Clinical Characteristics of COPD Patients According to COPD Assessment Test (CAT) Score Level: Cross-Sectional Study

The chronic obstructive pulmonary disease (COPD) assessment test (CAT) is widely used to assess the impact of COPD symptoms on health status. Whilst the CAT consists of eight different items, details on the distribution of each item are limited. This study aimed to investigate the distribution and clinical implication of each CAT item, stratified by CAT severity group, in stable COPD patients.

This was a cross-sectional study at a single referral hospital in South Korea. Spirometry confirmed COPD patients with CAT measured at the first clinical visit were retrospectively identified. Patients were categorized into three groups: low (0 ≤ CAT < 10), medium (10 ≤ CAT < 20), and high (20 ≤ CAT ≤ 40) impact group. For the purpose of this analysis, the first four items (cough, sputum, chest tightness, and dyspnea) and the remaining four items (activities, confidence, sleep and energy) were also grouped as "pulmonary" and "extra-pulmonary", respectively.

A total of 815 patients were included, and mean (SD) forced expiratory volume in 1 s (FEV₁) was 62.8 (17.4) % pred. Among them, 300 patients (36.8%) were in the high impact group and had a greater exacerbation history and lower lung function. The proportion of "extra-pulmonary" items score was greater in patients with higher total CAT scores, with the activity and confidence items showing higher scores.

In our study, in addition to dyspnea, activity limitation is a particular problem in individual patients with higher CAT total scores, for which physicians need to pay more attention. Our study suggests that whilst CAT total score captures the overall impact of COPD, each item of the CAT contains potentially useful information in understanding the patient's symptom burden.