D-Dimer Quantitative

What is a d-dimer quantitative test and why is it used?

A d-dimer quantitative test is a blood test that measures the levels of d-dimer in the blood. It is used to diagnose or rule out conditions like deep vein thrombosis (DVT) and pulmonary embolism (PE). Elevated d-dimer levels indicate potential blood clot formation and further investigation may be needed.

D-Dimer is one of the by-products that can be measured after the fibrinolytic system is turned on. Fibrinolytic activation and intravascular thrombosis can be measured by the amount of D-Dimer in the blood. D-Dimer is especially helpful when ruling out venous thromboembolism in people who are at high risk.

When is the D-Dimer Quantitative Test Used?

When there is a suspicion of deep venous thrombosis (DVTl), pulmonary embolism (PE), or disseminated intravascular coagulation, D-dimer testing is used in clinics.

There are numerous scoring systems that can be used to assess the a priori clinical probability of DVT and PE; the most well-known is the Wells score.

A D-dimer will make little difference for a high score, or pretest probability, and anticoagulant therapy will be commenced regardless of test findings, and additional testing for DVT or pulmonary embolism may be conducted.

What Does a Negative D-Dimer Test Mean?

A negative D-dimer test will virtually rule out thromboembolism for a moderate or low score, or pretest probability: the degree to which the D-dimer reduces the probability of thrombotic disease is dependent on the test properties of the specific test used in the clinical setting: most available D-dimer tests with a negative result will reduce the probability of thromboembolic disease to less than 1% if the pretest probability is less than 15-20%. When a D-dimer assay results in a negative result, chest computed tomography (CT angiography) should not be used to evaluate pulmonary embolism. A low pretest probability is also useful in excluding PE. If you are at low or intermediate risk for blood clotting (thrombosis) and/or thrombotic embolism, you can rely on the strength of the D-dimer test used in a hospital emergency room setting to determine the likelihood of a clot’s presence. A negative D-dimer test (below a predetermined cut-off threshold) indicates that it is highly unlikely that a thrombus is present. False negatives and false positives can occur in D-dimer tests. In the case of a false positive, a D-dimer test shows a positive result even though the person does not have a condition causing blood clots.

If the D-dimer level is elevated, further testing (ultrasound of the leg veins, lung scintigraphy, or CT scanning) is needed to confirm the presence of a thrombus. Depending on the clinical circumstances, anticoagulant medication may be started at this point or delayed until further testing confirm the diagnosis.

They are measured in some hospitals by laboratories after a form with the probability score is completed, and only if the probability score is low or intermediate. This lowers the need for needless tests in people with a high likelihood. By performing the D-dimer test first, you can avoid many imaging tests and be less invasive. Because the D-dimer can rule out the necessity for imaging, speciality professional organizations advise physicians to employ D-dimer testing as an initial diagnostic tool. If your test results show you have an elevated level of D-dimer, your healthcare provider will likely have you undergo further tests to determine a diagnosis. Your lab results will provide information indicating if your D-dimer level is normal, low or high or positive or negative. Additionally, D-dimer levels may be elevated in the setting of pregnancy, inflammation, malignancy, trauma, postsurgical treatment, liver disease (decreased clearance), heart disease, or recent surgery.

What Conditions Can Cause Elevated D-Dimer Quantitative Levels?

D-dimer concentrations are increased in all conditions associated with enhanced fibrin formation and fibrinolysis, such as the following:

• Venous thromboembolism (VTE); eg, deep vein thrombosis and pulmonary embolism
• Myocardial infarction and stroke
• Disseminated intravascular coagulation
• Malignancy
• Trauma or surgery within the previous 4 weeks
• Liver cirrhosis or disease
• Pregnancy
• Advanced age (>60 years)
• Sickle cell disease
• Large hematoma
• Fibrinolytic therapy within the previous 7 days
• Sepsis, severe infections, pneumonia
• Other atherosclerotic vascular disease

The cut-off value is 0.5 µg/mL (mcg/mL) FEU. In patients with a low to moderate clinical risk assessment and a D-dimer result below the cutoff value, the likelihood of a thrombotic event is very low. However, a thromboembolic event should not be excluded solely on the basis of the D-dimer level. The units of a D-Dimer test may be provided in milligrams per liter (mg/L) fibrinogen equivalent units (FEU). According to the American Board of Internal Medicine, a negative D-dimer level is below 0.50 mg/L FEU, and it’s positive if it’s above 0.50 mg/L FEU. D-dimer is a protein the body releases when blood clots break down. Its presence in the blood or urine may indicate that a person has developed a clot. D-dimer levels of 0.50 mg/L or higher may indicate blood clots somewhere in the body. This article explains the D-dimer test and what the results mean. It also outlines the next steps following a positive D-dimer test.

D-Dimer Testing in Clot Formation and Coagulation Disorders: Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE)

D-Dimer is a protein that is released when a blood clot breaks down. It is often used as a diagnostic tool to rule out the presence of deep vein thrombosis (DVT) or pulmonary embolism (PE). Coagulation, on the other hand, is the process by which blood clots form to prevent excessive bleeding. The coagulation process involves a complex interplay of proteins and enzymes, and any disruption in this process can lead to abnormal clotting or bleeding disorders. Understanding the relationship between D-Dimer and coagulation is crucial for diagnosing and treating various medical conditions related to blood clotting. The D-dimer can be measured via analysis of a blood sample, as it is a by-product of the blood clotting and break-down process. D-dimer is released when a blood clot begins to break down, and platelets in the blood are connected to a D subunit. High plasma D-dimer is an indicator of intravascular fibrin formation and plasmin-mediated fibrinolysis. Measurement of plasma D-dimer concentration is useful to aid in the diagnosis of systemic thrombosis, such as pulmonary thromboembolism (PTE) and disseminated intravascular coagulation (DIC). When you get a cut or wound, your body starts a process called hemostasis to form a clot and stop you from losing too much blood. It forms threads of a protein called fibrin to keep the clot in place. Once you've healed, the clot breaks down into fragments. One of those fragments is called D-dimer.

Symptoms of DVT include leg pain, tenderness, swelling, and redness or red streaks on the legs. Symptoms of PE include trouble breathing, cough, chest pain, rapid heartbeat, and a blockage in the pulmonary artery. It is important to seek medical attention if you experience these symptoms. Your healthcare provider may have you undergo a D-dimer test if you’re having symptoms of a blood clotting condition, which include disseminated intravascular coagulation (DIC) and stroke. The D-dimer test is helpful in ruling out causes of DVT and PE, as well as other parts of the body affected by blood clotting disorders.

Reference

Righini M, Perrier A, De Moerloose P, et al. D-Dimer for venous thromboembolism diagnosis: 20 years later. J Thromb Haemost. 2008;6(7):1059-1071. doi:10.1111/j.1538-7836.2008.02981.