COPD is commonly misdiagnosed — former smokers may sometimes be told they have COPD, when in reality they may have simple deconditioning or another less common lung condition. Likewise, many people who have COPD may not be diagnosed until the disease is advanced and interventions are less effective.
To diagnose your condition, your doctor will review your signs and symptoms, discuss your family and medical history, and discuss any exposure you've had to lung irritants — especially cigarette smoke. Your doctor may order several tests to diagnose your condition.
Tests may include:
Lung (pulmonary) function tests. Pulmonary function tests measure the amount of air you can inhale and exhale, and if your lungs are delivering enough oxygen to your blood.
Spirometry is the most common lung function test. During this test, you'll be asked to blow into a large tube connected to a small machine called a spirometer. This machine measures how much air your lungs can hold and how fast you can blow the air out of your lungs.
Spirometry can detect COPD even before you have symptoms of the disease. It can also be used to track the progression of disease and to monitor how well treatment is working. Spirometry often includes measurement of the effect of bronchodilator administration. Other lung function tests include measurement of lung volumes, diffusing capacity and pulse oximetry.
- Chest X-ray. A chest X-ray can show emphysema, one of the main causes of COPD. An X-ray can also rule out other lung problems or heart failure.
- CT scan. A CT scan of your lungs can help detect emphysema and help determine if you might benefit from surgery for COPD. CT scans can also be used to screen for lung cancer.
- Arterial blood gas analysis. This blood test measures how well your lungs are bringing oxygen into your blood and removing carbon dioxide.
- Laboratory tests. Laboratory tests aren't used to diagnose COPD, but they may be used to determine the cause of your symptoms or rule out other conditions. For example, laboratory tests may be used to determine if you have the genetic disorder alpha-1-antitrypsin (AAt) deficiency, which may be the cause of some cases of COPD. This test may be done if you have a family history of COPD and develop COPD at a young age, such as under age 45.