Methacholine challenge test

The methacholine challenge test is a technique use in the testing of asthma. It mimics the effects of histamine in triggering asthma attacks and impairing lung function, while at the same time breaking down quite quickly in the body and therefore presenting no long-term danger.

The test typically takes the form of an increasing dosage of inhaled methacholine, doubled at each test run. After each dose, lung function is measured. The concentration required to achieve a 20% reduction in lung function is noted. A low concentration (less than 4 mg/ml) is typical of asthma.