I would like to make a couple of other points regarding evidence
grading. There over 100 evidence grading systems, many complex and
difficult to use. No one system has been universally accepted. We
developed an evidence grading system that provides meaningful
information about both validity and clinical usefulness because many of
groups we work with have difficulty remembering and applying evidence
grades from other systems. Oursystem is easy to remember, easy to use
and can be applied to studies, evidence syntheses, clinical guidelines
and other health care information. The scale has four easy-to-remember
grades-A, B, U and X. The details are below:
Delfini Validity & Usability Grading Scale for Summarizing the Evidence
for Interventions
Grade A: Useful
The evidence is strong and appears sufficient to use in making health
care decisions - it is both valid and useful (e.g., clinical
significance, of sufficient magnitude, physician and patient
acceptability, etc.)
-- Evidence from well-designed and conducted systematic reviews
might fall into this category or they might be considered Grade B.
Suggestion is to do a careful analysis of the review and the studies
included.
-- Several well-designed and conducted studies that consistently
show similar results
-- For therapy, screening, prevention and diagnostic studies:
RCTs. In some cases a single, large well-designed and conducted RCT may
be sufficient.
-- For natural history and prognosis: Cohort studies
Grade B: Possibly Useful
The evidence is potentially strong and might be sufficient to use in
making health care decisions.
The evidence is strong enough to conclude that the results are probably
valid and useful (see above); however, study results from multiple
studies are inconsistent or the studies may have some (but not lethal)
threats to validity.
-- Evidence from well-designed and conducted systematic reviews
might fall into this category or they might be considered Grade A.
Suggestion is to do a careful analysis of the review and the studies
included.
-- Evidence from at least one well-designed and conducted RCT
(cohort studies for natural history and prognosis; for diagnosis, valid
studies assessing test accuracy for detecting a condition when there is
evidence of effectiveness from valid, applicable RCTs.)
Grade U Uncertain Validity and Usefulness (with 3 subgroups)
The evidence is sufficiently uncertain to urge caution regarding its use
in making health care decisions.
-- Uncertain Validity: This may be due to uncertain validity due to
methodology (enough threats to validity to raise concern - our
suggestion would be to not use such a study in most circumstances) or
conflicting results.
-- Uncertain Usefulness: This may be due to uncertain applicability
due to results (good methodology, but questions due to effect size,
applicability of results such as due to results relating to biologic
markers or other issues). These latter studies may be useful and should
be viewed in the context of the weight of the evidence.
-- Uncertain Validity and Usefulness: This is a combination of the
above.
Grade X: Not Useful
--The evidence reviewed has lethal threats to validity or other problems
(e.g., applicability) and should not be used in making health care
decisions.
C Delfini Group, LLC, 2005. All Rights Reserved World Wide.
Hope this is useful.
-- 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 Underhill
Jonathan
Sent: Friday, July 01, 2005 12:56 AM
To: [log in to unmask]
Subject: Re: Level of Evidence Assistance
->>>>>>>>>>>>>>>>>>>>
I would add that there are a number of systems out there that provide a
way to rank levels of evidence/grades of recommendation - which makes
things hard for us sometimes. Although rather complicated and perhaps
loosing something in user friendliness the CEBM at Oxford (Olive & Co)
presented a system which may assist in addressing your question. See
http://www.cebm.net/levels_of_evidence.asp, perhaps level 2a or 3a fit
(depending on the design of the observational studies). <<<<<<<<<<<<<<<,
Of course some would suggest that a more robust system of classification
is the SORT criteria, which takes into account both validity AND, very
importantly, relevance:
http://www.aafp.org/afp/20040201/548.html
Comments?
Cheers (8(|)
Jonathan
---------------------------------------------------------------------
Jonathan Underhill MRPharmS
Assistant Director, Education and Development
National Prescribing Centre
The Infirmary
70 Pembroke Place
Liverpool
L69 3GF
Tel: 0151-794-8143
Fax: 0151-794-8067
Mobile: 07968 851325
email: [log in to unmask]
website: www.npc.co.uk
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