D-dimer Test

The D-dimer test is a blood test used to diagnose or rule out thrombotic disorders, such as deep vein thrombosis (DVT), pulmonary embolism (PE), and disseminated intravascular coagulation (DIC).

What is D-dimer?

D-dimer is a protein fragment produced when a blood clot dissolves. It is a degradation product of fibrin, which is a key component of blood clots.

How is the test performed?

The D-dimer test is typically performed on a blood sample taken from a vein in the arm. The blood sample is sent to a laboratory for analysis, where it is tested for the presence and level of D-dimer.

Interpretation of results

A negative D-dimer result indicates that it is unlikely that a thrombotic disorder is present. A positive result, on the other hand, suggests that a blood clot may be present, but it does not confirm the diagnosis. Further testing, such as imaging studies or other laboratory tests, is usually necessary to confirm the presence of a thrombotic disorder.

Uses of the D-dimer test

The D-dimer test has several uses:

• Diagnosis of deep vein thrombosis (DVT): The D-dimer test can help diagnose DVT, which is a blood clot that forms in a deep vein, usually in the legs.
• Diagnosis of pulmonary embolism (PE): The D-dimer test can also help diagnose PE, which is a blood clot that travels to the lungs and blocks blood flow.
• Diagnosis of disseminated intravascular coagulation (DIC): The D-dimer test can be used to diagnose DIC, which is a condition in which blood clots form throughout the body.
• Ruling out thrombotic disorders: A negative D-dimer result can help rule out thrombotic disorders, such as DVT or PE, in patients who are at low risk for these conditions.

Limitations of the D-dimer test

The D-dimer test has several limitations:

• False positives: The D-dimer test can produce false-positive results in patients with other conditions, such as recent surgery, trauma, or infection.
• False negatives: The D-dimer test can also produce false-negative results in patients with thrombotic disorders, especially if the blood clot is small or has not yet dissolved.
• Limited specificity: The D-dimer test is not specific for any particular thrombotic disorder and can be elevated in a variety of conditions.

Reference ranges

The reference range for the D-dimer test varies depending on the laboratory and the specific assay used. In general, a D-dimer level of less than 250-500 ng/mL is considered normal, while a level above this range may indicate the presence of a thrombotic disorder.