Long-term follow-up of hexamethylene diisocyanate-, biphenylmethane diisocyanate-, and toluene diisocyanate-induced asthma

In 1976-1992 245 new cases of asthma induced by diisocyanates were diagnosed, caused by hexamethylene diisocyanate (HDI) in 39%, diphenylmethane diisocyanate (MDI) in 39%, and toluene diisocyanate (TDI) in 17% of the cases. Our aim was to study the clinical outcome of diisocyanate-induced asthma, A questionnaire was sent to the 235 patients alive in 7995, and validated by reexamining clinically 91 of them. The study was carried out on average 10 (3-19) yr after the diagnosis. Of the patients 82% experienced symptoms of asthma, 34% used no medication, and 35% were on regular medication. The patients having displayed immunoglobulin E (IgE) antibodies to isocyanates used less medication (OR 0.273; Cl 0.098, 0.758) and had fewer symptoms of asthma (OR 0.329; Cl 0.124, 0.875) than the IgE-negative ones. They also had a significantly shorter duration of symptoms (p = 0.0025), latency period (p = 0.0249), and duration of exposure (p = 0.0008) than the IgE-negative patients. This did not, however, entirely explain the more favourable outcome of the IgE-positive patients. Patients with HDI-induced asthma used less medication (OR 0.412; Cl 0.229, 0.739) than patients with MDI- and TDI-induced asthma. The results confirm the generally rather poor medical outcome of diisocyanate-induced asthma; the persistence of symptoms and unspecific bronchial reactivity were pronounced in TDI-induced asthma. A more favourable outcome was associated with IgE mediation and HDI inducement.