The D-dimer test should not be used in patients with a high clinical probability of pulmonary embolism, since the negative predictive value of this test is low for these patients. A negative D-dimer level (below 0.5 mg per liter), as assessed with the use of a highly sensitive enzyme-linked immunosorbent assay, reliably rules out the presence of circulating fibrin and, thus, essentially rules out the diagnosis of venous thromboembolism in patients with low clinical probability of disease. This test can eliminate the need for further diagnostic testing in almost 30% of patients with suspected pulmonary embolism. However, D-dimer testing should be omitted as a diagnostic step in patients who are older than 80 years of age, are hospitalized, or have cancer, as well as in pregnant women, because D-dimer concentrations are frequently (and nonspecifically) elevated in such patients.
Multidetector computed tomography (CT) is the preferred diagnostic test for pulmonary embolism in most hospitals. This test provides potentially useful prognostic information by also permitting an assessment of the right ventricle. Bedside echocardiography may be a valuable alternative, if CT is not immediately available or if the patient's condition is too unstable for transfer to the radiology department. Ventilation-perfusion lung scanning remains an alternative to CT angiography when injection of a contrast dye is a concern. Unfortunately, inconclusive findings on ventilation-perfusion scans are frequent.
When is thrombolysis indicated in a patient with pulmonary embolism?
Thrombolysis is indicated in the case of patients with pulmonary embolism who have arterial hypotension or are in shock. In contrast, the benefits of thrombolysis in patients with pulmonary embolism who have normal blood pressure are less well established.
What role, if any, do cardiac biomarkers play in the diagnosis and treatment of pulmonary embolism?
Cardiac biomarkers, particularly troponins and natriuretic peptides, have been used to detect myocardial dysfunction and injury, respectively, in patients with acute pulmonary embolism. These biomarkers have high negative predictive value (i.e., normal levels indicate a low risk of death or complications) but low positive predictive values, such that elevated levels alone do not dictate the need for aggressive early treatment other than anticoagulation with heparin.
New England Journal of Medicine - Vol. 359, No. 26, December 25, 2008