Strategy for diagnosis of patients with suspected acute pulmonary embolism.

STUDY PROTOCOL Two separate groups of clinical investigators have provided new information and divergent approaches to the management of acute pulmonary embolism (PE). In this position paper, investigators from both groups (Prospective Investigation of Pulmonary Embolism Diagnosis [PIOPED] and Canadian study groups) have utilized the combined scientific database in order to rationalize seemingly polarized diagnostic recommendations into a single practical algorithm. METHODS An in-depth review established the relative risks of deep venous thrombosis (DVT) and the related accuracy of diagnostic tests. In PIOPED, 640 of 887 patients at risk for PE had either an intermediate probability ventilation/perfusion (V/Q) scan or a V/Q scan probability that was discordant with the prior estimate of probability by clinical assessment. The risk of PE in these patients was 16 to 88 percent (average, 34 percent). In this group, we calculated the probability of PE assuming that tests for DVT had been performed and that 50 percent of patients with PE have detectable proximal DVT. By calculation, 108 in 640 patients of whom the diagnosis of PE was uncertain, would have shown proximal DVT. In 239 of these 640 patients, tests for DVT would have been negative and the risks of PE in these patients is calculated to be less than 10 percent. RESULTS Therefore, we calculate that in 347 of 640 patients, confident recommendations for treatment or no treatment could have been given without pulmonary angiography. Accordingly, in the PIOPED study group of 887 patients, the need for pulmonary angiography would have been reduced from 640 (72 percent) to 293 patients (33 percent). CONCLUSION In conclusion, a diagnostic strategy that includes the clinical evaluation, V/Q scan, and evaluation for DVT would decrease the number of patients who require pulmonary angiography from 72 to 33 percent.