The trial investigates and describes the prevalence of COPD among socially vulnerable individuals who come in contact with a mobile clinic and investigates the effect of opportunistic screening for COPD in these vulnerable persons. The study population is individuals who come in contact with a mobile clinic, that visits home shelters, open drugs scenes etc. in the Capital Region of Denmark during the inclusion period, and monitor them for up to 1 year in order to investigate variables that are significant in terms of the patients' treatment, hospitalizations, and mortality in relation to COPD. Our hypothesis is that there will be a higher incidence of COPD among socially vulnerable individuals who come in contact with the mobile clinic than in the general population.

The study consists of three sub-studies: A. a descriptive cross-sectional study "The prevalence of COPD among socially vulnerable individuals who come in contact with a mobile clinic" followed by study B a cohort study "The effect of opportunistic screening for COPD among socially vulnerable individuals who come in contact with a mobile clinic", based on a closed cohort, and study C "A qualitative study of patient experiences with screening and treatment of COPD.

People in the lower social classes are at increased risk of developing COPD due to their lifelong accumulation of risk factors, such as smoking, passive smoking and the influence of lifestyle and the environment. In the group with the socially vulnerable individuals, 70% are smokers compared to 18% in the general Danish population. The socially vulnerable individuals are defined here as people affected by homelessness, drug abuse, harmful alcohol consumption, mental illness and poverty. Despite the socially vulnerable group having an over-consumption of general practice visits, 25% of socially vulnerable individuals state that they do not have contact with or use their own doctor. Our hypothesis is therefore that there will be a higher incidence of COPD among socially vulnerable persons who come in contact with the mobile clinic. Purpose: To investigate and describe the prevalence of COPD among socially vulnerable individuals who come in contact with a mobile clinic and to investigate the effect of opportunistic screening for COPD in these vulnerable citizens, followed by a qualitative study of patient experiences with COPD treatment.

Data collection:

Baseline data from the cross-sectional study are derived from lung function measurement and REDCap online-questionnaires completed on inclusion. The data from the cohort study regarding disease burden and hospital visits originates from the national patient registry (LPR) and mortality data is retrieved from the Danish Register of Causes of Death. Data regarding redeemed prescriptions for COPD medicine originates from the Prescription Database. The patients' connection to the job market and income status are based on extracts from RAS (Registry-based Labour Force Statistics), which is administered by Statistics Denmark. Data regarding the highest acquired education (HFAUDD) is from Statistics Denmark.

Variables:

There will be collected the following variables at inclusion: information on demographics, lung function, selv-reported information on: risk factors, socioeconomic variables and symptoms of lung disease. Moreover register data on socioeconomic status, morbidity, physical health by Charlson score, mortality, hospital visits and prescriptions for COPD Medicine will be retrieved after a 1 year follow-up.

Sample size:

To detect a difference between the patient group and the Danish population of minimum 100% a total of 511 participants are needed in the study (power of 80%, p-values=0,05, an estimated COPD prevalence of 4,3% in the Danish population). The collected data will be kept in accordance to the Data Protection Agency guidelines. The studies are carried out in accordance with the principles of the Helsinki Declaration.

Inclusion Criteria:

• 18 years or older
• Able to speak and understand Danish or English to such an extent that informed consent can be obtained

Exclusion Criteria:

- Not having a Danish civil registration number, since foreign patients do not have free access to examinations and medical treatment, and cannot be followed up in the national patient registry