tested it is important to develop or modify and validate a locally relevant, more suitable baseline series which is based on the Shoe Series in Sri Lanka. This is further evidence for the continuously changing nature of allergens in the environment and the need to modify existing patch testing standards accordingly.
Highlights
Patch testing with a baseline series is a common tool employed when the sensitizing agent in contact dermatitis is unclear
Such series as the European Baseline Series (EBS), Shoe Series (SS) and International Comprehensive Baseline Series (ICBS) have various allergens some of which get updated based on continuous surveillance
The analysis presented here is a representative of the difficulty to diagnose cases of contact dermatitis in Sri Lanka
Summary
Patch testing with a baseline series is a common tool employed when the sensitizing agent in contact dermatitis is unclear. Pre-packaged tests are available, with a limited number of allergens determined by research and experience of Keragala et al BMC Dermatology (2019) 19:10 experts in working groups. Such series as the European Baseline Series (EBS), Shoe Series (SS) and International Comprehensive Baseline Series (ICBS) have various allergens some of which get updated based on continuous surveillance. When a positive reaction occurs to a mix, such as a fragrance mix, a subsequent breakdown test using its constituent ingredients is carried out. If all of this is inadequate, additional patch tests are carried with customized lists or series, according to the history of exposures of the patient. In the absence of alternative data, in developing countries like Sri Lanka, the “series” used in Europe or North America have been adopted in whole but so far its effectiveness in isolating the triggers in local patients has not been assessed
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