Sensitization to palladium in Europe

Background
Recently, sodium tetrachloropalladate (Na2PdCl4) was found to be a more sensitive palladium patch test allergen than palladium dichloride (PdCl2).

Objectives
To determine the optimal test concentration of Na2PdCl4, to evaluate the prevalence of palladium sensitization with Na2PdCl4 and PdCl2, and to compare the results with nickel sensitization in a European multicentre study.

Materials and methods
In addition to the European or national baseline series including NiSO4·6H20 5% pet., consecutive patients were tested with PdCl2 and Na2PdCl4 2%, 3% and 4% pet. in eight European dermatology clinics. The age and sex distributions were also evaluated in patients sensitized to nickel and palladium.

Results
In total, 1651 patients were tested. Relative to 3% Na2PdCl4, 4% Na2PdCl4 did not add any information. Two per cent Na2PdCl4 resulted in more doubtful reactions and showed suboptimal reactivity. The prevalence of palladium sensitization doubled with Na2PdCl4 and was similar to that of nickel. Interestingly, in contrast to nickel sensitization, palladium sensitization was not related to female sex.

Conclusions
Three per cent Na2PdCl4 pet. is the most suitable patch test concentration. Sensitization to palladium is almost as prevalent as sensitization to nickel. The sex distribution is different between nickel-sensitized and palladium-sensitized patients, suggesting different sources of exposure.