Surely these are used in Malaysia? Maybe not...
Basically they're a specific type of fibrin degradation product, whose
presence in the bloodstream at sufficient concentration indicates that the
patient is suffering from some sort of thromboembolism. The test is very
sensitive so actual disease is highly likely to produce a positive d-dimer
result. However specificity is relatively low, i.e. there are many false
positive tests found with various unrelated conditions. The problem with any
test with high sensitivity, is that emergency physicians leap at the chance
to use the test to "rule something out" and thereby send the patient home.
We're like that in emergency medicine, we often don't care what the precise
diagnosis is (as many patients have non-specific symptoms which defy
diagnosis) but we do care what the diagnosis isn't, if you see what I mean!
The problem with tests like d-dimers and troponins, is that even with a
sensitivity approaching 99%, it's very dangerous relying on the test to send
the patient home. In both these examples we're talking about MIs and PEs,
both of which are common and both of which can be rapidly fatal. Even if we
only miss one in a hundred using these tests, we see such large numbers of
patients, that we're gonna end up with dead bodies sooner or later! So
relying on these tests as a "rule out strategy" without taking other factors
into consideration is a recipe for disaster.
Adrian Fogarty
----- Original Message -----
From: "Ernest Yeoh Poh Yan"
Subject: Re: re-d dimers
> Forgive me , but could you enlighten me as to what a d-dimer is, its uses,
> indications etc.. Thanks
> Ernest
> "Dunn Matthew Dr. ACCIDENT & EMERGENCY - SwarkHosp-TR" wrote:
> > To clarify my previous post: our haematologists tell us that negative
> > d-dimers do rule out a DVT regardless of clinical findings. This seems
to
> > differ from other respondents.
> > Matt Dunn
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