Excluding Pulmonary Embolism Safely. Ann Intern Med. 2003;138:I-18. doi: 10.7326/0003-4819-138-12-200306170-00001
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Published: Ann Intern Med. 2003;138(12):I-18.
Pulmonary embolism involves blood clots in the lung (pulmonary emboli). Blood clots that end up in the lungs usually break off from clots in other parts of the body, such as the legs. Pulmonary emboli can block blood flow and lower oxygen levels. They can cause shortness of breath, coughing up of blood, and death. Doctors treat patients with pulmonary emboli with blood thinners. Blood thinners dissolve clots and prevent clots in the leg from breaking off and causing more pulmonary emboli. Because blood thinners can cause serious bleeding, it is important to use them only when necessary. There are many ways to diagnose pulmonary emboli, including special blood tests, different types of lung scans, radiographic and ultrasound tests to look for clots in the legs, and dye tests of the arteries in the lung (angiography). Some tests are more accurate than others, and none are perfect. Sometimes, doctors use many tests rather than single tests. Regardless, a main aim is to identify the patients who have no or very low likelihood of clots and do not need blood thinners. What does past research tell us about testing strategies that can be used to safely identify such patients?
To identify safe strategies for excluding pulmonary embolism.
More than 7000 patients with suspected pulmonary embolism.
Rather than doing a new study, the researchers looked at 25 previous studies that had assessed one or more strategies to diagnose or exclude pulmonary emboli. These included clinical assessments (history, symptoms, and risk factors), D-dimer blood tests, serial leg ultrasonography, radionuclide lung scans, helical computed tomography lung scans, and angiography. Some studies examined particular combinations or sequences of tests. All studies identified some patients who, according to the test or tests, did not have clots. These patients were not given blood thinners. They were followed for at least 3 months to detect recurring symptoms and evidence of clots in the legs or the lungs. The researchers summarized results of these studies and identified the testing strategies that were associated with very low rates (≤ 3%) of clots during follow-up.
Several strategies identified patients in whom the rate of clots was 3% or less during follow-up without blood thinners. Safe single-test results were normal lung scans and normal angiograms. Safe combinations were a low likelihood of clots based on clinical assessment and a normal result on a D-dimer test, a “nondiagnostic” lung scan followed by either normal results on angiography or normal results on serial leg testing, and a low likelihood based on clinical assessment followed by elevated D-dimer level and then a normal lung scan.
Techniques for diagnosing pulmonary emboli are evolving. Few studies that were reviewed assessed newer techniques, such as helical computed tomography.
Many testing strategies safely exclude pulmonary embolism.
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Emergency Medicine, Pulmonary/Critical Care, Venous Thromboembolism, Pulmonary Embolism.
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