Testing for your child's asthma

Asthma tests can show:

• if your child's airways are narrowed and how well your child's asthma treatment is working
• if your child's airways are inflamed.

There's no single test to diagnose asthma, so your child's GP might do a few different tests. Tests on their own are not enough to confirm a diagnosis. Your child's symptoms, how often they get them, and their family history are also an important part of the diagnosis.

Diagnosing asthma in children under five can be hard. This is because some children find it hard to do the tests well enough to get useful results. So, a diagnosis is usually based on how well they respond to their medicine.

Testing a treatment

If your child's GP thinks they might have asthma, they may give your child a very low dose of preventer medicine to see if their symptoms get better. Preventer medicine can help manage inflammation in your child's airways.

Your child's GP will then want to see your child again in 8 to 12 weeks to talk about how things are going.

• If your child's symptoms are getting better after taking the medicine, they're more likely to have asthma. If your child has no symptoms, their GP might suggest trying to stop the medicine. They should give you clear instructions on what to do if symptoms return.
• If your child has used the medicine in the right way and they're not getting better, their GP will look at what else could be causing the symptoms. They might also advise that your child stops taking the medicine.

When your child is five, they can try the asthma tests to see how their lungs are working. If your child struggles with the tests, they can try them again in six months to a year.

While you're waiting for your child's diagnosis, there's a lot you can do to help them stay well. Find out how to manage your child's suspected asthma.

There are four main asthma tests

• Fractional exhaled nitric oxide (FeNO) test
• Spirometry
• Peak flow
• Skin prick and blood tests

If the diagnosis is still not clear after these tests, your child's GP might ask your child to do them again in around 8 weeks.

They might also refer your child to an asthma specialist for a second opinion.

FeNO test

Your child will probably do a FeNO test first. During a FeNO test, your child will take a long steady breath into a mouthpiece. The test measures inflammation in your child's airways.

A positive test means that asthma is more likely, but a negative test won't rule out an asthma diagnosis. Your child's GP might refer them for a spirometry test if they need more information to confirm the diagnosis.

FeNO tests are not available in every GP surgery. If FeNO tests are not available at your child's GP surgery, their GP might arrange a spirometry test instead.

Spirometry 

Spirometry tests measure how much air your child can blow out in one forced breath.

You child will breathe into a mouthpiece as hard and fast as they can, for as long as they can. This can measure how well their lungs are working. This helps to show if their airways are blocked and narrow.

If your child's airways are blocked and narrow, the GP might want to see how they respond to reliever medicine. Reliever medicine opens the airways, so your child can breathe more easily.

After using the medicine, your child will need to do the spirometry test again. Any difference between the spirometry test before and after medicine can help diagnose asthma.

If the results of the spirometry tests are not clear, your child's GP might arrange skin prick or blood tests.

Peak flow

Your child's GP might suggest a peak flow test if FeNO and spirometry tests are not available.

Peak flow tests measure how fast your child can blow air out of their lungs. Your child will breathe into a small plastic tube, called a peak flow meter.

You'll need to take your child's peak flow readings twice a day, for two or more weeks, to show how your child's lungs are working. You'll be asked to keep a peak flow diary to record their scores and symptoms. The GP will then look for patterns in the readings.

Peak flow can be useful if your child has not been able to do a FeNO or spirometry test. If the peak flow does not confirm asthma, your child's GP might arrange skin prick or blood tests.

Skin prick and blood tests

Your child's GP might suggest a skin prick or blood test if the results from FeNO, spirometry or peak flow tests are not clear. But, they still suspect your child might have asthma.

• Skin prick tests check if your child has an allergy to house dust mites (tiny bugs in house dust). If your child has a positive skin prick test, they can be diagnosed with asthma.
• Blood tests can measure your child's immunoglobulin E (a protein called IgE) and blood eosinophil (a type of white blood cell) levels. They help protect your body from allergens. If your child has higher than normal levels in their blood, they can be diagnosed with asthma.

Using inhalers can affect your child's test results

Your child's GP may prefer to test for asthma before starting treatment. If your child is taking medicines for their symptoms, you should speak with your child's GP.