The development and course of test reactions to gold sodium thiosulfate

Abstract

In our department, gold sodium thiosulfate has become the 2nd most common allergen in routinely patch tested dermatitis patients, with a rate around 10%. Test reactions to this compound often appear late, sometimes so late that active sensitization may be suspected. This study was performed to study the time course of the allergic reaction to gold sodium thiosulfate and to elucidate whether late test reactions mean active sensitization. 10 patients with contact allergy to gold sodium thiosulfate (0.5% pet.) were retested epicutaneously (e.c.) and intracutaneously (i.c.) with dilution series. The clinical course was followed for 2 months with initially short intervals, later more extended. During the entire study, 26 positive e.c. reactions were diagnosed. Within the 1st week, 17 (65%) were recorded. 12 reactions (46% of 26) were noted at the ordinary reading, 3 days after test application. After 10 days, another 9 reactions (35%) appeared. The patients with the latter reactions also had positive test reactions within the 1st week. After 2 months, 9 reactions remained. Out of 30 i.c. tests applied, 25 became positive within 1 week. 19 (76%) of these reactions changed in morphology from thin infiltrates to deep nodules. Another 4 nodules appeared in patients with previous negative i.c. tests. All 23 nodules remained after 2 months. E.c. and i.c. test reactions to gold sodium thiosulfate are long-lasting. Positive patch test reactions emerging after 10 days do not automatically imply active sensitization. To diagnose contact allergy to gold sodium thiosulfate, the ordinary reading at day 3 is insufficient; even reading at 1 week is insufficient and must be supplemented by a reading at 3 weeks. All the i.c. test reactions, however, appeared within 1 week and, in several, a dermal nodule was formed.

Thoughts on sensitizers in a standard patch test series

“…Occasionally or frequently, most sensitizers seem to behave like this, with test reactions appearing later than on the ordinary reading day, D2 to D4. Gold and certain therapeutic agents such as corticosteroids and neomycin have this tendency (48)(49)(50). The significance of a late appearing, and hence possibly undetected, contact allergy differs according to the sensitizers involved.…”

“…On being repeated, the test is already positive at 2-4 days. However, it has recently been demonstrated that positive patch test reactions to gold salts can appear after 10 days without being due to patch test sensitization (50). Re-testing a patient after an interval may also reveal patch test sensitization, although there has been no known flareup reaction (52).…”

Gold – a controversial sensitizer

“…When patch tests are followed over an extended period of time, late-appearing reactions and longlasting reactions are considered to indicate allergic reactions. Positive patch test reactions to gold appear late and they are extremely long-lasting (1,14,18,23,(37)(38)(39).…”

“…When patch testing patients with suspected adverse reactions to dental materials with higher concentrations of either gold thrichloride or gold sodium thiosulfate, a higher number of patients with a clinically relevant contact allergy to gold was found (26,(57)(58)(59)(60). Whenever patch testing with gold, keep in mind that a test reading should also be performed after 1 week (38,39). Actually, read-ing even on D 14-21 may be indicated (38,39).…”

“…Whenever patch testing with gold, keep in mind that a test reading should also be performed after 1 week (38,39). Actually, read-ing even on D 14-21 may be indicated (38,39). However, we emphasize that an established contact allergy to gold does not mean that all oral symptoms and lesions can be attributed to the gold allergy.…”