A methacholine challenge test, also known as a bronchoprovocation test, can measure if your airways are reactive. This measurement can help a healthcare professional diagnose asthma.
But because asthma can be difficult to diagnose, the methacholine challenge test is one of several tests a doctor may use to assess if you could have the condition.
Keep reading to find out more about this test, including what to expect and who shouldn’t take the test.
The methacholine challenge test involves inhaling controlled amounts of methacholine. This is a medication known to cause the airways to get smaller in those with asthma.
The doctor may ask you to stop taking certain medications, such as your inhaler, on the day of your test. Also, refrain from drinking caffeinated products at least 4 hours before your test.
Here are the typical steps followed:
- Participating in a spirometry test. This involves inhaling and exhaling deeply to measure how well your lungs work. The spirometry test helps your doctor identify your baseline lung function.
- Breathing in a dose of methacholine. The dose is delivered via a mist.
- Repeating the spirometry test. This helps determine if or how much your airways narrow as a result of exposure to the methacholine.
The tests ends if you start experiencing breathing problems or if your airways narrow 20 percent or more. These results can indicate that you have asthma.
If you don’t have asthma, the test shouldn’t cause more than coughing or some mild chest tightness.
A doctor will say your methacholine challenge test is positive if you experience a reduction in your lung function by at least 20 percent after you breathe in methacholine, according to the American Academy of Allergy Asthma and Immunology. If the test is positive, you likely have asthma.
It’s possible to get a
But if the test is negative, you likely do not have asthma. The test’s ability to rule out asthma is one of the reasons doctors may find it helpful as part of their diagnostic criteria for confirming whether you have asthma.
No single test can confirm an asthma diagnosis.
Specialists such as pulmonologists or allergy, asthma, and immunology doctors may recommend different testing to diagnose or rule out asthma. The methacholine challenge test is one of several tests a doctor may recommend.
Examples of these tests include:
- Exercise test. According to 2017 research, this test involves exercising to increase heart rate and demands on the lungs. This test is helpful when a person notices their asthma symptoms get worse with physical activity.
- Spirometry. Spirometry is a part of the methacholine challenge test. But doctors can perform the test as a part of an asthma workup without the use of methacholine. Spirometry helps doctors understand how well your lungs are working.
- Fractional exhaled nitric oxide (FeNO) test. The Asthma and Allergy Foundation of America says that this test, also known as exhaled nitric oxide testing, can help a doctor determine if asthma-related inflammation is present in your lungs.
A doctor will consider your symptoms and overall health when determining what tests to order.
Some people shouldn’t undergo the methacholine challenge test, especially if their lung function isn’t very good. Because the challenge is meant to affect lung function, those with very sick lungs may not be able to recover as well.
The American Lung Association says the test may have too many risks for those with the following conditions:
- known aneurysm in the aorta or brain
- poor lung function as identified on a spirometry test
- medical history of heart attack or stroke within the past 3 months
- uncontrolled high blood pressure
- recent eye surgery
Also, notify a doctor if you have a cold or cough the day of the test.
If you are well enough to proceed with the test, the main risks of the test involve feeling lightheaded from having to participate in frequent spirometry tests.
Other possible side effects include:
- chest pain
- shortness of breath
Let the person performing the test know if you have any of these symptoms. The staff should have access to rescue medications, including oxygen. They should also be trained in treating breathing problems and identifying when to call for emergency help.
According to National Jewish Health, the cost for a methacholine challenge test before insurance was about $880 in 2019.
Insurance policies may cover part or all of the methacholine challenge test. The test may vary based on your location, provider, and insurance coverage.
Talk with a doctor about cost estimates to make sure the test is affordable for you before participating in it.
The next steps after this test depend upon your results.
If your test was positive
If your methacholine challenge test revealed airway reactivity, the doctor will consider other symptoms to rule out medical conditions other than asthma.
The doctor may prescribe medications that can help reduce asthma symptoms and assess how well these work for you at a follow-up visit.
If your test was negative
If your methacholine challenge test was negative, the doctor may recommend other testing to determine why you’re having certain symptoms.
Asthma is not the likely cause of your breathing difficulties if your test is negative.
The methacholine challenge is a test that can help a doctor diagnose your asthma or determine that you don’t have asthma.
While the test has few serious side effects, it’s important to share your full medical history and all the medications you’re taking to make sure you can safely perform the test. Always ask a doctor about costs and side effects before undergoing the test.