Asthma
Chronic airway inflammation causing reversible bronchoconstriction. Diagnosed clinically and by spirometry; lab work plays a supporting role.
What it is
Asthma is a chronic inflammatory disease of the airways characterised by reversible airflow obstruction, bronchial hyperresponsiveness and airway inflammation. Symptoms — wheeze, breathlessness, chest tightness, cough — vary over time and in intensity. Triggers include allergens, viral infections, exercise, cold air, smoke, occupational exposures and emotional stress. Global prevalence is rising; affects 1–18% of the population by country. The disease is diagnosed clinically with reversibility documented on spirometry — lab tests support phenotyping but don't make the diagnosis.
Key lab markers
- Spirometry — the diagnostic test; FEV1 improvement >12% after bronchodilator confirms reversibility.
- Eosinophil count, total IgE, allergen-specific IgE — phenotype-driven; high eosinophils suggest biologic therapy candidacy.
- Fractional exhaled nitric oxide (FeNO) — surrogate for eosinophilic airway inflammation.
- CBC — chronic eosinophilia in allergic asthma.
- CRP — generally not useful unless infection suspected.
Symptoms
- Wheezing
- Shortness of breath
- Chest tightness
- Cough, often worse at night or early morning
- Symptoms triggered by allergens, exercise, cold air, viral infections
- Diurnal variability — worse at night
- Response to bronchodilator (reversibility)
When to discuss with a doctor
Persistent or recurrent wheezing, breathlessness or chest tightness warrants spirometry and a primary-care or pulmonology evaluation. Patients already diagnosed should have a written action plan, peak-flow monitoring at home, and quick access to bronchodilators. Sudden severe asthma — difficulty speaking in full sentences, blue lips, exhaustion — is an emergency.