What Is D-Dimer Test? When Is This Test Done? Test Results, Role Of D-Dimer Test In Covid -19

What Is D-Dimer Test? When Is This Test Done? Test Results, Role Of D-Dimer Test In Covid -19

D-Dimer test is carried out to look for a substance called D-Dimer, which rules out a blood clot.

When blood clot slowly breaks down, a protein fragment called D-Dimer is formed, which is then released into the blood. This helps to rule out thrombosis or blood clotting.

D-Dimer test is also called as :
  • Fragment D-Dimer Test.
  • Fibrin Degradation Fragment Test.

What Is D-Dimer Test? When Is This Test Done? Test Results, Role Of D-Dimer Test In Covid -19

Usually, when a person is injured, a process of blood clotting occurs to prevent too much loss of blood. And when the injury is healed, the clot gets dissolved into the blood. 

One of the protein fragment of it is D-Dimer, which is also released into the blood.

At a very low level, this substance is undetectable unless it is dissolved into the blood after the breakdown of the blood clots.

When Is This Test Done?

D-Dimer test is performed to rule out blood clot (thrombus). This test Rules Out Conditions Like:

Deep Vein Thrombosis: 

Which affects the lower legs and detects the blood clot deep inside the vein.

Pulmonary Embolism: 

When blood clot breaks in any other part of the body, travels through lungs, thus causes blockage in the lungs.


Blockage in the blood supply to the brain.

Disseminated Intravascular Coagulation: 

A condition wherein many blood clots are formed through out the body which may cause organ damage due to traumatic injuries or due to cancer or certain types of infection. 

Snake Bite: 

Blood coagulation due to venom of certain types of snake (brown snake) incase of snake bite.

What Is D-Dimer Test? When Is This Test Done? Test Results, Role Of D-Dimer Test In Covid -19

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What Is Ferritin Test? Why It Is To Be Performed? Relation Between Ferritin Test And Covid-19

Symptoms Of Blood Clot

Blood clot may cause symptoms:

  • Leg swelling.
  • Leg pain.
  • Leg Redness.

D-Dimer test is performed if you have above symptoms and also if you have other symptoms like: 

  • Trouble in breathing
  • Sweating
  • Coughing
  • Fast Heart Beat
  • Chest Pain
  • Fainting

Test Results Of D-Dimer Test

Elevated D-Dimer level usually occurs after a clot has been formed and then break down. Hence, after blood clot formation and its break down process, an elevates D-Dimer occurs. 

Negative D-Dimer test means you probably don't have any clotting disorders. 

Positive D-Dimer test doesn't mean you have a blood clot only. There may be more reasons for the positive D-Dimer.

Also, a positive D-Dimer test may indicate the presence of an abnormally high level of fibrin degradation products which may indicate thrombus formation and breakdown but does not indicate the location. 

More testing is usually needed like
  • Ultrasonography
  • CT Angiography
  • Pulmonary Angiography
  • Ventilation/Perfusion Scanning

Also blood test including platelet count, fibrinogen and prothrombin time are also performed.

Any infection, heart attack, liver disease, cancer or any injury might affect the result of D-Dimer test.

What Sample Is Taken?

This Test Requires Special Preparation.

Blood sample from the veins of your arm is taken for D-Dimer test.

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Reference Range Value For D-Dimer Test

<250ng/mL or 0.4mcg/mL Fibrinogen Equivalent Units (FEU). 

Normal value is less then 0.5 and a positive D-Dimer is 0.5 Or greater. 

Role Of D-Dimer Test In Covid -19

What Is D-Dimer Test? When Is This Test Done? Test Results, Role Of D-Dimer Test In Covid -19

IFCC guidelines for Covid-19 strongly suggests D-Dimer test in Covid -19 patients. 

Many studies have revealed a high correlation between severity and outcome of Covid -19 patient with increased D-Dimer levels.

Covid-19 patients experience disease that cause severe pneumonia, hypoxia and severe respiratory failure, for all which require supportive care and nasal oxygen as supplementary. 

D-Dimer is one of the biomarker which is helpful in assisting the treatment of Covid-19 patients.

D-Dimer is commonly elevated in Covid-19 patients and it is related to the severity of the disease. 

Patient with Covid -19  likely undergo a dynamic coagulation process calling it as hypercoagulation state followed by activation of fibrinolysis.

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D-Dimer, a fibrinolytic coagulation factor is gradually increased throughout the disease and so it is being ruled out by D-Dimer test.

Very low level of D-Dimer are being observed for patients receiving anti-coagulation.

Hence, this test us performed for testing whole blood clot which helps to identify and treat patients with Covid-19 more effectively to prevent complications, particularly to prevent blood clots.

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