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D-Dimer, Quantitative

Test code(s) 8659

This is an outdated version of this FAQ. It was effective 07/08/2014 to 01/10/2017.

The current version is available here.

Question 1. What is D-dimer?

D-dimer is a product of fibrin clot digestion and therefore is an indicator of recent or current clot formation and lysis. It is the most frequently used marker of coagulation and fibrinolysis.1

Question 2. Which conditions are associated with an elevated D-dimer?

D-dimer concentration is increased in all conditions associated with enhanced fibrin formation and fibrinolysis including2:

  • Venous thromboembolism (VTE), eg, deep vein thrombosis and pulmonary embolism
  • Myocardial infarction and stroke
  • Disseminated intravascular coagulation
  • Post-operative state
  • Malignancy
  • Trauma
  • Liver disease
  • Pregnancy
  • Advancing age

Question 3. What is the clinical utility of the D-dimer assay?

The utility of the assay lies in its negative predictive value since a high D-dimer is a non-specific finding. A negative result (D-dimer concentration below the cut-off) can be used to assist in the exclusion of VTE in certain patient populations.

D-dimer testing is often utilized in a diagnostic algorithm which combines clinical decision rules and imaging studies. If the clinical decision rule categorizes a patient as low or unlikely to have VTE and the patient has a negative D-dimer test (using a sensitive assay), then the diagnosis is excluded.3,4 Examples of clinical decision rules can be found at: http://asheducationbook.hematologylibrary.org/content/2013/1/457/T1.large.jpg.

Question 4. What are the reporting units of the assay?

Quest Diagnostics reports D-dimer results in µg/mL fibrinogen equivalent unit (FEU). Other laboratories report D-dimer results using a D-dimer unit (DDU).

An FEU reflects the quantity of fibrinogen that was initially present that leads to the observed D-dimer. The molecular weight of a D-dimer fragment is approximately one-half the molecular weight of the fibrinogen molecule. Therefore 1.0 µg/mL FEU is equivalent to 0.5 µg/mL DDU.

Laboratories variously express results as ng/mL, µg/mL, µg/L, etc. When comparing results obtained from different laboratories it is important to note the type and magnitude of units in order to make accurate conclusions.1

Question 5. What is the cut-off value for the assay?

In contrast to most other laboratory assays, a reference interval is not reported with the D-dimer assay. As the utility of the assay lies in its ability to assist in VTE exclusion, only a cut-off value is reported. The cut-off value is 0.5 µg/mL FEU. In patients with a low to moderate clinical risk assessment and a result below the cut-off 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.5

Question 6. Can D-dimer be used to predict recurrent VTE?

Clinical prediction rules that incorporate D-dimer testing have been proposed for use in predicting recurrent VTE. However, these need further validation to determine safety.6

 

References
 
  1. Righini M, Perrier A, De Moerloose P, et al. D-Dimer for venous thromboembolism diagnosis: 20 years later. J Thromb Haemost. 2008;6:1059-1071.
  2. Quantitative D-dimer for the exclusion of venous thromboembolic disease. CLSI document H59-A. Wayne, PA: Clinical and Laboratory Standards Institute; 2011.
  3. Geersing GJ, Zuithoff NP, Kearon C, et al. Exclusion of deep vein thrombosis using the Wells rule in clinically important subgroups: individual patient data meta-analysis. BMJ. 2014;348:g1340. doi:10.1136/bmj.g1340.
  4. Wells P, Anderson D. The diagnosis and treatment of venous thromboembolism. Hematology Am-Soc Hematol Educ Program. 2013;2013:457-463.
  5. Wells PS, Owen C, Doucette S, et al. Does this patient have deep vein thrombosis? JAMA. 2006;295:199-207.
  6. Ageno W, Dentali F, Donadini MP, et al. Optimal treatment duration of venous thrombosis.J Thromb Haemost. 2013;11(suppl 1):151-160.
This FAQ is provided for informational purposes only and is not intended as medical advice. A physician’s test selection and interpretation, diagnosis, and patient management decisions should be based on his/her education, clinical expertise, and assessment of the patient.

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