Detecting Impaired Lung Growth Using the Conditional Change Score of FEV₁ in an Open Cohort of Children With Asthma

It has been suggested that a quarter of children with asthma show impaired lung growth, with better initial function as a risk factor. A conditional change score (CCS) for FEV1 that is independent of the initial FEV1 and that takes into account the time interval between the measurements has been proposed, a value < -1.96 being predictive of impaired growth. To evaluate whether the use of the CCS allows the identification of a subgroup of children with asthma that has an impaired lung growth, and to identify the risk factors of impaired growth. We reanalyzed the data of 295 children with confirmed asthma (199 boys) who had undergone at least 10 spirometry tests from the age of 8 who were selected from a single-center open cohort. The annualized rate of change (slope) for prebronchodilator FEV1 (percent predicted) was estimated for each participant. Using the first and last visit of follow-up, the CCS was calculated. In total, 46 children (16%, 95% confidence interval: 12-20) followed up for a median duration of 6.5 years [interquartile: 5.7-7.3] exhibited an impaired lung growth. The CCS correlated with the standard deviation of individual slopes (FEV1 variability criterion: R = 0.21; p < 0.001), the z-score of FEV1 at first visit (R = -0.22; p < 0.001), and the body mass index at final visit (R = 0.16; p = 0.005), which remained independently associated with the CCS. We confirm that some children with asthma (16%) show impaired lung growth with better initial lung function and decreased FEV1 variability as risk factors.