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.
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 with nickel sulfate. However, distinct allergens and test systems need to be evaluated separately.
Brasch
J
J
Department of Dermatology, University of Kiel, Germany. jbrasch@dermatology.uni-kiel.de
Henseler
T
T
Aberer
W
W
Fuchs
T
T
Hoeck
U
U
Kreilgård
B
B
D000328:Adult; D004396:Coloring Agents; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D006967:Hypersensitivity / Q000175:diagnosis* / Q000209:etiology; D007509:Irritants; D008297:Male; D008875:Middle Aged; D009532:Nickel; D010328:Patch Tests / Q000379:methods; D011192:Potassium Dichromate; D015203:Reproducibility of Results
D004396:Coloring Agents; D007509:Irritants; C029938:nickel sulfate; D009532:Nickel; D011192:Potassium Dichromate