Clinical Usefulness of Imaging Performed After CT Angiography That Was Negative for Pulmonary Embolus in a High-Risk Oncologic Population

OBJECTIVE: The purpose of our study was to determine the prevalence and types of additional imaging examinations that were performed, and whether anticoagulation therapy was started or continued, after CT angiography showed no pulmonary embolus in a high-risk oncologic population. MATERIALS AND METHODS: We reviewed the radiology report for each CT angiogram that was obtained for clinically suspected pulmonary embolism at our institution (a tertiary cancer center) during a 25-month period. The radiology information system was then searched for any additional confirmatory radiologic examinations performed within 2 days after a negative finding on CT angiography. Medical records were reviewed to determine whether anticoagulation therapy was started or continued despite a negative finding on CT angiography. RESULTS: Two hundred seventy-six CT angiograms were obtained in 260 oncology patients who were clinically suspected of having pulmonary embolism. The findings from 203 CT angiograms (74%) were interpreted as negative; 56 (20%), as positive; and 17 (6%), as equivocal for pulmonary embolism. Fifty-eight patients (21%) with negative findings on CT angiography subsequently underwent additional imaging, the results of which were potentially clinically important in 6% of the patients. Six patients began to receive and two continued to undergo anticoagulation therapy despite negative findings on CT angiography; three of the six patients received anticoagulation for new-onset atrial fibrillation. CONCLUSION: Negative results of CT angiography for pulmonary embolism did not deter referring physicians from ordering other confirmatory imaging tests in 21% of patients in a high-risk oncologic population. Those additional tests rarely revealed results that might have been clinically important.