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 FEF(25-75) and Airway Hyper-responsiveness (AHR), to specify whether a decrease in FEF(25-75) 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, 1000<PD20<2000 or >2000 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 FEF(25-75) 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 FEF(25-75). ROC analysis showed that FEF(25-75) could potentially be a predictor of AHR, but it could not confirm the cut-off value of FEF(25-75) for these patients. CONCLUSION: When asthma begins, AHR could be predicted by impaired FEF(25-75) 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 FEF(25-75) and a more severe AHR.