Doctors use several tests to diagnose chronic obstructive pulmonary disease (COPD):
Lung function tests
In a spirometry test, your doctor will place a clip on your nose and ask you to blow into a tube that's connected to a machine called a spirometer. The test measures how much air you breathe out, as well as how fast you exhale. This test may be used before COPD symptoms even develop, and can also track the progression of the disease. Often, the doctor will have you inhale medicine and try the test again to determine whether it improved results.
A chest x-ray rules out other conditions are causing your symptoms, such as heart failure. An x-ray also can reveal emphysema, one of the causes of COPD.
A CT scan of the lungs will also show signs of COPD, and can also be used to diagnose lung cancer.
An arterial blood gas test measures how well the lungs are bringing oxygen to the blood and removing carbon dioxide. Test results show how severe your COPD is, and whether you may benefit from oxygen therapy.
There are no other lab tests that can diagnose COPD, but your doctor may run them anyway to rule out other conditions that have symptoms similar to COPD.