How Is Asthma Diagnosed?

What tests are done to diagnose asthma?

There isn’t always a simple test that can confidently diagnose asthma.

Several different tests may be used along with other methods to identify patterns in symptoms, asthma triggers, and genetics that can help confirm an asthma diagnosis.

Here are some of the most effective tests that can be done to diagnose asthma:

• Breathing tests: These tests focus on your pulmonary function — basically, how much air you can breathe in and out of your lungs. The most commonly used breathing test is called spirometry, which measures your airflow and how fast you breathe using a machine that you blow into.
• Challenge test: This test is done by having you inhale a substance that triggers an asthma attack, such as methacholine. If you have symptoms after you breathe in methacholine, you likely have asthma.
• Exercise test: This test is done to see if your asthma symptoms arise when you exercise or do strenuous physical activity. You’ll take a spirometry test after you exercise to measure your airflow in order to help confirm an asthma diagnosis.
• Nitric oxide breathing (FeNo) test: This test measures how much nitric oxide is found in your breath when you breathe out. High levels of nitric oxide in your breath can indicate inflammation linked to asthma.
• Imaging tests: Detailed images of your airways and abdomen using X-rays, computed tomography (CT), or magnetic resonance imaging (MRI) can help rule out other causes of airway symptoms that can sometimes result from gastrointestinal issues like gastroesophageal reflux disease (GERD).
• Blood tests: Blood samples with high levels of eosinophils (a type of white blood cell) and immunoglobulin E (IgE, a type of antibody) can indicate that you have asthma.
• Phlegm tests: Tests of your phlegm (also called sputum) can also look for high levels of eosinophils and help confirm a diagnosis of asthma. Having a concentration of eosinophils higher than 3% in your phlegm can indicate asthma.

Other methods that may be used to confirm an asthma diagnosis include:

• Medical history: Having previous episodes of difficulty breathing or having close family members with asthma usually means that you’re more likely to develop asthma.
• Physical exam: A medical professional can use a stethoscope to listen to your lungs and airways as you breathe. A doctor or allergist can also use allergy testing, such as a skin test, to learn if you have specific allergies and triggers that result in your asthma symptoms.
• Medication: Since children can’t always perform breathing tests effectively, a doctor may prescribe asthma medications to find out if they help reduce your child’s symptoms. If the medications help reduce asthma symptoms, then it’s likely that your child has asthma.
• Bronchodilator: These medications help open up your airways when you have an asthma attack. If a bronchodilator, such as an albuterol rescue inhaler, helps relieve severe symptoms quickly, then you likely have asthma and not some other cause for your asthma symptoms.

How accurate are asthma tests? 

Most asthma tests aren’t accurate enough to be used on their own. That’s why many medical professionals recommend several tests or methods to confirm a diagnosis.

Spirometry is the most commonly used test, but it has been criticized for missing diagnoses of asthma when used on its own.

A 2017 study suggests that a combination of medical history, physical exam, and challenge test had a relatively high success rate in diagnosing asthma as well as identifying similar conditions like chronic rhinitis.

Other FAQs about asthma testing 

Here are some of the most frequently asked questions about asthma testing.

Does asthma show up in blood tests?

A blood test can’t definitively diagnose asthma on its own.

But high levels of eosinophils and IgE antibodies can indicate an asthma diagnosis along with other asthma tests.

Can you self-diagnose asthma?

It’s not recommended to self-diagnose asthma, even if you have severe symptoms that make it difficult for you to breathe.

That’s because you might not be able to get the right treatment for the cause or specific symptoms of your asthma without testing, such as allergy tests, that can help you narrow down your asthma triggers.

What’s the newest test for asthma?

Imaging techniques for asthma are constantly improving due to the increase in the quality of imaging over time.

Challenge tests and FeNo aren’t new, but they’re being used more frequently to help diagnose asthma and determine the best treatment for each person with it.

Takeaway

Asthma is a common disease with no single simple diagnostic tool, but several tests can help confidently confirm an asthma diagnosis.

If you’re concerned about symptoms that may indicate you have asthma, talk with a medical professional, such as an allergist or immunologist.