Severe Asthma: Medical History and Testing

Allergy Assessment

How are you diagnosed with Severe Asthma?

Diagnosing severe asthma doesn’t happen overnight. It can be a complicated disease to identify. Your doctor will need to examine your medical history and perform several tests before a diagnosis can be made. Asthma can also mimic other serious lung conditions such as pulmonary fibrosis  which will need to be ruled out.

The following blog will introduce to you a valuable guide that can help you understand what goes into diagnosing severe asthma. It will outline the steps and tests your medical team will take in order to make a diagnosis.

For more information on understanding your diagnosis of severe asthma please visit our blog on the Chronic Lung disease website by Respiplus Severe Asthma: Understanding your Diagnosis

Steps in Diagnosing Severe Asthma

1. Medical history

If your doctor suspects severe asthma, they will start by asking many questions about your medical history. 

Here are examples of questions your doctor will ask:

  • Have you ever experienced symptoms of asthma
  • In the last year have you had a sudden worsening of asthma symptoms (exacerbation)
  • Have your asthma symptoms ever caused you to be hospitalized
  • What medications do you take and when
  • Has a healthcare professional ever checked on how you take your inhaled medication
  • Where do you work and what you do for work
  • What is your smoking history
  • Have you been diagnosed with any other medical conditions

2. Physical exam

A complete physical exam will be done. This will include listening to your lungs with a stethoscope to identify any wheezing which is typical with severe asthma.

A respirologist is a lung specialist which you may be referred to, to help confirm your severe asthma diagnosis. Other medical conditions which can contribute to poor control of your asthma may require you to see an allergist, a gastroenterologist or an otorhinolaryngologist (ENT).

3. Test to help Diagnose Severe Asthma

Your doctor may also order some of the following tests to help diagnose severe asthma:

  1. Spirometry
  2. Methacholine challenge
  3. Allergy Assessment
  4. Blood tests
  5. Induce sputum tests
  6. Fractional exhaled nitric oxide
  7. Other: CT-scan and/or chest x-ray


Spirometry is the most common breathing test. Your doctor will order spirometry if you have wheezing, shortness of breath or cough. It is a useful tool to help diagnose certain lung conditions like asthma. Spirometry involves blowing into a device that measures how well and how fast you can blow air out of your lungs. It can measure the volume of air in your lungs and if anything (like severe asthma) obstructs airflow. 

Methacholine Challenge

In order to measure how “reactive” or “responsive” your lungs are, a methacholine challenge may be performed. Methacholine is a drug that can cause airway narrowing when inhaled at different doses. The amount of narrowing after increasing doses of methacholine is measured by spirometry.  Spirometry will tell us how fast and how constricted airways are after inhaling the methacholine.

Allergy Assessment

Oftentimes patients with severe asthma will consult an allergist for blood tests or skin prick tests. It is important to identify any allergies which may be triggering or making severe asthma worse.

Blood tests​

By ordering certain blood tests, your doctor can look for factors influencing the inflammation in your airways. Blood tests can even give information on the type of severe asthma you have and how to effectively treat it. The 2 most common blood tests are for IgE and the number of eosinophils in your blood.

Induced Sputum Tests

An induced sputum test uses an inhaled saline solution to promote coughing and help you bring up secretions or mucus from your lungs. These secretions are analyzed for eosinophils (a type of white blood cell) that can cause severe asthma.

Fractional Exhaled Nitric Oxide

This test gives instant results by analysing the amount of nitric oxide present in your breath. Your doctor will be able to see how much, if any inflammation is present in your airways.


CT-scan and/or chest x-ray will give your doctor a picture of what is going on inside your lungs.

Resources to Help you Better Understand the Steps Involved in Diagnosing Severe Asthma

As you can see there are many steps involved in diagnosing severe asthma. It is important to let your doctor know what symptoms you have and to attend all medical visits and tests.

For more information on understanding the steps involved in diagnosing severe asthma visit the following module: Understanding a diagnosis of severe asthma.

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About the author

Katrina Metz is currently working as a consultant for RESPIPLUS, striving to improve education in the respiratory domain for healthcare professionals and patients alike. She has over 16 years experience working as a respiratory therapist and clinical research coordinator for the Research Institute of the McGill University Health Center.

Katrina Metz


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