From the Guidelines
Diagnosing Pulmonary Embolism (PE)
To diagnose Pulmonary Embolism (PE), D-dimer test is the primary laboratory test recommended, as it measures the level of D-dimer, a protein fragment produced when a blood clot dissolves 1. This test is particularly useful for excluding PE in patients with a low pretest probability.
Key Laboratory Tests
- D-dimer test: A blood test that measures the level of D-dimer, which is elevated in the presence of a blood clot 1.
- Other tests such as Troponin, Brain Natriuretic Peptide (BNP), Arterial Blood Gas (ABG) analysis, Complete Blood Count (CBC), Electrolyte panel, and Liver function tests may also be used to support the diagnosis, but they are not as specific for PE as the D-dimer test.
Importance of Clinical Evaluation and Imaging
It's essential to note that these laboratory tests should be used in conjunction with clinical evaluation and imaging studies, such as CT pulmonary angiography (CTPA), to confirm the diagnosis of PE 1. The choice of imaging study depends on the patient's pretest probability and the availability of the test.
Strategy for Diagnosis
The diagnostic strategy for PE typically involves a combination of clinical assessment, D-dimer measurement, and imaging studies. For patients with a low pretest probability, a negative D-dimer result can rule out PE, while patients with a high pretest probability may require immediate imaging with CTPA 1.
Best Practice Advice
Best Practice Advice 3 from the American College of Physicians suggests obtaining a high-sensitivity D-dimer measurement as the initial diagnostic test in patients with an intermediate pretest probability of PE or in patients with low pretest probability of PE who do not meet all Pulmonary Embolism Rule-Out Criteria 1.
In summary, the D-dimer test is a crucial laboratory test for diagnosing PE, and it should be used in conjunction with clinical evaluation and imaging studies to confirm the diagnosis.
From the Research
Laboratory Tests for Diagnosing Pulmonary Embolism (PE)
The following laboratory tests are used to diagnose PE:
- D-dimer test: a relatively simple investigation to rule out venous thromboembolism (VTE) 2, 3, 4, 5
- Blood gas analysis: may be used to evaluate the clinical probability of PE before other testing is done, but it does not have sufficient sensitivity and specificity to confirm or exclude PE 2
- Alveolar dead space fraction: currently being investigated for its diagnostic value in patients with suspected PE, and initial data suggest that it needs to be combined with a D-dimer test to safely exclude PE 2
- Brain natriuretic peptide and cardiac troponin: have limited usefulness for diagnosing PE, but may identify patients with a poor prognosis 2
Non-Imaging Laboratory Tests
Non-imaging laboratory tests, such as the D-dimer test, can be used to rule out PE in patients with a low pretest probability 6, 5
- The D-dimer test can be used safely to withdraw anticoagulation when the pretest probability of PE is low or moderate 2
- The Pulmonary Embolism Rule out Criteria (PERC rule) can be used to exclude PE in patients with a low clinical suspicion for PE or a Wells score < 2 5
Clinical Decision Rules
Clinical decision rules, such as the Wells score, can be used to determine the pretest probability of PE 3, 4, 5