ABSTRACT
PURPOSE: Our study tried to find a relationship between baseline FEF25-75% and airway hyperresponsiveness (AHR) and whether a greater FEF25-75% impairment may be a marker of a more severe hyperresponsiveness in subjects with normal FEV1 and FEV1/FVC and suggestive asthma symptoms. Besides, we tried to asses a FEF25-75% cut-off value to identify hyper-reactive subjects. METHODS: 4,172 subjects (2,042 M; mean age: 38.3+/-14.9; mean FEV1 % predicted: 100.5+/-12.7 and FEV1/FVC: 85.4+/-6.8) were examined after performing a methacholine (Mch) test. All subjects reported a symptom onset within 3 years before the test. Subjects with PD20400 microg were arbitrarily considered affected by moderate/severe and borderline AHR, respectively. RESULTS: PD20 values were 213 (IQR:86-557), 340 (IQR:157-872) and 433 (IQR:196-1032) microg in subjects with baseline FEF25-7570% respectively (P70%. The hyperreactive subjects percentage, was higher in those with FEF25-7570% (P70%) was a higher AHR risk factor, especially in subjects with moderate/severe AHR (OR: 2.18 [IQR:1.41-3.37]; P50 and 70% levels were similar both in normoreactive and hyperreactive subjects. CONCLUSIONS: At asthma onset, reduced baseline FEF25-75 values with normal FEV1 and FEV1/FVC may predict AHR. Detectable predictive cut-off values do not exist because even normoreactive subjects can show lower FEF25-75 values. Furthermore, a greater FEF25-75 reduction may be associated to a more severe AHR, suggesting a possible FEF25-75 role in the management of asthma when FEV1 and FEV1/FVC are normal.