What is the research question, or key conclusion?
If there is any suggestion about effect of surgery on outcomes,
comparison with historical outcome rates, or increase or decrease in
outcomes then it would be classified as a "case series" because of lack
of control group.
For interventional studies the level 2 status of cohort studies is for
cohorts with exposed and unexposed individuals so that they can be used
for comparison.
If there is no comparison group (or comparisons are limited to
"pre-intervention" in the same patients) then you are almost always in
the lower levels of evidence for cause-and-effect relationships. (There
is an exception for "all or none" results but that does not appear to
apply here.)
Brian S. Alper, MD, MSPH
Editor-in-Chief, DynaMed (www.ebscohost.com/dynamed)
-----Original Message-----
From: Evidence based health (EBH)
[mailto:[log in to unmask]] On Behalf Of Declan Murphy
Sent: Sunday, November 01, 2009 1:31 AM
To: [log in to unmask]
Subject: Re: Inception cohort study and level I evidence
Dear Colleagues,
Many thanks for all your expert comments on this topic. This has been
most helpful.
The paper I am reviewing is a consecutive surgical series with accrual
of patients from 2001-2008. The intervention is a surgical procedure and
the primary outcome relates to cancer cancer recurrence and survival.
My question is does this constitute an inception cohort study? Excuse my
ignorance of this definition but this is not a commonly applied
methodology in surgical series. What is described in this paper appears
to be a consecutive case series and a number of other papers have been
published from this in the past six years. My understanding was that an
inception cohort was a group of patients assembled at the start of a
study period and followed throughout. If patients are continuously
accrued then like is not being compared with like, especially as the
authors have published a number of modifications to the intervention
over the past eight years which could clearly have an impact on
outcomes.
Once again, I am grateful for your expert comment!
Regards
Declan
Mr Declan G Murphy FRCS Urol
Consultant Urologist
The Urology Centre
Guy's Hospital
St Thomas' Street
London
SE1 9RT
Tel: +44(0)7880 731254
www.gstt.nhs.uk/urology
www.youtube.com/decmurphyurology
On Sat, 31 Oct 2009 12:56:17 -0400
"Dahm, Philipp" <[log in to unmask]> wrote:
>Dear Declan:
>
>Interesting to see a query from the urological literature; this may be
the first time.
>
>As stated by others previously, the CEBM grading system considers high
quality evidence from inception cohort studies as level I evidence for
questions of PROGNOSIS. I'd make sure though that what you are looking
at is not a surgical case series and that the question is indeed one of
prognosis (not therapy).
>
>I'm afraid I'd place relatively little stock in the authority of the
authors or the journal....
>
>Happy to discuss further off-line. Always keen to meet other urologists
interested in EBM!
>
>Greetings from Florida.
>
>Ph*
>
>Philipp Dahm, MD, MHSc, FACS
>Associate Professor of Urology, Associate Residency Program Director &
Director of Clinical Research
>Department of Urology
>University of Florida
>College of Medicine, Health Science Center
>Box 100247, Room N2-15
>Gainesville, FL 32610-0247
>Phone: (352) 273-7936
>Fax: (352) 273-7515
>Email: [log in to unmask]
>Website: http://evidence-based.urology.ufl.edu
>
>
>
>-----Original Message-----
>From: Evidence based health (EBH)
[mailto:[log in to unmask]] On Behalf Of Declan Murphy
>Sent: Saturday, October 31, 2009 3:08 AM
>To: [log in to unmask]
>Subject: Inception cohort study and level I evidence
>
>Sorry to bother you guys with a query. I am reviewing a paper which
claims to be CEBM Level Ib as it is an "inception cohort study with over
80% follow-up". It is not an RCT, it is simply a large surgical cohort
followed prospectively for a few years and the data is not comparative
in any way. Seven or eight papers have been published from this series
previously but this is the first time they have claimed level Ib
evidence status. Is it appropriate for the authors to claim this is
Level Ib evidence and to reference the CEBM in support? The authors are
well known in urology and this paper is under submission to the leading
urology journal so I am anxious to ensure they are not discrediting the
CEBM levels with this claim.
>I would very much appreciate your advice.
>
>declan
>
>
>Mr Declan G Murphy FRCS Urol
>Consultant Urologist
>The Urology Centre
>Guy's Hospital
>St Thomas' Street
>London
>SE1 9RT
>
>Tel: +44(0)7880 731254
>www.gstt.nhs.uk/urology
>www.youtube.com/decmurphyurology
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