How is a pulmonary embolism diagnosed?

On this page we explain the different tests you might have if you’re suspected to have a pulmonary embolism.

If you’re suspected to have a pulmonary embolism (PE) you should have an assessment to confirm the diagnosis.

If you’re pregnant or have given birth within the past six weeks and have symptoms of a potential pulmonary embolism, you should be assessed quickly. Any symptoms of deep vein thrombosis (DVT) or PE in a pregnant or postnatal person should be taken seriously and investigated immediately.

It can be hard for doctors to decide if you have a pulmonary embolism because the symptoms are similar to many other conditions. It’s important to have an accurate diagnosis because treating a pulmonary embolism isn’t always easy and treatments can cause side effects.

If your doctor suspects a pulmonary embolism they will assess your clinical probability with a risk score. Your risk score will give your doctor an idea how likely it is you have an pulmonary embolism. Depending on the risk score, you may have a blood test to look for a protein called D-dimer. Your doctor will discuss your symptoms and test results with the duty senior clinicians, and you may have one of the following tests:

• a computerised tomography pulmonary angiography (CTPA) to see the blood vessels in your lungs. This is when you are injected with a dye that helps to show your blood vessels. Then a scanner uses X-rays to build a detailed picture of the blood flow in your lungs.
• a ventilation-perfusion scan, also called a V/Q scan or isotope lung scanning, to examine the flow of air and blood in your lungs. You will be asked to inhale a slightly radioactive gas and given an injection of slightly radioactive material. The radioactivity in this test is considered low risk to adults, however women who are, or might be, pregnant should tell the radiographer. If the scan shows parts of your lungs have air in them but no blood supply, this may be the result of a pulmonary embolism.

If there are clinical signs of a DVT then your doctor may instead (or in addition) request a leg vein ultrasound to look at your blood as it flows through the blood vessels in your legs, to see if there are any blockages to blood flow.

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