D-Dimer Test – Meaning, Procedure and its Clinical Significance
Abstract
D-dimer is a bio-marker of coagulation and fibrinolysis, and it is used in diagnosing and managing conditions like venous thromboembolism (VTE), deep vein thrombosis (DVT), and pulmonary embolism (PE). It can also increase by strenuous physical activity, pregnancy, aging, etc. The increased level of D-Dimer shows different conditions or indicates various diseases. Here, we will discuss those conditions and why there is variation in the values. Let’s discuss it in detail!
Introduction
D-dimer is a fibrin degradation product (FDP). Due to the fibrinolysis process in the blood, a small protein fragment is released after a blood clot is broken. Its name is D-dimer because of a cross-link that joins the two D fragments of the fibrin protein, which produces a protein dimer (a compound formed by the union of two molecules of a simpler compound). It’s a test to indicate such as venous thromboembolism, while negative results practically rule out thrombosis, if it comes positive can indicate thrombosis but not show other potential causes. Its values are used as a possibility for the blood disorder disseminated intravascular coagulation. It is a degradation product of fibrin that reflects the activation of your blood clotting system.
Procedure
D-Dimer Test
D-Dimer test is a blood test that involves drawing a small amount of blood from the vein of the arm, then the sample is taken to the lab.
Indication
D-Dimer test is used if there is a scope of deep venous thrombosis (DVT), or disseminated intravascular coagulation (DIC), pulmonary embolism (PE), acute aortic dissection, or atrial fibrillation. Negative result of D-Dimer test can indicate the reduced probability of thromboembolic diseases less than 1%, not using CT angiography to evaluate pulmonary embolism for a person with a negative value of a D-Dimer. If D-Dimer is high, then investigations are advised to detect the thrombosis in the body, like a Doppler ultrasound of the veins or lungs, gamma scan, or CT scan.
It can be advised in some symptoms like swelling, pain, hyperpigmentation of the skin in arm or leg, chest pain, breathlessness, coughing, person having COVID-19 or after treatment of COVID-19, bleeding gums, seizures, decreased urine, etc.
False Positive
The results can be false positive sometimes in various causes like liver diseases, high rheumatoid factor, inflammation, malignancy, trauma, post-operative factor (recent surgery), and advanced age.
False Negative
It can occur if the testing is delayed for several days or a sample is taken too early after the clot formation. The anticoagulation medication can decrease D-Dimer level. Also, while collecting samples, the tube is not sufficiently filled.
Values
D-Dimer level is less than 0.50 micrograms per milliliter or fibrinogen-equivalent units (FEU). The level of 0.50 or higher is considered positive.
Conclusion
A D-Dimer test serves as a valuable clinical tool to assess the presence of clots in blood by measuring the breakdown products of fibrin. This test is easy, cheap compared to other tests, and is a non-invasive method to screen for potential venous thromboembolism (VTE) like deep vein thrombosis or pulmonary embolism. Elevated D-Dimer levels can occur due to various factors beyond thrombosis, including inflammation, pregnancy, or recent surgery, which needs to be clinically interpreted. It can monitor treatment efficacy for VTE by tracking changes in level over time. Its limitation includes potential false positives in certain patient populations and the need for further investigations to confirm a diagnosis if the D-Dimer level is elevated.
