Evaluation of the chronic obstructive pulmonary disease assessment test in Japanese outpatients

Objective The Chronic Obstructive Pulmonary Disease (COPD) Assessment Test (CAT) is a quality-of-life (QOL) questionnaire that proved to correlate with St. George's Respiratory Questionnaire. Correlations between CAT scores and other COPD parameters have not been thoroughly evaluated in Japanese outpatients. Methods Cross-sectional study of 85 outpatients with COPD at a Japanese community-based hospital. Patients We observed 70 men and 15 women, whose average age was 72.0 ± 9.0 years. Mean forced expiratory volume in 1 s (FEV1) (% predicted) was 45.8 ± 14.7%. Mean CAT score was 10.1 ± 7.9 (range: 0–31). We calculated Spearman's rank correlation coefficient for CAT score and the following variables: r = 0.81 for ‘the Body Mass Index, Airflow Obstruction, Dyspnea and Exercise Capacity Index’; r = −0.05 for body mass index; r = −0.56 for FEV1 (% predicted); r = 0.88 for Modified Medical Research Council Dyspnea Scale; r = −0.71 for 6-min walk distance; r = 0.68 for ‘the Age, Dyspnoea,and Airflow Obstruction Index’; and r = −0.40 for oxygen saturation in artery. Each COPD parameter, except for body mass index, had a significant (P < 0.001) correlation with the CAT score. Conclusions The CAT score, which is obtainable by a simple questionnaire originally designed for QOL assessment, had strong correlations with airflow obstruction, dyspnea, exercise tolerance, prognostic index and oxygenation in Japanese outpatients.