[Epicutaneous testing with gold salts. 2 multicenter studies of the German Contact Allergy Group].

Between 1992 and 1994 two multicentre studies were performed in order to determine the frequency of sensitization to gold salts. In the first study (1992-1993), 872 patients were tested with gold sodium thiosulfate (NTS) 0.25% in Vaseline (V), 0.5% V. and with potassium dicyanoaurate (KDC) 0.002% aqueous solution. 44 patients (5.1%) had a positive patch test reaction to gold salts: 40 (4.6%) to NTS 0.5% V., 20 (2.3%) to NTS 0.25% V. and 5 (0.6%) to KDC. A higher number of positive patch tests to gold salts was noted in patients also sensitized to another metal salt (8.5%) as compared to those who showed no other sensitivities (3.6%). In a second multicentre study (1993-1994), 135 patients with associated sensitization to metal salts or intolerance to costume [correction of custom] jewelry were tested with the same test series as in the first study and with gold sodium thiomalate (ATM) 0.25% V.17 patients (12.6%) had a positive patch test reaction to gold salts: 16 (11.8%) to NTS 0.5% V., 10 (7.4%) to NTS 0.25% V. and 5 (3.7%) to ATM. The clinical relevance of the patch test reactions was considered as being "probable" in 5 cases; 1 in the first and 4 in the second study. Considering these results, NTS 0.5% V. seems to be the most reliable allergen for detecting gold allergy. However, a high proportion of probably false-positive reactions may occur. Further studies are therefore needed to analyze if the high frequency of positive patch tests to NTS 0.5% V. are due to irritant reactions or to a weak sensitization to gold without clinical symptoms.