A methacholine challenge test evaluates your lung function and the reactivity (narrowing or tightening) of your airways. It helps diagnose and monitor asthma, a chronic lung disease marked by acute flare-ups of inflammation and swelling of the airways in the lungs. A methacholine challenge test is a type of bronchoprovocation test, which measures lung function after exposure to factors that commonly trigger wheezing and other asthma symptoms. A methacholine challenge test involves inhaling a mist that contains methacholine, a substance that causes lung constriction in people with asthma. A methacholine challenge test is only one method to diagnose asthma. Discuss all of your testing methods with your doctor to understand which options are right for you. Other procedures that may be performed Your doctor will likely recommend one or more other pulmonary or lung function tests to diagnose asthma and monitor your condition. Other pulmonary function tests include: Arterial blood gas test to measure oxygen and carbon dioxide levels and other factors in the blood Body plethysmography to determine how much air is present in your lungs when you take a deep breath and how much air is left in your lungs after you exhale as much as you can. A methacholine challenge test and other pulmonary function tests can be done at the same time as a body plethysmography using the same equipment. Lung diffusion capacity to measure how well oxygen moves into your blood from your lungs Other bronchoprovocation tests to measure lung function after exposure to factors that commonly trigger asthma. These tests use exercise, cold air, or histamine to trigger lung constriction and wheezing. Peak expiratory flow to measure the speed of exhaling and lung constriction. People with asthma use this test routinely to monitor their asthma control at home. Pulse oximetry to measure oxygen levels in the blood Spirometry to measure the amount of air and the rate that you inhale and exhale Your doctor may recommend a methacholine challenge to diagnose asthma if you have with some or all of the following symptoms: Chest tightness Persistent cough, especially at night or in the early morning Shortness of breath Wheezing or a high pitched whistling sound made when you breathe Not all people with these symptoms have asthma. There are other conditions that have similar symptoms, and sometimes asthma-like symptoms can occur briefly without a serious underlying disease. A methacholine challenge test helps determine if your symptoms are due to asthma. A methacholine challenge test is generally not the first test your doctor will use to diagnose your symptoms. Your doctor may consider the test when other tests, such as spirometry, have not diagnosed or ruled out asthma. Doctors also use methacholine challenge tests to evaluate asthma-like symptoms triggered by occupational, environmental or toxic exposures. A pulmonary function technologist, supervised by a doctor, performs a methacholine challenge test. A pulmonary function technologist is trained to perform lung function tests. These tests help diagnose and monitor asthma, chronic obstructive pulmonary disease (COPD), and other breathing problems. The following specialists supervise methacholine challenge tests: Allergist-immunologists specialize in caring for people with allergies, asthma, and other diseases of the immune system. Pediatric allergist-immunologists specialize in caring for children from infancy through adolescence with allergies, asthma, and other diseases of the immune system. Pulmonologists specialize in the medical care of people with breathing problems and diseases and conditions of the lungs. Pediatric pulmonologists specialize in the medical care of infants, children and adolescents with diseases and conditions of the lungs. Your methacholine challenge test will be performed in a pulmonary function test lab in a hospital or clinic setting. A methacholine challenge test takes up to two hours and generally involves these steps: You will blow forcefully into a spirometer, a device that measures the amount of air and the rate that you inhale and exhale. You will inhale a mist that contains methacholine through a mouthpiece. A nebulizer device makes the mist by changing liquid medications or substances into an aerosol. You will blow forcefully again into a spirometer. This process will be repeated using increasing doses of methacholine. If you have asthma, your airway will narrow and your lung function will drop by at least 20% during the test. You will receive a bronchodilator medication at the end of the test or when needed to reverse the effects of the methacholine. In some cases, methacholine challenge testing takes place as you sit inside a special clear cabinet or booth. This is called a body plethysmography. This test uses a computerized pulmonary function testing system that can also perform lung diffusion capacity and other pulmonary function tests. Will I feel pain with a methacholine challenge test? Your comfort and relaxation is important to getting the most accurate test results. A methacholine challenge test is not