Spirometry in children with asthma and/or allergic rhinitis: Comparison of FEF _25-75% with the standard measures

BACKGROUND: Forced expiratory flow between 25% and 75% of vital capacity (FEF _25-75% ), a spirometric measure of small airways, may predict the presence of airway responsiveness both in asthmatics and in allergic rhinitis (AR). We aimed to search the correlation between FEF _25-75% and standard measures of spirometry (forced expiratory volume in the first second [FEV _1% ] and FEV ₁ /FVC [forced vital capacity]) in different clinical conditions, that is in children with asthma, in children with asthma and AR, in children with AR and in healthy children. METHODS: Children with asthma (N.=116), asthma plus AR (N.=25), AR (N.=75) and healthy controls (N.=52) were evaluated. Clinical examinations, spirometry and bronchodilation tests were performed. RESULTS: In asthmatics there was a strong correlation between FEF _25-75% and FEV _1% (r=0.596, P<0.001); and between FEF _25-75% and FEV ₁ /FVC (r=0.740, P<0.001). In AR patients correlation between FEF _25-75% and FEV _1% (r=0.367, P=0.001); and between FEF _25-75% and FEV ₁ /FVC (r=0.534, P<0.001) were less prominent compared to asthmatics but they were still significant and strong. In children with both AR and asthma correlation between FEF _25-75% and FEV _1% (r=0.633, P=0.001) and between FEF _25-75% and FEV ₁ /FVC (r=0.539, P=0.005) were again significant. Pre-test FEV _1% and FEF _25-75% in AR patients were lower than that of the control subjects. After the bronchodilation, percentage change in the FEV ₁ in AR patients were significantly higher than the control subjects (P=0.010). AR patients showed significant increases in FEV _1% , (P<0.001), FEF _25-75% , (P<0.001) and (P=0.001) after the bronchodilation test. Within the AR patients, only 12/75 (16.0%) showed bronchodilation with salbutamol. Among the ones with a FEF _25-75% <65%, FEV _1% was normal in 6/43 (14%) patients in asthmatics, and FEV _1% was normal in 3/9 (33%) patients in asthma +AR patients. CONCLUSIONS: Besides the FEV _1% and FEV ₁ /FVC, the FEF _25-75% may be a useful and early spirometric parameter to evaluate the children with asthma and or AR.