Asthma Diagnosis and Testing

 

How is asthma diagnosed?

It is often not easy for a doctor to make a diagnosis of asthma, as symptoms often come and go. That’s why you should always talk with a doctor – preferably a board-certified allergist or pulmonologist – who is familiar with asthma diagnosis and treatment guidelines.

Like a skilled detective, the doctor combines the following information to determine whether asthma or some other cause is responsible for your symptoms:

  • Your family and symptom history
  • Physical exam
  • Medical tests

How is family and symptom history used in the diagnosis of asthma?

Your doctor may ask questions about your family and symptom history:

  • When did you first notice symptoms?
  • How would you describe them? Cough? Trouble catching your breath? Noisy breathing?
  • How often do they happen?
  • How long do they last?
  • What makes them better or worse?
  • Do you or anyone in your family have a history of asthma, environmental or food allergies, rhinitis, eczema (atopic dermatitis), bronchitis, or colds that linger for months instead of days?
  • Does anyone in your family, home or workplace smoke?
  • Do you cough or have problems catching your breath when exercising?
  • Do breathing problems disturb your sleep?
  • What is your home, school, and work environment like? 
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How is a physical exam used in the diagnosis of asthma?

The doctor will watch the way your chest and stomach muscles move when you breathe and use a stethoscope to listen to air flowing in and out of your lungs.

The doctor will look inside your nose, searching for signs of conditions that often go along with asthma, such as rhinitis (inflammation of the nose), sinusitis (inflammation of the sinuses) and nasal polyps (mucus-filled sacks in the nose), and examine skin for signs of eczema (atopic dermatitis).

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Spirometry Test

If signs begin to point to asthma, your doctor may use a computerized device called a spirometer to check how well your lungs are working. Spirometry is a type of pulmonary function test. You’ll be asked to take a deep breath in and then breathe out as hard as you can into the machine. The spirometer shows the amount of air you are able to breathe in and out and how fast you did it over a certain time period. If your airways are inflamed and narrowed, or if the muscles around your airways tighten up, the results will show it.

You may do this test several times, perhaps before and after using a quick-relief bronchodilator (albuterol) to relax the airways. Test results that improve after using the medicine are a strong indication of asthma.

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Methacholine Challenge Test

If you are having no symptoms on the day of your exam, the results of your lung function testing may be normal. In this case, your doctor may order another test called a methacholine challenge. This medication causes a brief tightening of the airways that is more intense in people who have asthma.

FeNO Test

FeNo stands for fractional exhaled nitrous oxide and measures the amount of nitrous oxide gas in your lungs. You slowly and steadily breathe out into a handheld tube. This will help your doctor measure how inflamed, or swollen, your lungs are to determine the best treatment for you.

Your doctor may use other medical tests to confirm a diagnosis of asthma.

  • A test to see how your airways react to exercise
  • Tests for related conditions, such as gastroesophageal reflux disease (GERD) or obstructive sleep apnea
  • A test for sinus disease
  • Allergy testing (skin prick or blood) to determine if allergens are triggering asthma
  • A chest x-ray or electrocardiogram to check for foreign objects in the airways or signs of separate lung or heart disease
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Are there other conditions that may look like asthma or complicate asthma?

There are other types of respiratory conditions that are different than asthma.  The symptoms, diagnosis and treatment can vary depending upon the condition. Here are some of them.

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COPD

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respiratory syncytial virus (RSV)

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alpha-1 antitrypsin deficiency

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COVID-19

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sleep apnea

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bronchiectasis

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influenza, infections and viruses

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Vocal cord dysfunction