According to World Health Organization (WHO), non-communicable diseases account for 70% of global mortality. Chronic Respiratory Disease (CRD) affects more than one billion people and is the third leading cause of annual death of five million people after cardiovascular disease and cancer. Asthma and chronic obstructive pulmonary disease (COPD) are the two most common diseases of CRD and are part of obstructive airway disease (OAD).

Asthma and COPD are distinguished by the clinical manifestations and therapeutic strategy according to Global Initiative for Asthma (GINA) and Global Initiative for Chronic Obstructive Lung Disease (GOLD). However, in Vietnam, most patients with OAD are treated with an inhaled corticosteroid (ICS) combined with a long-lasting bronchodilator because the specific diagnosis is not always possible.

In addition, a significant proportion of patients have clinical features of both asthma and COPD that is defined as the asthma COPD overlap (ACO). The definition of ACO remains controversial because it is not a distinct disease in which their specific treatment is still under debate that ICS is being generally proposed.

It is understood that most OAD in Vietnam is treated with ICS. However, it is now accepted that in COPD (or COPD-like ACO) patients receiving this treatment may promote respiratory infections and even tuberculosis in endemic countries including Vietnam.

Few data on the relative prevalence of asthma, COPD, and ACO are available in Vietnam. A recent study in Vietnam proposed defining asthma, COPD and ACO based on symptoms, ventilatory obstruction and bronchodilator (BD) reversibility, cumulative smoking, and age. Mites sensitization and exposure to biomass fume were then evaluated in patients having ACO. By doing so, COPD patients are smoking (≥ 10 pack-years) and have irreversible bronchial obstruction. Asthmatics are those with completely reversible bronchial obstruction OR non-smoking patients (<10 pack-years) and partially reversible obstructive. The other OAD patients were classified as having "ACO". Based on these definitions, the prevalence of COPD, asthma and ACO was 40%, 18% and 42%, respectively. Then ACO was defined as "from COPD, or ACO-COPD" in case of biomass exposure and negative mite skin tests, the others being ACO "from asthma or ACO-asthma".

Currently, several biomarkers have been evaluated in the differential diagnosis and prognosis of OAD. The concentration of immunoglobulin E (IgE), the number of eosinophils in blood and sputum, nitric oxide (NO) in exhaled air, and recently periostin have been associated with asthma. On the other hand, biomarkers of systemic inflammation (C-reactive protein (CRP), fibrinogen, TNFα, IL-6 and IL-8) have also been investigated in COPD. Few data are available on the ACO biomarkers.

In this study, the investigators will define the different phenotypes of chronic OAD (asthma, ACO-asthma, ACO-COPD and COPD) taking into account the reversibility of bronchial obstruction, cumulative smoking, biomass fume exposure and immediate sensitization to mites. Blood biomarkers and exhaled NO will be measured and analyzed in each phenotype.

The treatment of COPD, asthma, ACO-COPD, and ACO-asthma based on the GINA and GOLD recommendations will be compared to the current practice in Vietnam: use of ICS with or without long-acting beta-agonists (LABA).

Specific biomarkers will also be evaluated as predictors of treatment response.

Inclusion Criteria:

• Age: ≥ 18 years old
• Signed informed consent
• Out-patients at Nguyen Tri Phuong Hospital
• One or several symptoms suggesting chronic respiratory disease (cough, chest tightness, wheezing, dyspnea or sputum), lasting 3 months or more.
• Lung function abnormality (Forced Expiratory Volume in 1 Second /Forced Vital Capacity < Lower Limit of Normal)
• Patients are able to stop anti-histamine 5 days before evaluation
• Patients are able to stop bronchodilator treatment before performing lung function test according to standard practice (immediate release theophylline: 24 hours, long acting β2-agonist: 12 hours, short acting β2-agonist: 6 hours and short acting anticholinergic: 8 hours).

Exclusion Criteria:

• Presence of one or more chronic diseases: HIV infection, active tuberculosis, heart failure, cancers, auto-immune diseases, systemic diseases, low BMI (<18.5) or mental health disorders.
• Treatment with non-selective beta-blockers
• Severe exacerbation during the last month
• Corticosteroid-dependent patients
• Pregnant women

The out-patient population with chronic obstructive respiratory disease consulted at Nguyen Tri Phuong Hospital, Ho Chi Minh city, Vietnam.