This is an observational study in primary care aiming to validate biomarkers for chronic obstructive pulmonary disease (COPD).

Inclusion Criteria:

• 40 years old or more,
• diagnosis of COPD in primary care

Exclusion Criteria:

• Major psychiatric illness,
• inability to visit primary care doctor,
• inability to understand danish language,

Patients in primary care on the Fyn island, Denmark