6617 The relationship between CT scan findings and airway physiology, inflammation, and morphology in children with severe asthma

Objectives Computed Tomography (CT) scans have a diagnostic role in adult asthma as a biomarker of severity. CT scan abnormalities have been reported in paediatric severe asthma (SA), however, the utility of CT scans in children has not been established.¹ We hypothesised that CT scan abnormalities in children are related to airflow obstruction and aimed to assess the relationship of these abnormalities with measures of airway physiology, inflammation, and morphology in a well characterised cohort of children with SA Methods Retrospective study of 80 c asthma assessment. CT scans were classified as interspaced or volumetric. Anonymised CT scans were scored by a single-blinded radiologist using a semi-quantitative paediatric scoring system for the severity (none – severe) and extent (number of lobes involved); of bronchial wall thickening (BWT), bronchiectasis (BE), hyperinflation, parenchymal damage and mucus plugging (MP). A total lung score based on these measures was calculated. Pre and post bronchodilator spirometry, exhaled nitric oxide (FeNO), induced sputum and bronchoalveolar lavage (BAL) cytology data were collected. Endobronchial biopsy measurements included reticular basement membrane (RBM) thickness, mass of airway smooth muscle (ASM), and biopsy eosinophils. Asthma control was measured using the Asthma Control Test (ACT) score or childhood ACT. Quality of life was assessed using the mini Paediatric Asthma Quality of Life Questionnaire (PAQLQ). Results Fifty-four children (67.5%) had an abnormal CT scan. Table 1 shows that BWT was the most common finding (41.4%). Those with an abnormal CT scan had significantly lower mean BMI than those with a normal scan (20.2 ± 4.08 versus 22.9 ± 6.19 p=0.03) and higher median submucosal eosinophils/mm2 (54.1 (16.3–117 versus 10.8 (3.96- 44.9) p=0.04); however there were no differences in any other demographic measures, asthma control, spirometric indices, FeNO, sputum or BAL cytology, RBM thickening or ASM mass. There was a significant relationship between BE score and age and BE score and submucosal eosinophils/mm2; however, there was no significant relationship between the scores for BE, BWT, MP and hyperinflation, parenchymal damage or total lung score and measures of airway physiology, other measures of airway inflammation, airway morphology, mini-PAQLQ score, or ACT/cACT score. Conclusion Chest CT scans are frequently abnormal in children with severe asthma, however there is no relationship asthma control, airway physiology, inflammation, or morphology. Further work is needed to assess how these abnormalities are related to long term outcomes, particularly in adulthood. Reference Lo, et al. High prevalence of bronchiectasis on chest CT in a selected cohort of children with severe Asthma, 2019 Jul 26.