Because OLD is an umbrella term covering several different conditions such as asthma or COPD, your doctor will diagnose one of these conditions instead of diagnosing OLD. OLD is diagnosed based on your signs and symptoms, as well as your medical history, family history, and test results. Your doctor will likely ask whether you smoke and whether you have had contact with lung irritants like air pollution, dust, secondhand smoke, or chemical fumes. Your doctor will use a stethoscope to listen for wheezing or other abnormal sounds in your chest. Depending on which type of OLD your doctor suspects, they may order tests to diagnose the different types of OLD:
- Lung function tests: measure how much air you can breathe in and out, how fast you can breathe out, and how well your lungs deliver oxygen to the blood. The most common lung function test is called spirometry and measures how much air you can breathe out after taking a deep breath and how fast you can expel the air. Lung function tests can be used to diagnose asthma or COPD.
- X-ray or computed tomography (CT) scan: scans that provide images of the lungs. Doctors can visually inspect these images for signs of COPD. These tests may also help your doctor to diagnose asthma. CT scans are very important for the diagnosis of bronchiectasis.
- Arterial blood gas test: a simple blood test that allows a doctor to determine how much oxygen and carbon dioxide is in your blood. These tests are more common in those with severe OLD.
- Genetic tests: a sample of DNA is extracted from blood or tissue and can be examined to determine whether the defect on the gene that causes cystic fibrosis is present.
- Sweat test: a chemical that causes the body to produce sweat is applied to the skin. The sweat is collected and tested to determine if it is saltier than normal. This test is used in diagnosing cystic fibrosis.