And here is is…. the answer to our suspected DVT question:
d. It can be used to discharge patients based on their underlying estimated clinical risk score
D-dimer test can be used to exclude DVT in patients who are assessed to be in the category of “low clinical risk” of DVT.
An individuals pre-test risk can be estimated using a “Wells score”. A patient who is clinically “low risk” with a negative D dimmer can be reassured.
The Wells score is shown below.
|Paralysis Paresis or plaster to extremity||+1|
|Bedridden for 3 days/ surgery within last 12 weeks||+1|
|Localised tenderness along distribution of deep venous system||+1|
|Entire leg swollen||+1|
|Calf swelling >3cm compared to the other leg||+1|
|Pitting oedema confined to the symptomatic leg||+1|
|Collateral superficial veins (non-varicose)||+1|
|Alternative diagnosis at least as likely as DVT||-2|
|<0=Low Pre-test Probability
1-2=Moderate Pre-test Probability
>3=High pre-test probability
The Wells score and an example of its clinical application in terms of planning investigations into a DVT
Although you clearly can’t memorise a wells score its clear from the score itself that patients with numerous risk factors (e.g a man with lung cancer with a swollen right leg with pitting oedema) that a negative D-dimer is not sensitive enough to rule the diagnosis out.
D-dimer is still of some use in patients with a low pre-test probability score.
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