Interesting discussion. I am aware of publications being made " Evidence based
Cardiology and several others which are based on the "hierarchy of evidence".
When there is conflict, and the argument seems to be strong on both sides , how
do you resolve this?
> >So, you are saying that there is no such a thing as "hierarchy of evidence"
> >?
> >ben
> >
> As so often, Dave Sackett had it right when he wrote about "choosing the
> best research design for each question" (BMJ 1997;315:1636). The thing
> that worries me most about the hierarchy of evidence is the way it
> places the meta-analysis of RCTs at the top as though this is therefore
> the "best" evidence. It isn't. It's only the most valid experimental
> evidence (and if the extent of heterogeneity in various aspects of
> trials has been underestimated it might sometimes not even be so
> valid...).
>
> The danger is that we might assume that the most important questions are
> those that can be answered by evidence which is high in the hierarchy.
> So the question "do statins reduce cardiovascular morbidity and
> mortality in patients with raised cholesterol" might be thought a more
> valid or important question than "do people who eat a Mediterranean diet
> have a lower prevalence of ischaemic heart disease than people who eat a
> diet high in saturated fat?",or "why do poor people eat a diet high in
> saturated fat?", or "what stops people taking exercise?"
>
> Our strategy for reducing cardiovascular disease might therefore, if we
> prefer high hierarchy evidence, exclude interventions aimed at
> alleviating poverty or encouraging a healthy lifestyle "because there is
> little valid evidence that these interventions are effective"
>
> This is to take far too narrow a view, not only of what constitutes
> valid and (especially) applicable evidence, but of what health care
> consists of.
>
> The main use of hierarchies of evidence, in my view, is as a shorthand
> to link recommendations in evidence-based guidelines to the evidence, so
> that when you read the guideline you know what class of evidence has
> been used. The applicability of the evidence is related to its
> usefulness and relevance as much as to its position in the hierarchy.
> Thus qualitative evidence that people believe their children are at risk
> of developing pneumonia if they don't get antibiotics might be equally
> as useful as evidence that antibiotics don't prevent pneumonia in
> children with coughs (indeed you might find an attempt to use the latter
> very frustrating if you didn't understand the former!)
>
> Toby
> --
> Toby Lipman
> General practitioner, Newcastle upon Tyne
> Northern and Yorkshire research training fellow
>
> Tel 0191-2811060 (home), 0191-2437000 (surgery)
>
> .
Amit Ghosh, MD, DM
Director of General Internal Medicine Firms
University of Minnesota
Box 741, 420 Delaware St, SE
Minneapolis, MN 55455
Phone:612-624-8984
Fax:612-624-3189
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