Bronchial challenge test
Encyclopedia
A bronchial challenge test is a medical test
used to assist in the diagnosis
of asthma
. The patient breathes in nebulized
methacholine or histamine
. Thus the test may also be called a methacholine challenge test or histamine challenge test respectively. Both drugs provoke bronchoconstriction
, or narrowing of the airways. Whereas histamine causes nasal and bronchial mucus secretion and bronchoconstriction via the H1 receptor
, methacholine utilizes the M3 receptor for bronchoconstriction. The degree of narrowing can then be quantified by spirometry
. People with pre-existing airway hyperreactivity, such as asthmatics, will react to lower doses of drug.
Sometimes, to assess the reversibility of a particular condition, a bronchodilator
is administered to counteract the effects of the bronchoconstrictor before repeating the spirometry tests. This is commonly referred to as a reversibility test, or a post bronchodilator test (post BD), and may help in distinguishing asthma from chronic obstructive pulmonary disease
.
False positives and negatives are possible in the bronchial challenge test. In addition, asthma may be temporary due to an exposure to noxious stimuli or exercise.
The bronchial challenge test is physically demanding, and the results can be affected by muscular weakness or exhaustion. The inhaled drug can stimulate the upper airway sufficiently to cause violent coughing. This can make spirometry difficult or impossible. This test is contraindicated in patients with severe airway obstruction due to the obvious worsening of the obstruction.
Medical test
A diagnostic test is any kind of medical test performed to aid in the diagnosis or detection of disease. For example:* to diagnose diseases, and preferably sub-classify it regarding, for example, severity and treatability...
used to assist in the diagnosis
Diagnosis
Diagnosis is the identification of the nature and cause of anything. Diagnosis is used in many different disciplines with variations in the use of logics, analytics, and experience to determine the cause and effect relationships...
of asthma
Asthma
Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...
. The patient breathes in nebulized
Nebulizer
In medicine, a nebulizer is a device used to administer medication in the form of a mist inhaled into the lungs....
methacholine or histamine
Histamine
Histamine is an organic nitrogen compound involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter. Histamine triggers the inflammatory response. As part of an immune response to foreign pathogens, histamine is produced by...
. Thus the test may also be called a methacholine challenge test or histamine challenge test respectively. Both drugs provoke bronchoconstriction
Bronchoconstriction
Bronchoconstriction is the constriction of the airways in the lungs due to the tightening of surrounding smooth muscle, with consequent coughing, wheezing, and shortness of breath. Bronchoconstriction can also be due to an accumulation of thick mucus....
, or narrowing of the airways. Whereas histamine causes nasal and bronchial mucus secretion and bronchoconstriction via the H1 receptor
H1 receptor
The H1 receptor is a histamine receptor belonging to the family of Rhodopsin like G-protein-coupled receptors. This receptor, which is activated by the biogenic amine histamine, is expressed throughout the body, to be specific, in smooth muscles, on vascular endothelial cells, in the heart, and in...
, methacholine utilizes the M3 receptor for bronchoconstriction. The degree of narrowing can then be quantified by spirometry
Spirometry
Spirometry is the most common of the pulmonary function tests , measuring lung function, specifically the measurement of the amount and/or speed of air that can be inhaled and exhaled...
. People with pre-existing airway hyperreactivity, such as asthmatics, will react to lower doses of drug.
Sometimes, to assess the reversibility of a particular condition, a bronchodilator
Bronchodilator
A bronchodilator is a substance that dilates the bronchi and bronchioles, decreasing resistance in the respiratory airway and increasing airflow to the lungs. Bronchodilators may be endogenous , or they may be medications administered for the treatment of breathing difficulties...
is administered to counteract the effects of the bronchoconstrictor before repeating the spirometry tests. This is commonly referred to as a reversibility test, or a post bronchodilator test (post BD), and may help in distinguishing asthma from chronic obstructive pulmonary disease
Chronic obstructive pulmonary disease
Chronic obstructive pulmonary disease , also known as chronic obstructive lung disease , chronic obstructive airway disease , chronic airflow limitation and chronic obstructive respiratory disease , is the co-occurrence of chronic bronchitis and emphysema, a pair of commonly co-existing diseases...
.
False positives and negatives are possible in the bronchial challenge test. In addition, asthma may be temporary due to an exposure to noxious stimuli or exercise.
The bronchial challenge test is physically demanding, and the results can be affected by muscular weakness or exhaustion. The inhaled drug can stimulate the upper airway sufficiently to cause violent coughing. This can make spirometry difficult or impossible. This test is contraindicated in patients with severe airway obstruction due to the obvious worsening of the obstruction.