V/Q vs spCT for suspected PE

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V/Q vs spCT for suspected PE

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Justice
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05/05/07 - 05:16 PM

Colleagues,

Recently we had a discussion regarding what to choose for initial work-up of patients with suspected PE. The point of discussion was whether to choose V/Q scan or spiral CT.
Below I am giving you a summary of my investigation on this issue. I used many sources, so I have no reason to list all of them.

So, if you have a patient who you suspect to have PE, order CXR and ABG first, followed by EKG. If the Pt has on x-ray any chest/lung pathology, you offer spCT as the underlying pathology will compromise the V/Q scan. However, if the lungs are clear (as seen most of the times), it is OK/safe to go with V/Q scan. Next step will be Doppler USG for DVT.

Hope the above is helpful.

Please give you comments if you disagree.

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doyoudig
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05/05/07 - 06:49 PM

Hey Justice what is the Role of D Dimer as screening v.s V/Q scan??

Justice
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05/05/07 - 07:18 PM

doyoudig wrote:
Hey Justice what is the Role of D Dimer as screening v.s V/Q scan??

D-dimer is a unique degradation product produced by plasmin-mediated proteolysis of cross-linked fibrin. D-dimer is measured by latex agglutination or by an enzyme-linked immunosorbent assay (ELISA) test that is considered positive if the level is greater than 500 ng/mL.

o Latex agglutination tests are notoriously unreliable, with a historical sensitivity of only 50-60% for DVT and PE. Newer tests may provide improved reliability, but the claims of manufacturers have not always been supported by later studies.

o The ELISA test is more sensitive than the latex agglutination test, but in a population with a PE prevalence of 50%, the negative predictive value of the test is still as low as 79%. Under the best of circumstances, the D-dimer study misses 10% of patients with positive pulmonary angiograms, while only 30% of those with a positive D-dimer will have a positive angiogram.

o At the present time, D-dimer alone is not sensitive or specific enough to rule out or rule in the diagnosis of PE. Its adoption in many emergency departments has increased the number of patients undergoing some evaluation for PE but has not led to any significant change in the frequency with which the diagnosis is confirmed. A patient with signs or symptoms suggestive of DVT and PE may have a positive or a negative D-dimer and still may have a final diagnosis discordant with the D-dimer and/or discordant with the clinical impression.

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usmle12
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05/06/07 - 10:56 PM

well justice it is the protocol exactly i made it for my self while reading usmle world and kaplan

so i agree with it...

star1
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05/07/07 - 05:43 AM

Good work JUSTICE ... keep it up

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doyoudig
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05/07/07 - 08:55 AM

hey again justice
just to add I think you do EKG 1st then CXR then ABG
pls correct me if wrong (but I am thinking that the emergent things would preceded a CXR)

doc_clotaire
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05/07/07 - 09:47 AM

Very usefull Post nod

Thanks buddy !

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