Clinical predictors of non-acute airflow obstruction in children with asthma

<bold>Background:</bold> There is increasing concern about children with asthma developing progressive lung function impairment. The objective was to identify spirometry predictors of a subsequent airflow obstruction (AO) in children with asthma. <bold>Design:</bold> We assembled two retrospective cohorts of children aged 6-17 years with asthma, repeated spirometry testing, medical and drug coverage, treated in two tertiary-care asthma centres: Montreal Children’s Hospital (MCH) and Centre Hospitalier Universitaire Sainte-Justine (CHUSJ). The primary outcome was pre-BD AO defined as FEV₁ or FEV₁/FVC ratio below lower limit of normal (LLN). Lung function parameters, documented prior to index visit, included pre-BD FEV₁ Z-score, maximum between-visit variation in FEV₁ (highest—lowest Z-Score ever), and post-BD FEV₁ response ≥10% ever recorded. Potential covariates/confounders were adjusted in multivariable logistic regression models. <bold>Results:</bold> Of 716 eligible children (mean age:10 years), 24% developed a pre-BD AO. Three spirometric parameters were significantly associated with pre-BD AO: pre-BD FEV1 Z-score (previous visit), maximum variation in pre-BD FEV₁ Z-score, and, in the MCH cohort, a positive BD response. <fig><object-id>erj;64/suppl_68/PA3132/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig> Additional predictors included: suboptimal monitoring, higher Step therapy, and poor control. <bold>Conclusion:</bold> Higher FEV₁ was protective for, whereas higher (between-visit and post-BD) variation of FEV₁ significantly increased, the risk of developing AO.