D-Dimer, Quantitative

D-Dimer is one of the by-products that can be measured after the fibrinolytic system is turned on. Fibrinolytic activation and intravascular thrombosis can be measured by the amount of D-Dimer in the blood. D-Dimer is especially helpful when ruling out venous thromboembolism in people who are at high risk.

When is the D-Dimer Test Used?

When there is a suspicion of deep venous thrombosis (DVTl), pulmonary embolism (PE), or disseminated intravascular coagulation, D-dimer testing is used in clinics.

There are numerous scoring systems that can be used to assess the a priori clinical probability of DVT and PE; the most well-known is the Wells score.

A D-dimer will make little difference for a high score, or pretest probability, and anticoagulant therapy will be commenced regardless of test findings, and additional testing for DVT or pulmonary embolism may be conducted.

What Does a Negative D-Dimer Test Mean?

A negative D-dimer test will virtually rule out thromboembolism for a moderate or low score, or pretest probability: the degree to which the D-dimer reduces the probability of thrombotic disease is dependent on the test properties of the specific test used in the clinical setting: most available D-dimer tests with a negative result will reduce the probability of thromboembolic disease to less than 1% if the pretest probability is less than 15-20%. When a D-dimer assay results in a negative result, chest computed tomography (CT angiography) should not be used to evaluate pulmonary embolism. A low pretest probability is also useful in excluding PE.

If the D-dimer level is elevated, further testing (ultrasound of the leg veins, lung scintigraphy, or CT scanning) is needed to confirm the presence of a thrombus. Depending on the clinical circumstances, anticoagulant medication may be started at this point or delayed until further testing confirm the diagnosis.

They are measured in some hospitals by laboratories after a form with the probability score is completed, and only if the probability score is low or intermediate. This lowers the need for needless tests in people with a high likelihood. By performing the D-dimer test first, you can avoid many imaging tests and be less invasive. Because the D-dimer can rule out the necessity for imaging, speciality professional organizations advise physicians to employ D-dimer testing as an initial diagnostic tool.