From the Guidelines
Pulmonary embolism (PE) is best diagnosed through a combination of clinical assessment and diagnostic tests, with the initial evaluation typically including a D-dimer blood test, followed by imaging tests such as CT pulmonary angiography (CTPA) for patients with moderate to high clinical suspicion. The diagnostic approach for PE involves stratifying patients into different risk categories based on their pretest probability of having the disease.
- For patients with low pretest probability, the Pulmonary Embolism Rule-Out Criteria (PERC) should be applied, and if all criteria are met, a plasma d-dimer test is not necessary 1.
- For patients with intermediate pretest probability, a plasma d-dimer test is warranted, and if the result is normal, imaging studies are not indicated 1.
- For patients with high pretest probability, imaging studies such as CTPA should be performed, with ventilation-perfusion (V/Q) lung scanning used as an alternative when CTPA is unavailable or contraindicated 1. The choice of test depends on the patient's clinical presentation, risk factors, and contraindications to specific testing modalities.
- CTPA is the preferred method of diagnosis when available and there is no contraindication to radiographic contrast dye 1.
- V/Q scanning is an alternative for patients who cannot undergo CT, such as those with kidney disease or contrast allergies 1.
- Lower extremity ultrasound may be performed to look for deep vein thrombosis (DVT), which is often the source of pulmonary emboli 1.
- Bedside echocardiography can detect right heart strain indicative of significant PE in unstable patients or when other tests are unavailable 1. Overall, the diagnostic approach for PE should be guided by the patient's clinical presentation and risk factors, with the goal of minimizing unnecessary testing and reducing the risk of morbidity and mortality associated with the disease 1.
From the Research
Diagnostic Tests for Pulmonary Embolism (PE)
The diagnostic tests for pulmonary embolism (PE) include:
- Computed Tomographic Pulmonary Angiography (CTPA) 2, 3, 4, 5
- Ventilation-Perfusion (V/Q) scanning 2, 3, 6
- Single Photon Emission Tomography (SPECT) V/Q scanning 2, 6
- Perfusion lung scan 3
- D-dimer testing 6
- Lower limb venous compression ultrasound 6
Characteristics of Diagnostic Tests
- CTPA is the most sensitive test for the diagnosis of PE 2
- CTPA has a high sensitivity but may be associated with significant radiation exposure 2, 4
- V/Q scanning has a high specificity but a low sensitivity 3
- SPECT V/Q scanning has increased diagnostic accuracy compared to V/Q scanning 2, 6
- D-dimer testing can safely rule out PE in patients with low or intermediate clinical probability 6
Diagnostic Algorithms
- Diagnostic algorithms using CTPA or V/Q scanning have proven to be comparably safe to exclude the diagnosis of PE 2
- The use of clinical scoring systems and D-dimer testing can enhance the yield of diagnostic testing 2, 6
- CTPA is the recommended imaging technique in patients with high clinical probability or positive D-dimers 6