How Asthma Is Diagnosed

In This Article

Although you may receive an asthma diagnosis at any age, most people will be diagnosed in childhood. The classic signs of asthmawheezing, chest tightness, shortness of breath, and cough can make the diagnosis difficult because they are general and non-specific. Your doctor will ask you a number of questions and order several tests to arrive at the diagnosis and ensure the symptoms are not due to another condition mimicking asthma.

Self Checks/At-Home Testing

As the diagnosis of asthma starts with assessing the symptoms and medical history, you can begin by noting your symptoms (or your child's). Keeping a record of these in a symptom diary will help your doctor make a correct diagnosis.

Classic Symptoms

The classic triad of symptoms are a cough, shortness of breath, and wheezing—a high pitched whistling when you breathe out. Your chronic cough is characteristically dry, non-productive, and will most commonly be worse at night. Some patients also describe the shortness of breath as a chest tightness or band-like feeling.

Episodic Symptoms

Typically in asthma, your symptoms will come and go over time and your doctor will likely ask you to explain how quickly the symptoms came on and what led to the relief of the symptoms. He or she may also ask you to think about specific triggers of past symptoms, such as exposures to allergens like dust, smoke or changes in the weather, such as cold air.

Exercise Symptoms

Asthma symptoms brought on by exercise typically occurs after about 15 minutes of activity and resolves after resting for 30 minutes to an hour—so the shortness of breath felt after walking up a flight of stairs that gets better in a few minutes is not likely exercise-induced asthma. Exercise symptoms are generally more severe and occur more commonly with exposure to cold air.

Allergic Symptoms and History

Asthma is more common in people with a family history of asthma, other allergies in their family, or certain atopic diseases-meaning prone to allergic illness, like hay fever. Your doctor will probably ask about symptoms such as:

  • Not being able to keep up with classmates in physical activity
  • A chronic or nighttime cough in the absence of an infection

The doctor will also ask if there is a history of atopic conditions such as:

  • Hay fever
  • Allergic rhinitis
  • Atopic dermatitis

A history of any of these conditions in a patient with symptoms compatible with asthma makes asthma much more likely. Your doctor will also likely ask about exposure to and occurrence of symptoms with certain allergens. Your doctor will want to know if you develop symptoms when:

  • You are around furry pets
  • The pollen counts increase
  • You are exposed to dust and molds

Home Spirometry

As part of the diagnosis, or for ongoing checks, your doctor may have you use an at-home spirometer. Only use a home spirometer if your doctor recommends it. Make sure you understand how to correctly use the unit you purchase and that you follow your doctor's instructions for reporting results accurately.

Labs and Tests

In order to make a diagnosis, your doctor will use a combination of history, physical exam, and tests to decide what treatment is appropriate for you.

An asthma diagnosis requires evidence of:

  1. Presence of symptoms compatible with asthma such as cough, wheezing, or shortness of breath.
  2. Objective measurement of decreased airflow in your lungs that either partially or completely improves spontaneously or with treatment.

In the physical examination, your doctor will look for wheezing. Characteristically, your physician will hear a high-pitched musical sound on expiration—when you breathe out or exhale—that is typical of, but not specific for asthma (meaning other conditions can also cause wheezing). You will probably not wheeze all of the time and wheezing does not indicate how mild or severe your asthma is. The doctor will also check for nasal inflammation, which is a pale swelling of the nasal cavities that suggests allergic rhinitis that can worsen asthma symptoms.

If it is clear that your symptoms are due to asthma, your doctor may run a test to help confirm a diagnosis or the doctor may want a more detailed report outlining what the problems were and how they have been resolved. Some tests that may be ordered include:

  • Peak Expiratory Flow Rate (PEFR): PEFR is measured with a simple hand-held device that you forcefully exhale into your lungs. A normal PEFR is generally 80 percent of your predicted or greater, Your physician may have you keep a measurement record at home. You will develop a personal best PEFR that will tell you how well your asthma is controlled. You and your physician will develop a plan for what to do if your PEFR is below 80 percent of normal.
  • Spirometry: This is a test similar to the PEFR that requires more advanced equipment and is usually done in your physician's office, although there are a number of companies that sell home spirometry equipment. This test allows your doctor to better determine how severe your airflow obstruction may be and if you may benefit from treatment for your asthma.

If it is unclear that asthma is the likely diagnosis your doctor may consider bronchoprovocation tests to help your doctor make a diagnosis of asthma. Commonly an order for bronchoprovocation testing is placed if symptoms that suggest asthma are present, but the patient has normal spirometry testing and no response to rescue medications. These tests include:

  • Bronchodilator Response: A characteristic of asthma is an improvement after treatment with a bronchodilator, a fast-acting quick-relief medication. Generally, your doctor will repeat spirometry 10-15 minutes after treating you with a bronchodilator. Increases in the airflow of 12 percent are considered positive and assist in making a diagnosis of asthma.
  • Bronchoprovocation Challenge Testing: Just the opposite of looking for an improvement in lung function with a bronchodilator, bronchoprovocation testing attempts to provoke airflow obstruction after having you inhale an irritative substance. This testing is usually only done when persons present with atypical symptoms.

Blood Tests

There are no diagnostic blood tests for asthma. Your health care provider may order some blood tests to help rule out other causes of your symptoms.


Chest X-rays are usually normal in patients with asthma, but your physician may order one if you are presenting for the first time with wheezing. If asthma has gone undiagnosed for a long time, the chest X-ray may demonstrate hyperexpansion.

Differential Diagnoses

Not all that wheezes is asthma. Asthma can sometimes be very tricky. You may experience all of the signs of asthma that will be discussed here or you may not experience any of these symptoms. If you suspect that you have asthma then you need to see a doctor to get your symptoms checked out.

There are also a number of diseases that lead to wheezing but are not asthma such as:

  1. Congestive heart failure: This is a heart condition where the heart's pump is failing and unable to provide adequate blood supply. In addition to some similar symptoms to asthma, patients have swelling in both legs and difficulty breathing while lying down.
  2. Pulmonary Embolism (PE): A PE sometimes leads to wheezing, a classic asthma symptom, but sudden onset shortness of breath and chest pain are much more common.
  3. Cystic Fibrosis (CF): CF patients will wheeze, shortness of breath and cough. However, this chronic illness is also associated with poor growth and a number of other problems in early childhood.
  4. Gastroesophageal Reflux Disease (GERD): GERD may lead to wheezing and cough and commonly is responsible for nighttime asthma symptoms. Patients commonly experience a painful burning sensation as well as a sour or bitter taste in the back of the mouth.

A Word From Verywell

Being worried that you or your child has an asthma diagnosis can be a scary time. Knowing some of the questions your doctor may ask and some of the tests that may be ordered in diagnosing asthma will help you get the most out of your doctor's visit and alleviate some of the anxiety of the "unknown" that going to the doctor can create.

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Article Sources

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Additional Reading

  • Asthma. In Chest Medicine: Essentials Of Pulmonary And Critical Care Medicine. Editors: Ronald B. George, Richard W. Light, Richard A. Matthay, Michael A. Matthay. May 2005.

  • National Heart, Lung, and Blood Institute. Expert Panel Report 3 (EPR3): Guidelines for the Diagnosis and Management of Asthma

  • Patient information Asthma symptoms and diagnosis in children

  • Asthma. Centers For Disease Control and Prevention.