Wow, learn something new every day. I haven't hear of this test but my ashma diagnosis is newer then yours. After reading about it, I am assuming that my doctor has never suggested this test for me because my baseline on the spirometry test is usually about 40% which he says is lower then he would like. I do take 3 different ashma meds daily and am still between 40% and 50% baseline every time I go in. The test is trying to test how much (if any) change in breathing capacity happens with each dose of the methacholine drug. It states that it is to see if there becomes a 20% or greater drop in your breathing ability. A positive test suggests that your airways are "reactive," and a diagnosis of asthma should be considered. A negative test means a diagnosis of asthma is unlikely. I don't think you should worry about the test due to the doctor having access to all the meds to open you back up if you do drop in breathing capacity.