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No accurate blood test is available to diagnose deep vein thrombosis. A variety of imaging tests are used to confirm the diagnosis.
- Doppler ultrasound: Using high-frequency sound waves, this system can visualize the large, proximal veins and detect a clot if one is present. Painless and without complications, this is the most commonly used method to diagnose deep vein thrombosis. However, sometimes the test can miss a clot, especially in the smaller veins.
- Venography: A liquid dye is injected into the veins for imaging studies. It highlights blockage of blood flow by a clot. This is the most accurate test, but also the most uncomfortable and invasive. It is rarely done today because of the availability of improved ultrasound technology.
- Impedance plethysmography: Electrodes are used to measure volume changes within veins. Because this test does not detect clots better than ultrasound and is harder to perform, it is rarely used.
- CT scan: This is a type of X-ray that gives a very detailed look at the leg veins in cross section and can detect clots. It is rarely used for this purpose as it is more difficult to interpret and is time consuming. The CT scan is more useful for identification of blood clots in the lung.
For more information, read our full medical article on deep vein thrombosis.
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Centers for Disease Control and Prevention. Venous Thromboembolism. (Blood Clots).
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