Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory lung disease mainly caused by long-term exposure to certain irritants, including cigarette smoke, chemical fumes, dust, and air pollutants. In rare cases, the disease may also be triggered by a genetic disorder called alpha-1-antitrypsin (AAT) deficiency.
COPD is not always clinically evident, and some patients may be initially misdiagnosed. In general, the diagnosis of COPD requires physicians to assess a patient’s medical and family history, and to evaluate their symptoms. Tests that include assessments of lung function are typically required.
Clinical and family history
A physician may ask for a patient’s complete medical and family history, to verify if a close relative had this disease and to determine possible exposure to lung irritants, including cigarette smoke. Symptoms are also evaluated at this point.
Family history of COPD is seen to be a key risk factor for the disease, regardless of personal smoking habits, family history of smoking, or exposure to tobacco smoke during childhood.
Lung function tests
The main test for COPD is spirometry, a painless test in which a machine (spirometer) measures how much air a person can breathe in and out, as well as the speed of breathing. One of its main advantages is that it can detect signs of COPD before symptoms are evident. In addition, it may also be used to monitor and track disease progression.
Spirometry can also be used to measure respiratory volumes, or the total volume of air in the lungs at a given time while a person is breathing.
Other lung function tests include measures of diffusing capacity. This test measures how well a gas in the air that is breathed in can cross from the alveoli — the small sacs involved in lung gas exchange — to the bloodstream.
The six-minute walk test may be also used to assess a person’s overall fitness, and the healthiness of their heart and lungs. This exercise capacity test measures the distance a person can walk on a flat surface in six minutes.
Another test used to help assess lung function is pulse oximetry. This painless test uses a pin-like device that is attached to a patient’s finger to measure oxygen saturation, or oxygen levels, in the blood.
Arterial blood gas test
This test uses a blood sample drawn from an artery to measure blood oxygen levels. These levels indicate how well the lungs are transferring oxygen into the bloodstream, and how well carbon dioxide (a waste gas) is being removed. This type of test can also be used to measure blood’s pH and determine how acidic it is.
Results can help to determine the severity of COPD and whether a patient may require oxygen therapy, or supplemental oxygen provided through nasal prongs, a mask, or a breathing tube.
Chest X-ray and chest CT scans
Both are imaging tests that physicians can use to examine the interior of a patient’s chest. They are used to diagnose COPD, or to determine whether another condition (e.g., asthma or heart failure) may be causing a person’s symptoms.
For a chest X-ray, the patient is asked to stand in front of an X-ray machine, and take and hold a deep breath. Chest X-rays are often used to detect the presence of fluid inside or around the lungs.
For a chest computed tomography (CT) scan, a patient is told to lie still on a table that will slide into the scanner. The machine takes several detailed pictures, which a computer then combines to create a 3-D image. Sometimes patients are injected with a contrast dye before having this test, to highlight certain areas inside the chest. This procedure can help to detect COPD and to determine if patients might benefit from surgery.
Blood tests are not used to diagnose COPD, but rather to exclude other conditions that can cause similar symptoms.
These tests can be performed to determine, for example, if a patient has AAT deficiency, which is characterized by low levels of the AAT protein in the blood. AAT is normally produced in the liver and helps to protect lungs from damage. In AAT deficiency, the protein is defective or fails to reach the lungs. This lung disorder that shares many symptoms with COPD and may, in rare cases, trigger its onset.
Additional tests may be used to confirm the diagnosis of COPD, determine its severity, and help define a future course of treatment.
These include heart tests, such as an electrocardiogram (ECG, a painless test that measures heart’s electrical activity) and an echocardiogram (a test that uses sound waves to create pictures the heart).
A mucus sample may also be analyzed to look for signs of respiratory infections, as these are known to be involved in the chronic airway inflammation that leads to COPD progression.
Last updated: May 7, 2021
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