Your doctor will use a combination of your medical history, physical exam, and lung function tests to diagnose whether or not you have asthma.
This includes information about your symptoms, any family history of asthma or allergies, and related health conditions that may interfere with managing asthma, like a runny nose, sinus infections, reflux disease, stress, and sleep apnea.
Your doctor may physically examine you with a stethoscope to listen for abnormal breathing sounds like wheezing (a high-pitched whistling sound) and other signs of asthma. Remember—even if you don’t have these signs on the day your doctor examines you, you could still have asthma.
ASTHMA LUNG FUNCTION TESTS
Your doctor may recommend one or more tests to help determine if you have asthma. Spirometry is a lung function test that measures how much air you can breathe in and out. It also measures how fast you can blow out. You’ll start by taking a deep breath, and then blowing as hard as you can into a machine called a spirometer, which will record measurements like the amount of air you can breathe out, usually in 1 second (FEV1). If your airways are narrowed because of inflammation, or the muscles around your airways have tightened up, the results can show it.
A peak flow test is another way to measure air flowing out of your lungs. Measuring peak flow, using an instrument called a peak flow meter (PFM), can reveal an asthma attack before you feel symptoms.
Your doctor may order allergy tests to find out what kinds of things trigger your asthma; tests to measure how sensitive your airways are to exercise; testing for other conditions like rhinitis, sinus disease, or obstructive sleep apnea that could make your symptoms worse; and maybe a chest x-ray or electrocardiogram (ECG) to see if other factors like a foreign object or heart disease could be causing your symptoms.
These tests, along with lung function tests, can help your doctor determine the severity of your asthma and guide further treatment.