REPRODUCIBILITY OF PATCH TESTS - A MULTICENTER STUDY OF SYNCHRONOUS LEFT-SIDED VERSUS RIGHT-SIDED PATCH TESTS BY THE GERMAN-CONTACT-DERMATITIS-RESEARCH-GROUP

Background: The efficiency and reproducibility of patch tests remain controversial. Objective: Our purpose was to determine the efficiency and reproducibility of patch tests and to identify factors influencing these features. Methods: We double-tested 1285 patients concomitantly with 10 standard allergens by manually filled test chambers. Additional information was obtained from all patients with a standardized protocol. Results: Patch test efficiency was good (greater than or equal to 0.94) with an 10 allergens. In contrast, nonreproducibility of patch tests was strongly allergen dependent, ranging from 0.2 for nickel sulfate to 0.6 for formaldehyde. The likelihood of nonreproducible allergic reactions increased when more than four positive reactions were seen at the same time, and with another positive reaction located in close proximity to an allergic reaction. Sex and age of patients, atopy, dermatitis at distant sites, sleeping habits, and the time of allergen exposure (24 or 48 hours) did not affect the rate of nonreproducible results. Conclusion: To increase patch test reproducibility, specific preparations of patch test allergens need to be improved. Furthermore, amplification effects by synchronous neighboring positive reactions should be excluded.