Bronchodilator Response in FEF for the Diagnosis of Asthma in Children.

Background: Spirometry tests with a bronchodilator response (BDR) in FEV a methacholine concentration that produces a 20% drop in FEV (PC) ≤ 2 mg/mL, and a positive exercise test have high specificity for the diagnosis of asthma in children. However, the value of forced expiratory flow during the middle half of the FVC maneuver (FEF) in spirometry has been questioned. The objective of this study was to relate the BDR in FEF of spirometry tests with normal FEV and FEV/FVC to airway hyper-responsiveness (AHR) to methacholine or exercise in children age 5-15 y with clinical suspicion of asthma.