Diagnosing pulmonary embolism.

Objective testing for pulmonary embolism is necessary, because clinical assessment alone is unreliable and the consequences of misdiagnosis are serious. No single test has ideal properties (100% sensitivity and specificity, no risk, low cost). Pulmonary angiography is regarded as the final arbiter but is ill suited for diagnosing a disease present in only a third of patients in whom it is suspected. Some tests are good for confirmation and some for exclusion of embolism; others are able to do both but are often non-diagnostic. For optimal efficiency, choice of the initial test should be guided by clinical assessment of the likelihood of embolism and by patient characteristics that may influence test accuracy. Standardised clinical estimates can be used to give a pre-test probability to assess, after appropriate objective testing, the post-test probability of embolism. Multidetector computed tomography can replace both scintigraphy and angiography for the exclusion and diagnosis of this disease and should now be considered the central imaging investigation in suspected pulmonary embolism.