Asthma Diagnosis

It can be hard to tell if someone has asthma, especially in children under age 5. Having a doctor check how well your lungs work and check for allergies can help you find out if you have asthma.

During a checkup, a doctor will ask if you cough a lot, especially at night. He or she will also ask whether your breathing problems are worse after physical activity or at certain times of year. The doctor will then ask about chest tightness, wheezing, and colds lasting more than 10 days. He or she will ask whether anyone in your family has or has had asthma, allergies, or other breathing problems. Finally, the doctor will ask questions about your home and whether you have missed school or work or have trouble doing certain things.

The doctor may also do a breathing test, called spirometry, to find out how well your lungs are working by testing how much air you can breathe out after taking a very deep breath before and after you use asthma medicine.

If you think you have asthma, see your doctor. They may refer you to a lung doctor, called a pulmonologist, or a specialist in allergy and immunology.

The doctor will start with a physical exam and ask about your symptoms and medical history.

You’ll have tests to see how well your lungs work, which may include:

Spirometry. This simple breathing test measures how much air you blow out and how fast.

Peak flow. These measure how well your lungs push out air. They’re less exact than spirometry, but they can be a good way to test your lungs at home, even before you feel any symptoms. A peak flow meter can help you figure out what makes your asthma worse, whether your treatment is working, and when you need emergency care.

Methacholine challenge. This and similar tests involve using triggers or challenges. Adults are more likely to have this test than children. You might get it if your symptoms and spirometry test don’t clearly show asthma. During this test, you inhale a chemical called methacholine before and after spirometry to see if it makes your airways narrow. If your results fall at least 20%, it is possible that you have asthma. Your doctor will give you medicine at the end of the test to reverse the effects of the methacholine.

Exhaled nitric oxide test. You breathe into a tube connected to a machine that measures the amount of nitric oxide in your breath. Your body makes this gas normally, but levels could be high if your airways are inflamed.

Other tests you might get include:

Chest X-ray. It isn’t an asthma test, but your doctor can use it to make sure nothing else is causing your symptoms. An X-ray is an image of the inside of your body, made with low doses of radiation.

This test takes a series of X-rays and puts them together to make a view of your insides. A scan of your lungs and sinuses can identify physical problems or diseases (like an infection) that may cause breathing problems or make them worse.
Allergy tests. These can be blood or skin tests. They tell if you’re allergic to pets, dust, mold, and pollen. Once you know your allergy triggers, you can get treatment to prevent them — and asthma attacks.

Sputum eosinophils. This test looks for high levels of white blood cells (eosinophils) in the mix of saliva and mucus (sputum) that comes out when you cough.

What Triggers Asthma?

Asthma symptoms can appear when you are exposed to a trigger. A trigger is something you are sensitive to that makes your airways become inflamed. This causes swelling, mucous production and narrowing in your airways. Common asthma triggers are pollen, chemicals, extreme weather changes, smoke, dust mites, stress and exercise.

How Can I Prevent an Asthma Episode?

The best way to prevent an asthma episode, or attack, is to follow your treatment plan. Learn your triggers and avoid them. Take your allergy and asthma medicines when you should. Use your quick-acting medicine as soon as you start to notice symptoms.

Many people live normal lives with asthma if it’s properly managed. With a good treatment plan and guidance from your doctor, you can still do much of what you enjoy. For example, many professional athletes have asthma.

Asthma Facts

More Americans than ever before have asthma — about 25 million people in the U.S. have asthma. It is one of the most common and costly diseases.