What is the point of taking a specimen at the time of presentation for
analysis 6-8 hours later.? Surely the idea of taking a specimen at
presentation is to start treatment as early as possible if the result is
positive.
-----Original Message-----
From: David Parry [mailto:[log in to unmask]]
Sent: Tuesday, 15 January 2002 0:21
To: [log in to unmask]
Subject: Troponin timings
I agree with Paul Collinson (message 1/9/02) that timing depends upon prior
probability and acceptable miss rate, but disagree with the way he has
calculated miss rate. Missing 45 out of 50 MIs is a miss rate of 10% in my
book, not 0.5% as was calculated based on a population tested of 1000.
I am also concerned with the testing policy (of Jonathan Kay) that states
that a second specimen at 12 hour post onset of symtoms should always be
collected for TnI in addition to a first specimen obtained when patient is
first seen. The concern I have with this strategy is that many of the
patients tested (>50% in our locale) at 1 or 2 hours after presentation do
not get another blood sample collected for TnI for a number of reasons, one
being that the patient has been sent home. It does not seem practical to me
to force the Emergency Dept to test again at 12h in all patients initially
tested because a TnI was ordered on presentation, as much as we may think
this is the right thing to do.
This takes me back to the point made by Paul Collinson that a testing
strategy should take into account timing practicality and acceptable miss
rate. If a 10% miss rate is acceptable (as was suggested it is) and this is
acheived at 6h post onset of symptoms, then I would suggest that the first
specimen be collected at this time and not before. This way no patient would
be sent home with a TnI test performed on blood collected 1 hour after
presentation as is the case now.
I can think of one other testing strategy alternative when troponin is the
only biochemical marker available. Collect first specimen on presentation
and again after 6-8 hours, but analyze TnI on both only when the second
specimen is taken.
I would appreciate any feedback on this.
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