Diagnostic methods in pulmonary embolism

Diagnosing pulmonary embolism (PE) is challenging since clinical signs and symptoms are non-specific. The diagnostic tests available for demonstrating PE all have their drawbacks and are often costly and consume considerable amounts of resources. Simple tools that have become available in the last several years include clinical prediction rules and D-dimer testing. Assessment of the clinical probability, combined with a D-dimer test, can limit the need for additional diagnostic tests by 30%. For outpatients with a normal, sensitive ELISA D-dimer test and a low-to-moderate clinical probability, PE can safely be ruled out. Pulmonary angiography, though still the gold standard, is rarely used nowadays because of its invasiveness, its high costs and limited availability, and the declining experience of radiologists with the technique. Two imaging techniques--lung scintigraphy and helical CT--are the diagnostic methods of choice. A normal perfusion lung scan can safely exclude PE. However, 55-65% of patients have indeterminate lung scan results, making additional imaging tests necessary. Helical CT is increasingly being used as the first-line test because it can directly visualize a thromboembolus, it can suggest an alternative diagnosis, and there is excellent inter-observer agreement. A normal helical CT, followed by compression ultrasonography of the leg veins, can safely rule out PE. Finally, the safety of withholding anticoagulant treatment from patients with a normal multi-row detector helical CT as the sole test has not yet been demonstrated.