Detection of specific IgE in isocyanate and phthalic anhydride exposed workers: comparison of RAST RIA, Immuno CAP System FEIA, and Magic Lite SQ

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Abstract
Sera from 94 workers occupationally exposed to isocyanate were tested by RAST RIA, Immuno CAP FEIA, and Magic Lite SQ (ML) against the allergens HDI, MDI, TDI, and phthalic anhydride. Twenty sera showed increased levels of diisocyanate-specific IgE antibodies, and five sera were phthalic anhydride positive. High total IgE titer was not correlated with positive specific IgE titer (r = 0.47), showing that nonspecific IgE binding was low. The results of ML and CAP correlated well (r = 0.91), but tended to be slightly higher than the results obtained with the RAST isotope test. CAP and RAST data also correlated significantly (r = 0.90), but the correlation between ML and RAST data was lower (r = 0.82). The results of the new in vitro tests, CAP and ML, showed good reproducibility (5% CV for CAP and 8% CV for ML). In summary, the CAP and ML methods were found to be appropriate for routine diagnosis of specific IgE antibodies against the allergens HDI, MDI, TDI, and phthalic anhydride.