D Dimer Quantitative Plasma Test

D Dimer test must be taken to rule out clotting (thrombotic) episodes and to help diagnose conditions linked to thrombosis.

D-dimer testing is often recommended when someone shows symptoms of a serious condition like chest pain and breathing difficulty.

It is also ordered when someone has symptoms of deep vein thrombosis, such as:

• Leg pain or tenderness, mainly in one leg
• Leg swelling
• Discoloration of the leg

Or symptoms of pulmonary embolism such as:

• Sudden shortness of breath, laboured breathing
• Coughing, haemoptysis (presence of blood in sputum)
• Lung-related chest pain
• Rapid heart rate

When a blood vessel or tissue is injured and starts to bleed, a process called haemostasis is started by the body to create a blood clot to restrict and eventually stop the bleeding. This process produces fibrin threads which is a protein which links with the haemostasis to form a fibrin net. That net along with the platelets, helps hold the creation blood clot in place at the injury until the wound is healed.

Once the injury is healed and a clot is no longer needed, the body uses plasmin, an enzyme to break the thrombus (clot) into small pieces so that it can be removed. The pieces of the disintegrating fibrin in the clot are called fibrin degradation products (FDP), which consist of variously sized pieces of crosslinked fibrin. One of the final fibrin degradation products produced is D-dimer. The level of D-dimer in the blood can significantly rise when there is a critical formation and breakdown of fibrin clots in the body.

For a person who is at low or intermediate risk for blood clotting and/or thrombotic embolism, the strength of the D-dimer can help determine the strength of the fibrin and if needed, the person can be hospitalised.

This test is useful in the diagnosis of Disseminated intravascular coagulation and fibrinolysis (DIC), Deep Vein Thrombosis (DVT) & pulmonary embolism (PE) and also in stroke.

The test measures the levels of D-Dimer in the blood.

This test requires a blood sample. A tourniquet (elastic) band is placed tightly on the upper arm. The patient is then asked to make a fist. This helps in the build-up of blood filling the veins. The skin is disinfected before needle insertion and the blood sample is collected in vacutainer. 

Elevated D-dimer is seen in hypercoagulability, DVT (Deep Vein Thrombosis, DIC (Disseminated Intravascular Coagulation), 
recent surgery, trauma or infection.
False Positive may occur in the elderly, in liver disease, pregnancy, eclampsia, Heart disease, rheumatoid arthritis, and in some cancers, triglycerides, hemolysis,lipemia, hyperbilirubinemia etc. 
False Negative may occur in patients on anticoagulant therapy

• Fragment D-dimer test
• Fibrin degradation fragment test