A decision analysis approach to the treatment of patients with suspected pulmonary emboli and an intermediate probability lung scan.

There remains no clear consensus as to the appropriate further investigation and management of the patient suspected of pulmonary embolism (PE) who has an intermediate lung scan. Clinical assessment is documented as unreliable, yet many of these patients are unlikely to be treated or to have further tests despite a 36% chance of having PE. Using Medical Decision Analysis, four management strategies for such patients have been examined in terms of mortality and morbidity up to 6 mo post-presentation. The strategies were: (1) treat all patients; (2) treat no patients; (3) perform pulmonary angiography; and (4) perform contrast venography. In the last two strategies, the patients with positive examinations are treated; those with negative examinations are not treated. An extensive literature review was performed to provide probability estimates of chance events and outcomes. If all patients are treated, there is 96.8% chance of survival, with an 85.8% chance of survival with no major complications. If no patients are treated, survival is 89.3% and complication-free survival is 89.3%. Angiography and venography results were 96.7%, 93.1% and 94.6% and 89.6%, respectively. We conclude that in patients suspected of PE who have intermediate lung scan results, the optimal strategy is pulmonary angiography since this results in the highest survival with the lowest complications.