Out of all pulmonary function tests, bronchoprovocation test provides the most accurate results for diagnosing patients with asthma. To provide the hyper-responsiveness of the lungs, this test works by triggering bronchoconstriction in patients. This test may also be ordered as a part of routine health assessment for people who are suspected to have a lung disease or for managing chronic lung diseases over time.
The test may have certain risks and requires some preparation. Precautions are taken to avoid any mishap during the test because the procedure can trigger an asthma attack (maybe severe) in patients. Keep reading to learn more about this test.
What is a bronchoprovocation test?
Bronchoprovocation test, also known as bronchoprovocation challenge or bronchial provocation test, is a pulmonary function test used to evaluate how the lungs respond or react. As the name suggests, this test is employed to provoke the airways by giving triggers to the patient to test the hyper-responsiveness of their airway and to make an initial diagnosis of asthma. The chronic lung disease, asthma, is associated with acute flare-ups of inflammation and swelling of the airways in the lungs.A bronchoprovocation test helps in analysing the severity of the airway dysfunction in patients who have asthma. The test procedure involves inhaling triggers, such as aerosolised chemicals, cold air, or some exercises, to evaluate if the activity induces an asthmatic response from the patient. A doctor may be able to determine whether the patient has asthma by simply measuring the lung function after trigger exposure. Depending on the type of the trigger used, bronchoprovocation tests are majorly categorised into three types:
- Cold air challenge: Used to measure the lung response after exposure to cold air
- Exercise challenge: Utilised to measure the lung response after exercise on a treadmill
- Inhalation tests: Employed to measure the lung response after exposure to aerosolised chemicals such as histamines, mannitol, or methacholine. This test is often performed with methacholine, and thus, is referred to as methacholine challenge as well.
Why is bronchoprovocation test performed?
Usually, the doctor orders a bronchoprovocation challenge to have a definitive diagnosis of asthma when the results of other pulmonary function tests (or PFTs) are inconclusive. The spirometer test, a type of PFT, is often used to diagnose asthma by evaluating the improvement of the lung function after inhaling a short-acting bronchodilator designed to open/dilate the airways. However, this test is not always definitive. In such a case, the healthcare provider usually takes the opposite approach and evaluates the deterioration of the lung function after administrating asthma triggers to the patient; this causes the airways to constrict and helps with diagnosing asthma.Patients experiencing the following symptoms are recommended a bronchoprovocation challenge:
- Tightness in the chest
- Persistent cough, especially at night or early morning
- Shortness of breath
- Wheezing
Bronchoprovocation test procedure
A technologist, with a special training and education in pulmonary function tests, performs the bronchoprovocation test under the supervision of a doctor. The test is usually supervised by any of the following:- Pulmonologists (specialised doctors that provide care for the respiratory system)
- Allergists and immunologists (doctors specialised in the diagnosis and treatment of asthma, allergies, and immune deficiency disorders)
1. Pre-test evaluation
Since asthma attacks can severely affect the patient’s health if they occur, a pre-test evaluation is done to ensure the bronchoprovocation test is safe for the patient. The healthcare provider can identify contraindications for the test and ensure that the test is effective by performing this step. The healthcare provider will calculate the patient’s forced expiratory volume in 1 second or (FEV1) value, which is essential for performing the test, with the help of a spirometer at this stage.It is important to note that people with FEV1 of less than 50% of the predicted value, which indicates severe airflow restriction, should never go through with the bronchoprovocation test. People who have moderate restriction or FEV1 of less than 60% may not be allowed to go through with the test if they have other risk factors. Additionally, people who have less than 75% FEV1 usually require other means of testing apart from exercise triggers.
2. During the test
After checking the patient’s vitals and FEV1 and confirming that other dietary and medication restrictions have been followed, a healthcare provider will take the patient to the examination room.The goal of the test is to trigger bronchoconstriction by using various triggers, but the exact process may differ based on the use of the trigger. For example, the procedure listed below is used for a methacholine challenge, which is the most common way of performing the bronchoprovocation test:
- The patient is given a nose clip to put on their nose so that they can breathe only through the mouth.
