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Asthma in Teens and Adults - Exams and Tests

A diagnosis of asthma is based on your medical history, a physical exam, and lung function tests.

Lung function tests

Lung function tests can diagnose asthma, show how severe it is, and check for complications.

  • Spirometry is the most common test to diagnose asthma. It measures how quickly you can move air in and out of the lungs and how much is moved.
  • Testing of daytime changes in peak expiratory flow (PEF) may be done over 1 to 2 weeks. This test is needed when you have symptoms off and on but have normal spirometry test results.
  • An exercise or inhalation challenge may be used if the spirometry test results have been normal or near normal but asthma is still suspected. These tests measure how quickly you can breathe in and out after exercise or after using a medicine. An inhalation challenge also may be done using a specific irritant or allergen if your doctor suspects occupational asthma.

Tests for other diseases

Asthma can be hard to diagnose because the symptoms vary widely. And asthma-like symptoms can also be caused by other conditions, such as a viral lung infection or a vocal cord problem. So your doctor may want to do one or more extra tests.

  • More lung function tests may be needed if your doctor suspects another lung disease, such as COPD.
  • An electrocardiogram (EKG, ECG) might be done to rule out serious conditions with similar symptoms, such as chronic heart failure. This test measures the electrical signals that control the rhythm of your heartbeat.
  • A bronchoscopy test can be done to examine the airways for problems such as tumors or foreign bodies. This test uses a long, thin, lighted tube to look at your airways.
  • Biopsies of the airways can be done to look for changes that point to asthma.
  • A chest X-ray may be used to look for signs of other lung diseases, such as fibrous tissue caused by chronic inflammation (pulmonary fibrosis).
  • Blood tests, such as a complete blood count (CBC), may be done to look for signs of an infection or other condition.
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