A negative MCT result does rule out asthma in patients who have had asthma symptoms, according to asthma experts Florence Chau-Etchepare, MD, Robert M. Bayliss Jr, RCP, RRT, and Samuel Louie, MD. When there is a moderate to high clinical suspicion of asthma, a negative MCT result has a greater than 90% negative predictive value.
Read more about challenging the diagnosis of asthma with methacholine here.