Asthma, FEF_25-75, and Hospitalizations in Children

Asthma is a common chronic pediatric respiratory disease associated with significant morbidity. Current guidelines recommend monitoring forced expiratory volume in 1 s (FEV₁) as part of the assessment of asthma severity and control; however, many children with asthma have a normal FEV₁ despite significant symptoms. Reduced forced expiratory flow between 25%-75% of forced vital capacity (FEF_25-75) may be an important measure of asthma severity and control in children with normal FEV₁. This study examines the association between FEF_25-75 and asthma-related hospitalizations. Pulmonary function tests and records of 925 children ≤19 years of age seen for an initial evaluation of physician-diagnosed asthma at a community-based asthma clinic between 1999 and 2011 were reviewed. FEV₁ ≥80% predicted and FEF_25-75 ≥60% were considered normal. The associations between FEV₁ and FEF_25-75 and asthma-related hospitalizations were examined using logistic regression models. Thirteen percent (n=118) of the children were hospitalized for asthma at least once in the previous year. Fifty four percent (n=501) of the children met criteria for uncontrolled asthma symptoms. Asthma-related hospitalization was associated with reducing categories of FEF_25-75, but not FEV₁. Among the 693 children with normal FEV₁ (≥80%), those with FEF_25-75 <60% were more likely to have been hospitalized in the previous year (odds ratio 2.50, confidence interval 1.17-5.35) as compared to those with FEF_25-75 ≥60% of predicted. In a diverse urban cohort of children with asthma, asthma-related hospitalization in the previous year was associated with reduced FEF_25-75 even among those with normal FEV₁. Our results suggest that FEF_25-75 may provide important information in the assessment and management of asthma in children.