Summary

This test measures D-dimer in the blood. D-dimer tests are ordered along with other lab tests and imaging scans to help rule out, diagnose, and monitor a range of blood clotting conditions. It is a quick test to do and is often used as a first-line test to rule out clotting conditions – D-dimer is especially useful when your doctor thinks that something other than a major blood clot is causing your symptoms. If you have a positive D-dimer test result you will need other tests to find out the cause. If you have a negative result, it is unlikely that you have abnormal blood clotting.

Why get tested?

D-dimer is part of one of the proteins found in your blood when a blood clot is dissolved. It is normally undetectable and only seen when a clot is breaking down. 

Clotting is a normal part of healing. When you have an injury and it starts to bleed, your body triggers a sequence of clotting steps to create a blood clot and plug the hole. To do this, threads of a protein called fibrin are produced. 

These threads are glued together to form a fibrin net that catches platelets and helps hold the blood clot together. Once the area has healed, the clot breaks down into small pieces so that it can be disposed of. The fragments of the fibrin in the clot are called fibrin degradation products (FDP). One of these FDPs is D-dimer.

Different types of blood clots 
Measuring D-dimer in the blood is a quick, non-invasive way to help rule out clotting, especially if you are considered to be at low risk. It is usually ordered when you have symptoms of a disease or condition that causes acute and/or chronic inappropriate blood clot formation such as: DVT (deep vein thrombosis), PE (pulmonary embolism), or DIC (disseminated intravascular coagulation).

DVT (deep vein thrombosis) is clotting that occurs in the deep veins of the body, mostly in the legs. These clots can block blood flow and it’s possible for a piece to break off and travel, causing a blood clot in the lungs, called a pulmonary embolus (PE).

PE (pulmonary embolism) This is a blood clot that blocks and stops blood flow to an artery in the lung. Clots in arteries leading to the heart are the major cause of heart attacks. They can also form on the lining of the heart or its valves, especially when the heart is beating irregularly (atrial fibrillation) or when the valves are damaged. Clots can also form as a result of hardening of the arteries. Pieces can break off and cause a blockage in an artery in the brain (causing a stroke) or the kidneys.

DIC (disseminated intravascular coagulation) is a condition in which many tiny blood clots form inside blood vessels. It can be caused by an infection, inflammation or injury that makes the body’s normal blood clotting processes become overactive. This uses up all the blood’s clotting factors which can lead to severe, life-threatening bleeding. It can occur as a result of a surgical procedure, septic shock, severe immune reaction, cancer, liver disease, heat stroke, pregnancy complications and birth, and poisonous snake bites.

Having the test

Sample
Blood 

Test preparation?
None

Your results

Reading your test report

Your results will be presented along with those of your other tests on the same form.  You will see separate columns or lines for each of these tests.

D-dimer results may be given as positive or negative depending on where they sit against a pre-determined cut-off threshold, or they may be expressed as a number.

D-dimer is recommended as an additional test. In other words, it should not be the only test used. Both positive (increased) and negative (normal) D-dimer levels may require follow-up and can lead to further testing.

A positive D-dimer indicates the presence of an abnormally high level of fibrin degradation products in your body. It tells your doctor that there has been significant clot formation and breakdown in the body, but it does not tell the location or cause.

An elevated D-dimer may be due to a venous thromboembolism (VTE) or DIC but it may also be due to a recent surgery, trauma or infection. Elevated levels are also seen with liver disease, pregnancy, eclampsia, heart disease, and some cancers.

If you have a positive result, more than likely your doctor will order a non-invasive scanning procedure, such as a venous ultrasound. Even if you have a blood clotting disorder, you will probably only need treatment when a blood clot develops. Anticoagulant drugs help prevent additional clots because they decrease the blood’s ability to coagulate.

Most doctors agree that a negative D-dimer is most valid and useful when the test is done on people who are considered to be low-risk. The test is used to help rule out clotting as the cause for the symptoms.
 

Any more to know?

Anticoagulant therapy can cause a false negative D-dimer. 

There are several different methods of testing for D-dimer. Most of the D-dimer tests that yield quantitative (the amount of D-dimer) results are done in a hospital laboratory, while those that yield qualitative (positive or negative) results are performed at the patient’s bedside. 

D-dimer concentrations may rise in the elderly, and false positives may be seen with high levels of rheumatoid factor (a protein seen in patients with rheumatoid arthritis). 

Substances such as high triglycerides, lipaemia (a large amount of fats in the blood that can be caused by the patient consuming a greasy meal prior to testing), and bilirubin can also cause false positives as can haemolysis caused by improper sample collection and handling.
 

More information

Pathology and diagnostic imaging reports can be added to your My Health Record. You and your healthcare provider can now access your results whenever and wherever needed.

Get further trustworthy health information and advice from healthdirect.