Specific bronchial reactivity to toluene diisocyanate: relationship with baseline clinical findings

One hundred and fourteen subjects with asthma induced by toluene diisocyanate were identified and the pattern of their bronchial responses to challenge with toluene diisocyanate was studied. An occupational type specific bronchial provocation test with toluene diisocyanate (10-25 parts per thousand million for 10-15 minutes) elicited an immediate response in 24, a late response in 50, and a dual response in 40 patients. Subjects with a dual response showed at diagnosis a longer duration of symptoms and a greater prevalence of airway obstruction; in these subjects FEV1 (percentage of predicted value) was lower than in subjects with immediate or late reactions to toluene diisocyanate. The percentage of current smokers and ex-smokers was significantly lower in subjects with a late response (26%) than in subjects with immediate or dual responses (56% and 57% respectively). In 27 of the 114 subjects a non-specific challenge test with methacholine was performed and subjects with dual responses showed greater non-specific bronchial hyperresponsiveness than the other groups. These results suggest that a dual response to specific challenge in bronchial asthma related to toluene diisocyanate may be associated with more severe disease than other types of response, as assessed by duration of symptoms, baseline airway obstruction, and non-specific bronchial hyperresponsiveness. The high prevalence of non-smokers and low prevalence of smokers in the group with a late response to specific challenge is so far unexplained.