Paranasal sinus opacification and lower airway mucus plugs and wall thickening in asthma: a two-cohort computed tomography study.

BACKGROUND: Chronic rhinosinusitis and asthma frequently coexist, yet the morphological relationship between paranasal sinus and lower airway in asthma remains unclear. We hypothesized that paranasal sinus opacification is closely associated with lower airway structural abnormalities in asthma. METHODS: We analyzed two independent asthma cohorts: the Kyoto asthma cohort (discovery) and the Hi-CARAT study (validation). Paranasal sinus opacification was identified as the Lund-Mackay score (LMS) ≥ 6 on paranasal sinus CT. Mucus plugs score in upper-middle lobe airways and lower lobe airways, wall area percentage (WA%) of the right apical (RB1) and posterior basal (RB10) bronchi, and total airway count on inspiratory CT were compared between those with LMS ≥ 6 and LMS < 6. Small airway dysfunction (SAD%) was measured on registered inspiratory and expiratory CT in the discovery cohort. RESULTS: Of 96 and 180 patients in the discovery and validation cohorts, 21 and 75 had LMS ≥ 6. Patients with an LMS ≥ 6 had higher mucus plugs scores in both upper-middle and lower lobe airways. WA% was also increased, particularly in RB10. In multivariable analyses, LMS ≥ 6 was independently associated with greater mucus plugs and increased WA% in the subsegmental RB10 airways independent of oral corticosteroid use, biologics use, blood eosinophil counts, and fractional exhaled nitric oxide. LMS ≥ 6 was also associated with greater SAD%. CONCLUSIONS: Paranasal sinus opacification on CT was associated with lower airway mucus plugs and wall thickening in asthma, independent of type 2 inflammation, supporting the unified airway concept.