Methacholine Challenge

Definition
The methacholine challenge test is a type of test used in the testing for asthma. It mimics the effects of histamine in triggering asthma attacks and impairing lung function. Methacholine breaks down in the body quickly, so there is no long-term danger from this test.

How the test is performed
The test typically consists of inhaling increasing doses of methacholine and measuring lung function after each inhalation. The concentration of medication required to decrease lung function by 20% is noted. A 20% drop from the baseline measurements is considered to be diagnostic, but there is the possibility of false positives as well as false negatives in this test.