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Background: We designed a prospective multicentre outcome study to evaluate a diagnostic strategy based on clinical probability, spiral CT, and venous compression ultrasonography of the legs in patients with suspected pulmonary embolism (PE). The main aim was to assess the safety of withholding anticoagulant treatment in patients with low or intermediate clinical probability of PE and negative findings on spiral CT and ultrasonography., Methods: 1041 consecutive inpatients and outpatients with suspected PE were included. Patients with negative spiral CT and ultrasonography and clinically assessed as having a low or intermediate clinical probability were left untreated. Those with high clinical probability underwent lung scanning, pulmonary angiography, or both. All patients were followed up for 3 months., Findings: PE was diagnosed in 360 (34.6%) patients; 55 had positive ultrasonography despite negative spiral CT. Of 601 patients with negative spiral CT and ultrasonography, 76 were clinically assessed as having a high probability of PE; lung scanning or angiography showed PE in four (5.3% [95% CI 1.5-13.1]). The remaining 525 patients were assessed as having low or intermediate clinical probability, and 507 of them were not treated. Of these patients, nine experienced venous thromboembolism during follow-up (1.8% [0.8-3.3]). The diagnostic strategy proved inconclusive in 95 (9.1%) patients, and pulmonary angiography was done in 74 (7.1%)., Interpretation: Withholding of anticoagulant therapy is safe when the clinical probability of PE is assessed as low or intermediate and spiral CT and ultrasonography are negative.

Background: Low-molecular-weight heparin appears to be at least as effective and safe as standard, unfractionated heparin for the treatment of deep-vein thrombosis, but only limited data are available on the use of low-molecular-weight heparin to treat acute symptomatic pulmonary embolism. Methods: We randomly assigned 612 patients with symptomatic pulmonary embolism who did not require thrombolytic therapy or embolectomy to either subcutaneous low-molecular-weight heparin (tinzaparin) given once daily in a fixed dose or adjusted-dose, intravenous unfractionated heparin. Oral anticoagulant therapy was begun between the first and the third day and was given for at least three months. We compared the treatments at day 8 and day 90 with respect to a combined end point of recurrent thromboembolism, major bleeding, and death. Results: In the first eight days of treatment, 9 of 308 patients assigned to receive unfractionated heparin (2.9 percent) reached at least one of the end points, as compared with 9 of 304 patients assigned to low-molecular-weight heparin (3.0 percent; absolute difference, 0.1 percentage point; 95 percent confidence interval, -2.7 to 2.6). By day 90, 22 patients assigned to unfractionated heparin (7.1 percent) and 18 patients assigned to low-molecular-weight heparin (5.9 percent) had reached at least one end point (P = 0.54; absolute difference, 1.2 percentage points; 95 percent confidence interval, -2.7 to 5.1). The risk of major bleeding was similar in the two treatment groups throughout the study. Conclusions: Under the conditions of this study, initial subcutaneous therapy with the low-molecular-weight heparin tinzaparin appeared to be as effective and safe as intravenous unfractionated heparin in patients with acute pulmonary embolism. (N Engl J Med 1997;337:663-9.) [ABSTRACT FROM AUTHOR]