Introduction
As reported by Martinez,1 approximately 40% of the deficits in maximal expiratory flow observed at 6 to 7 years of age in children with asthma were present at birth, whereas 60% of the deficits develop during the preschool years.2 A further decline in FEV1 occurs during the school years as part of the natural history of asthma.3 Only one study has demonstrated that asthmatic children can exhibit a loss of lung function during childhood based on spirometry.4 In this study, a reduction in postbronchodilator FEV1% predicted was observed in 25.7% of children with mild to moderate asthma who were enrolled in the Childhood Asthma Management Program (CAMP).4 Factors associated with a reduction in postbronchodilator FEV1% predicted included a younger age at enrollment, male sex, study site and higher postbronchodilator FEV1% predicted at baseline. As a consequence, the results of Covar and colleagues should be confirmed (1) using a more common asthma definition criteria, as hyperresponsiveness to methacholine was an inclusion criterion in their study,4 and (2) in an out-of-hospital series of children that is more representative of childhood asthma than a cohort included in a therapeutic trial involving children with mild to moderate persistent asthma.
The objective of our prospective observational study was to assess whether an abnormal decline in the trajectory of lung function by means of serial FEV1 monitoring can be identified in asthmatic children participating in out-of-hospital follow-up.