Which diagnostic test for exercise-induced bronchospasm shows a FEV1 decrease of 20%?

The methacholine challenge is a well-established diagnostic test used to evaluate airway hyperreactivity, particularly in cases of exercise-induced bronchospasm or asthma. During this test, patients inhale increasing concentrations of methacholine, which acts as a bronchoconstrictor. A significant decrease in forced expiratory volume in one second (FEV1) — typically defined as a drop of 20% or more from baseline — indicates a heightened sensitivity of the airways and suggests the presence of asthma or exercise-induced bronchospasm.

This specific threshold of a 20% decrease in FEV1 is a key diagnostic criterion because it indicates the presence of hyperreactive airways. The methacholine challenge is particularly useful because it can provoke bronchoconstriction in individuals who may not exhibit symptoms during unchallenged states.

The other tests listed evaluate airway function or response to stimuli but do not specifically relate to a standard decrease in FEV1 indicative of exercise-induced bronchospasm in the same manner as the methacholine challenge. Thus, it is the most appropriate test for demonstrating such bronchial hyperreactivity.