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D-dimer testing for suspected pulmonary embolism in outpatients
A Perrier1, S Desmarais, C Goehring
1Medical Clinic 1, Geneva University Hospital, Switzerland.
American Journal of Respiratory and Critical Care Medicine
|August 1, 1997
Summary
A normal D-dimer level below 500 micrograms/L can reliably exclude acute pulmonary embolism (PE) in outpatients. Withholding anticoagulation in these patients is safe, with a low 1% risk of thromboembolic events during follow-up.
Area of Science:
- Clinical Medicine
- Diagnostic Accuracy
- Thromboembolic Disease
Background:
- Elevated plasma D-dimer levels are common in acute pulmonary embolism (PE).
- A D-dimer cutoff of 500 micrograms/L is often used to exclude PE.
Purpose of the Study:
- To evaluate the negative predictive value of D-dimer < 500 micrograms/L in outpatients with suspected PE.
- To assess the safety of withholding anticoagulant therapy in patients with D-dimer < 500 micrograms/L.
Main Methods:
- Prospective study of 671 outpatients with suspected PE.
- D-dimer assays, lower limb venous compression ultrasonography, and lung scans were performed.
- Pulmonary angiography reserved for inconclusive noninvasive workup; patients with normal D-dimer were followed for 3 months.
Main Results:
- PE prevalence was 29%.
- D-dimer sensitivity for PE was 99.5% with a 500 micrograms/L cutoff.
- Negative predictive value was 99% (95% CI: 96.4 to 99.9), with a 1% risk of thromboembolic events in patients with D-dimer < 500 micrograms/L.
Conclusions:
- A plasma D-dimer concentration below 500 micrograms/L effectively excludes PE in 29% of outpatients.
- Withholding anticoagulation in patients with D-dimer < 500 micrograms/L is a safe strategy with a low thromboembolic risk.