What are the causes of d-dimer being high?
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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.
Pulmonary angiogram. This test provides a clear picture of the blood flow in the arteries of your lungs. It's an accurate way to diagnose pulmonary embolism, but because it requires a high degree of skill to administer and carries potentially serious risks, it's usually performed when other tests fail to provide a definitive diagnosis. In a pulmonary angiogram, a flexible tube (catheter) is inserted into a large vein — usually in your groin — and threaded through your heart into the pulmonary arteries. A special dye is then injected into the catheter, and X-rays are taken as the dye travels along the arteries in your lungs. A risk of this procedure is a temporary change in your heart rhythm. In addition, the dye may cause kidney damage in people with decreased kidney function (renal insufficiency). Although the damage is usually temporary, it occasionally may become permanent. There is also the risk of developing a hematoma — a bruise that occurs when blood collects under the skin at the puncture site in your groin.
Spiral (helical) computerized tomography (CT) scan. A CT scan allows your doctor to see your organs in two-dimensional "slices." Split-second computer processing creates these images as a series of very thin X-ray beams pass through your body. A dye (contrast medium) is commonly used to help visualize the area. Now, a newer type of CT scan, called a spiral or helical CT, is fast becoming the first-line test for diagnosing suspected pulmonary embolism. A spiral CT differs from conventional computerized tomography in several ways: The scanner rotates continuously around your body, following a spiral path to create three-dimensional images; it can detect abnormalities with a greater degree of accuracy, and it's faster, scanning your pulmonary arteries in less than 20 seconds as opposed to 20 minutes or more for a standard CT. Speed is important because it allows the dye to be "captured" while still in your arteries. Spiral CT is nearly as sensitive in detecting most cases of pulmonary embolism as a pulmonary angiogram and much more sensitive than a lung scan. A spiral CT exposes you to more radiation than a standard X-ray does, as well as to the risk of an allergic reaction to the contrast medium.
Tests to detect blood clots
In addition to tests that check for pulmonary embolism, you may also have tests that help detect blood clots in your veins, such as:
D-dimer blood test. Having high levels of the clot-dissolving substance D dimer in your blood may indicate an increased likelihood of blood clots, although D-dimer levels may be elevated by other factors, including recent surgery. Drawing the blood takes just a few minutes, and the risks — which include slight bleeding or a small accumulation of blood at the puncture site — are minor. The results are available in less than an hour. Normal test results are actually much more meaningful than abnormal ones. That's because many conditions other than blood clots can cause elevated D-dimer levels, while a normal result usually rules out the possibility of VTE.
Ultrasound. A noninvasive "sonar" test known as duplex venous ultrasonography (sometimes called duplex scan or compression ultrasonography) uses high-frequency sound waves to check for blood clots in your thigh veins. In this test, your doctor uses a wand-shaped device called a transducer to direct the sound waves to the veins being tested. These waves are then reflected back to the transducer and translated into a moving image by a computer. The test is quick and painless, but it's not very useful for detecting clots below the knee. If your doctor suspects that you have deep vein thrombosis below the knee, but you have no signs or symptoms and your D-dimer test is normal, you may have another ultrasound of the upper thigh in two or three days. If the repeat test reveals a clot, your doctor will start therapy right away.
Venography. A more complex and invasive procedure called venography can help reveal blockages caused by blood clots at any point in your arms or legs. During the test, a catheter is inserted into a vein in your foot or ankle. Because blood vessels aren't normally seen on X-rays, a contrast dye is injected into the vein to make it visible just before the X-rays are taken. Although venography generally takes less than an hour, you'll need to keep your leg straight for six hours after the procedure. There are some risks, including an allergic reaction to the dye and a chance that the catheter may damage blood vessels or dislodge part of a clot. Although venography can accurately detect DVT, it's been replaced in large part by duplex ultrasonography.
Magnetic resonance imaging (MRI). This test uses no X-rays. Instead, a computer creates tissue "slices" from data generated by a powerful magnetic field and radio waves. Because MRI is expensive, it's usually reserved for pregnant women and people whose kidneys may be harmed by dyes used in other tests.
Blood tests. If you have a family history of blood clots, have had more than one episode of blood clots or have experienced clots for no known reason, your doctor may order a series of blood tests to look for inherited defects in your clotting system. If genetic abnormalities are found and you have a history of blood clots, your doctor may recommend lifelong therapy with anticoagulants to prevent future clotting problems.
D-Dimer is your clotting factor. It could be high because you have had a recent surgery or your body is trying to heal from a major disruption. Your doctor would tell you if it is high enough for concern. If you are a female on birth control or if you smoke and you have an increased d dimer than it could indicate a clot.
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