Table 1 Criteria for making the diagnosis of asthma

1. History of variable respiratory symptoms

Generally more than one type of respiratory symptom (in adults, isolated cough is seldom due to asthma)

 Symptoms occur variably over time and vary in intensity

 Symptoms are often worse at night or on waking

 Symptoms are often triggered by exercise, laughter, allergens, cold air

 Symptoms often appear or worsen with viral infections

2. Confirmed variable expiratory airflow limitation

At least once during diagnostic process (e.g. when FEV 1 is low), confirm that FEV 1 /FVC is reduced (normally > 0.75–0.80)

 Positive bronchodilator (BD) reversibility Test: increase in FEV 1 of > 12% and > 200 mL from baseline, 10–15 min after 200–400 mcg albuterol or equivalent (greater confidence if increase is > 15% and > 400 mL);

 Excessive variability in twice-daily PEF over 2 weeks: average daily diurnal PEF variability > 10%;

 Significant increase in lung function after 4 weeks of anti-inflammatory treatment: increase in FEV 1 by > 12% and > 200 mL (or PEF † by > 20%) from baseline after 4 weeks of treatment, outside respiratory infections;

 Positive exercise challenge test: fall in FEV 1 of > 10% and > 200 mL from baseline;

 Positive bronchial challenge test: Fall in FEV 1 from baseline of ≥ 20% with standard doses of methacholine, or ≥ 15% with standardized hyperventilation, hypertonic saline or mannitol challenge;

 Excessive variation in lung function between visits: variation in FEV 1 of > 12% and > 200 mL between visits, outside of respiratory infections