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This discussion would be strengthened by recognizing that therapy and prevention pose very different questions:
The more serious an illness is, the greater the likelihood that a therapy supported only by observational studies will make the patient better.
In the case of an asymptomatic person without illness the evidence for a preventive intervention must be much stronger (that is, RCT level) for there to be the same likelihood that the person will be made better by the intervention. 

Jim

James M. Walker, MD, FACP
Chief Medical Information Officer
Geisinger Health System

>>> Mike/Linda Stuart <[log in to unmask]> 08/25/06 5:41 PM >>>
I've noticed that several list members have advocated the use of
observational studies if they are the "best available" evidence. For
interventions dealing with therapy, prevention or screening it has been
well-established that even well-done observational studies can provide
completely misleading results. For example, the observational studies
done on HRT were correct in that there was an association between HRT
use and secondary prevention of cardiac events, but it was false that it
was a cause-effect relationship (it was confounded by the healthy-user
effect). The following reading might be helpful to those who would like
further evidence as to why observational studies can mislead in
addressing these kinds of clinical questions. At the following link,
chose the title, "The Problems with the Use of Observational Studies to
Draw Cause and Effect Conclusions About Interventions [PDF] " 

-- Michael Stuart MD
President, Delfini Group, 
Clinical Asst Professor, UW School of Medicine
6831 31st Ave N.E.
Seattle, Washington 98115
206-854-3680 Mobile Phone
206-527-6146 Home Office
[log in to unmask] 
www.delfini.org


-----Original Message-----
From: Evidence based health (EBH)
[mailto:[log in to unmask]] On Behalf Of brnbaum
Sent: Friday, August 25, 2006 6:22 AM
To: [log in to unmask] 
Subject: Re: Deconstructing the evidence-based discourse in
healthsciences)


From my perspective as a hospital epidemiologist, the important division
of perspective here certainly isn't simply quantitative vs. qualitative
and nursing vs. medicine. Infection control, for example, cuts across
all these disciplines and much of the evidence behind infection control
is based on knowledge gleaned from observational study designs in areas
where RCT's aren't ethical, feasible or both. Much in healthcare
administration and management has been rooted in tradition and
assumption, dealing with fundamental questions where a mix of
quantitative and qualitative research would better guide decisions. Many
decisions in medicine need to be informed about effectiveness as well as
efficacy... 

We certainly need to advance our knowledge by critical appraisal and
grading of research evidence. When information needs relate to questions
of efficacy, then RCT's are the best form of evidence. When questions
relate to effectiveness, then observational studies like cohort &
case-referent studies probably are best. When questions relate to
efficiency or cost-effectiveness or perceived utility, yet other
research paradigms are better tools. 

That being said, I believe educational deficits are part of the root
cause for the chasm between these various camps. Poor numeracy skills
hamper many of the students, entering nursing and other disciplines,
that I've seen over the years. Inadequate emphasis on interdisciplinary
education reinforces many of the silo mentalities I've encountered
throughout health care organizations. Simplistic audit approaches
reinforced by well-intentioned but short-sighted accreditation mandates
have kept the position qualifications and program expectations too low
in hospitals' safety, infection control, quality improvement and other
such programs. There have been a number of interesting articles
published in CLINICAL GOVERNANCE related to these points, including one
with a nice flowchart to help distinguish audit from quality improvement
from research per se - a spectrum of activity we should be seeing within
every healthcare organization (not a spectrum dividing hospital-based
health professional activity from university-based researcher activity).

This has been an interesting thread. Let's bring our focus back to a
convergence of useful tools!

--
David Birnbaum, PhD, MPH
Adjunct Professor
School of Nursing
University of British Columbia
Principal, Applied Epidemiology
British Columbia, Canada


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