Detection of immunologically sensitized isocyanate workers by RAST and intracutaneous skin tests

Antibody estimations by RAST were performed on 621 partially selected isocyanate workers whose case histories were well-documented. Two hundred forty-seven of the workers were clinically suspected to be sensitized to isocyanates since they had suffered from occupationally related recurrent asthmatic attacks, chronic obstructive lung diseases, bronchitis, rhinitis, conjunctivitis, cutaneous hypersensitivity reactions, and/or fever. RAST studies with seven different isocyanates conjugated to human serum albumin (HSA) demonstrated that 14% of these symptomatic subjects had significant levels of specific-IgE antibodies. On the other hand, only one of the 374 asymptomatic workers had such antibodies. In contrast to toluene diisocyanate (80:20% mixture of 2, 4 and 2, 6-isomers, if not otherwise mentioned)-HSA, a toluene diisocyanate-ovalbumin conjugate exhibited no antigenicity in nearly all of the cases. Intracutaneous skin testing with five different isocyanate-HSA conjugates performed in 203 workers produced immediate-type wheel-and-flare reactions in 14 of the 53 symptomatic persons but in none of the 150 asymptomatic probands. There was a good overall correlation between RAST and skin test results. Our findings provide strong evidence for IgE-mediated sensitization to isocyanates in a subgroup of the subjects with isocyanate-induced diseases. By means of RAST and/or skin testing these immunologically sensitized persons can be identified.