Background The standard assay for the detection of chromium sensitization, the patch test, does not allow discrimination between patients with and without clinical symptoms of allergy.
Objective The aim of this study was to prove whether cellular in vitro tests are predictive of chromium allergy.
Methods Chromium-sensitized volunteers with and without clinically manifest allergy and non-sensitized healthy controls (n=37, 19, and 26, respectively) were analysed by cellular in vitro methods using tri- and hexavalent chromium (chromium chloride and potassium dichromate) as stimuli. The results were correlated with clinical and anamnestic data.
Results Sensitized individuals with an allergy displayed significantly higher lymphocyte transformation test (LTT) responses than sensitized volunteers without allergy and controls (P<0.05 and P<0.01, respectively). 12.5 μg/mL of chromium chloride and 50 ng/mL of potassium dichromate were found to be optimal to discriminate between sensitized individuals with and without allergy. Combining the results of chromium chloride and potassium dichromate LTT, a positive reaction to at least one of the stimuli was highly predictive of allergy [sensitization with vs. without allergy: Odds ratio (OR)=6.4, P=0.004; sensitization with allergy vs. controls: OR=11.5, P<0.0001]. On the contrary, IFN-γ, IL-2, IL-4, IL-10, and IL-12 production to the ELISpot, patch test results, sensitization against other metals, and atopy score did not significantly discriminate between sensitization with and without allergy. However, IFN-γ responses towards chromium chloride were significantly correlated with the strength of patch test reactivity (r=0.49, P=0.002). By IFN-γ ELISpot, the average precursor cell frequency reactive to trivalent chromium could be defined as 26, 15, and 11 : 106 in volunteers with sensitization and allergy, with sensitization without allergy, and controls, respectively.
Conclusions In contrast to the patch test, the LTT appears to be a method that is predictive of chromium allergy.