| Bronchial challenge test | |
|---|---|
| MeSH | D001985 |
| OPS-301 code | 1-714 |
| LOINC | 65806-2 |
Abronchial challenge test is amedical test used to assist in thediagnosis ofasthma,[1] by evaluating existence of possibleairway hyperresponsiveness. The patient breathes innebulizedmethacholine orhistamine. Thus the test may also be called amethacholine challenge test orhistamine challenge test respectively. Both drugs provokebronchoconstriction, or narrowing of the airways. Whereas histamine causes nasal and bronchial mucus secretion and bronchoconstriction via theH1 receptor, methacholine utilizes theM3 receptor for bronchoconstriction. The degree of narrowing can then be quantified byspirometry. People with pre-existingairway hyperreactivity, such asasthmatics, will react to lower doses of drug.
Sometimes, to assess the reversibility of a particular condition, abronchodilator is administered to counteract the effects of the bronchoconstrictor before repeating the spirometry tests. This is commonly referred to as areversibility test, or apost bronchodilator test (post BD), and may help in distinguishing asthma fromchronic obstructive pulmonary disease. Also, aDLCO test can be used to distinguish asthma (normal to high DLCO) from COPD (reduced DLCO).
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. It is also contraindicated by the presence of an aortic aneurysm, as spirometry will increase blood pressure, in proportion to both the patient's effort and the degree of obstruction in the lungs.
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