What is the next step after a positive D-dimer (D-dimer test) result?

From the Guidelines

After a positive D-dimer test result, the next step is typically further diagnostic imaging to confirm or rule out a blood clot, most commonly a computed tomography pulmonary angiogram (CTPA) for suspected pulmonary embolism or compression ultrasound for suspected deep vein thrombosis. The specific imaging choice depends on the clinical suspicion and symptoms. A positive D-dimer only indicates increased fibrin degradation products in the blood, which can occur with blood clots but also in many other conditions like infection, inflammation, pregnancy, or cancer 1. It's essential to understand that D-dimer is a sensitive but not specific test, meaning it can effectively rule out clots when negative but produces many false positives. While awaiting further testing, if there is high clinical suspicion for a dangerous clot, the physician might start anticoagulation therapy with medications like enoxaparin (Lovenox) or direct oral anticoagulants 1. Some key points to consider in the diagnostic process include:

• The diagnostic yield of D-dimer relies on its specificity, which varies according to patient characteristics, such as age and the presence of conditions like cancer or pregnancy 1.
• Compression ultrasonography (CUS) can be used to diagnose deep vein thrombosis (DVT) and is sufficient to warrant anticoagulant treatment without further testing if a proximal DVT is found 1.
• Computed tomography (CT) venography can be combined with CT angiography as a single procedure but adds significant radiation and is not useful when using multidetector CT (MDCT) 1. The patient should be monitored for symptoms like worsening shortness of breath, chest pain, or leg swelling during this period. In patients with a high clinical probability of pulmonary embolism, D-dimer measurement is not recommended as a normal result does not safely exclude PE, even when using a highly sensitive assay 1. Instead, CT angiography or other diagnostic tests should be considered directly in these cases. Ultimately, the choice of next steps after a positive D-dimer test must be tailored to the individual patient's clinical presentation and risk factors.

From the Research

Next Steps After a Positive D-Dimer Test

The next steps after a positive D-dimer test result depend on various factors, including the patient's clinical presentation, medical history, and the presence of other diagnostic indicators.

• If the patient has a high clinical probability of deep vein thrombosis (DVT) or pulmonary embolism (PE), further diagnostic testing, such as compression ultrasonography or computed tomography (CT) angiography, should be performed 2, 3.
• The D-dimer test can be used to exclude DVT or PE in patients with a low clinical probability, but it should be interpreted in conjunction with other diagnostic indicators 3, 4.
• In patients with a positive D-dimer test result, the timing of the test in relation to the onset of symptoms is important, as D-dimer concentrations may decrease over time 5.
• The D-dimer test can also be used to monitor the effectiveness of fibrinolytic therapy in patients with PE, with decreasing D-dimer levels indicating successful thrombolysis 6.

Diagnostic Considerations

• The sensitivity and specificity of the D-dimer test vary depending on the population being tested and the cutoff value used 2, 4.
• The negative predictive value of the D-dimer test is generally high, making it a useful tool for excluding DVT or PE in patients with a low clinical probability 3, 4.
• However, the positive predictive value of the D-dimer test is lower, and further diagnostic testing is often necessary to confirm the diagnosis 2, 3.

Clinical Applications

• The D-dimer test can be used in a variety of clinical settings, including the diagnosis of DVT, PE, and disseminated intravascular coagulation (DIC) 3.
• It can also be used to identify patients at increased risk of recurrent VTE and to monitor the effectiveness of anticoagulant therapy 3.
• In patients with suspected upper extremity DVT, the D-dimer test can be a useful diagnostic tool, with a high negative predictive value 4.