Methacholine Challenge Test (Bronchoprovocation Test)
Last Updated 11/02/2020
Authors:Diego Maselli Caceres, MD, FCCP; Stuart Garay, MD, FCCP; Mary Hart, RRT, MS, FCCP; Sandhya Khurana, MD, FCCP
About Methacholine Challenge Test (Bronchoprovocation Test)
- This test can show whether you have asthma by using a drug to simulate an asthma attack.
- You breathe in (inhale) a dose of methacholine to narrow your airways. Then, you take a breathing test (spirometry). You may repeat these steps depending on the test result.
- The test ends when:
- You start to feel discomfort (wheezing, shortness of breath); or
- The breathing test shows that your airways have gotten narrow.
- If the drug causes a 20% or more loss in your breathing ability, you may be diagnosed with asthma.
- Most patients experience no symptoms during the test besides coughing or chest tightness.
- If you have certain conditions, you won’t be given this test.
The methacholine challenge test (also known as a bronchoprovocation test) is used to diagnose asthma. It can find out how “reactive” or “responsive” your lungs are to things you inhale that can cause asthma symptoms. These symptoms include cough, a tight feeling in your chest, and shortness of breath.
During the test, you’re asked to inhale doses of methacholine, a mist that can make your airways narrow, the way asthma does. After each dose, you take a breathing (spirometry) test. This test measures how narrow your airways have become.
What to expect
Your health care provider will ask which medications you’re taking. Then, he or she may ask you to stop using some of your inhalers several hours or days before the test. This will prevent those drugs from interfering with the test. Also, you may be asked not to drink any products with caffeine (coffee, tea, or soda) for at least 4 hours before the test.
To begin, you take a lung function test to note your typical lung function (your baseline). Then, you receive a small dose of methacholine. You inhale this medication as mist from a nebulizer (a machine that turns liquid drugs into breathable mist). You may cough or feel your chest getting tight, but most patients don’t have any symptoms.
Next, you will be asked to repeat the lung function test to check for any narrowing (or constriction) of your airways. Depending on these results, you may receive a second, larger dose of methacholine, followed by another lung function test.
Your health care provider will stop the test when:
- You start to feel discomfort, such as wheezing and greater shortness of breath;
- The breathing test shows that your airways have become narrow; or
- You reach the largest dose with no change in your breathing.
Understanding the results
If your ability to breathe drops by 20% or more, the test is positive: Your airways are reactive, and your health care provider may diagnose you with asthma. A negative test means that a diagnosis of asthma is unlikely.
What are the risks?
Although the test is safe, the methacholine test has several possible side effects:
- It can make your airways tighter (called bronchoconstriction).
- Rarely, you may feel symptoms of an asthma attack, such as:
- It may make you feel dizzy or uncomfortable.
During the test, the technician performing the challenge will watch you closely. If the test results show that there is constriction of your airways, you will be given a bronchodilator (a medication that opens your airways) to relieve your symptoms.
You won’t be given the challenge if you have 1 or more of the following conditions:
- Low lung function on the baseline spirometry test
- Heart attack or stroke in the past 3 months
- Uncontrolled high blood pressure
- Aneurysm (a bulge in a blood vessel wall) of the aorta or in your brain
- You are pregnant or nursing
The testing center staff will review your medical history before the test. Let them know if you have any of the above conditions or if you have a cold, are coughing more, or feel unwell on the day of the test.
Diego Maselli Caceres, MD, FCCP, University of Texas Health Science Center at San Antonio;
Stuart Garay, MD, FCCP, New York University Langone Medical Center;
Mary Hart, RRT, MS, FCCP, Baylor Scott & White Health;
Sandhya Khurana, MD, FCCP, University of Rochester