From the Guidelines
The diagnostic test for pulmonary embolism is typically CT pulmonary angiography (CTPA) for patients with high pretest probability, while D-dimer testing is useful as a rule-out test in patients with low to moderate clinical probability. The choice of diagnostic approach should be tailored to the patient's clinical presentation, risk factors, and pre-test probability of pulmonary embolism, often determined using validated tools like the Wells score or Geneva score 1.
Diagnostic Approach
The diagnostic approach for pulmonary embolism involves the following steps:
- Initial evaluation with D-dimer testing for patients with low to moderate clinical probability
- CT pulmonary angiography (CTPA) for patients with high pretest probability or if D-dimer is elevated
- Ventilation-perfusion (V/Q) scanning as an alternative to CTPA in cases where it is contraindicated
- Additional tests such as lower extremity ultrasound, echocardiography, and arterial blood gases may be used to evaluate the patient's condition further
Rationale
The use of CTPA as the gold standard diagnostic test is supported by the 2019 ESC guidelines, which state that multidetector CTPA is the method of choice for imaging the pulmonary vasculature in patients with suspected PE 1. The guidelines also highlight the importance of considering pre-test clinical probability when interpreting CTPA results.
Considerations
In cases where CTPA is contraindicated, V/Q scanning is an alternative, which identifies areas of the lung that are ventilated but not perfused due to embolic obstruction. The choice of diagnostic approach should be tailored to the patient's clinical presentation, risk factors, and pre-test probability of pulmonary embolism, often determined using validated tools like the Wells score or Geneva score 1.
Key Points
- CTPA is the gold standard diagnostic test for pulmonary embolism
- D-dimer testing is useful as a rule-out test in patients with low to moderate clinical probability
- V/Q scanning is an alternative to CTPA in cases where it is contraindicated
- The choice of diagnostic approach should be tailored to the patient's clinical presentation, risk factors, and pre-test probability of pulmonary embolism.
From the Research
Diagnostic Tests for Pulmonary Embolism
The diagnostic tests for pulmonary embolism include:
- Computed Tomography Pulmonary Angiography (CTPA) 2, 3, 4, 5, 6
- Ventilation-Perfusion (V/Q) scanning 3, 4
- Compression ultrasonography 2
- Magnetic Resonance Pulmonary Angiography (not a suitable alternative for CTPA) 2
- Single Photon Emission Tomography (SPECT) V/Q scanning 3
- D-dimer test 2, 3, 4, 6
Characteristics of Diagnostic Tests
- CTPA has high sensitivity and specificity for the diagnosis of pulmonary embolism 2, 3
- CTPA is the imaging test of first choice 2
- Negative CTPA results essentially rule out the diagnosis of pulmonary embolism without the need to routinely exclude the presence of deep vein thrombosis 3, 4
- V/Q scanning is a safe alternative to CTPA in some patient populations 3, 4
- Compression ultrasonography is reserved for patients with concomitant symptomatic deep vein thrombosis 2
- Magnetic Resonance Pulmonary Angiography is not a suitable alternative for CTPA 2
Diagnostic Algorithms
- Diagnostic algorithms using CTPA or V/Q scanning have proven to be comparably safe to exclude the diagnosis of pulmonary embolism 3, 4
- Excluding low-risk patients for pulmonary embolism as defined by clinical scoring systems and D-dimer testing would enhance the yield of diagnostic testing 3
- The addition of computed tomography venography (CTV) increases the sensitivity of CTPA, which may be worth the added radiation in certain patient populations 5