Doctors diagnose asthma using your symptom pattern, family history, physical exam, and test results. The exact process for figuring out whether you have asthma depends on your age and other factors. An accurate diagnosis is important so your doctor can help you find the best treatment.
After diagnosis, doctors will assess the severity of your asthma and what triggers cause symptoms. All this information can help lead to a treatment plan that is right for you. The treatment plan will include actions you can take to best manage your symptoms. It is known as an asthma action plan.
How is asthma diagnosed?
Pattern of symptoms
The most typical symptoms of asthma are:1
- Wheezing
- Shortness of breath
- Chest tightness
- Coughing
The exact pattern of symptoms is important to share with your doctor. This is because other conditions also cause these symptoms. Be ready to talk to your doctor about when and how often you experience certain symptoms. They may also want to know if you have:2
- More than 1 of these symptoms
- Worse symptoms at night or in the early morning
- Symptoms that change over time and in intensity
- Symptoms that seem to triggered by infections, exercise, allergens, weather, and irritants like smoke or strong smells
Family history and physical exam
If your symptoms are typical of asthma, your doctor will then look at your family history and perform a physical exam. Your health history or family history may suggest you have asthma if you have:2
- Breathing problems that started during childhood
- A history of allergic rhinitis (hay fever) or eczema (skin irritation)
- Family history of asthma or allergies
A physical exam may also reveal other signs you may have allergies and asthma. During the exam, your doctor will look in your ears, throat, and nose. They will listen to your heart and lungs and watch you breathing. Some physical signs of asthma include:2
- Wheezing sounds when exhaling
- Shortness of breath
- Runny nose, swollen nasal passages, and nasal polyps
- Skin redness, rash, or hives
- Hunched shoulders or barrel-shaped chest
Physical exams are often not as helpful as other tests in diagnosing asthma. That is because many of the physical exam results common to asthma are also common in other conditions. And, some people with asthma may have normal physical exams.2
Spirometry
Tests to measure your lung function are the best tool to diagnose asthma. The main diagnostic measure that suggests asthma is “variable airflow limitation.” This means that lung function and airway obstruction vary over time and in severity. Poor asthma control is linked to more variable lung function.2
The best way to measure lung function is a test called spirometry. This test measures how much and how fast you can blow air out of your lungs. Some spirometry results that indicate asthma include:1,2
- Low amount of air forced from your lungs in 1 second (forced expiratory volume)
- Lung function improving after taking a bronchodilator drug to open up the airways
- High variation in lung function results between visits
- Lower lung function after exercise or exposure to methacholine (a drug that narrows the airways)
Other diagnostic tests
If spirometry results are unclear, your doctor may run other tests. Some of these tests may also help identify your asthma triggers or rule out other conditions. Possible tests include:2
- Lung function tests such as exhaled nitric oxide and peak expiratory flow
- Allergy tests
- Tests for inflammation
- Tests for airway sensitivity
Experts recommend using these tests when other methods fail to identify whether you have asthma. These tests are rarely used alone to diagnose or monitor asthma.3
Asthma diagnosis in children
Diagnosing asthma in small children can be a little different than in adults. Doctors also look at symptom patterns, physical exams, and lung function tests. But, children under age 5 generally cannot perform breathing tests. Instead, doctors:2
- Pay more attention to symptom pattern and family history than tests
- Try a new medicine or lifestyle change for 2 to 3 months to see how symptoms change
Your child’s doctor may prescribe an inhaled drug called a bronchodilator. This is a drug that helps with breathing. It works to relax the smooth muscles around the airway that are tight with asthma. If this drug works, your child’s doctor might then diagnose your child with asthma.
Complicated asthma diagnosis
An asthma diagnosis is easier before starting treatment. If you already take drugs for asthma, your doctor may need to adjust your dose to make a diagnosis. An asthma diagnosis may also be harder if you have:2
- Cough-variant asthma, in which a persistent cough is the only symptom
- Work-related asthma
- Asthma in athletes, pregnant women, or people over age 65
- Asthma in those who smoke or smoked in the past
- People who have both asthma and chronic obstructive pulmonary disease (COPD)
Symptoms of asthma are harder to tell from other conditions in many people in these groups. Symptoms may also be easier to miss completely. And, certain lung function tests may not be possible for people in these groups.2