Absence of airway hyperreactivity to methacholine in a worker sensitized to toluene diisocyanate (TDI).

A worker with occupational asthma due to toluene diisocyanate (TDI) was studied. Detailed immunologic studies, including those for p-tolyl isocyanate IgE antibodies and the presence of leukocyte inhibition factor for isocyanate antigen, were negative. Clinically, the subject noted more pronounced symptoms beginning on Monday morning, followed by weekend off work, and lessening of her symptoms over the working week. Methacholine challenges were negative when performed on three separate occasions, including the time when maximum symptoms were present, and again six months later, before and after bronchial challenge testing. A dose-related response to TDI was observed on bronchial provocation testing using nonirritating concentrations of TDI of 0.0165 and 0.030 ppm. This case provides evidence that the response of the airway to TDI may not always be accompanied by hyperreactivity to methacholine. Screening programs utilizing methacholine challenges may not always identify sensitized workers, since a negative methacholine challenge test does not exclude TDI sensitization.