From the Guidelines
D-dimer testing is highly valuable in excluding pulmonary embolism (PE) when used appropriately, particularly in patients with low to intermediate clinical probability, as it can safely rule out PE without the need for further imaging, as supported by the most recent guidelines 1.
Key Points
- A negative D-dimer result (typically <500 ng/mL FEU) in patients with low to intermediate clinical probability can safely rule out PE without the need for further imaging.
- Age-adjusted D-dimer cutoffs (age × 10 ng/mL for patients >50 years) improve specificity without compromising safety, as recommended by recent guidelines 1.
- D-dimer has limitations: it's often elevated in pregnancy, cancer, inflammation, recent surgery, and hospitalized patients, reducing its utility in these populations.
- A positive D-dimer requires follow-up imaging (typically CT pulmonary angiography) for definitive diagnosis.
- D-dimer should always be interpreted alongside clinical assessment tools like the Wells or PERC score to optimize diagnostic accuracy, as suggested by recent studies 1.
Clinical Considerations
- The diagnostic approach for patients with suspected PE should involve clinical decision tools, such as the Wells criteria or the Pulmonary Embolism Rule-Out Criteria (PERC), to stratify patients into different risk categories.
- For patients with high pretest probability of PE, imaging studies, such as CT pulmonary angiography (CTPA), should be performed, as recommended by recent guidelines 1.
- Ventilation-perfusion (V/Q) lung scanning should be reserved for patients who have a contraindication to CTPA or if CTPA is not available.
- D-dimer testing should not be obtained in patients with high pretest probability of PE, as it is unlikely to change management, as suggested by recent studies 1.
From the Research
Utility of D-dimer in Pulmonary Embolism Diagnosis
- The D-dimer test is a useful tool in diagnosing pulmonary embolism (PE), with high sensitivity and negative predictive value, even in patients with high pretest probability for PE 2.
- A study found that integrating D-dimer levels with computed tomography pulmonary angiography (CTPA) findings can improve diagnostic accuracy and efficiency for PE 3.
- The simplified Geneva score, which assesses clinical probability of PE, can be used in conjunction with the D-dimer test to safely manage patients with suspected PE 4.
- A systematic review found that a negative D-dimer test is valuable in ruling out PE in patients with a low pretest probability, but may have less utility in older populations 5.
- Clinical decision-making strategies in the diagnosis of PE should take into account the D-dimer result, as well as pretest probability, to minimize diagnostic error and limit unnecessary investigation or anticoagulation 6.
D-dimer Test Characteristics
- The D-dimer test has high sensitivity, ranging from 80% to 100%, but may have high levels of false-positive results, especially among older adults 5.
- The specificity of the D-dimer test is generally lower, ranging from 23% to 63% 5.
- A negative D-dimer test can be used to rule out PE in patients with a low pretest probability, but the post-test probability of PE may still be significant in patients with a high pretest probability 2.
Clinical Applications
- The D-dimer test can be used to facilitate the safe discharge of patients with suspected PE and limit unnecessary investigation or anticoagulation 6.
- The test can also be used to stratify patient risk and make informed decisions about the need for imaging, thereby optimizing resource utilization and minimizing unnecessary CTPA scans 3.