Screening and diagnosis

Pulmonary embolism can be difficult to diagnose, especially in people who have underlying heart or lung disease. For that reason, your doctor will perform one or more tests to help find the cause of your symptoms. These tests may include the following:

Chest X-ray. This noninvasive test shows images of your heart and lungs on film. Although X-rays can't diagnose pulmonary embolism and may even appear normal when pulmonary embolism exists, they can rule out conditions that mimic the disease.

Lung scan. This test, also called a ventilation/perfusion scan (V/Q scan), uses small amounts of radioactive tracers (radioisotopes) to study airflow (ventilation) and blood flow (perfusion) in your lungs. The radioisotopes are attached to substances known as radiopharmaceuticals. In the first part of the test you inhale a small amount of radiopharmaceutical while a camera that's able to detect radioactive substances takes pictures of the movement of air in your lungs. A small amount of a different radiopharmaceutical is then injected into a vein in your arm and pictures are taken of blood flow in the blood vessels of your lungs. Comparing the results of the two studies helps provide a more accurate diagnosis of pulmonary embolism than does either study alone. The entire procedure usually takes less than an hour. Although you're exposed to radioactive material, the amount of radioactivity is small. Still, the findings of about half of all lung scans are indeterminate, requiring other tests to confirm a diagnosis of VTE. Furthermore, although a "normal" lung scan can rule out the possibility of pulmonary embolism, it doesn't rule out deep vein thrombosis (DVT) — the cause of pulmonary embolism. For these reasons, lung scans are being replaced by more sensitive and rapid tests, such as spiral computerized tomography (CT) scans.