Updated 04 September 2018

How is asthma diagnosed?

If you regularly have breathing problems, your doctor should investigate whether or not you may be suffering from asthma.


Asthma should be considered if you have breathing problems that come and go. For an accurate diagnosis, your doctor will do a careful medical examination.

Diagnosis not straightforward

Many people with asthma don't know that they have the disease. In young patients with recurrent coughing and wheezing, the diagnosis of asthma is not always straightforward, and it is important to think of other causes for the symptoms. In the older child and in adults, where an accurate history is available and lung function tests are easy to perform, the diagnosis is less complicated.

Other respiratory problems such as emphysema, bronchitis and lower respiratory infections may masquerade as asthma, as many of these illnesses share similar symptoms. The distinguishing factor between asthma and COPD is early-childhood onset in the case of asthma.

Asthma should always be considered in children with a chronic, recurrent wheeze, with or without a cough, with symptoms of breathlessness and chest tightness, which respond to an inhaled short-acting beta-agonist bronchodilator (the reliever therapy used in an acute asthma attack). In children younger than five years, symptoms are variable and non-specific and it is impossible for the doctor to measure airflow (see below) and inflammation.

Asthma should definitely be considered if you have breathing problems that come and go. Persistent cough and recurrent wheezing are also good indicators, which may suggest you are asthmatic.

For an accurate diagnosis your doctor will do a careful medical examination, take note of your medical history and conduct breathing tests which may include:

Spirometry or lung function tests, using an instrument that measures the air taken into and out of the lungs during normal periods, during attacks and immediately following inhalation of medications that will dilate the airways.

Peak flow monitoring is another measure of lung function, which monitors the rate of air exhaled in one breath. Peak flow decreases before an attack and as the condition becomes more serious. It's a good idea to keep a peak flow meter with you and to know your normal peak flow values.  Children may need “low-reading” peak flow meters, as adult peak flow meters may not measure accurately at low air speeds.

Other tests that may be useful include:

  • Allergy skin tests
  • Blood tests
  • Exercise challenges
  • A chest X-ray. In asthmatics these are usually normal when there is no underlying lung illness.

Your doctor may also want to perform other tests to exclude conditions that can also cause shortness of breath or other lung problems. 

How severe is your asthma?

Asthma severity is assessed to decide which treatment is suitable. Grade one is the mildest grade (known as mild intermittent asthma) and grade four the most severe.

Since a doctor will initiate treatment based on the severity of your asthma at diagnosis, they will assess and classify the severity of your asthma according to the latest guidelines for the management of asthma in adults and adolescents (2015), or the latest guidelines for children (2015).

Asthma severity is assessed only at the first consultation to decide which initial treatment to start, but after this the doctor will use a similar system (see below) to assess asthma control  in order to guide decisions to either maintain or adjust therapy, i.e. to step it up if necessary, or down if possible.

The assessment of severity is used as a starting point to assign a child to a particular treatment group. This assessment is performed between acute episodes in a patient who is not receiving long-term therapy. Assessment of severity depends on the frequency of symptoms and the peak flow reading obtained (the latter in children five years and older).

Symptoms are divided into day- and night-time symptoms (essentially cough and wheeze). Asthma attacks are typically episodic. The intervals between the attacks may be days, months or even years. For severe asthmatics, however, attacks can take place on a daily basis.

Grade one is the mildest grade (known as mild intermittent asthma) and grade four the  most severe. Grades two, three and four are classified as chronic or persistent asthma. The doctor will assign you to the most severe grade in which any feature occurs.

Reviewed and updated by Prof Eugene Weinberg, Paediatrician Health24. April 2015

Image credit: iStock


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Professor Keertan Dheda has received of several prestigious awards including the 2014 Oppenheimer Award, and has published over 160 peer-reviewed papers and holds 3 patents related to new TB diagnostic or infection control technologies. He serves on the editorial board of the journals PLoS One, the International Journal of Tuberculosis and Lung Disease, American Journal of Respiratory and Critical Medicine, Lancet Respiratory Diseases and Nature Scientific Reports, amongst others.Read his full biography at the University of Cape Town Lung Institute

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