Challenging the Airways

To the Editor: Challenge with methacholine or histamine is frequently used during bronchial inhalation to distinguish normal persons from those with hyper-reactive airways. With such challenges, the point of distinction between the two groups is an arbitrary one and depends on the test of pulmonary function used. A group sponsored by the National Institute of Allergy and Infectious Diseases published a statement about the standardization of challenge procedures during bronchial inhalation.¹ This group suggested that a 20 per cent drop in the one-second forced expiratory volume (FEV₁) and a 35 per cent drop in the specific conductance (SG.