Pulmonary embolism and lung scanning: cost-effectiveness and benefit:risk.

The cost-effectiveness of pulmonary imaging (lung scan) on the management of 2,023 patients was studied. Prior and postscan probabilities of pulmonary embolism (PE) were obtained from referring physicians. After the scan, anticoagulant therapy (ACT) was appropriately changed in 20% of the patients and confirmed in 67%. The incremental cost of scanning was $124 per patient when the prior probability was 0.01-9.99%, dropping to $38 when the probability was 10-25%. Hospitalization and ACT cost was reduced when the prior probability was 25.01-99.99%. The greatest benefit in lives saved was when the prior probability was 25-74.99%; 1.5% of this probability group would survive as a result of the change in management attributable to the scan, at a cost of $117 per life saved. The benefit:risk ratio, as measured by lives saved compared to estimates of lives lost due to radiation exposure, was of the order of 6,000:1.