| Summary: | Despite the availability of many diagnostic modalities and the advent of new tests, the diagnosis of pulmonary embolism (PE) remains a challenge. Clinical manifestations can be notoriously deceptive and there is not a single test, that can be relied on solely, to exclude PE. Although it has been regarded as the gold standard test, pulmonary angiography has not been tested against a reference standard and thromboembolic events have been reported after a normal study. Therefore the diagnosis of PE depends on judicious utilization of the available tests in the right clinical setting, as the accuracy of the results of the investigations, depends largely on the pretest clinical probability. Simple investigations such as chest radiograph, electrocardiogram and arterial blood gas, are used to enhance the clinical probabilities, rather than confirming or refuting the diagnosis of PE. On the other hand, Perfusion ventilation (VQ) scan and computerized tomographic pulmonary angiography (CTPA), are the main screening tests used for patients with suspected PE. Recently CTPA has largely replaced VQ scan, in many centres. As both VQ scan and CTPA have their limitations, other diagnostic modalities, such as D-dimer and Compression ultrasound of the legs (CUS), are used as adjunctive diagnostic investigations. High probability and normal VQ scan, especially when combined with the concordant clinical probability, has a high positive and negative predicative value, respectively. On the other hand, CTPA is more sensitive and specific than VQ scan, though it has to be combined with CUS and clinical probability, to reduce the chance of missing PE.<b> </b> Although many diagnostic algorithms have been advocated, the discretion of the clinician and clinical experience, still has a major role to play in the diagnosis of PE. In this article, we try to come with a plausible approach to the diagnosis of PE, based on the current literature.
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