Methacholine Challenge: Physiology, Methodology, and Clinical Interpretation

This review article explores the methacholine challenge test (MCT), a bronchoprovocation technique used to assess airway hyperresponsiveness (AHR), a hallmark of asthma. The article begins by tracing the historical development of the MCT, including early studies that established its clinical relevance in diagnosing asthma. The physiological mechanisms underlying AHR are discussed, with emphasis on how these contribute to bronchoconstriction. The article also highlights advances in MCT methodology, clinical utility in ruling out asthma, factors that influence the interpretation of MCT results, and limitations of the test. Finally, the review suggests future directions for improving MCT.