D Dimer Quantitative, Sodium Citrate Plasma

D-dimer tests are used to help rule out the thrombosis in the body. Thrombosis is formation of an inappropriate blood clot. Thrombus or the blood clot occurs when the coagulation factors in the body are activated. The coagulation pathway can be extrinsic or intrinsic, both these pathways leads to a common pathway and formation of thrombin. This thrombin in presence of factor XIII cross links the fibrin at the D fragments and results in a stable clot. This blood clot will be degraded by the fibrinolytic system. Plasmin is a fibrinolytic enzyme which cleaves the fibrin into fibrin degradation products and D-dimers. D-dimers are not seen in the blood normally. D-dimer is useful in conditions like Deep vein thrombosis (DVT), Pulmonary embolism (PE), Stroke, Disseminated Intravascular Coagulation (DIC) etc and to monitor the effectiveness of its treatment. D-Dimer helps to determine if any further investigations are needed for the diagnosis of hypercoagulability conditions, where there is tendency for inappropriate clot formation. If the D-dimer test result is negative, it helps to rule out thrombosis and if the D-dimer test result is positive, it indicates thrombosis, but doesnot rule out other causes. Hence the D-dimer test is a test that helps to exclude thromboembolic disease. The D-dimer assay involves binding of a monoclonal antibody to D-dimer fragment epitope, if present in the sample and the amount of it is estimated.

1. What are the risk factors for inappropriate blood clotting?

Major surgery, major trauma, prolonged immobilisation, hormone replacement therapy, obesity, smoking, antiphospholipid syndrome etc. are some of the risk factors for inappropriate blood clot.

2. If D-dimer test is positive, what other tests may be useful?

Venous ultrasound, CT, pulmonary angiography or ventilation-perfusion scan may be useful.

3. Mention few conditions where D-dimer levels are increased?

Deep vein thrombosis and pulmonary embolism, stroke, DIC, malignancy, trauma, surgery, pregnancy, sepsis, large hematoma etc.

4. What is the clinical use of the D-dimer assay?

D-dimer is a non specific test and it helps in excluding a thromboembolism, if the test result is negative.