B98-03 Reframing Dysanapsis: Evidence of Underlying Airway Obstruction in Children

Abstract Rationale In spirometry, a dysanaptic pattern is characterized by a low FEV1/FVC despite a normal FEV1 and normal-to-high FVC, suggesting a mismatched growth of the airways compared to the lungs. While often considered a physiologic variant, recent studies have demonstrated that a dysanaptic pattern is associated with obesity and increased childhood asthma morbidity. This study aimed to examine the association between a dysanaptic pattern and positive bronchodilator response (BDR), a marker of underlying airway obstruction in children. Methods We downloaded all spirometries performed at Monroe Carell Jr. Children’s Hospital at Vanderbilt between 2002-2024 from the electronic health record system. Tests were categorized based on z-scores into 1) normal (FEV1/FVC, FEV1, and FVC −1.645), 2) dysanapsis (FEV1/FVC −1.645, FEV1 ≥ −1.645, and FVC ≥ +0.674 the 75th percentile), 3) obstruction with normal FEV1 (FEV1/FVC −1.645, FEV1 ≥ −1.645, and −1.645 FVC +0.674), 4) obstruction with reduced FEV1 (FEV1/FVC and FEV1 −1.645, FVC ≥ −1.645), and 5) “other” as per current ATS/ERS spirometry interpretation guidelines and Global Lung Function Initiative race-neutral reference equations. Spirometries without BDR testing, those categorized as “other,” and repeated tests were excluded. Positive BDR was defined as (post-bronchodilator FEV1L−pre-bronchodilator FEV1L)*100/predicted FEV1(L) 10%. Logistic regression was used to assess the association between dysanapsis and positive BDR adjusting for age, sex, race, body mass index, and diagnosis (categorized as asthma, non-specific respiratory symptoms, cystic fibrosis, and “other”). Results Out of 64,315 total spirometries, 3,819 tests from distinct children met eligibility criteria. Of these, 2,132 (55.83%) were categorized as normal, 491 (12.86%) as dysanapsis, 429 (11.23%) as obstruction with normal FEV1, and 767 (20.08%) as obstruction with reduced FEV1. Median age was 12.11 years (interquartile range=8.56-16.25) and the majority of children were male (53.2%). The proportion of positive BDR in tests with dysanapsis (51.32%) was substantially higher than in those with a normal pattern (17.31%) and comparable to that in tests with obstruction with normal FEV1 (56.64%) (Figure 1). Compared to children with normal spirometry, those with dysanapsis had ∼5-fold higher odds of positive BDR (adjusted OR aOR=5.49, 95%CI=4.41-6.83, p 0.01). These estimates were similar to those for children with obstruction with normal FEV1 (aOR=5.66, 95%=CI 4.52-7.12, p 0.01). Conclusion Our findings demonstrate that positive BDR is common in children with a dysanaptic pattern on spirometry and that this pattern likely reflects underlying airway obstruction rather than a physiologic variant. Health care providers should strongly consider testing for BDR in children with a dysanaptic pattern in spirometry. This abstract is funded by: None