Table 1 Methods of classification of asthma phenotypes in children
Methods based on clinical features
Symptom based
    Age at onset
    Natural history
Defined by triggers
    Allergic versus non-allergic
    Exercise induced
    Viral-triggered versus multi-triggered wheeze
Response to treatment
    Corticosteroid responsive
Methods based on pathophysiological features
Pathological tests (biopsy, induced sputum & bronchoalveolar lavage)
Non-invasive markers of airway inflammation
    Exhaled nitric oxide
    Exhaled breath condensate
Pulmonary function tests
    Fixed versus bronchodilator-reversible airway obstruction
    Bronchial responsiveness to exercise, cold air, chemical challenge