[The rational use of various tests for the diagnosis of pulmonary embolism]

The patient's history, physical examination, chest X-ray, electrocardiogram and blood gas analysis cannot provide a firm diagnosis of pulmonary embolism, but they can help to assess its clinical or a priori probability. Lung perfusion scan, associated with ventilation scan or not, can modulate the probability of pulmonary embolism (post-test or a posteriori) as a function of the scan result (high probability, low probability, or indeterminate result). To define the proper indication for pulmonary angiography, it is necessary to examine all the factors related to the nature of the test, the risk, and the data related to pulmonary embolism (outcome, efficacy and side effects of treatment). Decision analysis provides an opportunity to integrate all these factors, and may help in the diagnosis of pulmonary embolism by establishing the indication for pulmonary angiography, depending on clinical probability and the result of the lung scan.