Investigation of the Clinical, Radiological and Biological Factors Associated with Disease Progression, Phenotypes and Endotypes of COPD in China (COMPASS): study design, protocol and rationale.

COPD is heterogeneous, and its presentation varies between countries. The major COPD cohort studies have only been performed in Western populations; the disease is not well characterised in other regions. The COMPASS (Investigation of the Clinical, Radiological and Biological Factors, Humanistic and Healthcare Utilisation Burden Associated with Disease Progression, Phenotypes and Endotypes of COPD in China; NCT04853225) is a prospective, 2.5-year-long, multi-centre, longitudinal, observational study with three aims: 1) to characterise stable and exacerbation phenotypes/endotypes in terms of clinical characteristics, blood and sputum biomarkers, lung microbiome and lung imaging; 2) to understand the relevance of markers of COPD disease progression identified in Western cohorts to Chinese patients; and 3) to characterise treatment pathways and healthcare resource utilisation. COMPASS will recruit 2000 participants, of which 1700 will be in Global Initiative for Chronic Obstructive Lung Disease (GOLD) Grades I-IV (n=700, 700, 200 and 100, respectively), 180 participants with chronic bronchitis without airflow limitation and 120 never-smoker healthy controls. Study visits will be at baseline, 6, 18 and 30 months and at exacerbation. Assessments include lung function, exacerbation frequency, health status, blood biomarkers and, in a sub-cohort of 400 patients, chest high-resolution computed tomography, additional blood and sputum biomarkers, airway micro-, viral- and myco-biome, and physical activity. COMPASS will establish a unique clinical and biological dataset in a well-characterised cohort of individuals with COPD in China, with a particular focus on milder patients. As the first study of its kind attempting to understand the disease in an Asian setting, it will provide valuable insights into regional and ethnic differences in COPD.