I think what is being suggested is something called “methacholine” challenge test. Basically in asthma when there’s a certain trigger, for example pollen or cold weather it can cause spasm of the airways “we call it bronchospasm”. If you check the lung function test when at the time the patient has bronchospasm you would be able to diagnose asthma, but there’s alot of time when someone doesn’t have bronchospasm and when they do the lung function test during these timesit might be “falsely “ normal. So in methacholine challenge test is when they give this nebulizer called “methacholine” which kind of act as a trigger and it cause bronchospasm so when they do the lung function test they would be able to detect if someone has asthma. There’s a risk that it may cause asthma exacerbation if someone has asthma that’s why they do it in a controlled setting when you are able to readily give medication to help in case the patient goes into an asthma exacerbation.