painful. Be assured that your care team is trained to monitor your condition, and recognize and reverse serious effects of the methacholine quickly, including severe lung constriction (rare). Tell your pulmonary function technologist right away if you feel any effects, such as chest tightness, shortness of breath, and wheezing. A methacholine challenge test is generally a safe procedure when performed by a qualified pulmonary function technologist, supervised by a doctor. Many people do not have side effects or symptoms from methacholine, which causes airway narrowing in people with asthma. When symptoms appear, they are generally mild and go away after inhaling a bronchodilator medication. Symptoms include: Chest tightness Coughing Dizziness Headache Shortness of breath Wheezing Rarely, methacholine can cause serious narrowing of the airways. Your pulmonary function technologist is trained to recognize a serious situation and treat it immediately using resuscitation equipment if necessary. You should not have a methacholine challenge test in the following situations: You are pregnant. You have had a stroke or heart attack in the past three months. You have had an aortic or cerebral aneurysm. You have uncontrolled high blood pressure. Reducing your risk of complications You can reduce the risk of certain complications by: Following activity, dietary and lifestyle restrictions before and after your test Notifying your doctor if you are nursing or there is any chance of pregnancy Taking or stopping your medications exactly as directed by your doctor Telling your doctor and technologist of your complete medical history including any history of high blood pressure, aneurysms, heart attack, or stroke Telling all members of your care team if you have any allergies You are an important member of your own healthcare team. The steps you take before your test can improve your comfort, reduce the risk of side effects, and help get the most accurate test results. You can prepare for a methacholine challenge test by: Avoiding excessive sugar and products that contain caffeine including coffee, tea, chocolate, sodas, and energy drinks Avoiding exercise and cold air the day of the test Answering all questions about your medical history, allergies, and medications. This includes prescriptions, over-the-counter drugs, herbal treatments, and vitamins. It is a good idea to carry a current list of your medical conditions, medications, and allergies at all times. You will need to provide this information to the pulmonary function technologist and your doctor. Not smoking the day of the test or stopping smoking altogether, which is even better Taking or stopping medications exactly as directed. This often includes not taking asthma medications, such as short- and long-acting bronchodilators and allergy drugs, for a short period before the test. Your doctor will give you instructions for your medications and what to do if you start having asthma symptoms during this time. Telling your doctor and the pulmonary function lab if you develop a fever, cold symptoms, or other symptoms of illness within a week of the test. You will likely need to reschedule the test until you feel better. Questions to ask your doctor or pulmonary function technologist It is common for patients to forget some of their questions during a doctor’s visit. You may also think of other questions after your appointment. Contact your doctor with concerns and questions before your procedure and between appointments. It is also a good idea to bring a list of questions to your appointments. Questions can include: Why do I need a methacholine challenge test? Are there other options for diagnosing my condition? What are the qualifications of the pulmonary function technologist who will perform the test? Is the pulmonary function technologist certified in advanced cardiac life support? What other qualified healthcare providers respond to help with resuscitation if needed? How should I take my medications before and after the test? How can I expect to feel after the test? When can I return to normal activities? When and how will I get my test results? When should I follow up with you? How should I contact you? Ask for numbers to call during and after regular hours. Knowing what to expect after a methacholine challenge test can help you get back to your everyday life as soon as possible. How will I feel after my methacholine challenge test? You should be breathing normally after your methacholine challenge test. Your pulmonary function technologist will give you a bronchodilator to reverse the effects of methacholine before you go home. You should not have any asthma symptoms, such as wheezing, coughing, chest tightness or shortness of breath, when you leave. Tell your technologist if you have symptoms, even if they are mild. When should I call my doctor? You should keep your follow-up appointments after a methacholine challenge test. Contact your doctor if you have any concerns between appointments. Seek emergency medical care or call 911 if shortness of breath or other breathing problems are getting worse quickly.