Assessment of CT quantitative characteristics derived from CT in connective tissue disease-associated interstitial lung disease.

Background: Connective tissue disease-associated interstitial lung disease (CTD-ILD) is a severe complication, yet early objective detection of pulmonary structural and microvascular alterations remains challenging. This study aimed to quantitatively compare pulmonary structural alterations between connective tissue disease (CTD) patients with and without interstitial lung disease (ILD) and to identify independent computed tomography (CT)-derived discriminators for ILD diagnosis by means of quantitative computed tomography (QCT). Methods: Fifty-one CTD patients with ILD (median age, 51 years; 66.7% female) and thirty-three CTD patients without ILD (median age, 33 years; 69.7% female) who underwent paired inspiratory and expiratory non-contrast chest computed tomography (CT) scans and pulmonary function testing were retrospectively collected. The lung density, functional small airway and pulmonary vessel parameters were analyzed using computer software. Differences in these CT quantitative parameters between the patients with CTD-ILD and those with CTD without ILD were compared using Mann-Whitney U tests. Furthermore, univariable and multivariable logistic regression analyses were used to establish nomograms to identify the independent predictors associated with the presence of ILD in patients with CTD. The calibration curve evaluates the predictive accuracy, while the decision curve analysis (DCA) evaluates clinical applicability. Results: The forced vital capacity (FVC), forced expiratory volume in the first second (FEV Conclusions: QCT can serve as a crucial and highly promising imaging biomarker for the diagnosis and assessment of CTD-ILD.