Comparison of intravenous digital subtraction angiography with radionuclide ventilation-perfusion lung scanning in patients with suspected pulmonary embolism.

Fifty one patients with suspected pulmonary embolus were studied by radionuclide ventilation-perfusion scanning and intravenous digital subtraction pulmonary angiography. In 31 patients the results of both investigations were reported as negative and in a further 11 both results were reported as positive, giving a concordance rate of 82.3%. In nine patients there was disagreement between the two investigations and an attempt to resolve this difference on the basis of clinical data was made. On this basis digital subtraction angiography would have falsely classified three patients as not having an embolus who were correctly identified by radioisotope scanning. Angiography would, however, have correctly classified four patients misclassified by ventilation-perfusion scanning. The relative merits of digital subtraction angiography and radionuclide lung scanning are discussed.