Mercury intolerance and lymphocyte transformation test with nickel sulfate, palladium chloride, mercuric chloride, and gold sodium thiosulfate

Interferon-γ secreted from peripheral blood mononuclear cells as a possible diagnostic marker for allergic contact dermatitis to gold

10% of patch-tested patients have a positive reaction to gold. Most lack clinical symptoms, but allergic contact dermatitis (ACD) to gold is increasing. In this study, 77 dermatological outpatients were divided into 3 groups depending on epicutaneous patch test outcomes: a group positive to gold (EPI+), a group negative to gold (EPI-), and a group with irritant reactions to gold (EPI-IR). Lymphocytes were stimulated in vitro with gold sodium thiosulfate. Proliferation was assessed using the lymphocyte transformation test (LTT), and cytokine secretion was assessed using a multibead array (Luminex; Linco Research Inc., St. Charles, MO, USA), in order to evaluate whether an in vitro method with high diagnostic accuracy could be devised. The EPI+ group showed a significantly increased secretion of interferon (IFN)-gamma, interleukin (IL)-2, and IL-13 and also showed a significantly higher stimulation indexes for LTT, compared to the other 2 subject groups. Sensitivity and specificity were calculated for all methods individually and combined, but IFN-gamma assessment alone was the most accurate method for identifying ACD to gold, with sensitivity and specificity of 81.8% and 82.1%, respectively. This method also identified 87.5% of the EPI-IR subjects as non-allergic. Therefore, assessment of secretion of IFN-gamma should be a valuable complement to patch test for diagnosing gold allergy.

[In vitro testing for allergic contact dermatitis]

Patch testing is the standard method to identify allergic contact dermatitis. Simple, safe and accurate in vitro methods identifying contact allergies would offer both theoretical and practical advantages. Using the lymphocyte transformation test (LTT), allergen-specific lymphocytes central to the pathogenesis of Type IV allergies can be identified. Various studies have assessed the value of LTT in the diagnosis of contact allergies. The current assessment is that the test can be helpful in distinguishing between irritant and allergic reactions. LTT is especially useful in demonstrating drug allergies and can also be employed to prove sensitization to gases or toxic substances. At the present time, it is not an alternative for patch testing in daily practice.