What is it used for? These disorders include: Deep vein thrombosis DVT , a blood clot that's deep inside a vein. These clots usually affect the lower legs, but they can also happen in other parts of the body. Pulmonary embolism PE , a blockage in an artery in the lungs. It usually happens when a blood clot in another part of the body breaks loose and travels to the lungs.
DVT clots are a common cause of PE. Disseminated intravascular coagulation DIC , a condition that causes too many blood clots to form. They can form throughout the body, causing organ damage and other serious complications. DIC may be caused by traumatic injuries or certain types of infections or cancer.
Stroke , a blockage in the blood supply to the brain. Why do I need a D-dimer test? What happens during a D-dimer test? Will I need to do anything to prepare for the test? You don't need any special preparations for a D-dimer test.
Are there any risks to a D-dimer test? What do the results mean? If you have questions about your results, talk to your health care provider. People with blood clots often have one or more risk factors. These risk factors include:. Major surgery for example, hip surgery or injury for example, a broken leg. Not being able to move for long periods of time for example, from being in the hospital, or taking long trips by plane or car.
You may also need this test to help diagnose and monitor treatment for other conditions. You may need more blood tests, including platelet count, fibrinogen, and prothrombin time. If your D-dimer test is positive, you will have other tests. You may have the following imaging tests to look for blood clots:. These tests help your healthcare provider diagnose blood clots in your legs, arms, lungs, or other parts of the body.
Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. An even more accurate way to rule out VTE is to add a clinical pretest probability score to D-dimer testing. A low clinical pretest probability score plus a low D-dimer value can rule out the need for further testing with ultrasound because DVT will develop in only 0.
An elevated D-dimer level suggests persistent activation of clotting or inflammatory pathways, and extremely elevated levels may be a predictor of post-thrombotic syndrome. More recent studies suggest that the rate of recurrent VTE—whether provoked or not—is too high, even in the patients who test negative for D dimer. Future studies are needed to identify those most likely to benefit from long-term therapy without bleeding complications.
The risk for recurrence is high in patients with cancer and VTE, and anticoagulant therapy is not stopped.
After 3 months of anticoagulant therapy for VTE provoked by surgical resection of a tumor, however, D-dimer levels are measured to assist in determining the duration of anticoagulation.
Practice patterns may change in response to clinical trial data showing that the rate of recurrence is high even in those who have a negative D-dimer test result after a provoked blood clot, 7 and as researchers discover newer agents that can prevent recurrence with a lower rate of bleeding.
Patients with cancer are at high risk for VTE. Because of the poor specificity of the clinical scores and the D-dimer test, initial D-dimer testing is of limited usefulness, and these patients must undergo ultrasonography and imaging studies. Therefore, the usefulness of D-dimer testing for the inpatient evaluation of VTE is limited.
D-dimer levels also are age-dependent, and because levels increase with age, it is less common for individuals older than 60 years to have a negative D-dimer test result unless age-adjusted values are used. Assay results should always be paired with a clinical pretest probability score for outpatients presenting with signs or symptoms of VTE. This reduces the percentage of patients in whom the combination of a low pretest clinical probability score and a negative D-dimer test result is clinically useful.
Nonetheless, there are some clinical settings in which the combination may be useful. One example is the patient who presents to the emergency department with symptoms consistent with VTE and who is in remission following cancer chemotherapy. In a pregnant patient with a low pretest probability score, a negative D-dimer test result is useful to exclude VTE, especially in the first trimester. Furthermore, D-dimer testing may help to define the cause of thrombocytopenia in pregnancy.
D-dimer levels can be used to monitor the response to anticoagulant therapy. A decline in the D-dimer level provides assurance that the dose of anticoagulant being used is suppressing blood coagulation. In these algorithms, low D- dimer cut-off values are used to generate a dichotomous test result that is sensitive, but very non-specific for VTE. A consequence of any test dichotomisation is loss of information that is hidden in the continuous spectrum of results.
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