PATCH TESTING WITH NICKEL SULFATE - COMPARISON BETWEEN 2 NICKEL SULFATE PREPARATIONS AND 2 DIFFERENT TEST SITES ON THE BACK

Among patients routinely undergoing patch testing for suspected allerg ic contact dermatitis (ACD), nickel is the most frequently sensitizing hapten, with a clear predominance in the female population. However, some patients who report the appearance of dermatitis upon exposure to metal objects show negative patch test results to a nickel sulfate 5% pet. application. In some cases, a positive response to nickel can be observed simply by repeating the patch test. The objective of our stu dy was to assess if, during routine patch testing, positive responses to nickel sulfate are missed owing to contingent problems, referring t o application site, patch test execution or variations in skin reactiv ity. To this end, we applied 2 different patch test materials containi ng nickel sulfate 5% pet. to 3040 consecutive patients, undergoing pat ch testing for suspected allergic contact dermatitis, during the same session. The role of the lest site was also investigated by applying t he preparation on 2 different sites of the back in 30 patients. Of the whole, 612 patients (20%) showed positive patch test responses. The 2 nickel materials were almost equivalent: 78% of nickel-sensitive pati ents had positive reactions to both, whereas 11% showed a positive res ponse to 1 preparation alone. No variations in patch test responses in relation to application site were observed. Our data show that false- negative patch test responses to nickel are frequent. The use of 2 dif ferent preparations during the same patch test session increases the r esponse rate by 10%.