How is asthma diagnosed?

Recommendation based on the research evidence

If your healthcare professional thinks you might have asthma, they will ask you about your symptoms and medical history. Here’s what they will check for:

• Symptoms. They will ask if you have had:
  • wheezing
  • noisy breathing
  • coughing
  • shortness of breath
  • chest tightness.

They will also ask if these symptoms get worse at night, early in the morning or during certain seasons

• Triggers. They will ask what makes your symptoms worse, like exercise, cold air or allergens
• Personal or family history. They will ask if you or anyone in your family has had asthma or have hay fever (allergic rhinitis)
• Other conditions. They will check if your symptoms could be caused by something other than asthma.

Recommendation based on the research evidence

The tests you might get include:

• A blood test called an eosinophil count. This test checks for high levels of eosinophils, a type of white blood cell often increased in people with asthma.
• A breath test to measure nitric oxide, which can indicate lung inflammation. This is called a fractional exhaled nitric oxide (FeNO) test.
• A test to measure how much air you can breathe out and how fast.
• A test to measure how fast you can blow air out of your lungs, done before and after using a bronchodilator (a medicine that opens your airways). This is called peak expiratory flow (PEF).

Recommendation based on the research evidence

If you are very unwell or have severe symptoms, tests may be delayed until you are feeling better. If you get worse while waiting for these tests, contact your healthcare professional immediately.

Be aware that if you have been using inhaled steroids (a type of asthma medicine), it might affect the results of spirometry and breath tests, making them more likely to be normal.

Recommendation based on the research evidence

Your healthcare professional will confirm that you have asthma if your symptoms and medical history suggest it. A test is also needed to support the diagnosis. Until then, healthcare professionals will consider it ‘suspected asthma’.

Recommendation based on the research evidence

If asthma is confirmed, your healthcare professional will note this in your medical records.

Recommendation based on the research evidence

If asthma is not confirmed by blood test or breath test, your healthcare professional will consider doing some more tests.

• Bronchodilator reversibility (BDR) with spirometry. If your lung function improves a lot after using a bronchodilator, it could suggest asthma.
• Peak expiratory flow (PEF) You will be asked to check how much air you can blow out of your lungs twice a day for two weeks. If the amount you can blow out changes a lot during this time, it might mean you have asthma.

Recommendation based on the research evidence

If these tests do not confirm asthma but your healthcare professional still thinks you might have it, you might be referred for a bronchial challenge test. This test checks how your airways react to a substance that can cause them to narrow. If your airways are over-responsive, it confirms asthma.