A forced expiratory flow at 25-75% value <65% of predicted should be considered abnormal: a real-world, cross-sectional study.

Forced expiratory volume in 1 second (FEV1) is considered an important parameter for asthma diagnosis and follow-up. However, it has been proposed that forced expiratory flow at 25-75% (FEF(25-75)) could be more sensitive than FEV1 to detect slight airways obstruction. In this regard, a cutoff FEF(25-75) value has been recently established in a group of asthmatic children: FEF(25-75) < 65% of predicted has been considered impaired. However, the considered population was specifically selected. Therefore, the aim of the present study was to confirm an FEF(25-75) cutoff value in a large cohort of asthmatic children. Seven hundred allergic children (493 male subjects; median age, 11 years) with controlled and partly controlled asthma were evaluated by performing spirometry and skin-prick tests. Three hundred thirteen (44.7%) patients had FEF(25-75%) values of <65% of predicted. Two predictors were significantly associated with impaired FEF(25-75) values: (i) sensitization to perennial allergens (adjusted odds ratio [OR(Adj)], 3.4) and (ii) FEV(1) ≤ 86% of predicted (OR(Adj), 3.8). This study, conducted in real life, could suggest that FEF(25-75) value of <65% of predicted may be considered abnormal.