CT predictors of outcomes in patients with connective tissue disease and progressive lung fibrosis

Progressive fibrosing interstitial lung disease (PF-ILD) is a phenotype defined by rapid clinical progression towards respiratory failure. While idiopathic pulmonary fibrosis is the archetype of PF-ILD, connective tissue disease associated interstitial lung disease (CTD-ILD) can also manifest as PF-ILD. Few studies have described the value of serial computed tomography (CT) in predicting clinical progression of ILD. We explore which single and serial clinical and radiographic variables, in particular serial CT variables and a novel variable, the right lower lobe anterior bronchial angle (RLL-ABA), best predict mortality, oxygen requirement, hospital admissions, and lung transplant in CTD-ILD.This is a single-center retrospective study of 84 patients with a history of CTD-ILD. Cox survival analysis was used to predict two endpoints, all-cause mortality and composite negative outcomes (CNO): new oxygen requirement, respiratory admission, lung transplant, and death.On serial CT, change in pulmonary artery (PA) size and RLL-ABA were predictive of mortality and CNO, and change in fibrosis was predictive of mortality alone. On single CT, the extent of fibrosis, PA size, and PA to aorta ratio were predictive of mortality and CNO. Among clinical variables, oxygen requirement, forced vital capacity (FVC), change in FVC, and worsening shortness of breath were predictive of mortality and CNO, and diffusing capacity for carbon monoxide was predictive of mortality alone.In addition to clinical and single CT variables, serial CT measurements such as change in extent of fibrosis, PA size, PA to aorta ratio, and RLL-ABA were predictive of mortality and CNO.