Current Limitations of Immunologic Testing
IgE antibodies specific to diisocyanate-HSA conjugates have been detected in 21 to 55% of cases of diisocyanate-induced OA confirmed by SIC or workplace challenge in different studies, with an assay specificity of 89 to 100%. Diisocyanate-specific IgG antibodies appear to be a good marker for recent diisocyanate exposure, rather than diisocyanate asthma, since they can be detected in a substantial buy Cialis online proportion of asymptomatic exposed workers. Active exposure to diisocyanate increases the sensitivity and specificity of specific IgE antibodies reactive with diisocyanate conjugate by RAST. The detection of diisocyanate-specific IgE antibodies fell if assayed > 30 days after the cessation of occupational exposure, with a calculated half-life of 5 to 7 months.
The clinical data examining in vitro antigen-specific cellular immune responses to establish a diagnosis of chemical sensitizer-induced OA are limited. In vitro proliferative responses to plicatic acid-HSA antigen have been demonstrated in 24% of workers with red cedar-induced asthma, compared to 0% in exposed workers without red cedar-induced asthma. In vitro monocyte chemotactic protein-1 production by mononuclear cells cocultured with diisocyanate-HSA antigens exhibited 79% test sensitivity and 91% specificity for the diagnosis of OA compared with SIC results among 54 exposed workers.
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Current Limitations of Immunologic Testing: There are several limitations to immunologic testing 24S for determining a patient’s sensitization to LMW chemical agents. Antigens are prepared by conjugating chemicals with a protein such as HSA; however, the chemical-protein conjugate antigens and protocols have not been standardized, and results cannot be compared between laboratories.
Test extracts for most HMW proteins that cause OA are not commercially available and are frequently prepared differently by different investigators. Commercial extracts, if available, may not be standardized with regard to allergenic potency. The test sensitivity of in vitro specific IgE antibody assays and SPTs likely decrease after the cessation of exposure due to the half-life of the IgE antibody.