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D-Dimer, Quantitative

Test code(s) 8659

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 embolis
  • Myocardial infarction and stroke
  • Disseminated intravascular coagulation
  • Malignancy
  • Trauma or surgery within the previous 4 weeks
  • Liver cirrhosis or disease
  • Pregnancy
  • Advanced age (>60 years)
  • Sickle cell disease
  • Large hematoma
  • Fibrinolytic therapy within the previous 7 days
  • Sepsis, severe infections, pneumonia
  • Other atherosclerotic vascular disease

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 value is a non-specific finding. A negative result (D-dimer concentration below the cutoff) can be used to assist in the exclusion of VTE in certain patient populations.

D-dimer testing is often utilized in a diagnostic algorithm that combines clinical decision rules and imaging studies. If the clinical decision rule categorizes a patient as low risk 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 mg/mL fibrinogen equivalent units (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 reference interval 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 the cut-off value is reported.

Question 6. What is the cutoff value for the assay?

The cut-off value is 0.5 mg/mL FEU. In patients with a low-to-moderate clinical risk assessment and a D-dimer 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

Age-adjusted D-dimer thresholds (rather than a fixed cut-off value) have been recommended by the Clinical Guidelines Committee of the American College of Physicians. In patients older than 50 years, the age-adjusted cutoff can be used to determine whether imaging is warranted in patients with suspected pulmonary embolism. The formula one would use is the following: age x 0.01 mg/mL (FEU). For example, the D-dimer threshold for a 57-year-old would be 57 x 0.01 mg/mL (FEU), or 0.57 mg/mL (FEU).6

Question 7. Can D-dimer be used to predict recurrent VTE?

Not yet. Clinical prediction rules that incorporate D-dimer testing have been proposed for use in predicting recurrent VTE and justifying continued anticoagulation. However, these need further validation to determine their safety, as recurrent VTE risk also depends on clinical variables.7-9

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. Raja AS, Greenberg JO, Qaseem A, et al; Clinical Guidelines Committee of the American College of Physicians. Evaluation of Patients With Suspected Acute Pulmonary Embolism: Best Practice Advice From the Clinical Guidelines Committee of the American College of Physicians. Ann Intern Med. 2015;163:701-711.
  7. Ageno W, Dentali F, Donadini MP, et al. Optimal treatment duration of venous thrombosis. J Thromb Haemost. 2013;11(Suppl 1):151-160.
  8. Kearon C, Akl EA, Ornelas J et al. Antithrombotic Therapy for VTE Disease: CHEST Guideline and Expert Panel Report. Chest. 2016;149:315-52.
  9. Streiff MB, Agnelli G, Connors JM, et al. Guidance for the treatment of deep vein thrombosis and pulmonary embolism. J Thromb Thrombolysis. 2016;41:32-67.
This FAQ is provided for informational purposes only and is not intended as medical advice. A clinician’s test selection and interpretation, diagnosis, and patient management decisions should be based on his/her education, clinical expertise, and assessment of the patient.
Document FAQS.149 Version: 2
Version 2 effective 05/30/2018 to present
Version 1 effective 01/10/2017 to 05/30/2018
Version 0 effective 7/18/2014 to 01/10/2017