Provocholine is a Diagnostic Bronchoconstrictor for the Diagnosis of Bronchial Airway Hyperreactivity
When to Consider Methacholine Challenge Testing?
Always consider objective measurements when contemplating an asthma diagnosis. There are several consequences associated with improper treatment such as: lost opportunity to diagnose the cause of symptoms, potential exposure to inappropriate medications, lost employment opportunities (i.e., military, public services), social consequences and economic factors.
Several studies have shown that patients with physician diagnosed asthma may have been misdiagnosed in approximately 1/3 of cases. To confirm a diagnosis of asthma, objective testing should be performed.
1999 ATS Guidelines Indication:
Methacholine challenge testing is most often considered when asthma is a serious possibility and traditional methods, most notably spirometry performed before and after administration of a bronchodilator, have not established or eliminated the diagnosis.
ERS Technical Standard Indication:
Apart from epidemiological or clinical research, these tests are most often done to exclude or confirm a suspected diagnosis of asthma. Demonstration by spirometry of reversible airflow obstruction is considered confirmatory; however, spirometry is often not available at the time of symptoms and may be inconclusive when it is done, especially in those with normal or near-normal lung function values. If symptoms, spirometry or response to therapy are atypical, a bronchial challenge test is appropriate and can increase or decrease the probability of asthma. In the setting of ongoing clinical symptoms, a negative result to a test with relatively high sensitivity, such as a methacholine challenge test, may be most helpful in making current asthma unlikely. In Contrast, a positive methacholine challenge test, unless at a very low dose, cannot confirm asthma. Bronchial challenge tests are also used in screening applicants for situations where airway hyperreactivity would present a high safety risk, such as commercial diving, submarine service and some occupational exposures.