Is Forced Expiratory Volume in One Second the Best Measure of Severity in Childhood Asthma?

This essay focuses on whether FEV1 is the best measure of asthma severity in childhood asthma. For better or worse, FEV1 has become the gold standard lung function measurement in asthma, as it can be easily and quickly measured with relatively simple equipment. The current asthma guidelines use FEV1 in addition to daytime and nighttime symptoms in judging asthma severity (1, 2). Patients with mild persistent asthma are said to have FEV1 values of more than 80% of predicted, patients with moderate persistent asthma have values of 60 to 80% of predicted, whereas those with severe persistent asthma have values of less than 60% of predicted (1, 2). Despite widespread acceptance, neither are these criteria evidence-based nor is the basis of criteria described. FEV1 is also the outcome variable favored by the U.S. Food and Drug Administration to judge efficacy of asthma-controller medications. Thus, nearly all studies evaluating response to medications in asthma require subjects to have FEV1 values of 60 to 80% of predicted as essential entry criteria. Although this approach provides objective data to evaluate efficacy, it may not be the best measure for children with asthma. This is in large part because children with asthma are likely to have FEV1 values within the normal range when clinically stable.