Asthma Diagnosis

Talk to your healthcare provider if you or your child have asthma symptoms. Tell them about any possible risk factors you have. You may need to see a team of healthcare professionals, including your primary care provider, an asthma specialist, or an allergy specialist (called an allergist).

FACT SHEET

Tips for Talking With Your Healthcare Provider

Get tips for talking to your healthcare provider and sample questions to ask at your next appointment.

View the fact sheet

Diagnostic tests

Your healthcare provider may want to run some tests to diagnose your asthma.

Lung function tests

Lung function tests measure how well you can breathe in and out:

• Spirometry measures how much air you breathe out and how fast. Some people feel lightheaded or tired from the breathing effort for this test.
• Peak expiratory flow (PEF) tests measure how fast you can blow air out using maximum effort. The test can be done during spirometry or with a small handheld device.
• Bronchodilator responsiveness tests measure how much better you can blow air after inhaling a fast-acting bronchodilator, a medicine that helps open your airways by relaxing the muscles around them. The test compares your spirometry or PEF results before and after the medicine.

Challenge tests

Challenge tests, also called bronchial provocation tests, assess how sensitive your airways are. These tests compare how fast you can blow air before and after a challenge agent. Challenge agents are substances or activities that may tighten the muscles in your airways if they become irritated from being too sensitive, including:

• Inhaled medicines such as methacholine, mannitol, or histamine

Allergens

Allergen

(AL-er-jen):

A substance that when eaten or breathed in can trigger a response in the immune system that results in an allergic reaction.

or irritants that cause no reaction in people who do not have asthma

• Exercise, which cools and dries the airways
• Hyperventilation, or breathing in short, quick breaths

Other diagnostic tests

Your healthcare provider may want to run other tests to help diagnose your asthma. Some of them can also assess your risk of asthma flare-ups and predict how well you will respond to medicine:

• Allergy tests can find which allergens, such as pet dander or pollen, cause a reaction in your body when you are around them. Your provider may run these tests if you have a history of allergies.
• Fractional exhaled nitric oxide (FeNO) tests measure how much nitric oxide is in your breath. High levels of nitric oxide may mean that your airways are inflamed, which can make it hard to breathe. This test does not require heavy breathing and has few risks.
• Blood tests can measure levels of

white blood cells

white blood cell

A type of cell that is part of the body’s immune system. White blood cells help the body fight infection and other diseases.

, which can indicate inflammation. Blood tests can also help find your allergies.

• A chest CT scan may show whether the walls of your airways are thicker.

Most diagnostic tests for asthma do not work well for young children. This can make it difficult to diagnose asthma in children.

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