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

Background: 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.

Objective: 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.

Methods: 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.

Results: 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.

Conclusion: We confirm that some children with asthma (16%) show impaired lung growth with better initial lung function and decreased FEV₁ variability as risk factors.