Objectives: Fibrotic interstitial lung disease (ILD) is a progressive lung disease characterised by loss of lung volume, resulting in a leading cause of death in patients with rheumatoid arthritis (RA). Crucially, acute exacerbation (AE) of ILD shows higher morbidity and mortality with rapid deterioration of the lungs. However, a quantitative assessment for physiological changes at AE has yet to be performed. This study hypothesised that quantitative assessments of lung volume (LV) accurately indicate disease severity and mortality risk in patients with AE-RA-ILD.
Methods: This multicentre cohorts study quantitatively assessed physiological changes of RA-ILD at diagnosis (n = 54), at AE (Discovery-cohorts; n = 20, and Validation-cohort; n = 33), and controls (n = 35) using 3D CT (3D-CT) images. LV was quantitatively measured using 3D-CT and standardised by predicted forced vital capacity.
Results: Patients with RA-ILD at diagnosis showed decreased LV, predominantly in lower lobes, compared with controls. Further substantial volume loss was found in upper- and lower lobes at AE compared with those at diagnosis. During AE, decreased standardised 3D-CT LV was associated with a worse prognosis in both cohorts. Subsequently, standardised 3D-CT LV was identified as a significant prognostic factor independent of age, sex, and the presence of UIP pattern on CT by multivariate analyses. Notably, a composite model of age and standardised 3D-CT LV successfully classified mortality risk in patients with AE-RA-ILD.
Conclusion: Volume loss at AE in patients with RA-ILD was associated with increased mortality. Assessing physiological change using standardised 3D-CT might help evaluate disease severity and mortality risk in patients with AE-RA-ILD.
Keywords: acute exacerbation; lung volume; rheumatoid arthritis-associated interstitial lung disease; three-dimensional computed tomography.
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