D-Dimer Test

Overview

The D-dimer blood test can be used to rule out serious blood clots.

Your body takes many steps to make your blood clot after you have received a cut. This is a normal part of healing. Without it, you would have to keep bleeding and face a more serious problem.

The clot is no longer necessary once the bleeding stops. Your body then takes a series of steps in the opposite direction to break down the clot.

You will still have leftover substances in your blood. D-dimer is one of these leftovers. It is part of the protein. It usually disappears in a few days. However, you may have high levels of D-Dimer in your blood if there is a major clot such as deep vein thrombosis (DVT).

DVT is a condition where a clot forms in your veins. This can be found in your legs and cause serious complications.

This test is used by your doctor to determine if you have a blood clot.
This test may also be called:

• Fragment D-dimer test
• Fibrin degradation fragment test

D-dimer tests are blood tests that measure D-dimer. This is the protein fragment your body produces when a blood clot breaks down in your body. D-dimer can be detected at very low levels or is usually not detectable unless you are forming and breaking down large blood clots.

Although a positive or elevated D2-dimer test result could indicate you have a clotting condition it does not guarantee you have one. The D-dimer test cannot tell you what kind of clotting disorder you have, or where the clot is situated in your body.

How does blood clotting function?

When blood clotting is working for its intended purpose or normal function, it is an essential process that protects you from bleeding too often when you are injured. Your body creates a blood clot when a blood vessel or tissue is damaged and starts bleeding. This helps to reduce blood loss and ultimately stop bleeding.

Your body creates fibrin nets by weaving together threads of fibrin protein during hemostasis. The net along with a type of cell called a platelet helps to anchor the blood clot until it heals. These blood clots can appear as scabs or bruises underneath your skin.

After your injury is healed, and the blood clot has been removed from your body, your body will make an enzyme called Plasmin to break it down into smaller fibrin pieces. These fibrin fragments are called fibrin degradation products or fibrin split products. D-dimer is one such fibrin degradation product.

A blood-clotting condition may cause blood clots to form even if you don’t have any injuries. Your body’s blood clotting process may not be working properly. A blood-clotting condition can pose serious health and safety risks.

A high level of D-dimer in your blood could indicate a blood-clotting disorder. This is because D-dimer levels can increase when blood clots are formed or broken down.

Also Read: What is Prothrombin Time & International Normalized Ratio (PT-INR) Test?

Why Test Is Done?

To determine if you have a blood-clotting disorder, a D-dimer test can be used. These conditions include:

• Deep Vein Thrombosis (DVT) is a blood clot found deep within a vein. These clots are most common in the lower legs but can also occur elsewhere.
• A blockage in an artery of the lungs is known as Pulmonary Embolism (PE). This happens when blood clots in other parts of the body break loose and travel to the lungs. DVT clots can be a common cause for 
• A condition where too many blood clots form, is called Disseminated Intra-vascular Coagulation (DIC). They can cause organ damage and other serious complications. DIC can be caused by trauma, certain infections, or cancer.
• A stroke is a blockage of blood supply to the brain.

When To Get Tested?

This test may be required if you have signs of a blood-clotting disorder such as deep vein embolism (DVT), or pulmonary embolisms (PE).

DVT symptoms include:

• Tenderness or pain in the legs
• Leg swelling
• Redness on the legs or red streaks

The following symptoms are indicative of PE:

• Trouble breathing
• Cough
• Chest pain
• Rapid heartbeat

This test is usually done in an emergency department or another health care setting. If you experience DVT symptoms but are not in a medical setting, contact your doctor.

How To Get Tested?

A phlebotomist is a healthcare provider who draws blood. However, any healthcare provider with a background in blood drawing can do this job. The provider will then send the samples to a laboratory where a medical lab scientist prepares them and performs the tests using machines called analyzers.

Also Read: Know Everything About a Blood Test 

Before the Test

You don’t need any special preparations for a D-dimer test.

