What Can Cause a Positive D-Dimer?

D-dimer test is a blood test that is usually done to find out any blood clotting disorders.

When you have any cut or injury and you bleed, a series of steps take place to form a blood clot. This is part of the normal healing process, and once the bleeding stops, the clot dissolves. The dissolved clot may leave a few proteins, such as D-dimer.

Blood clots are formed when the blood vessel is damaged by any injury or atherosclerosis (plaque buildup on the walls of the blood vessels), which causes restricted blood flow. Usually, the D-dimer will not be able to detect them. It is produced only when the blood clot dissolves.

An elevated or positive D-dimer test indicates any blood clot disorder, such as:

• Deep vein thrombosis: A serious condition that can occur due to the blood clots that are formed in the deep veins, especially in the legs. This causes severe pain and swelling in the legs.
• Disseminated intravascular coagulation: Causes multiple blood clots that may result in organ failure and many other serious complications. The D-dimer test is considered the first-line assessment to find out disseminated intravascular coagulation.
• Pulmonary embolism: Occurs when the blood clot travels to the lungs and results in difficulty breathing, increased heart rate, chest pain, and coughing.
• Stroke: This happens when a blood vessel in the brain is blocked due to any blood clots or damage to the blood vessel.

Your healthcare provider may recommend you for a D-dimer test if you show any symptoms of blood clots, such as:

• Swelling, tenderness, warmth, and change in color of the skin, especially in the hands and legs.
• Chest pain, difficulty breathing, rapid heartbeat, and coughing up blood.
• Severe stomach pain, seizures, nausea, vomiting, muscle tenderness, and decreased urination.

D-dimer test procedure

A D-dimer test is done by collecting blood samples from the person with suspected symptoms of clotting disorders. The healthcare provider will withdraw blood through a needle from the vein in the arm. A person may feel mild pain at the site of needle insertion. No prior preparation is required before the blood withdrawal.

The normal D-dimer is less than 0.50 mg/L fibrinogen equivalent units (FEU), and a positive D-dimer is greater than 0.50 mg/L FEU.

• Elevated levels of D-dimer indicate some underlying conditions, such as deep vein thrombosis (DVT), pulmonary embolism (PE), and disseminated intravascular coagulation (DIC).
• If the results are negative, there are no clotting problems.
• If the results are positive with increased D-dimer values, then you may need other tests to confirm DVT, PE, and DIC.
• This does not confirm DVT, PE, or DIC. This test is only done to rule out the conditions.

Sometimes, false negatives and false positives can occur. Because of false negative results of the D-dimer tests, it is used in the case of low-suspicion DVT, DIC, or PE.

In the absence of deep vein thrombosis, pulmonary embolism, and disseminated intravascular coagulation, a few other physiological or medical conditions that can elevate D-dimer values are:

• Pregnancy
• Malignant tumors
• Smoking
• Infections
• Autoimmune disorders
• Older people because D-dimer is increased with age
• Immobilized people
• People with severe COVID-19
• Any recent surgeries

If the D-dimer tests are high, your healthcare provider may advise you for some other diagnostic methods, such as:

• Doppler ultrasound: A noninvasive test that uses sound waves to estimate the blood flow in the blood vessels.
• CT angiography: Dye is injected, and a special X-ray machine is used to see the blood vessels.
• Ventilation-perfusion scan (VQ): Contains two tests. This scan can be done either separately or together, and both tests are safe and simple. During the tests, small amounts of radioactive materials are used to measure how well the air and blood move in your lungs.
  • Ventilation (V) to check the airflow in the lungs
  • Perfusion test (Q) to check where the blood flows in the lungs