Overview

Lung function tests commonly used in the diagnosis of asthma in children 6 years and older, adolescents and adults include spirometry, peak expiratory flow monitoring and fractional exhaled nitric oxide (FeNO) measurements. Total immunoglobulin E (IgE), specific IgE to perennial allergens and blood eosinophils may be measured by specialists in patients with severe asthma in whom treatment with monoclonal antibodies is considered. Lung function testing cannot be used for the assessment of respiratory symptoms suggestive of asthma in children aged 5 years and younger; see Assessment of wheeze and asthma in children 5 years and younger.

Repeated measurements of lung function are more informative than a single measure. All people have some day-to-day variation in lung function, but patients with asthma have more pronounced variation than is seen in a healthy person. In a patient with a symptom pattern consistent with asthma (see Clinical features that increase and decrease the probability of asthma in children 6 years and older, adolescents and adults), frequent and significant variation in lung function supports the diagnosis of asthma.

For further information on lung function tests, including tests that may require specialist referral, see Pulmonary function tests.