From the Guidelines
The diagnostic criteria for Pulmonary Embolism (PE) should be based on a combination of clinical assessment, laboratory testing, and imaging studies, with an initial evaluation using validated clinical prediction rules and D-dimer testing, followed by imaging with CT pulmonary angiography (CTPA) for patients with high pretest probability of PE 1.
Diagnostic Approach
The diagnosis of PE relies on a step-by-step approach, starting with:
- Risk stratification using validated clinical prediction rules such as the Wells score or Geneva score, which consider symptoms and risk factors including immobility, recent surgery, cancer, or prior venous thromboembolism.
- D-dimer testing, which is useful for ruling out PE in patients with low or intermediate clinical probability, with a negative result effectively excluding PE.
Imaging Studies
Imaging is the cornerstone of definitive diagnosis, with:
- CT pulmonary angiography (CTPA) being the gold standard due to its high sensitivity and specificity, directly visualizing emboli as filling defects within pulmonary arteries.
- Alternative imaging options including ventilation-perfusion (V/Q) scanning, particularly useful in patients with contraindications to CTPA such as renal impairment or contrast allergy.
Patient-Specific Approach
The diagnostic approach should be tailored to the individual patient's:
- Clinical presentation
- Risk factors
- Comorbidities For patients with low pretest probability of PE, the Pulmonary Embolism Rule-Out Criteria (PERC) should be applied, and if all criteria are met, no further testing is needed 1.
Age-Adjusted D-Dimer Thresholds
For patients older than 50 years, age-adjusted D-dimer thresholds (age × 10 ng/mL) should be used to determine whether imaging is warranted, as this approach maintains a sensitivity for PE above 97% while significantly increasing specificity 1.
From the Research
Diagnostic Criteria for Pulmonary Embolism (PE)
The diagnostic criteria for Pulmonary Embolism (PE) involve a combination of clinical assessment, laboratory tests, and imaging techniques. The following are some of the key criteria:
- Clinical symptoms such as sudden onset dyspnea, chest pain, and fainting, associated with electrocardiographic signs of right ventricular overload, radiographic signs of oligemia, amputation of hilar artery, and pulmonary consolidations compatible with infarction 2
- Laboratory tests, including D-dimer assays, which have a high sensitivity for diagnosing PE, but low specificity 3
- Imaging techniques, such as Computed Tomographic Pulmonary Angiography (CTPA), which is the imaging test of choice due to its high sensitivity and specificity 4
- Clinical decision tools, such as the age-adjusted D-dimer (AADD), which can help improve the usefulness of D-dimer cutoffs and reduce unnecessary testing 5
- Pretest assessment of the probability of PE using clinical decision rules, which can help restrict the need for angiography to a minority of patients with suspected PE 6
Laboratory Tests
Laboratory tests play a crucial role in the diagnosis of PE. Some of the key laboratory tests include:
- D-dimer assays, which can be used to safely rule out PE in patients with low pretest probability 3
- Blood gas analysis, which can be used to evaluate the clinical probability of PE before other testing is done 3
- Brain natriuretic peptide and cardiac troponin, which have limited usefulness for diagnosing PE, but may identify patients with a poor prognosis 3
Imaging Techniques
Imaging techniques are essential for confirming or ruling out the diagnosis of PE. Some of the key imaging techniques include:
- Computed Tomographic Pulmonary Angiography (CTPA), which is the imaging test of choice due to its high sensitivity and specificity 4
- Compression ultrasonography and ventilation perfusion scintigraphy, which are reserved for patients with concomitant suspicion of deep vein thrombosis or contraindication for CTPA 4