Small Airway Impairment and Bronchial Hyperresponsiveness in Asthma Onset

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.

Seasons can influence the results of the methacholine challenge test

This study tried to evaluate whether a methacholine test may be influenced by the seasons. We considered 4826 consecutive subjects with normal spirometry [50.53% males; age: 35.1 +/- 16.2; forced expiratory volume in one second: 99.5 +/- 13.0%] who underwent a methacholine test for suspected asthma symptoms between 2000 and 2010. They were subdivided into four groups, like the seasons, according to the test dates. A total of 1981 [41%] resulted normal [no PD [20] was obtained with 2400 micro g of methacholine]; the others showed a mean LogPD[20] of 2.52 +/- 0.5 micro g. The number of subjects with bronchial hyper-responsiveness [BHR] found in autumn [789, 62.3%] was higher than in summer [583, 56.7%; P=0.03]. A higher number of females and overweight/obese subjects showed a BHR in autumn compared with the other seasons. The spring mean LogPD[20] value [2.48 +/- 0.48 micro g] was lower if compared with the one measured in summer [2.59 +/- 0.49 micro g; P=0.05]. LogPD 20 value was lower in females and non-smokers in spring compared with summer [P<0.05]. Overweight/obese non-smokers showed a lower LogPD[20] in spring and autumn compared with that in summer [P<0.05]. Autumn was a risk factor [OR: 1.378; P=0.001] for BHR [using a PD [20] <2 400 micro g as BHR limit], while spring [OR: 1.330; P=0.021] and autumn [OR: 1.331; P=0.020] were risk factors for a more severe BHR [using a PD[20] <400 micro g as BHR limit]. There was a higher probability of finding BHR in outpatients with suspected asthma in autumn and spring compared with summer. Spring is the season where BHR may be more severe. Females and overweight/obese subjects were those mainly involved in this seasonal variability of BHR