CT angiography is becoming more and more used to perform diagnoses of pulmonary embolism, replacing perfusion lung scintigraphy, which, up to some time ago, was considered the gold standard in this diagnosis. In order to compare these two techniques, an international multicentric randomized trial was performed, involving 1417 patients with a high probability to develop pulmonary embolism (Wells score ≥ 4.5 or positive D-dimer). The subjects with scintigraphy suggesting pulmonary embolism or positive CT angiography were treated with anticoagulants; the ones with negative examinations were not treated. All the others were investigated with lower limbs US and treated with anticoagulants if found affected by deep venous thrombosis. Out of 694 patients randomized at CT angiography, 19.2% resulted positive for pulmonary embolism or DVT, compared to 14.2% of those examined with scintigraphy. Out of the remaining 561 patients examined with CT angiography, 0.4% developed thromboembolic events, compared to 1.0% of those examined with scintigraphy.
CT angiography detected 30% more of pulmonary embolism compared to perfusion lung scintigrahpy. In the scintigraphy group, however, this lack of recognition is not associated with important clinical evidences, so probably there are mild conditions of pulmonary embolism which are asymptomatic and for which it is not opportune to undergo coagulation. In practice, the authors suggest that the correct approach to pulmonary embolism diagnosis should imply the evaluation of pre-test probabilities, D-dimer dosage, lower limbs echodoppler, CT angiography if not contraindicated and perfusion scintigraphy if available.
