RESUMO
PURPOSE: Although asthma is generally understood as a disease of the the small airways, FEF25-75%, an index representing peripheral small airways, is a appropriately used in the diagnosis of asthma. The objectives of this study are to assess the usefulness of FEF25-75% in children with asthma for clinical application. METHODS: Five hundred sixty two 5- to 15-year-old children with symptoms suggestive of asthma were enrolled. Methacholine bronchial provocation tests were performed and the children were divided into two groups according to their test results. RESULTS: Forced expiratory flow between 25-75 percent of vital capacity (FEF25-75%) was significantly lower in asthma group (P< 0.001). A 25 percent fall of FEF25-75% of percentage predicted value was correlated with PC20FEV1 (provacation concentration of methacholine required to reduce FEV1 by 20 percent) (r=0.601, P< 0.001). The sensitivity of PC25FEF25-75% (provocation concentration of methacholine required to reduce FEF25-75% by 25 percent) was 94.11 percent when PC20FEV1 was a point of reference. Youden's index was 0.64. CONCLUSION: FEF25-75% is an useful and sensitive index that predicts the presence or absence and the degree of bronchial hyperresponsiveness and PC25FEF25-75% should be brought into clinical application in asthmatic children.