D-Dimer

D-Dimers are fibrin degradation products formed as a result of fibrinolysis or clot degradation by plasmin. Although plasmin cleaves fibrinogen, fibrin, and cross-linked fibrin during fibrinolysis, only the degradation of cross-linked fibrin, formed during active coagulation, results in D-Dimer formation. This fibrin-derived peptide can therefore be used as an effective biomarker to identify active coagulation and fibrinolysis.
 

Background

The D-Dimer assay is now now recognized as a valuable tool in the evaluation and management of deep-vein thrombosis (DVT), a manifestation of thromboembolism, over conventional diagnostic tools due to its specificity and non-invasive nature.
 

Clinical Applications

As a biomarker, the D-Dimer assay provides critical diagnostic inputs to the clinician in the diagnosis and management of thromboembolism. Evaluation of D-Dimer levels is carried out in conjunction with the clinical probability of thromboembolism, as specified by Wells, et al. (2007).

  • Patients suspected of thromboembolism demonstrate significantly elevated levels of D-Dimer.
  • Despite its high sensitivity, D-Dimer is a non-specific marker for DVT1,2,3 as it cannot distinguish thrombus related to spontaneous venous thromboembolism and other causes of clot formation.1 Apart from thromboembolism, elevated levels of D-Dimer may be indicative of non-thromboembolic conditions such as:

       - Major surgery
       - Trauma
       - Sepsis
       - Malignancy
       - Postoperative state
       - Posttraumatic state
       - Infection
       - Autoimmune disease
       - Inflammatory disease4

  • Several studies have demonstrated the high negative predictive value of the D-Dimer assay. Negative D-Dimer results are sufficient to rule-out DVT and pulmonary embolism (PE) in patients with low clinical probability.4
  • With low/unlikely clinical probability and a negative D-Dimer, the need for ultrasound testing can be omitted for diagnosing DVT. However, ultrasound may be useful in establishing an alternative diagnosis.4
  • Apart from thromboembolism, the D-Dimer test is used to aid in the diagnosis of disseminated intravascular coagulation (DIC).

 

Whom to Test

Patients with high pre-test probability of thromboembolic disease should be tested for D-Dimer levels:

  • Patients with suspected PE, DVT, or aortic dissection (AD)
  • Patients with chest pain or dyspnea may require D-Dimer testing to rule out PE

 

Interpreting the D-Dimer assay results

Clinical Category D-Dimer Test Interpretation
Low-risk patients Negative Imaging tests can be avoided
Moderate-risk patients Negative Venous thromboembolism can be excluded
No need for imaging

Impact on Management4

The integration strategy of combining clinical assessment with the D-Dimer assay and imaging tests enable safer, more convenient, and cost-effective patient care by enabling:

  • Safe PE exclusion protocols even without imaging
  • Identification of false-positive results of imaging tests

 

 

References:
1. Wells PS, et al. Circulation. 1995;91:2184-87.
http://content.nejm.org/cgi/ijlink?linkType=ABST&journalCode=circulationaha&resid=91/8/2184
2. Freyburger G, et al. Thromb Haemost. 1998;79:32-37.
View source.
3. Brill-Edwards P, et al. Thromb Haemost. 1999;82:688-94.
http://www.ncbi.nlm.nih.gov/pubmed/10605769?dopt=Abstract.
4. Wells PS. J Thromb Haemost. 2007;5:41-50.
http://www3.interscience.wiley.com/cgi-bin/fulltext/117994001/PDFSTART.


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