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Radiology. 2000 May;215(2):535-42.

Subsequent pulmonary embolism: risk after a negative helical CT pulmonary angiogram--prospective comparison with scintigraphy.

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Department of Radiology, Division of Pulmonary Medicine and Critical Care Medicine, 9200 W Wisconsin Ave, Milwaukee, USA.



To determine whether a helical computed tomographic (CT) scan that is negative for pulmonary embolism (PE) is a sufficiently reliable criterion to safely withhold anticoagulation therapy.


Patients with negative helical CT scans were prospectively compared with patients with negative or low-probability scintigrams. In a 460-bed university hospital and clinic, 1,015 adult patients underwent either scintigraphy or helical CT for possible PE for 25 months. Five hundred forty-eight patients who had negative images and were not receiving anticoagulation therapy were prospectively followed up for 3 months for clinical, new imaging, death certificate, or autopsy evidence of subsequent PE. Ninety-seven patients were lost to follow-up.


Subsequent PE was found in two (1.0%) of 198 patients with negative CT scans, none of 188 patients with negative ventilation-perfusion (V-P) scans, and five (3.1%) of 162 patients with low-probability V-P scans (not statistically significant). Patients in the helical CT group were hospitalized more often, had more severe disease, had more substantial PE risk factors, and had a higher death rate. No deaths were attributed to PE in either group.


The frequency of clinical diagnoses of PE after a negative CT scan was low and similar to that after a negative or low-probability V-P scan. Helical CT is a reliable imaging tool for excluding clinically important PE.

[Indexed for MEDLINE]

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