FEF75 in asthma management

Diagnosis of asthma is based on the presence of symptoms (clinical diagnosis) supported by lung function measurements, such as forced expiratory volume in one second (FEV1) and peak expiratory flow (PEF) variability. Recently, it has been reported that the forced expiratory flow at 25-75 of the pulmonary volume might be considered as a possible marker of early bronchial impairment in patients with allergic rhinitis.

The aim of this retrospective study was to identify the most reliable spirometric parameter for the follow up of intermittent allergic asthma.

Data from 108 outpatients with intermittent allergic asthma was studied. The spirometric parameters before and after 1 week of short aerosol therapy were analyzed. Patients were divided into three groups according to basal FEV1 values: those with all spirometric values normal, those with reduced FEV1 and those with normal FEV1 but reduced FEF75.

There was a good correlation between the spirometric parameters analysed. FEF75 showed a greater significant reduction than FEV1 and PEF. Moreover, 26 of 38 patients with normal FEV1 (68 %) showed a reduction in FEF75. No significant differences were observed between FEV1 and PEF. After short aerosol therapy, FEV1 improved in 93% of patients, but many (61%) still had a reduced FEF75 value, thus the correlation between the two parameters decreased (from r= 0.68 to r = 0.40).

On the basis of these observations, FEF75 should be reconsidered a usefull spirometric parameter for allergic asthma follow up.