Accuracy of CT pulmonary angiogram in the diagnosis of of pulmonary embolism.

January 28, 2003

June 27, 2003

Dr Kerstin Hogg, Clinical Research Fellow (Manchester Royal Infirmary)

Ged Brown, Manchester Royal Infirmary

In [a patient with symptoms and signs of pulmonary embolism] what is the [diagnostic utility] of a [CT pulmonary angiography]?

You have reviewed a 48 year old man who presents with isolated pleuritic chest pain on the left side. His fingers are nicotine stained. He tells you he regularly coughs up yellow phlegm in the morning. His PaO2, PaCO2 are normal and D-dimers elevated. You would like to discharge him to the care of his GP if you are able to rule out pulmonary embolus. Would a CT pulmonary angiogram allow you to do this?

Medline 1966-05/03 using the OVID interface.

[Exp Tomography, X-ray Computed, OR CT.mp OR Computed tomograph$.mp] AND [exp pulmonary embolism OR pulmonary embol$.mp. OR PE.mp. OR exp thromboembolism OR pulmonary infarct$.mp] LIMIT to human AND English.

2291 papers were found. 47 addressed the question. Six were excluded on the grounds of weak reference standard. Four were excluded because they used highly selected patient populations, not representative of patients in the emergency department. One study looked specifically at chronic PE. Six studies used a retrospective methodology. One study used a theoretical approach. All meta-analysis were excluded.

The studies vary in quality and patient demographics. Only one study, Perrier et al (17) looked at unselected emergency department patients and is probably the most relevant study with a robust methodology. In the study by Qandil et al (13) 87% patients were outpatients making the study relevant and they used an excellent gold standard (pulmonary angiography). The management studies tended to exclude any patient diagnosed with a DVT immediately following negative CTPA – I have included these as false negative patients, wherever possible. This may overestimate prevalence of PE, however is generally accepted as a common reference standard for PE.
Almost all of these studies used single detector CT scanners. These are being replaced across the UK with multiscanners of superior quality.
No study looked at the diagnostic accuracy of the combination of CTPA and D-dimer.

CT pulmonary angiogram is not accurate enough to be used as a stand alone diagnostic tool for PE, but appears to perform well in combination with other tests such as Doppler or VQ scan.

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