There are many different tests that help doctors determine if a pulmonary embolism (PE) is present. The doctor's decision about which tests to use and in which order depends on the patient’s condition, their risk factors for PE, available testing options, and other conditions the patient may have.
The following tests are used to diagnose PE:
Spiral computed tomography (CT) scan or CT angiogram. Doctors use this test to look for blood clots in the lungs and legs. Dye is injected into a vein to make the blood vessels visible on X-ray image. This test allows doctors to detect PE in most patients. The test only takes a few minutes. Results are available shortly after the scan is completed.
Ventilation–perfusion lung scan (VQ scan). Doctors use this test to detect PE. The VQ scan uses a radioactive material to show how well oxygen and blood are flowing to all areas of the lungs.
Pulmonary angiography is another test used to diagnose PE. It is not available at all hospitals, and a trained specialist must perform the test.
A D-dimer test measures a substance in the blood that is released when a clot breaks up. High levels of the substance mean there may be a clot. If the test is normal and there are few risk factors for thrombosis, PE is unlikely.
Other blood tests check for inherited disorders that cause clots and measure the amount of oxygen and carbon dioxide in the blood (arterial blood gas). A PE can lower the level of oxygen in the blood.