Evaluation of a Self-Test Device Used in Allergic Contact Dermatitis

Considering the scarcity of dermatologic resources in many parts of the world, self-testing by patients is not only of interest for internal medicine but also for dermatology. In this open, nonrandomized, multicenter diagnostic trial involving subjects with suspected contact sensitization to nickel and/or a fragrance mix, we assessed the agreement of self-testing by subjects with readings made by dermatologists. The self-test product (Nixema(TM)) is based on Thin-Layer Rapid Use Epicutaneous Test (TRUE Test®) technology. One hundred and sixty-five subjects self-tested the ready-made patch-test product. The test was applied for 48 h and then read after 3 or 4 days. It was also evaluated independently by experienced dermatologists after 3 or 4 days. In the 162 evaluable subjects, the proportion of agreement for both allergens together was 89.5% [95% confidence interval (CI) 83.7-93.8], the sensitivity was 97.5 % (95% CI 86.8-99.9) and the specificity was 86.9% (95% CI 79.6-92.3). Cohen's kappa was also high at 0.749 (95% CI 0.637-0.862). Discrepancies between the subjects' readings and the dermatologists' readings were mainly due to the subjects interpreting reactions of 'irritant' or 'doubtful' as 'positive'. Apart from itching and burning sensations and tape irritation, no side effects were observed. In conclusion, this study showed a high rate of agreement between the self-reading of the upper arm and the readings made by the dermatologists. The upper arm proved to be an appropriate area for self-testing. Self-testing may improve the screening for contact sensitization for patients, particularly where dermatologic health resources are scarce.