A seven-year follow-up study of lung function and methacholine responsiveness in sensitized and non-sensitized...

Lung function, studied with spirometry, nitrogen washout technique, and methacholine responsiveness, was prospectively investigated in a seven-year follow-up study of 35 laboratory animal workers (19 women and 16 men) of whom 11 were skin prick test (SPT) positive to laboratory animal allergens; five had asthma and six had rhinitis symptoms. During the follow-up, 82% of the SPT positive subjects had stopped animal work, compared with 29% of the SPT-negative subjects. In baseline spirometry, there was no decrement in the lung volumes or differences between SPT-positive and SPT-negative subjects. At follow-up, no difference was found in vital capacity (VC), forced expiratory volume during one second (FEV1), or residual volume (RV), but the volume of trapped gas (VTG), which is assumed to measure small airways, had increased with a median of 11 mL (P = 0.03). Subjects sensitized to laboratory animals had a minor increase in methacholine responsiveness in FEV1 at follow-up (P = 0.03). The VTG responsiveness was already increased in the first examination (P = 0.035) and remained so at follow-up. Furthermore, the FEV1 responsiveness could predict a subsequent decline in baseline VC and FEV1. In conclusion, our results support the hypothesis that airway responsiveness in immunoglobulin E-mediated allergy might start in small airways and subsequently affect large airways.