- A methacholine dose is administered to the patient through a nebuliser.
- The patient inhales and exhales in the nebuliser mouthpiece with the air pressure turned on. Some patients, who are not comfortable with breathing through a nebuliser, are given a nebuliser face mask.
- After this, the mouthpiece is removed, and the machine is turned off.
- A second FEV1 reading is taken 30–90 seconds after the mouthpiece is removed. The healthcare provider may take additional FEV1 readings at different intervals and record the highest on the lab results.
3. Concluding the test
After ensuring that satisfactory results have been recorded, the healthcare provider will give the patient a bronchodilator at the end of the test to reverse the effects of the triggers. The reports are shared with the concerned doctors, usually on the same day. The bronchoprovocation test can be performed to diagnose asthma definitively if the FEV value drops by a certain percentage.Preparing for the test
Patients are recommended to wear loose-fitted comfortable clothing for the bronchoprovocation test if they are not taking the exercise challenge. Doctors recommend wearing sportswear for the exercise challenge to prevent loose clothes from hindering the patient’s movement. The workout clothes you wear must allow the healthcare provider to use a heart monitor on the patient.To prevent discomfort and nausea, the patient should not eat a heavy meal or drink a large beverage. Apart from this, the patient is required to stop consuming any caffeine on the day of the test in forms, such as tea, coffee, and chocolate; caffeine can increase airway hyper-responsiveness and falsify the results.
Additionally, the patient must inform the healthcare provider about every medication they are consuming at the time of test, as some of them can interfere with the test results, including the following:
- Short-, medium-, and long-acting beta-agonists
- Oral bronchodilators
- Leukotriene inhibitors
- Antihistamines
Interpreting results
The doctor can review test results soon after the test is conducted if the test is performed in their office or the same hospital. If the test is performed at a different diagnostic centre the reports are usually delivered to the doctor within a day or two. The test results include the patient’s FEV1 values before and during the test. A decline of 20% or more in FEV1 is observed in patients who have asthma. Thus, if the FEV1 decline is less than 20%, the patient does not have asthma, and a negative result is shared with the doctor.However, some people may experience bronchoconstriction without having asthma, which is why borderline test results (nearing 20%) can be harder to interpret and may require additional tests. If the test’s accuracy is affected by the testing protocols or other parameters, the patient may be required to get the test again on a later day.
If the test results indicate a strong negative with persisting symptoms, the doctor/pulmonologist will recommend further tests; they may also consider other health problems, including congestive heart failure, chronic obstructive pulmonary disease (COPD), cystic fibrosis, and pulmonary sarcoidosis, while making a diagnosis.
Associated risks
Bronchoprovocation tests are generally safe when performed by a trained medical staff under a doctor’s supervision, and most people do not experience any side effects. The patient might experience mild to moderate symptoms during the test, which go away on their own in a while. Common symptoms from a bronchoprovocation test include tightness in the chest, coughing, dizziness, headache, shortness of breath, and wheezing.Although people rarely get any serious symptoms during the test, proper preparation should be done to handle any kind of medical emergency. People who fall under the following category should inform their doctor about such conditions to avoid complications from certain types of triggers during the bronchoprovocation test:
- Pregnant women
- People who have a cerebral or aortic aneurysm
- People with uncontrolled high blood pressure
- People who have experienced a heart attack or stroke in the duration of three months before the test
Other pulmonary function tests
Apart from bronchoprovocation test, the doctor will likely recommend other pulmonary function tests to create a suitable care plan for the patient.- Arterial blood gas test is used to measure the levels of oxygen and carbon dioxide in the blood and the pH balance of the blood.
- Body plethysmography is utilised to measure the amount of air present in the lungs when the patient takes a deep breath and the amount of air left in their lungs after exhaling.
- Lung diffusion capacity test are done to evaluate the movement of oxygen from the lungs to the blood.
- Peak expiratory flow is used to measure the patient’s speed of exhaling and lung constriction. This is a routine test performed on patients with asthma to monitor their progress at home as well.
- Pulse oximetry is used to measure oxygen levels in the blood
- Spirometry is done to measure the rate and amount of air that a person inhales and exhales.
