Forced Expiratory Flow at 25–75% as a Marker for Airway Hyper Responsiveness in Adult Patients with Asthma-like Symptoms

Background: The aim of the present study was threefold: to assess the association between baseline FEF25-75 and Airway Hyper-responsiveness (AHR), to specify whether a decrease in FEF25-75 may reflect severe hyper- responsiveness, and finally to confirm a FEF 25-75 cut-off value. Materials and Methods: In a cross sectional study in Imam Khomeini Hospital, Ahvaz, patients suffering from respiratory symptoms due the 2013 autumn rainfall with normal FEV1 and FEV1/FVC were evaluated by methacholine challenge test. Those with PD20<1000, 10002000 μg were classified as severe, moderate and mild AHR, respectively. Data were analyzed using Chi-square, Independent t-test, One-way ANOVA and Receiver Operating Characteristic (ROC) curve. Results: Among the 234 patients, mean baseline FEF25-75 was 84.2±22.7% for 54 patients having a negative bronchial provocation test result and 70.9±19.2% for 179 patients with a positive bronchial provocation test result (P < 0.0001). No change was observed in the median PD20 among patients with a higher baseline FEF25-75. ROC analysis showed that FEF25-75 could potentially be a predictor of AHR, but it could not confirm the cut-off value of FEF25-75 for these patients. Conclusion: When asthma begins, AHR could be predicted by impaired FEF25-75 with normal FEV1 and FEV1/FVC. However, we could not determine a cut-off value, and no association was found between a greater impairment of FEF25-75 and a more severe AHR.