Sera of 54 symptomatic workers showing sensitization to isocyanate-human serum albumin (HSA) conjugates were subjected to parallel enzyme allergosorbent test (EAST) and CAP measurements to determine IgE antibodies to diphenyl-methane diisocyanate-HSA, toluene diisocyante-HSA and hexamethylene diisocyanate-HSA. Results of both methods correlated rather well with each other. In comparison to the EAST results, the CAP values were twice as high, and 4, 17 and 13) more frequently positive findings were obtained with the three different antigens. Autoinhibition performed with both methods proved the specificity of IgE binding in 92 of sera in EAST and in 89 of sera in CAP if values of ≥ 0.35 kU/l were considered. The total IgE level in sera influenced the antibody results. Four of 20 sera studied by autoinhibition had a total IgE of > 700kU/l, and two of them did not show significant autoinhibition with all conjugates by CAP and one serum by EAST. In addition, three of these sera showed an elevated binding to control HSA only (0.31–0.5 kU/l), and two revealed only a slightly increased IgE binding when compared with the HSA control (ratio of isocyanate-HSA to HSA, 700 kU/l, should by confirmed by inhibition experiments. Twelve of 40 symptomatic isocyanate workers exhibited borderline or weakly increased IgG values for diisocyanate-HSA conjugates in the CAP system and IgG-EAST. HSA tested in EAST as a reference showed nearly the same results as the isocyanate-HSA conjugates. In the 23 inhibition experiments, IgG-binding specificity was not confirmed. These findings imply IgG measurement to be of no diagnostic value in isocyanate-induced airway diso
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