Hi Janet and Chris,
Thank you both for these excellent resources. Chris' article is very close
to what I am looking for. The issue of 'confirmation bias' (strongly held
prior beliefs) is an interesting topic and seems to be under-investigated in
the literature.
If anyone has any ideas, comments or literature to share, I would be happy
to discuss this further.
All the best,
Ahmed
-----Original Message-----
From: Evidence based health (EBH)
[mailto:[log in to unmask]] On Behalf Of Chris Del Mar
Sent: Thursday, November 08, 2012 3:18 PM
To: [log in to unmask]
Subject: Re: Author Bias and Objective Outcome Measures
Ahmed
.and here's an example from SRs and meta-analysis (although the outcomes is
less objective than 'death'):
Analysis of decisions made in meta-analyses of depression screening and the
risk of confirmation bias: A case study BMC Medical Research Methodology
2012, 12:76 doi:10.1186/1471-2288-12-76
http://www.biomedcentral.com/1471-2288/12/76
Chris Del Mar
From: Evidence based health (EBH)
[mailto:[log in to unmask]] On Behalf Of Janet Martin
Sent: Friday, 9 November 2012 7:08 AM
To: [log in to unmask]
Subject: Re: Author Bias and Objective Outcome Measures
Hi Ahmed,
This may be related to what you are looking for:
JAMA. 2004 May 26;291(20):2457-65.
Empirical evidence for selective reporting of outcomes in randomized trials:
comparison of protocols to published articles.
Chan AW, Hróbjartsson A, Haahr MT, Gřtzsche PC, Altman DG.
Centre for Statistics in Medicine, Institute of Health Sciences, Headington,
Oxford, England. [log in to unmask]
CONTEXT: Selective reporting of outcomes within published studies based on
the nature or direction of their results has been widely suspected, but
direct evidence of such bias is currently limited to case reports.
OBJECTIVE: To study empirically the extent and nature of outcome reporting
bias in a cohort of randomized trials.
DESIGN: Cohort study using protocols and published reports of randomized
trials approved by the Scientific-Ethical Committees for Copenhagen and
Frederiksberg, Denmark, in 1994-1995. The number and characteristics of
reported and unreported trial outcomes were recorded from protocols, journal
articles, and a survey of trialists. An outcome was considered incompletely
reported if insufficient data were presented in the published articles for
meta-analysis. Odds ratios relating the completeness of outcome reporting to
statistical significance were calculated for each trial and then pooled to
provide an overall estimate of bias. Protocols and published articles were
also compared to identify discrepancies in primary outcomes.
MAIN OUTCOME MEASURES: Completeness of reporting of efficacy and harm
outcomes and of statistically significant vs nonsignificant outcomes;
consistency between primary outcomes defined in the most recent protocols
and those defined in published articles.
RESULTS: One hundred two trials with 122 published journal articles and 3736
outcomes were identified. Overall, 50% of efficacy and 65% of harm outcomes
per trial were incompletely reported. Statistically significant outcomes had
a higher odds of being fully reported compared with nonsignificant outcomes
for both efficacy (pooled odds ratio, 2.4; 95% confidence interval [CI],
1.4-4.0) and harm (pooled odds ratio, 4.7; 95% CI, 1.8-12.0) data. In
comparing published articles with protocols, 62% of trials had at least 1
primary outcome that was changed, introduced, or omitted. Eighty-six percent
of survey responders (42/49) denied the existence of unreported outcomes
despite clear evidence to the contrary.
CONCLUSIONS: The reporting of trial outcomes is not only frequently
incomplete but also biased and inconsistent with protocols. Published
articles, as well as reviews that incorporate them, may therefore be
unreliable and overestimate the benefits of an intervention. To ensure
transparency, planned trials should be registered and protocols should be
made publicly available prior to trial completion.
PMID: 15161896 [PubMed - indexed for MEDLINE]
Many thanks,
Janet
____________________________________________________________
Janet Martin, PharmD, MSc(HTA&M)
Director, Medical Evidence*Decision Integrity*Clinical Outcomes (MEDICI)
Assistant Professor, Department of Anesthesia & Perioperative Medicine
Department of Epidemiology & Biostatistics Schulich School of Medicine &
Dentistry University of Western Ontario Room C3-172, 339 Windermere Road
London, Ontario Canada N6A 5A5
email: [log in to unmask]
tel: 519-685-8500 x33031
>>> "Ahmed Abou-Setta, M.D." 11/08/12 3:52 PM >>>
Hello,
I am looking into the issue of ?author bias? especially with the reporting
of ?objective outcomes? (e.g. mortality). I know that bias from known
sources like sponsorship (e.g. pharmaceutical industry) has been well
investigated, but about just purely ?author bias?. Often authors are biased
one way or another for a vast number of reasons including but not limited to
personal beliefs of efficacy/effectiveness, prior observations in clinical
practice, etc. I am looking for publications which measure or test this bias
especially for objective outcomes since it?s much easier to bias subjective
outcomes (e.g. pain scores) than objective ones (e.g. mortality) especially
if the trials were randomized.
Thanks.
Ahmed
P.S. Here is the search strategy I used in PubMed: ("bias
(epidemiology)"[MeSH Terms] AND (prejudice[MESH] OR Conflict of
Interest[MESH])) NOT Letter [Publication Type]. It yielded some interesting
citations but nothing hit the nail on the head.
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