Diagnostic strategies for excluding pulmonary embolism in clinical outcome studies. A systematic review.

BACKGROUND Pulmonary embolism is a common clinical disorder that is associated with high morbidity and mortality if untreated. It is important to confirm or rule out the diagnosis in patients with clinical suspicion of the disease. PURPOSE To evaluate various diagnostic strategies for excluding pulmonary embolism. DATA SOURCES MEDLINE (1966 to February 2003), EMBASE, and DARE; study investigators; and reference lists. STUDY SELECTION Prospective clinical outcome studies. DATA EXTRACTION The researchers recorded the frequency of symptomatic venous thromboembolism over 3 months of follow-up in patients in whom pulmonary embolism had been excluded according to various strategies. Strategies were divided into three categories according to the number of rounds of diagnostic tests needed to exclude pulmonary embolism. DATA SYNTHESIS 25 studies involving more than 7000 patients were included. In all referred patients, two strategies-normal results on pulmonary angiography or lung scintigraphy and normal d -dimer levels combined with low clinical probability-safely excluded pulmonary embolism (failure rates < or = 3%). In the second round of diagnostic tests, in patients who had had a nondiagnostic lung scan, both pulmonary angiography and serial leg testing for venous thrombosis were accurate and safe. When d -dimer testing combined with clinical probability was inconclusive, a normal perfusion lung scan safely excluded pulmonary embolism. Accumulating evidence shows that normal results on spiral computed tomography may also safely exclude the disease. CONCLUSIONS Many diagnostic strategies to exclude pulmonary embolism have been evaluated in consecutive patients. Interest is likely to increase in a simple, fast strategy, starting with a normal perfusion lung scan or a combination of normal d -dimer levels and low clinical probability. After the initial round of testing, a reliable diagnostic method, such as angiography or lung scintigraphy, is warranted.