6 Easy Tests to Diagnose Asthma

Asthma is today a common lung condition that creates difficulty in breathing. There are several factors on which asthma is diagnosed, such as detailed medical history, symptoms, physical exam, and overall health results and tests.

Your doctor may ask for these details when you go for asthma tests:

  • Symptoms
  • How often are your symptoms?
  • Is there anything that triggers your asthma attack?
  • Do you have any allergies?
  • Family history of asthma.

Then some tests may be suggested for the confirmation of having asthma.

  • Medical history

    It is the first step in diagnosing asthma when you talk to your doctor about your health and the symptoms you have. It provides clues that can help to diagnose whether it is asthma or any other condition that is causing these symptoms. You will also be asked about exposure to substances that can be linked to asthma.

    These questions may include:

    • What are the symptoms you have?
    • When does it occur?
    • Are you often exposed to tobacco smoke or chemical fumes?
    • Is there any blood relative who has asthma?
    • What medications or supplements do you take?
    • What is your occupation?
    • Do you have pets?
  • Physical Examination

    When you visit your doctor, he may perform the following examination:

    • Examines your nose, throat, and upper airways.
    • Listens to your breathing using a stethoscope.
    • Is there any wheezing, or high-pitched whistling sound while breathing out?
    • Also, your doctor may examine your skin for any signs of allergic reactions such as eczema and hives.

    He may also ask about the symptoms you have and see if they are related to asthma. For example:

    • Repeated wheezing
    • Coughing
    • Trouble in breathing
    • Tightness in chest
    • Are there any symptoms that get worst at night?
    • Symptoms triggered by cold air.
  • Diagnostic tests

    There are no specific tests to diagnose asthma. All the diagnostic tests either measure the lung function or check if you are having any allergies, which may help the doctor diagnose your condition.

    There are several tests that can tell how well your lungs are functioning. Some of the most common ones include:


    A spirometer is a device that measures the volume of air inspired and expired by the lungs and the time taken to exhale completely after a deep breath. In other terms, it measures the capacity and amount of air that passes in and out of the lungs. The procedure is termed spirometry.

    It is the main test used to diagnose asthma in people 5 years or older.


    • To know the performance of your lungs (pulmonary function), you have to take a deep breath and breath out forcefully into the connected tube of the spirometer.
    • It records the amount of air you exhale and how quickly you do it. If the measurements are less than normal for a person, the airways have been narrowed, which could be due to asthma.
    • Having taken lung test measurements, you will be asked to inhale an asthma drug to open air passages, and the test is performed again. If there is significant improvement after having that drug, it could be a sign that you have asthma.

     Challenge test:

    Methacholine or Bronchoprovocation test: If spirometer tests seem normal or near to it, your doctor may tell you to go for a bronchoprovocation test. In this test, you will be asked to inhale increasing doses of medicine (methacholine) that may cause airways to narrow in people with asthma, to trigger asthma symptoms.

    Treadmill test:

    If you experience asthma-like symptoms while doing exercise or physical activity, then your doctor may ask you to go for this test. It helps to find out how physical activity is impacting your health and triggering your symptoms. 

  • Lung tests in children

    Doctors rarely perform lung tests in children under age 5. Mostly, diagnosis is based on signs and symptoms, medical history, and physical examination. It can be difficult to diagnose asthma at a young age because there are many symptoms that are like asthma but actually, it is not in this age group.

    If your child has been suspected of asthma, he will be prescribed a bronchodilator (an airway opening drug). If the signs and symptoms improve after the drug, your child may have asthma.

  • Exhaled nitric oxide test

    In this test, you breathe into a tube connected to a machine that takes the measurement of the nitric oxide amount present in your breath. Nitric oxide gas is normally produced in the body. But if it is found in high amounts, that could be an indication of having asthma.

  • Additional tests

    If your doctor suspects you have a condition other than asthma, you may be asked for some tests, such as:

    • X-ray or computerized tomography (CT) imaging of your chest.
    • CT scans of your sinuses
    • Blood test
    • Gastroesophageal reflux assessment
    • Phlegm examination in your lungs (sputum indication and examination) for viral and bacterial infection signs.

    You can also be examined for the other conditions that often go along with asthma, and symptoms may get worse.
    They include:

    • Heartburn
    • Hay Fever
    • Sinusitis
  • Allergy test

    Your allergy tests may also be performed. This includes skin, blood tests, or both. Allergy tests diagnose an allergic reaction, such as hay fever, that may cause your symptoms or worsen existing asthma. Many people with asthma may be allergic to something that may trigger their symptoms.


    Asthma is an inflammatory condition of smooth muscles lining the airways. It is affecting millions of people in the world today. If you feel a problem with breathing, or have a long-running or continuous cough, visit your health care provider.


What is the role of chest X-rays in asthma?

Chest X-ray is the first imaging technique that is done for people with asthma-like symptoms. Typically, a chest X-ray may not help to diagnose asthma, but it may help to rule out other conditions that can cause similar symptoms to asthma, such as pneumonia.

Can blood test help in the diagnosis of asthma?

Many blood tests are helpful in the diagnosis of asthma

  • CBC (Complete Blood Test) can help to find if there is inflammation or infection.
  • WBC (White Blood Cells) - The number of WBCs are generally increased in people with asthma. It is indicative of infection and inflammation in the body.
  • Absolute Eosinophil Count: This is a specific test to diagnose asthma. Eosinophil is a type of WBC which is generally high in people with asthma.
  • Erythrocyte Sedimentation Rate (ESR) and C-reactive protein (CRP): These tests usually indicate inflammation in the body.
  • Total IgE

What is the role of a CT scan in the diagnosis of asthma?

It illustrates several findings that can help a doctor diagnose asthma, such as thickening of the bronchial wall or narrowing of the bronchial lumen.

Can iron deficiency affect asthma?

Yes, iron deficiency is the most common deficiency found in the world, and people with this deficiency are at a higher risk of having asthma.

What colour is asthma phlegm?

Generally, people with asthma have a dry cough, but some people may have a cough with phlegm (mucus). The mucus is generally of white colour due to the presence of increased white blood cells, which indicates inflammation in the airways.


  1. Saglani S, Menzie-Gow AN. Approaches to Asthma Diagnosis in Children and Adults. Front Pediatr. 2019 Apr 17;7:148. doi: 10.3389/fped.2019.00148. PMID: 31058123; PMCID: PMC6478800.
  2. https://www.karger.com/Article/Fulltext/486797
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