Patch testing with expired Indian patch test kits: Results of a pilot study

The reliability of patch testing with expired Indian standard patch test kits has been not evaluated before.

Thirty adults (men:women 25:5) with allergic contact dermatitis were divided into three groups of ten patients each for patch testing by Finn chamber® method using Indian standard patch test kits having expiry in 2016, 2015 and 2014. The results were compared with those from a new kit with 2018 expiry.

Ten patients in group-1, eight patients in group-2 and seven patients in group-3 developed positive reactions of identical intensities and mostly from identical allergens from all four kits. The major contact allergens eliciting positive reactions of identical intensities were parthenium in nine, five and three patients, colophony in four, one and zero patients, fragrance mix in three, three and one patients, thiuram mix in three, one and one patients, and paraphenylene diamine in two, one and three patients from group-1,-2, and -3, respectively.

Small number of patients in each group remains the major limitation of the study. Whether or not these results can be extrapolated with patch test results from other similar patch test kits available across countries also needs confirmation.

The patch test allergens can be used beyond labeled expiry dates but needs confirmation by a few large studies and using other available patch test kits. This is important as the relevance of patch test results for individual allergen in this scenario may remain debatable requiring careful interpretation.