Introduction
D-dimer is a protein fragment formed when cross-linked fibrin is broken down by plasmin during fibrinolysis. It is present in very low concentrations in the bloodstream. Under normal physiological conditions, clot formation and destruction remain balanced, preventing excess bleeding and ensuring proper blood flow after blood vessel healing.
Elevated D-dimer levels are found in disseminated intravascular coagulation (DIC), deep vein thrombosis (DVT), and pulmonary embolism (PE). Other circumstances, such as old age, pregnancy, cancer, liver disease, and infection, may also lead to high D-dimer levels. The ELISA system has higher sensitivity than latex agglutination tests, providing improved aid in the diagnosis and exclusion of venous thromboembolism (VTE).
Clinical Significance of D-Dimer
D-dimer plays an essential role in diagnosing, managing, and monitoring several medical conditions involving thrombosis and coagulation disorders.
1. Diagnosis of Venous Thromboembolism (VTE)
D-dimer testing is extensively used to rule out venous thromboembolism, including:
- Deep Vein Thrombosis (DVT)
- Pulmonary Embolism (PE)
2. Disseminated Intravascular Coagulation (DIC)
D-dimer concentrations increase significantly in patients with DIC due to widespread activation of coagulation and fibrinolysis. It is an important laboratory marker included in DIC diagnostic scoring systems.
3. Cardiovascular Diseases
Elevated D-dimer levels have been found in Patients diagnosed with cardiovascular disorders, including acute coronary syndrome, ischemic stroke, peripheral arterial disease, and atrial fibrillation.
4. COVID-19 and Critical illness
During COVID-19 pandemic, D-dimer was recognised as a valuable prognostic marker . Elevated D-dimer levels were frequently associated with severe disease, thromboembolic complications, the need for intensive care, and an increased risk of mortality. Consequently, D-dimer testing became an integral part of clinical assessment, helping clinicians monitor disease progression and identify patients at greater risk of adverse outcomes.
5. Other Clinical Applications
Elevated D-dimer levels are also observed in malignancies, pregnancy, liver disease, trauma, major surgery, sepsis, and advanced age.
Different Methods for D-Dimer Diagnosis
Doctors recommend D-dimer testing to measure D-dimer levels in serum or plasma. Normal D-dimer levels vary depending on factors such as the individual’s age and sex. For a healthy human body, the reference range is generally less than 500 ng/mL (nanograms per millilitre) or less than 0.50 mg/L (milligrams per litre).
Conclusion
D-dimer is a vital biomarker for evaluating thrombotic and fibrinolytic activity in patients with suspected coagulation disorders. Elevated D-dimer levels are not specific for any single disease; they provide critical diagnostic and prognostic information when interpreted in conjunction with clinical assessment and imaging studies. Various laboratory methods—including ELISA, latex agglutination, immunoturbidimetric assays, fluorescence immunoassays, and CLIA—are available for D-dimer estimation, each with different advantages and limitations. The chemiluminescence-based tests are a better diagnostic approach due to higher accuracy and excellent reproducibility. The advancement of CLIA-based diagnostic platforms is expected to enhance the clinical utility of D-dimer testing further and improve patient outcomes across a broad range of medical specialities.
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