Role of FEF25%-75% as a predictor of bronchial hyperreactivity in allergic patients.

The small airways may play an important role in the clinical manifestations of asthma. Forced expiratory flow between 25\% and 75\% (FEF25\%-75\%) has been proposed as an approximate measure of the caliber of distal airways. Bronchial hyperreactivity (BHR) is a feature of asthma.To evaluate the possible role of FEF25\%-75\% as a predictor of BHR in allergic patients with asthma and rhinitis.A total of 726 patients (mean +/- SD age, 24.7 +/- 6.3 years) were evaluated. Spirometry and methacholine bronchial challenge were evaluated in all the participants.A difference between forced expiratory volume in 1 second and FEF25\%-75\% greater than 20 or a ratio between these variables greater than 1.24 discriminates between patients with no response to a mild response to methacholine vs patients with a moderate-to-severe response with high sensitivity (P < .001).This study highlights the possible role of FEF25\%-75\% in predicting BHR in allergic individuals with airway disorders.