From the Guidelines
D-dimer testing is recommended in outpatients with chest pain and dyspnea when the clinical probability of pulmonary embolism (PE) is low or intermediate, as it can help rule out PE and reduce the need for unnecessary imaging. According to the 2020 ESC guidelines for the diagnosis and management of acute pulmonary embolism 1, plasma D-dimer measurement is recommended in outpatients/emergency department patients with low or intermediate clinical probability, or those that are PE-unlikely, to reduce the need for unnecessary imaging and irradiation. The guidelines suggest using a highly sensitive assay and consider an age-adjusted cut-off (age × 10 mg/L, in patients aged >50 years) for excluding PE in patients with low or intermediate clinical probability, or those that are PE-unlikely.
Key Points to Consider
- D-dimer testing is most useful when there is a low clinical suspicion for PE and can help rule out PE when negative in this context 1.
- Clinicians should first assess the patient's clinical risk for PE using validated tools like the Wells score or PERC rule 1.
- For patients with low pre-test probability, a negative D-dimer can safely exclude PE, but for those with moderate to high risk, imaging studies like CT pulmonary angiography should be considered directly 1.
- D-dimer testing should be part of a structured diagnostic approach rather than used in isolation, as it has poor specificity and can be elevated in many conditions including infection, inflammation, cancer, pregnancy, and advanced age, leading to false positives.
Diagnostic Approach
- Assess clinical risk for PE using validated tools
- Use D-dimer testing in patients with low or intermediate clinical probability
- Consider imaging studies like CT pulmonary angiography for patients with moderate to high risk or those with a positive D-dimer test
- Use a highly sensitive D-dimer assay and consider an age-adjusted cut-off for excluding PE in patients with low or intermediate clinical probability, or those that are PE-unlikely 1.
From the Research
D-dimer Testing in Patients with Chest Pain and Dyspnea
- D-dimer testing can be used to rule out pulmonary embolism (PE) in patients with chest pain and dyspnea, particularly in those with a low clinical pretest probability 2, 3, 4.
- The D-dimer test is a laboratory assay that measures the levels of D-dimer in the blood, which is a fragment of protein released into the circulation when a blood clot breaks down 3.
- A negative D-dimer test is valuable in ruling out PE in patients who present to the emergency setting with a low pretest probability 3.
- However, D-dimer testing may have less utility in older populations, and the diagnostic threshold of interpretation of D-dimer results may need to be adjusted for patients over the age of 65 years 3.
Clinical Probability Assessment
- The clinical probability of PE can be assessed using a structured score or clinical gestalt, and patients with a low or intermediate clinical probability may undergo D-dimer testing 2.
- Patients with a high probability of PE should undergo chest imaging, and D-dimer testing is not necessary 2.
- A combination of a low clinical pretest probability and a D-dimer level of less than 1000 ng per milliliter can identify a group of patients at low risk for PE during follow-up 4.
Diagnostic Strategy
- A diagnostic strategy that uses a combination of clinical pretest probability assessment and D-dimer testing can reduce the need for chest imaging and anticoagulant therapy 4.
- Patients with a low clinical pretest probability and a negative D-dimer test can be safely ruled out for PE without further testing 4.
- However, patients with intermediate or high probability of PE require further investigation, such as computed tomography pulmonary angiography, to confirm the diagnosis 5.
Potential Pitfalls
- D-dimer testing may suffer from diagnostic errors occurring throughout the pre-analytical, analytical, and post-analytical phases of the testing process 6.
- The intended use of the tests depends largely on the assay used, and local guidance should be applied to ensure accurate interpretation of results 6.