Our labs were complaining for a long time about the
waste of money & time they spent doing lab d-dimers (?
elisa i think). £30,000 of so, often for inpatients.
We offered to take it over and run the d-dimer testing
from the ED - no inpatients, they all have raised
d-dimers anyway. To use the SIMLIFY test kit,
permission is required from the ED registrar - the
gatekeeper.
We use simplify, which I believe has 98% negative
predictive value, (with due regard to simon's
infinitely more scientific posting), and is very easy
to use - no need to refridgerate, foolproof to read.
Only bin going three months so no audit data
yet.Needless to say though, it is clear that
inappropriate use of the test is a fraction of what it
was previously so we get a better test, immesurably
quicker and I believe higher neg predictive value than
the lab one.

SteeveMeek
Bath

We only use it for PE, as part of a risk strat as
simon and others said.
We do not use it for DVT - I thought the evidence ws
lacking for a use in dvt - am I wrong?
--- "s.carley" <[log in to unmask]> wrote:
> Well they might!!!!
>
> It all depends on where you put the cut off and
> which test you use. This is
> something that has not yet been discussed. With a
> continuous value such as
> d-dimer level (or CKMBmass, or amylase etc. etc.)
> the ability of the test to
> rule out or rule in depends on where you put the
> marker. For example a
> CKMBmass on our testing less than 5 is pretty good
> at ruling out AMI (or
> less than 3 rise & with reference to timings), but
> at this level it has poor
> rule in value (you probably need to get above 8).
>
> There is also quite a lot of variation between
> different tests. It is not
> fair to compare SimpliRED against lab based
> quantitive assays (except in a
> trial) for example.
>
> Anyway we constantly interpret such tests as yes/no
> values. For example a
> d-dimer of 270 is negative, whereas one of 279 is
> positive. Rubbish!! it
> just means that one of those results makes a DVT/PE
> slightly more likely. It
> is definately not positive/negative.
>
> So in our example if we set the d-dimer cut off at 5
> then it would work,
> though it would be no use in practice at all.(very
> sensitive but not
> specific enough). That is the thrust behind using
> the results of thes tests
> in the context of a clinical risk stratification. By
> manipulating the
> pretest probability in  a structured manner you get
> much more benefit out of
> your test.
>
> Wouldn't it be nice if all continuous data tests
> like these were given with
> two values, a rule in and a rule out level. And in
> the middle it is
> equivocal and you need to do more work, or another
> test. Interestingly many
> levels are set at the point at which they are most
> "accurate", i.e. a
> compromise of sensitivity against specificity. Where
> is the sense in that!
> It does not reflect our clinical practice.
>
> Simon
> Hi Ho Silver (hobby horse)
>
> Simon Carley
> SpR in Emergency Medicine
> [log in to unmask]
> Evidence based emergency medicine
> http://www.bestbets.org
> ----- Original Message -----
> From: "Dunn Matthew Dr. ACCIDENT & EMERGENCY -
> SwarkHosp-TR"
> <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Thursday, October 18, 2001 10:07 AM
> Subject: Re: re-d dimers
>
>
> > 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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