How is Asthma Diagnosed?

Sometimes asthma can be tricky to diagnose. One can have asthma like symptoms and wonder if they indeed have asthma. There are two main tests used to diagnose asthma. Lung function testing such as spirometry, and a methacholine challenge test. The most common test is Spirometry.

When asthma is suspected, generally your primary care doctor will refer you to either an asthma specialist or a Pulmonologist for adequate testing and diagnosis. Once there, the doctor will ask you all kinds of questions pertaining to your medical history and family medical history. Often times asthma seems to have a genetic component. But not always. He or she will perform a physical exam which involves listening to your lungs, looking in your throat & in your nose. He will ask about your symptoms and how long you've had them, what exactly your symptoms are and if you can pinpoint any triggers that make your symptoms worse. In many asthmatics, symptoms seem to get worse at night.

After the initial medical history and exam, he will more than likely have you perform a spirometry test. Many people are nervous about this test, but truth be told it's a quite simple test. You'll be asked to stand (unless you are unable, in which case the test can be done while sitting down). You will be given nose clips to prevent air escaping through your nose. You will be instructed to seal your lips around a plastic tube and breathe normally through your mouth. When instructed you'll take as deep of a breath in as you can and then blow out as hard & as fast as you can until you can't get any more air out and then take another deep breath in as far as you can before removing the mouthpiece. Often times, you'll be looking at a computer screen with candles and the idea is to blow out as many candles on the screen as you can and as quickly as you are able. What this test measures is the forced expiratory volume in the first second (FEV1).

With asthmatics, this number can be lower than normal, although sometimes this number can be completely normal when not having an asthma flare up. You will then be given usually two puffs of a rescue inhaler (such as albuterol) and repeat the test. If the number increases from before the inhaler, the asthma diagnosis is confirmed in most cases. If the spirometry test is inconclusive and doesn't show a typical asthma pattern, another test called the Methacholine Challenge can be given. During this test you are given increasing doses of inhaled methacholine which will cause asthma like symptoms in asthmatics. You will be only given very small amount of the methacholine at a time and in between each inhalation, perform a spirometry test. If at any time, your FEV1 drops 20% or more the test is stopped and the asthma diagnosis is confirmed. You may or may not experience shortness of breath and chest tightening, which is reversed by taking your rescue inhaler. This is done in a controlled environment and you are monitored the entire time. The purpose of this test is not to induce a large scale asthma attack, but to more definitively diagnose asthma if the diagnosis is in question. If you do not have any asthma symptoms at all during the test and your FEV1 remains unchanged, it's possible that you have something other than asthma going on.

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