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CT Angiography and CT Venography for Pulmonary Embolism

Adding CT venography to CT angiography improved sensitivity somewhat, but positive and negative predictive values changed minimally.

Increasingly, computed tomographic angiography (CTA) is used as a stand-alone test for diagnosing pulmonary embolism. Some authorities have advocated addition of venous-phase CT venography (CTV), in which pelvic and thigh veins are imaged after the pulmonary arteries. With CTA-CTV, screening can be accomplished for both deep-vein thrombosis and pulmonary embolism during the same examination.

In the Prospective Investigation Of Pulmonary Embolism Diagnosis II (PIOPED II), researchers performed multidetector CTA-CTV in 824 patients (mostly outpatients) with suspected pulmonary embolism. According to a complex reference standard (involving ventilation-perfusion scanning, conventional pulmonary angiography, leg ultrasound, and the Wells score to determine clinical pretest probability), 23% of patients had pulmonary embolism. The performances of CTA alone and CTA-CTV for diagnosing pulmonary embolism are shown in the Table. Although the addition of CTV improved sensitivity somewhat, positive and negative predictive values changed minimally.

Comment: In this study, the accuracy of CTA (mostly 4-slice multidetector scanning) was similar to that found in previous studies. The 83% sensitivity suggests an unacceptable false-negative rate; however, other studies indicate that CTA-negative patients whose clinical probability of pulmonary embolism is low can safely be followed without anticoagulation and that D-dimer testing can help to refine clinical probability (Journal Watch Apr 29 2005 and Journal Watch Jan 31 2006). An editorialist believes that CT venography does not improve diagnostic accuracy sufficiently to justify the additional radiation dose.

— Allan S. Brett, MD

Published in Journal Watch General Medicine June 20, 2006

Citation(s):

Stein PD et al. Multidetector computed tomography for acute pulmonary embolism. N Engl J Med 2006 Jun 1; 354:2317-27.

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Perrier A and Bounameaux H. Accuracy or outcome in suspected pulmonary embolism. N Engl J Med 2006 Jun 1; 354:2383-5.

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• Medline abstract (Free)