Diagnosing pulmonary embolism

No single non invasive test has sufficient diagnostic accuracy to be used alone for diagnosing or ruling out pulmonary embolism. Therefore, modern diagnostic strategies for pulmonary embolism rely on combinations of non invasive tests such as plasma D-dimer measurement, lower limb venous compression ultrasonography, ventilation-perfusion lung scan and/or spiral CT, the results of which should be interpreted according to the clinical likelihood of pulmonary embolism. Pulmonary angiography is rarely necessary. Clinical probability of pulmonary embolism can be assessed with fair accuracy, either implicitly or by clinical prediction rules. Management studies in which patients deemed not to have pulmonary embolism are left untreated and followed up to assess their 3-month thromboembolic risk have become the benchmark for the validation of diagnostic algorithms. Haemodynamically unstable patients should be managed by quick strategies including echocardiography and ventilation-perfusion scintigraphy or spiral CT.