If the D-dimer (D-dimer test) is elevated, do we need to order a CT angiogram (Computed Tomography angiogram)?

From the Guidelines

An elevated D-dimer test alone does not automatically necessitate ordering a CT angiogram, but rather should prompt further evaluation based on clinical probability and presentation. While an elevated D-dimer suggests increased fibrin degradation products that may indicate thrombosis, it has low specificity and can be elevated in many conditions including infection, inflammation, pregnancy, cancer, and advanced age 1. Clinical assessment using validated tools like the Wells score or Geneva score should guide the decision. For patients with low clinical probability of pulmonary embolism (PE) or deep vein thrombosis (DVT), a negative D-dimer can safely rule out thrombosis, but a positive result requires further evaluation. In patients with moderate to high clinical probability, imaging is often warranted regardless of D-dimer results.

• CT angiogram should be ordered when there is sufficient clinical suspicion based on both the D-dimer result and the patient's presentation, including symptoms like unexplained dyspnea, chest pain, tachycardia, or risk factors for thromboembolism 1.
• This approach balances the need to diagnose potentially life-threatening conditions while avoiding unnecessary radiation exposure and contrast-related complications from CT angiography.
• According to the 2014 ESC guidelines, computed tomographic angiography has become the main thoracic imaging test for investigating suspected PE, but since most patients with suspected PE do not have the disease, CT should not be the first-line test 1.
• In most centers, MDCT angiography is the second-line test in patients with an elevated D-dimer level and the first-line test in patients with a high clinical probability 1.
• The American College of Physicians also recommends that an elevated plasma d-dimer level should prompt imaging studies, but notes that a d-dimer assay should not be obtained in patients with a high pretest probability of PE because a negative value will not obviate the need for imaging 1.

From the Research

D-Dimer Elevation and CT Angiogram Ordering

• If the D-dimer test is elevated, it may indicate a high probability of pulmonary embolism (PE) or other serious conditions such as deep vein thrombosis (DVT), sepsis, or cancer 2, 3, 4.
• The D-dimer test is often used as a screening tool to rule out PE or DVT, but it is not specific for these conditions and can be elevated in other situations, such as recent surgery, trauma, or malignancy 5, 6.
• A high-sensitivity D-dimer assay can help detect PE, but it may also produce false-positive results, particularly in patients with other conditions that elevate D-dimer levels, such as cancer or recent surgery 6.
• The decision to order a CT angiogram (CTA) should be based on a combination of clinical assessment, D-dimer results, and other diagnostic tests, such as ventilation-perfusion scanning or impedance plethysmography 3, 6.
• In patients with a high clinical probability of PE and an elevated D-dimer, a CTA may be necessary to confirm the diagnosis and guide treatment 4, 6.
• However, in patients with a low clinical probability of PE and an elevated D-dimer, alternative explanations for the elevated D-dimer should be considered, and a CTA may not be necessary 6.
• Age adjustment of the D-dimer threshold may help reduce the number of false-positive results and unnecessary CTAs in older patients 6.