No abstract

Eighty-seven cases of occupational asthma induced by toluene diisocyanate (TDI) were diagnosed by an inhalation challenge with TDI and methacholine. After an average follow-up interval of 11 yrs, all subjects were re-examined.Of the 87 subjects examined, 13 (15%) had remained in the same job, 44 (50.5%) had been removed from exposure forv10 yrs and 30 (34.5%) had been removed forw10 yrs. The proportion of subjects who experienced symptoms of asthma and those who were hyperresponsive to methacholine was significantly lower. Of the patients, 59% used short-acting bronchodilators, 8% long-acting bronchodilators and 18% were on regular inhaled glucocorticoids. Thus, multiple regression analysis showed a positive correlation between forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) at follow-up and FVC and FEV1 at diagnosis, and a negative correlation with smoking and with therapy with bronchodilators. Stepwise logistic regression showed that the follow-up provocative dose causing a 20% fall in the FEV1 (PD20) could be predicted from baseline PD20.These results indicate that respiratory symptoms and airway hyperresponsiveness to methacholine persist in subjects removed from exposure to TDI for w10 yrs. A more favourable prognosis was associated with a better lung function and a lower degree of airway hyperresponsiveness to methacholine at diagnosis. Eur Respir J 2003; 21: 637-640.

The results of this study indicate that HLA-regulated immune mechanisms are involved in TDI-induced asthma and that, in exposed subjects, specific factors may increase or decrease the risk of developing disease.

These results suggest that HLA class I antigens and TNF-alpha A-308G are not associated with susceptibility or resistance to the development of TDI-induced asthma.