Hi again, iamkathleenj. Thank you for the great question. If you have controlled asthma, you would experience no symptoms. Asthma can still be diagnosed when you are experiencing no symptoms. The way to do this is by a PFT (https://asthma.net/living/pulmonary-function-testing-to-diagnose-asthma/) test, as you note. What will happen is described in the article, but it basically involves doing a pre and post bronchodilator forced vital capacity. If your lung function improves after the bronchodilator by 15% then you can probably be diagnosed with asthma . This shows that you have a reversible condition (https://asthma.net/living/what-does-reversible-mean/), which is how asthma is defined (reversible obstructive airway disease). Also, if this test does not confirm your asthma diagosis, and your doctor still thinks you might have asthma, there are a couple other options. One, is you could do bronchoprovocation test. This is a PFT test where they give you a medicine to inhale that causes you to have an asthma attack (mild land under supervision). Then you do the pre and post FVC. When this test shows a 15% increase in your post treatment lung, you can most assuredly be diagnosed with asthma. There is also another test where you can run on a treadmill instead of bronchoprovocation. I have done this before. If running on a treadmill makes you experience asthma, then this test may also be an option. Does this help? What test you do depends on your doctor and probably how close you are to a center that performs these tests. John. asthma.net community moderator.