A diagnosis of chronic obstructive pulmonary disease (COPD) starts with a history of your symptoms. For example, a nagging cough in a smoker, gradual worsening of fatigue, or breathlessness with activity can steer a health-care provider toward the diagnosis.

A physical exam is performed to look for the causes of these symptoms and direct further testing. A combination of tests is used to rule out other problems, such as heart disease or infection.

Once a diagnosis of COPD is confirmed, a chest X-ray, chest computed tomography (CT, or CAT) scanning and lung function tests can help define the degree of lung damage.

Your health-care provider will ask about your cough and shortness of breath and will ask how long you have had any symptoms and any signs of infection, such as fever and sweats. He or she will ask if you have any chest pain, leg swelling or other heart-related symptoms and about your personal and family medical history.

Your health-care provider will particularly want to know whether you smoke, how much and for how long. In general, people who have smoked more than 20 cigarettes a day (one pack) for more than 20 years usually develop smoker's cough by their late 40s or early 50s. Such people may not complain of shortness of breath until they are in their 50s or 60s.

During the physical examination, your health-care provider will use a stethoscope to listen for signs of lung and heart problems, such as wheezing and other abnormal breath sounds and heart sounds.

Images of the lungs and blood vessels obtained with chest X-rays or computed tomography (CT, or CAT) scans can help rule out other causes of your symptoms, such as pneumonia, lung cancer, blood clots in the lung and tuberculosis. Although a diagnosis of COPD cannot be based on lung imaging, your health-care provider may suspect COPD based on the appearance of these images. The bronchial tubes may appear thickened, and the lungs may look larger than normal. You can see large air sacs or "bullae," which are large empty spaces formed by fused air sacs. Lung imaging also gives a rough estimate of the neighboring heart's size and shape.

Spirometry (also called pulmonary function testing) is an important test of lung function that is used to diagnose COPD, assess its severity and follow its progress. A spirometry machine includes a large tube through which you breathe. Spirometry is also used to test for asthma and other lung diseases.