OUTCOME DETERMINANTS FOR ISOCYANATE INDUCED OCCUPATIONAL ASTHMA AMONGCOMPENSATION CLAIMANTS

Objectives-To compare the outcome of occupational asthma (OA) induced by isocyanates in Ontario (where a surveillance programme for exposed workers has been in place for over 15 years), with the outcome of OA i nduced by other work agents. Methods-Compensated OA claims during the period 1984-88 in Ontario were retrospectively reviewed in a standardi sed way. Results-136/235 compensated claims were attributed to isocyan ates. Compared with other causes of OA, those attributed to isocyanate s had a shorter latent period before onset (5.9 v 7.9 years, P<0.05), shorter duration of symptoms before diagnosis (2.0 v 3.0 years, P<0.05 ), and less associated atopy (43% v 58%, P<0.05). Outcome at a mean of 1.9 years after initial assessment was significantly better in those with OA induced by isocyanates; 73% cleared or improved v 56% with oth er causes of OA (P<0.05). Ten subjects with OA induced by isocyanates stayed at the same work; none cleared and four had worsened at follow up. A better outcome in OA induced by isocyanates was associated with early diagnosis (P<0.05), and early removal from isocyanates after the onset of asthma. Conclusions-The outcome in the group with OA induced by isocyanates is similar to previous follow up studies. However, it is better than the outcome in our comparison group with OA due to othe r causes, perhaps because of earlier diagnosis in the group with OA in duced by isocyanates. This may be attributable to the medical surveill ance of workers exposed to isocyanates in Ontario, either directly fro m the surveillance assessments, or indirectly by increasing awareness of the condition.