Ability of the COPD Assessment Test to evaluate lung‐specific quality of life in systemic sclerosis‐associated interstitial lung disease

INTRODUCTION: The COPD Assessment Test (CAT) is utilised to evaluate the treatment outcome regarding the health status in idiopathic interstitial pneumonia (IIP). However, the ability of the CAT to evaluate the lung-specific quality of life in systemic sclerosis-associated interstitial lung disease (SSc-ILD) is not established. Therefore, we investigated whether CAT scores can be used to evaluate SSc-ILD as they are for IIP. METHODS: A total of 150 patients with IIP or SSc-ILD who were evaluated by the CAT were retrospectively assigned to this study. Clinical data at the visit for the CAT were analysed. RESULTS: The forced vital capacity and distance walked during the 6-minute walk test (6MWD) were significantly correlated with the CAT score for SSc-ILD and IIP, and the CAT scores were similarly distributed in SSc-ILD and IIP. The CAT score of SSc-ILD patients was negatively affected by pulmonary arterial hypertension, but not by corticosteroids, which affected it in IIP patients. CAT scores of patients with either disease receiving home oxygen therapy were poor. In multiple regression analysis, pulmonary arterial hypertension and 6MWD were independent predictors for the CAT score in patients with SSc-ILD, while corticosteroid administration was selected as an independent factor in patients with IIP. CONCLUSIONS: Our study suggests that the CAT can be applied to evaluate the lung-specific quality of life in SSc-ILD similar to IIP regarding the pulmonary function, but it should be noted that pulmonary arterial hypertension in SSc-ILD influences the CAT score.