Diagnosing Asthma

What are the common ways to test for asthma?

Asthma is a complex condition. Diagnosing asthma is not simple.

Before a diagnosis of asthma can be made, a doctor will take a medical history and order some lung-function tests, such as a spirometry test.

If you have eczema or hay fever, or have close relatives with allergies or asthma, a diagnosis is more likely.

Asthma is also more likely to be diagnosed if your symptoms:

  • keep coming back, or happen at the same time each year
  • are worse at night or in the early morning
  • are clearly triggered by exercise, allergies or infections, or have a seasonal pattern
  • improve quickly with reliever medication

It’s often difficult to diagnose asthma in children under 5, especially as they find breathing tests difficult.  Your doctor will assess the symptoms and your explanation of your child’s symptoms and may give your child asthma medicine to measure its effect – this is  called a ‘treatment trial’. Your doctor will monitor the effect this medicine has on your child and will use the results as part of their diagnostic process.

How to diagnose asthma in young children

It’s often difficult to diagnose asthma in children under five years old, especially as they find breathing tests difficult. Doctors do not always choose to conduct a breathing test for children.

Your doctor will assess the symptoms and your explanation of your child’s symptoms and may give your child asthma medicine to measure its effect.

This is  called a treatment trial. Your doctor will monitor the effect this medicine has on your child and will use the results as part of their diagnostic process.

Spirometry tests

A spirometry test, or lung function test, measures how well your lungs are working, and whether a condition (such as asthma) could be affecting your breathing.

This test could be in the doctor’s room, or sometimes you’ll need to go to another clinic or hospital to have it done. It depends on where the equipment is available.

A spirometry test is safe, simple and painless. It involves blowing as hard as you can, for as long as you can, into a tube or mouthpiece, which is connected to a special measuring machine. You’ll need to do this several times, but you can rest for as long as you need in between each test. Most of the time you will be asked to take your reliever medicine in the middle of the test. This will show what effect the medication has on your lungs.

Spirometry tests are not usually performed on children under six years old.

Allergy testing

Asthma is strongly linked with allergies.

Many people may have allergy tests as part of their diagnosis. These tests can be skin prick tests or blood tests and they detect allergen sensitivities.

Skin prick testing is usually done on the forearm. A drop of allergen is put on the skin and a small prick into the skin is made through the drop to allow a tiny amount of allergen to enter. If you are allergic, a small lump will appear over the next 15 to 20 minutes. Blood testing may be performed if skin testing is not possible, such as in cases of severe eczema. This test involves taking a sample of blood which is checked for antibodies to specific allergens.

A chest X-ray is not generally helpful in diagnosing or monitoring asthma, but you might have one if your doctor wants to rule out other problems such as pneumonia.