Along with your medical and family history and the results of your physical examination, certain tests will help your doctor determine if you have asthma. Your doctor may:

  • Evaluate your breathing and lung function
  • Check for any allergies
  • Check for other disorders that could cause asthma symptoms or trigger asthma attacks

Tests and Evaluations to Help Diagnose Asthma

Spirometry

This test is done to assess how well your lungs work, determine the extent of airway obstruction and measure lung capacity. Using a mouthpiece, you breathe into a spirometer (a device that measures airflow), which tests how much air you can breathe in and out over a set amount of time, and how fast. You may breathe in only air, a gas like nitrogen or helium or a medicine to show its effect on your lungs.

Methacholine Challenge Test

This test is done to help confirm or rule out an asthma diagnosis if spirometry results are unclear. It evaluates your ability to expel air quickly from your lungs. You fully inhale increasing doses of methacholine (an airway-narrowing agent), then expel your breath as quickly as possible. Spirometry is done before and after each dose to compare results. At the end of the test, medication is given to reverse methacholine’s effects.

Peak Flow Meter Monitoring

This test is done to assess your asthma severity and monitor your treatment’s effectiveness. While standing, you take a deep breath and breathe into the meter as hard and fast as you can.

Challenge Test for Exercise and Cold Air

This test is done to determine the effect of exercise and cold air on your airflow. Your airflow is measured by spirometry before and after you exercise on a stationary bike or treadmill or take several breaths of cold air. For most people with asthma, airflow is reduced during or after they exercise or inhale cold air.

Sputum Testing

This test looks for a type of white blood cell that appears in the sputum of people with asthma. You will be asked to cough to produce the sputum sample.

Blood or Skin Tests for Allergy

You may be sent to an allergist for specific allergy testing if your doctor thinks you have allergic asthma.

Testing to for Other Disorders

Other health conditions can cause symptoms that mimic asthma, or they may trigger asthma symptoms. Testing may include imaging studies of your lungs and sinuses, and tests, such as endoscopy or X-ray, to look for conditions such as sleep apnea or gastroesophageal reflux disease.