In a methacholine bronchial provocation test, what indicates a positive result?

Prepare for the Registered Respiratory Therapist CSE with comprehensive flashcards and multiple-choice questions, including hints and explanations. Ace your exam with confidence!

Airway hyperresponsiveness is the key idea here. In a methacholine challenge, you provoke the airways with increasing amounts of methacholine and measure how much lung function changes. A positive result means the airways are reactive enough to constrict noticeably in response to the stimulant, which is reflected by a fall in FEV1 from baseline. The standard threshold is about a 20% decrease in FEV1; this level indicates clinically significant bronchoconstriction in susceptible individuals. A smaller change, like a 10% drop, is not enough to call the test positive, and a much larger drop (such as a 50% decrease) would indicate very severe obstruction but still centers on the same reactive pattern rather than changing the threshold. An increase in FEV1 would mean bronchodilation or no response, not a positive test.