Other names: Fibrin Degradation Fragment; Fragment D-Dimer

D-dimer is a fibrin degradation product. Fibrins are fine threads of protein, which are produced when bleeding occurs as part of the coagulation process. The fibrins are cross-linked and form a net, which help to hold the clot in place. Once the wound has healed, the body starts to break down the clot by using a protein known as plasmin; the pieces of the disintegrating blood clot are known as the fibrin degradation products. D-dimer is not usually present in the bloodstream; it is only released into the blood when a blood clot is being broken down.

When is the test used?

The D-dimer test is usually ordered along with a range of other tests when a patient shows signs of hypercoagulability (when the blood clots inappropriately). The most common example of this kind of condition include DVT (deep vein thrombosis), which occurs when a blood clot appears in the deep veins, most often in the legs.

The test can also be used to detect DIC (disseminated intravascular coagulation), which is an acute condition which may be caused by several illnesses, including certain forms of cancer, liver disease, burns and infections. The test can also be repeated once a patient has been diagnosed with DIC to monitor the efficacy of the treatment.

The test is usually ordered by doctors if a patient has signs of DVT, including tenderness, swelling, pain and discolouration or symptoms of PE (pulmonary embolism), including chest pain, breathing difficulties and coughing. The test is also ordered when a doctor suspects a patient may have DIC; symptoms include bruising, nausea, severe abdominal pain, muscular pain, vomiting and mucosal bleeding (this may be from the mouth, nose, bowels or bladder).

How is the test carried out?

The test is performed by analysing a sample of blood. The sample is obtained by inserting a needle into a vein in the arm (usually on the inside of the elbow); the blood is drawn out and collects in a syringe. Once the sample has been collected, it will be bottled and labelled with the patient’s name before being sent away to the laboratory for analysis.

In small children, the blood may be taken from the fingertip as this is less traumatic for the child.

What do the test results mean?

A positive results indicates that there is a high level of fibrin degradation products in the blood; this means a significant clot has occurred in the body (this may indicate DVT or DIC). Levels may also be elevated after surgery or following an accident or injury.

Levels of fibrin degradation products may also be higher during pregnancy; patients with health conditions including liver disease, heart disease and certain forms of cancer and pregnant women with eclampsia may also have higher levels of D-dimer.

In most cases, further tests will be carried out in addition to the D-dimer test.

Specific Blood Tests

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