Sodium tetrachloropalladate (Na2[PdCl4]) as an improved test salt for palladium allergy patch testing.

In the last decades, palladium is widely used in dentistry. Allergic reactions to palladium are rarely diagnosed with patch testing, even when positive results would be expected. Palladium tends to cross-react with nickel, which should give rise to more positive reactions to palladium dichloride (standard test salt). The aim of the study was to test whether or not mono-nuclear sodium tetrachloropalladate (Na(2)[PdCl(4)]) in petrolatum is a better test salt for diagnosing palladium allergy. Positive reactions to the investigated test salt are compared not only with PdCl(2(aq.)), but also to NiSO(4(aq.)) and NiSO(4(pet.)). Concentration series of Na(2)[PdCl(4)] were carried out. 164 consecutive patients were patch tested. 3% of Na(2)[PdCl(4)]((pet.)) was found to be the highest non-irritative concentration. The results show (n = 164) that Na(2)[PdCl(4)] covers all reactions to PdCl(2) (1.8%) and provokes more positive reactions (14%). From the 164 patients, 18.3% reacted positively to at least 1 of the nickel salts. The sensitivity of patch testing with Na(2)[PdCl(4)] is increased compared with the PdCl(2) salt. Therefore, it can be concluded that Na(2)[PdCl(4)] is to be a better test salt for diagnosing palladium allergy with patch testing.