Did methocholine challenge and only dropped 12%. dr says negative for asthma. how accurate is test? did pft as well and was normal.

Quite Accurate: The methacholine challenge is useful to see if you have hyper-reactive airways that are seen in patients with asthma. If you have shortness of breath but a normal methacholine challenge and normal pulmonary function tests, there is likely a non-asthma cause for your shortness of breath. Depending on your symptoms, though could be a vocal cord disorder, for example.