Description of Treatment/Procedure

Deep vein thrombosis (DVT) and pulmonary embolism (PE), forms of venous thromboembolism (VTE), can result in significant morbidity and mortality if not treated. An accurate diagnosis is essential given the risks associated with anticoagulation therapy. D-dimer testing has been proposed as a non-invasive, inexpensive, rapid, and simple test in the evaluation of suspected VTE. D-dimer assays detect the presence of plasmin-mediated degradation products of fibrin. Levels increase following a thrombotic event with normalization within 15 to 20 days. Recent trauma or surgery, cancer, intravascular coagulation, serious infection, and other conditions can elevate D-dimer levels so D-dimer assays are typically sensitive but not specific. Different D-dimer assays have been developed. There is no standard D-dimer level, the units of measure vary, the data from one test cannot be transferred to another, and each laboratory needs to establish and validate cut-off points for the test(s) they are using.

Committee Summary

With regard to vision therapy, the ICSI Technology Assessment Committee finds:

1. Many D-dimer assays are available; they are not equivalent. It is imperative that an assay is applied only to a population in which it has been clinically validated.
   
2. Many factors must be considered before ordering a D-dimer test including: the population to which it is being applied, the presence of comorbid conditions, the use of anti-coagulation therapy, and the length of symptoms. D-dimer testing is best used in an ambulatory care setting rather than for hospitalized patients.
   
3. D-dimer testing must be preceded by an assessment of clinical pre-test probability and the D-dimer assay results should be linked to the probability model results.
   
4. Selected D-dimer assays are highly sensitive. Therefore, a negative D-dimer can be used in combination with pretest probability to rule-out disease. However, D-dimer testing is highly non-specific. Therefore, a positive result should not be used to diagnose VTE.
   
5. For patients with suspected DVT, D-dimer testing, in the correct setting, has the potential to significantly decrease the need for initial and subsequent radiological investigation. (Conclusion Grade II)
   
6. The risks associated with a misdiagnosis of PE are typically more severe than those associated with a misdiagnosis of DVT. Higher negative predictive values are required to safely use D-dimer to exclude PE. The evidence, to date, suggests that current assays, with the possible exception of ELISA and rapid ELISA (VIDAS) methods, are not acceptable for use in excluding PE in patients with clinical suspicion of PE. (Conclusion Grade III)
   
7. D-dimer testing is a safe procedure requiring only a blood sample. However, false negative findings may result in insufficient patient follow-up and withholding of appropriate therapy. Misinterpretation of elevated D-dimer levels may lead to unnecessary invasive procedures and anticoagulation therapy.