Patch Testing of Nickel Sulfate and Potassium Dichromate with a Standardized Ready-to-use Test System Gives Highly Reproducible Results: A Double-blind Multicentre Study
Jochen Brasch, Tilo Henseler, Werner Aberer, Thomas Fuchs, Ulla Hoeck, Bo Kreilgård
There is still some doubt about the reproducibility of patch tests. A sound assessment needs optimized and unbiased studies. This study analysed the results of a double-blind multicentre study with nickel sulfate and potassium dichromate patch tests attached synchronously to both sides of the back of patients with a history of nickel allergy, conducted with a highly standardized randomized test system (TRUE-test ®). Out of 589 patients tested, a total of 388 had responded with allergic reactions to nickel sulfate and 130 to potassium dichromate. The reproducibility of positive nickel (dichromate) patch tests was 99.2 % (90.8 % ). The reaction index was also calculated, which relates the number of allergic reactions obtained with a test preparation to the number of questionable and irritant reactions; the reaction index can range from -1 (questionable and irritant reactions only occur) to 1 (allergic reactions only occur). For nickel sulfate the reaction index was 0.91, but it was only 0.23 for potassium dichromate, as a result of considerably more questionable reactions. In conclusion, a highly synchronous reproducibility of results can be achieved by using a well-standardized patch-test system, especially withnickel sulfate. However,distinct allergens and test systems need to be evaluated separately.