Hi Matt,
This is probably the BIG question in EBM. Is there an absolute value
of any evidence? Can we define it with a single number or
classification system? Or, as the postmoderns say, is all evidence so
value laden as to be basically meaningless EXCEPT in context, and then
(in the extreme) interpretable by anyone in any way.
Having said it this way, I tend to lean towards the postmodernists
(never thought that I would hear myself saying that) in that the value
of any evidence lies in the context in which it is interpreted and used.
Two IIa level studies may look at slightly different populations,
slightly different outcomes, or slightly different interventions. How
we decide to use them will depend on the context of our patient, and the
values of our patient, ourselves, and our society.
EBM cannot be a one size fits all. I have heard it said that "EBM does
not define truth, truth defines EBM". But what is truth? The eternal
philosopher's dilemma, or some objectivized outcome. After all, EBM is
not "paint by numbers", it is Renoir (or Seargent, Turner, Picasso,
DaVinci, etc.).
Not to be too nihilistic, but I think of EBM as a tool to reduce
uncertainty. To try to make a single definition of what is certain and
not, is doomed to failure. This is why the three (or four) intersecting
circles model of EBM (clinical evidence, clinical predicament, patient
values and (+ / -) clinical experience) works best for me. After all,
it is our patients who are going to be most affected by how we interpret
the evidence and our society that will pay for it. Even the idolized
(almost) RCT is prone to problems from lack of generalizability or
manipulation of input or output variables to improper interpretation of
the results.
How about if we call EBM just another way of saying that we are
improving the abilities of physicians to be good critical thinkers?
Does that help? We must all be able to interpret the overload of
information that we get every day and put it into perspective. Should
we use Recombinant Factor VIIa in non-hemopheliac patients with bleeding
(anywhere, but specifically in the head, or Iraq), or is the pro
thrombotic risk (heart attacks or strokes) too great? How about
Silicone Breast Implants, which are now off the FDAs banned list? These
were both in the news this week (and it is only Tuesday). What should
we tell our patients? Our interpretations of the evidence will inform
that discussion. The more critically we approach our own
interpretation of the evidence, and know when to let someone else (EBM
leaders, drug companies, textbook publishers) inform our thoughts about
that, the better we can serve our patients.
Sorry for this rant, but I had not said anything for a while, so I
guess it is about time.
Best wishes,
Dan
>>> Matt Williams <[log in to unmask]> 11/21/2006 9:36 AM
>>>
Dear List,
I was wondering if anyone knows (& could tell me) of any work that
explores how clinicians weigh evidence.
I am well aware of the levels of evidence, but there are times when
this
is too blunt (e..g studies are both 2b but disagree) and I am looking
fro any evidence of how clinicians weigh up the options and what they
consider important (e.g. study size, journal of publication, etc.)
Thanks a lot,
Matt
--
http://acl.icnet.uk/~mw
http://adhominem.blogsome.com/
+44 (0)7834 899570
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Dan Mayer, MD
Professor of Emergency Medicine
Albany Medical College
47 New Scotland Ave.
Albany, NY, 12208
Ph; 518-262-6180
FAX; 518-262-5029
E-mail; [log in to unmask]
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