How are you diagnosed with asthma?

Asthma is diagnosed by reviewing your medical history and performing a variety of tests and examinations. Often an allergy test is performed, a lung function examination (spirometry), as well as measuring levels of nitric oxide in the exhaled air, or an exercise test. Sometimes even more advanced examinations are necessary to diagnose asthma.

Physical examination

Especially when it comes to small children, a diagnosis is based on the information provided by parents. The doctor will listen to the lungs, map risk factors including heredity, as well as check whether fast-acting bronchodilating medicine eases breathing difficulties. Sometimes radiography is needed in order to exclude other more uncommon causes of symptoms.


A spirometry examination is performed in order to determine the lung function in terms of volume and flow. Such an examination is usually performed from the age of 6-7 years old. You will be required to exhale air via a mouthpiece connected to a spirometer device.

The most common examination is dynamic spirometry. This is a good method to confirm an asthma diagnosis, but also for making sure that your existing medication is sufficient.

Your spirometry results are compared to normal parameters such as, sex, age, weight and height. Another less common form of spirometry is static spirometry. This test may have to be done in rare cases, but does require more sophisticated equipment.


PEF (Peak Expiratory Flow), and a PEF-measurement stands for the maximum speed of expiration. The PEF-number will indicate the size and degree of functioning of the airways. The contraction of the airways characterising asthma will give a reduced PEF-status. The benefit of a PEF-examination is that it is easily performed. PEF-measuring can be done on children from as young as 5-7 years old. A PEF-measurement can also be performed at your home and will then give an indication of the variation in the lung function over a period of time.

Exercise challenge testing

Given that asthma symptoms often appear in connection with physical exertion, an exercise challenge test can be performed using a treadmill or an exercise bicycle. During the exercise the doctor will listen to your lungs and measure your lung function, before and after 6-8 minutes of exercise.

Reversibility test

A reversibility test can be performed with a PEF or spirometry examination. The reversibility test is done by first measuring the lung function using PEF or spirometer without medication. After that you are given fast-acting bronchodilating medication and after about 15 minutes another PEF- or spirometry measurement is done. In this way you will find out whether the differences in results are big enough for them to be caused by asthma.

Read more on asthma diagnosis in children.

UK/GEN/15/0055d     Date of Preparation: December 2015 

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