From the Guidelines
A d-dimer test is most useful for ruling out thrombotic conditions such as deep vein thrombosis (DVT) or pulmonary embolism (PE) in patients with low clinical probability, due to its high negative predictive value, as indicated by the 2019 ESC guidelines 1. The d-dimer test measures the presence of blood clot fragments in the bloodstream and can help diagnose or rule out thrombotic conditions.
- Elevated d-dimer levels suggest active blood clot formation and breakdown in the body, which may indicate conditions such as DVT, PE, disseminated intravascular coagulation (DIC), or other conditions involving abnormal clotting.
- The test is most valuable for its negative predictive value—a normal d-dimer level can effectively rule out DVT or PE in patients with low clinical probability, often eliminating the need for further imaging studies, as supported by the European Respiratory Journal study 1. However, d-dimer levels can also be elevated in many non-thrombotic conditions including:
- Pregnancy
- Recent surgery
- Infection
- Inflammation
- Cancer
- Advanced age making it less specific as a diagnostic tool. For this reason, d-dimer results must be interpreted in the context of clinical assessment and may require follow-up testing such as ultrasound or CT angiography when levels are elevated, as recommended by the 2019 ESC guidelines 1. The test is particularly useful in emergency settings when evaluating patients with symptoms suggestive of thromboembolism, where a negative ELISA D-dimer can, in combination with clinical probability, exclude the disease without further testing in ∼30% of patients with suspected PE 1.
From the Research
D-Dimer Test Results
The D-dimer test can tell us about a patient's:
- Coagulation and fibrinolytic system activation, as D-dimers derive from degradation of cross-linked fibrin by plasmin 2
- Risk of venous thromboembolism (VTE), either deep vein thrombosis or pulmonary embolism, with guidelines recommending D-dimer testing if pretest probability (PTP) is low or intermediate 2, 3
- Clinical severity of COVID-19, with D-dimer levels predicting severity and escalated anticoagulation based on D-dimer levels associated with lower risk of mortality in patients with severe COVID-19 2
Diagnostic Accuracy
The diagnostic accuracy of D-dimer levels can be improved by:
- Adjusting cutoffs according to patient characteristics, such as age, PTP, pregnancy, renal function, or cancer 2
- Using a selective D-dimer testing strategy based on clinical pretest probability (C-PTP) for DVT, which can reduce the need for testing 3
- Combining D-dimer testing with clinical decision rules, such as Wells score, to assess the need for objective imaging to rule out deep vein thrombosis (DVT) 4, 5
Specific Conditions
D-dimer testing can be used to: