Evaluation of algorithms for the diagnosis of pulmonary embolism

The development of new diagnostic tests for diagnosing pulmonary embolism (PE) has not yet resulted in any single algorithm being universally accepted. It is at least partially due to the perception by the clinicians ordering the tests that insufficient weight is given to the actual mortality and morbidity costs of pulmonary angiography in comparison to those associated with PE and its treatment. It also becomes more difficult to intuitively integrate all of the competing factors (e.g., sensitivity, specificity, costs, morbidity, mortality) for the different algorithms to choose the most cost-effective sequence. We evaluated the algorithm recommended by the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) investigators, designated by V, and compared it to pulmonary arteriography (A), MR angiography (M), and CT angiography (C) which directly visualize the pulmonary arteries. Using standard economic approaches to loss of life and morbidity to determine the possible costs, we compared the different algorithms for all possible prevalence values. The sensitivity and specificity rates used in making these comparisons were the average values reported in the literature. We found that the recommended algorithm, V, had the lowest cost, provided that economically reasonable morbidity and mortality costs were used. It seems that this algorithm provides sufficient sensitivity and specificity to compensate for the risks of angiography as compared with the other algorithms that avoid these risks. Neither M nor C can compete with this standard algorithm despite their lower mortality and morbidity costs, and the costs of A alone are too high. In the future, however, the inclusion of venous studies with M and/or C may improve the results sufficiently to become more cost-effective than V.