Performance of Helical Computed Tomography in Unselected Outpatients with Suspected Pulmonary Embolism

used to diagnose pulmonary embolism, although its operating characteristics have been insufficiently evaluated. Objective: To assess the sensitivity and specificity of helical CT in suspected pulmonary embolism. Design: Observational study. Setting: Emergency department of a teaching and community hospital. Patients: 299 patients with clinically suspected pulmonary embo-lism and a plasma D-dimer level greater than 500 mg/L. Intervention: Pulmonary embolism was established by using a validated algorithm that included clinical assessment, lower-limb compression ultrasonography, lung scanning, and pulmonary angiography. Measurements: Sensitivity, specificity, and likelihood ratios of helical CT and interobserver agreement. Helical CT scans wer