Pulmonary embolism revealed on helical CT angiography: Comparison with ventilation-perfusion radionuclide lung scanning

OBJECTIVE. We compared helical CT angiography and ventilation-perfusion rad ionuclide lung scanning as initial tests in the diagnosis of acute pulmonar y embolism. SUBJECTS AND METHODS. Two hundred sixteen consecutive patients who were cli nically suspected of having acute pulmonary embolism underwent helical CT a ngiography, ventilation-perfusion radionuclide lung scanning, and Doppler s onography of the veins of the legs. On the basis of concordance of the resu lts for ventilation-perfusion radionuclide lung scanning and helical CT ang iography and on the degree of clinical suspicion, certain patients underwen t pulmonary angiography. Patients without pulmonary embolism at initial eva luation 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 insufficien t data to assess the initial event. Final diagnosis for the 179 remaining p atients was pulmonary embolism in 68 (37.9%) and no pulmonary embolism in 1 11 (62.0%), based on pulmonary angiography in 23 patients (12.8%) and conco rdant imaging findings and outcome in the remaining patients. Statistically significant differences (p < 0.05) were found between sensitivity, specifi city, 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 angiog raphy (kappa = 0.72) and moderate for ventilation-perfusion radionuclide lu ng scanning (kappa = 0.22). CONCLUSION. Helical CT angiography could replace ventilation-perfusion radi onuclide lung scanning as the initial test for screening patients who are c linically suspected of having pulmonary embolism.