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Publication bias in clinical trials. Kamran Abbasi Deputy editor, BMJ. Merhaba. I want to talk about . . . What is publication bias? Why does it matter? What is the evidence for it? What can be done about it? How has the BMJ responded?. There are many types of bias.

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publication bias in clinical trials

Publication bias in clinical trials

Kamran Abbasi

Deputy editor, BMJ

i want to talk about
I want to talk about . . .
  • What is publication bias?
  • Why does it matter?
  • What is the evidence for it?
  • What can be done about it?
  • How has the BMJ responded?
there are many types of bias
There are many types of bias
  • Selection bias: biased allocation to comparison groups
  • Performance bias: unequal provision of care except treatment being evaluated
  • Detection bias: biased assessment of outcome
  • Attrition bias: biased occurrence and handling of deviations from protocol and loss to follow up
  • . . . and on and on

(From Egger et al BMJ 2001;323:42-46 (7 July)

what is publication bias 1
What is publication bias (1)?
  • A definition:

“Publication bias refers to the greater likelihood that studies with positive results will be published”

JAMA 2002;287:2825-2828

what is publication bias 2
What is publication bias (2)?
  • An alternative definition:

Publication bias is the selective or multiple publication or suppression of trial results so that the scientific record is distorted

why does it matter
Why does it matter?
  • Distorts the scientific record
  • Hides the “truth”
  • Influences doctors’ decision making
  • Misleads policy makers
  • Causes harm to patients
  • Costly for the health service
  • A form of scientific and research misconduct
who is to blame
Who is to blame?
  • Wicked researchers?
  • Very wicked sponsors?
  • Editors: the wickedest of all?
  • (and let’s not forget reviewers)
what is the evidence for it 1
What is the evidence for it (1)?
  • Stern and Simes BMJ 1997;315:640-645
  • Question: To what extent is publication influenced by study outcome?
  • Studies submitted to an Australian ethics committee over 10 years
  • Examined protocols
  • Questionnaire to authors (70% response)
stern and simes results
Stern and Simes: results

Clinical trials

(n=130)

All studies

(n=520)

Positive> negative

2.32

(1.47 to 3.66)

3.13

(1.76 to 5.58)

Time to publication

4.8 vs

8.0 yrs

4.7 vs 8.0 yrs

stern and simes conclusions
Stern and Simes: conclusions
  • Positive trials are more likely to be submitted for publication
  • Positive trials are more likely to be published
  • Positive trials are more likely to be published quickly
  • Implications for systematic reviews
  • Important to register all trials
what is the evidence for it 2
What is the evidence for it (2)?
  • Lexchin and Bero BMJ 2003;326:1167-70
  • Question: Does drug industry sponsorship influence research quality and outcome?
  • Meta-meta-analysis
  • Industry research less likely to be published (more likely in symposium proceedings)
  • No difference in methodological quality
  • More likely to have a positive finding (OR 4.05 95% CI 2.98 to 5.51)
lexchin and bero
Lexchin and Bero
  • A wide range of diseases

eg osteoarthiritis of the knee, multiple myeloma, psychiatric problems, Alzheimer’s disease, venous thromboembolism

  • A wide range of drugs

eg tacrine, clozapine, 3rd generation OCP, erythropoietin, antidepressants, topical glucocorticoids, treatment for HIV

lexchin and bero conclusions
Lexchin and Bero: conclusions
  • Published research from drug companies is more likely to be favourable to the product
  • Do companies selectively fund trials?

Unlikely

  • Is it of poorer quality?

No

  • Are inappropriate comparators chosen?

Sometimes/often/a lot

  • Is it publication bias?

Yes

what is the evidence for it 3
What is the evidence for it (3)?
  • Melander et al BMJ 2003;326:1171-3
  • Question: Is there selective reporting of sponsored studies by drug companies?
  • Trials submitted to the Swedish drug regulatory authority (5 SSRIs, 42 trials)
  • Multiple publication
  • Selective publication
  • Selective reporting
melander et al conclusion
Melander et al: conclusion
  • “Any attempt to recommend a specific selective serotonin reuptake inhibitor from the publicly available data ONLY is likely to be based on biased evidence.”
what is the evidence for it 4
What is the evidence for it (4)?
  • Olson et al JAMA 2002;287:2825-2828
  • Question: Is there publication bias in editorial decision making?
  • 3 years, 745 manuscripts
  • Positive vs negative OR 1.30 (0.87 to 1.86)
  • Small effect of editorial decision making, much less than researchers not submitting negative studies
  • Will this be true for journals less grand than JAMA?
what can be done about it 1
What can be done about it (1)?
  • Better conduct and reporting of RCTs (CONSORT)
  • Better conduct and reporting of systematic reviews (QUORUM)
  • “Publication” of unpublished trials
  • Enlightened sponsors (a code of good practice Wager et al 2003 http://www.gpp-guidelines.org)
  • Better editorial policies
  • Vigilant editors and reviewers
  • Responsible authors
what can be done about it 2
What can be done about it (2)?
  • Publication of original protocols and deviations from protocol
  • Declaration of competing (financial) interests by authors, reviewers, and editors
  • Declaration of sponsorship/funding
  • Registering all clinical trials
how has the bmj responded
How has the BMJ responded?
  • A change in editorial thinking: Is it the question that matters?

It is

  • Amnesty on unreported clinical trials
  • More transparency (CONSORT, QUORUM, sponsorship, funding, competing interests)
  • Theme issue on doctors and the drug industry
  • ?Protocols
  • ?Registering clinical trials
conclusions
Conclusions
  • Publication bias is an important problem that impacts on patient care
  • There is much evidence to support its existence
  • There are many players
  • There are many ways to reduce its effect, examples of good practice
  • Ultimately there is a big responsibility on sponsors of trials, authors, and editors