Challenge Tests

Challenge tests are also called bronchial provocation tests or trigger tests. They measure how reactive your airways and lungs are to certain triggers. Airway sensitivity is a sign of asthma.1,2

Your doctor may have you do a challenge test to:1,2

  • Confirm you have asthma
  • Rule out asthma if other tests did not give a clear diagnosis
  • Identify triggers of asthma symptoms

During a challenge test, your doctor will use spirometry to measure lung function. They will do this before and after exposing your airways to a certain asthma trigger. This will tell them how much your lung function changes.1,2

What are some types of challenge tests?

Exercise challenge

Exercise is a common trigger of asthma symptoms. An exercise challenge test can help determine if exercise triggers your asthma. During the test, you will exercise while your oxygen and heart rate are monitored.1,2

Methacholine challenge

If you have asthma, methacholine is a drug that makes your airways tighten at a lower dose. During a methacholine challenge test, you will inhale increasing doses of methacholine. Your doctor will use spirometry to see how lung function changes.3,4

A methacholine challenge test is used when you have symptoms of asthma but a normal lung function test. It is a tool that helps identify people who have an uncertain asthma diagnosis. If your lungs do not react to lower doses of methacholine, you may not have asthma. Many other conditions may show similar symptoms, including:4

  • Pneumonia
  • Upper airway obstruction
  • Viral infections
  • Chronic obstructive pulmonary disease (COPD)

Irritant challenge

During an irritant challenge test, your doctor will expose you to a certain asthma trigger. This may include:4

  • Chemicals
  • Perfume
  • Smoke
  • Allergens

You will take a breathing test before and after exposure. This helps your doctor confirm an asthma diagnosis and any possible triggers.4

How are challenge tests done?

Exercise challenge

During an exercise challenge test, you will undergo spirometry before and after exercise. The exercise usually includes running on a treadmill or riding a stationary bike. Your doctor will measure heart rate and blood oxygen levels during the exercise. This helps ensure the exercise is intense yet safe.5

You will exercise for about 6 to 8 minutes. After exercising, you will undergo spirometry every few minutes for about 30 minutes. Your breathing ability is usually lowest 5 to 10 minutes after exercise. The airways then open, and breathing ability improves within 30 minutes.5

If your breathing ability decreases by 10 percent or more after exercising, you likely have exercise-induced asthma. This is measured using the forced expiratory volume (FEV1) by spirometry.5

Your doctor may use an inhalation test instead of a direct exercise challenge test. Certain inhalation challenges simulate exercise conditions. Three alternatives to an exercise challenge test include:3

  • Eucapnic voluntary hyperpnea challenge
  • Mannitol challenge
  • Hypertonic saline challenge

Methacholine challenge

During a methacholine challenge test, you will undergo spirometry before and after inhaling a dose of methacholine. This will measure how much your airway narrowed. The test will start with a very small dose of methacholine. Depending on your response, the dose will be gradually increased.3

This process will be repeated until your breathing ability drops by 20 percent. This is determined by your FEV1 in spirometry. You will then use a rescue inhaler to open the airway back up. Spirometry will confirm that your airways are opening.3

The dose that causes your breathing ability to drop by 20 percent is called the PC20. A lower dose means your airways are more sensitive and you are likely to have asthma. If you reach the maximum dose without breathing ability dropping by 20 percent, you have a normal airway sensitivity. This means you are unlikely to have asthma.3

You may experience coughing or chest tightness during the test. But most people do not experience any symptoms.3

How do I prepare for a challenge test?

Prepare for any challenge test exactly as your doctor describes. For example, you may need to stop taking certain medicines before the test. This is because some inhalers make your airway less sensitive and interfere with the test.3,5

Your doctor may also ask you to avoid caffeine or large meals before a challenge test. They also may tell you what clothing to wear to the test.3,5

Tell your doctor about your full medical history. There are some situations when a challenge test should not be performed. This includes people who:3,5

  • Have had a heart attack or stroke in the last 3 months
  • Have uncontrolled high blood pressure
  • Are pregnant or nursing

Also tell your doctor if you feel unwell on the day of the test. If you have a cough or a cold on the day of the test, they may want to do the test when you feel better.

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Written by: Matt Zajac | Last reviewed: September 2021