Absence of Airway Hyperreactivity to Methacholine in a Worker Sensitized to Toluene Diisocyanate (TDI)

Abstract

A worker with occupational asthma due to toluene diisocyanate (TDI) was studied. Detailed immunologic studies, including those for p-tolyl isocyanate Ig[immunoglobulin]E antibodies and the presence of leukocyte inhibition factor for isocyanate antigen, were negative. Clinically, the subject noted more pronounced symptoms beginning on Monday morning, following a weekend off work, and lessening of the symptoms over the working week. Methacholine challenges were negative when performed on 3 separate occasions, including the time when maximum symptoms were present, and again 6 mo. later, before and after bronchial challenge testing. A dose-related reponse to TDI was observed on bronchial provocation testing using nonirritating concentrations of TDI of 0.0165 and 0.030 ppm. The response of the airway to TDI may not always be accompanied by hyperreactivity to methacholine. Screening programs utilizing metacholine challenges may not always identify sensitized workers, since a negative methacholine challenge test does not exclude TDI sensitization.