During the Test

The following procedure is carried out during the D-dimer test:

• A healthcare provider will examine your arms and check for veins. It is located on the inside of your arm, usually to the side of your elbow.
• Once they have located the vein, they will clean it and disinfect it.
• The doctor will then insert a tiny needle into your vein to collect a sample of blood. It may feel like a tiny pinch.
• A small amount of blood will be collected in a tube after the needle is inserted.
• Once they have sufficient blood for testing, they will remove the needle from the site and place a gauze or cotton ball on the area to stop bleeding.
• The bandage will be placed over the area and you’ll be done.

The whole process takes about five minutes.

After The Test

Once your blood sample has been collected by a healthcare provider, it will be sent to a laboratory for testing. Your healthcare provider will share your results once the test results have been returned.

Medical testing is a common and important part of the medical process. Blood tests are very safe. The site of your blood draw may cause slight tenderness or bruises, but these usually disappear quickly.

Test Results

There are many ways to test your blood for D-dimer levels. There is no universal standard. The lab results will indicate if your D–dimer level has changed.

Your lab tests will show that your D-dimer levels are normal, low, or negative in your blood. This means that you don’t likely have a clotting disorder.

You are likely to be receiving treatment for Disseminated Intravascular Coagulation (DIC).

Interpreting Results

Normal Results

Normal tests are negative. This indicates that there is no problem with blood clotting.

A normal or decreasing level means that treatment for DIC is working.

What Are Abnormal Results?

Positive results could indicate that your blood is clotting. This test cannot tell you where or why your clots are occurring. To determine the location of clots, your provider might order additional tests.

You may have clots, but a positive test could be due to other factors. Positive D-dimer levels may be due to:

• Pregnancy
• Liver disease
• Recent surgery or trauma
• High levels of triglyceride or lipids
• Heart disease
• Over 80 years of age

The test is most useful when it is negative. This means that many of the causes above can be ruled.

What To Do in Case of High Levels?

Your blood tests may reveal higher than normal levels of D-dimer. This could indicate that you have a blood-clotting condition. The D-dimer test cannot determine the type or location of your blood clots.

A high level of D2-dimer in the blood indicates that you are not receiving effective treatment for Disseminated Intravascular Coagulation (DIC).

You can have high levels of D-dimer without having a blood condition. You may also experience higher levels of D-dimer in certain situations and conditions.

• Pregnancy
• Heart disease
• Recent surgery
• Trauma
• Infection

Also, D-dimer levels tend to increase in older people. False-positive results can occur if you have Rheumatoid Arthritis.

Your healthcare provider may order additional tests or imaging to confirm a diagnosis if your results indicate abnormal D-dimer levels.

Also Read: Top 9 Annual Blood Tests to Keep You Healthy and Active

What next?

Your healthcare provider may order you to undergo imaging tests if your D-dimer test results are abnormal. This will allow you to determine if you have a blood condition called blood clotting and the location of your blood clots. These imaging tests are:

• Doppler ultrasound – This imaging test uses sound waves and creates images of your veins.
• Computed Tomography (CT) angiography: A healthcare provider injects a special dye into one of your veins to perform this imaging test. This allows your blood vessels to be visible on an X-ray machine.
• Lung ventilation-perfusion (V/Q) scan: A lung VQ scan is an imaging test that uses a ventilation (V) scan to measure airflow in your lungs and a perfusion (Q) scan to see where blood flows in your lungs. Both scans use safe and small amounts of radioactive substances that allow a scanner to see the movement of blood and air through your lungs.

Final Takeaway

If doctors think you may have a blood clot, they might order a D–dimer test. Two conditions that could prove fatal are deep vein thrombosis (a blood clot within a vein) and pulmonary embolism (a blood clot inside the lungs).

If your test results are negative, it means that you don’t have blood clots. You won’t usually need to undergo any additional tests. But, even if you get high results, it doesn’t mean that you have a tumor. However, the test is not definitive. Most likely, your doctor will order additional tests.

FAQs

Sources

• Lab Tests Online: “D-dimer,” “Disseminated Intravascular Coagulation,” “Tips on Blood Testing.”
  https://labtestsonline.org.uk/tests/d-dimer
• University of Rochester Medical Center: “D-Dimer.”
  https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid=d_dimer

• U.S. National Library of Medicine: “D-Dimer Test”
  https://medlineplus.gov/lab-tests/d-dimer-test/