From the Guidelines
No laboratory testing is necessary for a patient with a low pre-test probability of pulmonary embolism (PE), specifically a Wells' score of 0 or 1, as the risk of PE is essentially excluded with a negative D-dimer assay. For these low-risk patients, the recommendation is to stop further testing and consider alternative diagnoses. No D-dimer or imaging studies, such as CT pulmonary angiography, are required, as stated in the American Thoracic Society/American College of Chest Physicians policy statement 1. This approach is based on the Wells' criteria, which are validated clinical decision rules for assessing PE probability. A score of 0-1 indicates a very low risk of PE, and multiple studies have shown that among patients with a low clinical probability of PE and a negative D-dimer, clinically important PE is essentially excluded 1. The rationale is to avoid unnecessary testing, reduce healthcare costs, and prevent potential complications from invasive procedures in patients who are unlikely to have PE, such as radiation-induced cancers and kidney injury from contrast administration 1. However, it's crucial to reassess the patient if symptoms worsen or new concerning signs develop, and clinical judgment should always be used alongside these scoring systems. Some key points to consider include:
- The pretest probability of PE can be calculated using simple clinical prediction tools such as the Wells or Geneva scores
- A negative D-dimer assay can essentially exclude PE in patients with a low clinical probability
- Overuse of CT pulmonary angiography can lead to overdiagnosis and overtreatment of clinically insignificant PE, with rising harms associated with anticoagulation of these patients 1.
From the Research
Laboratory Testing for Pulmonary Embolism with Low Pre-test Probability
- The necessity of laboratory testing for patients with a low pre-test probability of pulmonary embolism (PE) can be assessed using clinical probability scores such as the Wells' score or the Geneva score 2, 3, 4.
- A study published in the Journal of Thrombosis and Haemostasis found that the simplified Geneva score can be used to safely manage patients with suspected PE, and that a low or intermediate clinical probability with a negative D-dimer test can rule out PE 2.
- Another study published in Chest found that clinical probability assessment is crucial in interpreting a normal D-dimer test result, and that patients with a likely clinical probability of PE should undergo further testing regardless of the D-dimer test outcome 3.
- The combination of a negative D-dimer result and a non-high pre-test probability can effectively and safely exclude PE in outpatients with suspected PE 5.
Clinical Probability Scores and Diagnostic Algorithms
- Clinical probability scores such as the Wells' score or the Geneva score can help determine the pre-test probability of PE and assess the need for laboratory testing 2, 3, 4.
- A study published in Archivos de Bronconeumologia found that clinical probability scores are rarely calculated in the diagnosis of PE, and that diagnostic algorithms are not always followed in clinical practice 4.
- Another study published in Internal and Emergency Medicine found that combining pre-test probability with blood gas analysis can help reduce unnecessary computed tomography pulmonary angiography (CTPA) scans in patients with low pre-test probability of PE 6.
Laboratory Testing with Low Wells' Score
- For patients with a Wells' score of 0 or 1, the combination of a negative D-dimer result and a low pre-test probability can be used to rule out PE 3, 5.
- A study published in Thrombosis and Haemostasis found that the combination of a negative VIDAS D-dimer result and a non-high pre-test probability can safely exclude PE in outpatients with suspected PE 5.
- Another study published in Internal and Emergency Medicine found that combining pre-test probability with blood gas analysis can help reduce unnecessary CTPA scans in patients with low pre-test probability of PE, and that a D-dimer cut-off of <1.5 mg/L can be used in patients with a low Wells' score 6.