Pulmonary Embolism Revealed on Helical CT Angiography

OBJECTIVE: We compared helical CT angiography and ventilation-perfusion radionuclide lung scanning as initial tests in the diagnosis of acute pulmonary embolism. SUBJECTS AND METHODS: Two hundred sixteen consecutive patients who were clinically suspected of having acute pulmonary embolism underwent helical CT angiography, ventilation-perfusion radionuclide lung scanning, and Doppler sonography of the veins of the legs. On the basis of concordance of the results for ventilation-perfusion radionuclide lung scanning and helical CT angiography and on the degree of clinical suspicion, certain patients underwent pulmonary angiography. Patients without pulmonary embolism at initial evaluation in whom no treatment was instituted were followed up for at least 3 months to determine the potential recurrence of thromboembolic disease. RESULTS: Of the 216 patients, 37 (17%) were excluded because of insufficient data to assess the initial event. Final diagnosis for the 179 remaining patients was pulmonary embolism in 68 (37.9%) and no pulmonary embolism in 111 (62.0%), based on pulmonary angiography in 23 patients (12.8%) and concordant imaging findings and outcome in the remaining patients. Statistically significant differences (p < 0.05) were found between sensitivity, specificity, positive predictive value, and negative predictive value for helical CT angiography and ventilation-perfusion radionuclide lung scanning (94.1% versus 80.8%; 93.6% versus 73.8%; 95.5% versus 82%; and 96.2% versus 75.9%, respectively). Interobserver agreement was excellent for helical CT angiography (kappa = 0.72) and moderate for ventilation-perfusion radionuclide lung scanning (kappa = 0.22). CONCLUSION: Helical CT angiography could replace ventilation-perfusion radionuclide lung scanning as the initial test for screening patients who are clinically suspected of having pulmonary embolism.