From the Guidelines
D-dimer testing is a valuable tool for ruling out deep vein thrombosis (DVT) due to its high sensitivity but low specificity, and a negative D-dimer result (typically <500 ng/mL FEU) in a patient with low clinical probability effectively excludes DVT without requiring further imaging, as supported by the most recent and highest quality study 1. When evaluating suspected DVT, clinicians should first assess clinical probability using validated tools like the Wells score, then selectively order D-dimer testing for low-risk patients. Moderate to high-risk patients should proceed directly to ultrasound regardless of D-dimer results. This approach optimizes resource utilization while ensuring appropriate diagnosis and treatment of DVT. Some key points to consider when using D-dimer testing include:
- D-dimer levels naturally increase with age, so using an age-adjusted cutoff (age × 10 ng/mL for patients over 50) improves specificity without compromising sensitivity 1.
- The test has limitations—it's often elevated in pregnancy, inflammation, cancer, recent surgery, and hospitalized patients, reducing its utility in these populations 1.
- A positive D-dimer is not diagnostic of DVT and requires additional testing, usually ultrasound 1.
- Ultrasonography shows a proximal DVT in 50% of patients with proven PE, but a normal ultrasonography exam of the leg veins does not rule out PE 1. Overall, the use of D-dimer testing in conjunction with clinical probability assessment and selective use of ultrasound can help optimize the diagnosis and treatment of DVT, as supported by the highest quality and most recent study 1.
From the Research
D Dimer and DVT
- D-dimer tests are used to diagnose deep vein thrombosis (DVT) 2
- A normal D-dimer level can exclude DVT, while an increased level requires further testing with compression ultrasound 2
- D-dimer assays can be used in combination with clinical scoring systems, such as Wells' score, to diagnose DVT 3
Diagnosis and Management of DVT
- Diagnosis of DVT requires a multifaceted approach, including clinical assessment, evaluation of pre-test probability, and objective diagnostic testing 2
- Anticoagulation is indicated to control symptoms, prevent progression, and reduce the risk of post-thrombotic syndrome and pulmonary embolism 2
- Low-molecular-weight heparins (LMWHs) and direct oral anticoagulants (DOACs) are effective treatments for DVT, with DOACs being the preferred treatment due to their efficacy, safety, and convenience 2
Role of Low-Molecular-Weight Heparins in DVT Prophylaxis
- LMWHs, such as enoxaparin and dalteparin, are effective in preventing DVT in high-risk patients, including postoperative and critically ill patients 4, 3
- LMWHs have a lower affinity for heparin cofactor II, platelet factor 4, von Willebrand factor, and vascular epithelium, making them a valuable alternative to unfractionated heparin for DVT treatment 4
- The use of LMWHs in DVT prophylaxis may reduce the risk of bleeding complications compared to unfractionated heparin 5, 6
Comparison of Unfractionated and Low Molecular Weight Heparin
- Studies have compared the efficacy and safety of unfractionated heparin and LMWH in the treatment of DVT, with LMWHs showing similar or better outcomes in terms of recurrent thromboembolism and bleeding complications 5, 6
- The use of LMWHs may require less frequent dose adjustments and have a more predictable plasma heparin concentration compared to unfractionated heparin 6