If the symptoms and history are indicative of asthma, your doctor will usually perform pulmonary (lung) function tests to confirm the diagnosis and determine the severity of the disease.

Lung Function Test

This test is done using the Spirometer. It helps to measure the:

  • Vital capacity (VC) which is a measurement of the maximum amount of air that can be inhaled (breathe in) or exhaled (breathe out).
  • Peak Expiratory Flow Rate (PEFR) which is the maximum flow rate that can be produced during forced expiration.
  • Forced Expiratory Volume (FEV1) which is the maximum amount of air that can be forced out in 1 second.



During the asthmatic attack because of narrowing of the airways, there is decrease in PEFR and FEV1.

Other tests may include

  • Allergy test : This test is to look for the trigger factors causing asthma. It can also diagnose the cause of occupational asthma. Allergy test is generally useful in diagnosing seasonal asthma by detecting the triggers causing the attack.
  • Blood test : Peripheral blood smear shows increased eosinophilic count especially in allergic asthma.
  • Chest X-Ray : This is usually done to rule out other diseases like chronic bronchitis, emphysema etc. Chest x-ray is usually normal in asthma.
  • Exercise test : This test can be done to detect mild asthma or asthma in children.