Development of the chronic obstructive pulmonary disease activity rating scale: reliability, validity and factorial structure.

The purpose of the present study was to develop the Chronic Obstructive Pulmonary Disease (COPD) Activity Rating Scale (CARS) to measure life-related activity in patients with COPD, and to confirm its reliability and constructive validity in a factorial structure model. The subjects consisted of 114 patients with COPD. An 88-item life-related activity list, generated previously from a literature review, was administered. The secondary structural model consisted of four factors with 12 items. The results of the confirmatory factor analysis by structural equation modeling showed the fit criteria to be statistically significant. The internal consistency of the 12 items was highly reliable (Cronbach's alpha = 0.924). The CARS score was correlated with pulmonary function tests, breathlessness, and the health-related quality of life (QOL) scales in Pearson correlation coefficient. The results suggest that the COPD Activity Rating Scale is a valid scale for the assessment of life-related activity in patients with COPD.