Development of systematic reviews of randomised clinical trials

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Development of systematic reviews of randomised
clinical trials

• Tahany Awad
• Cochrane Hepato-Bilary Group, Denmark

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Outline

• Development of systematic reviews
• Systematic reviews in various databases
• - Quantitatively
• - Qualitatively

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Development of systematic reviews(1904)
Pearson K (1904). Report on certain enteric fever
inoculation statistics. British Medical Journal
31243-6.
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Development of meta-analyses(1976)

• Gene Glass coined the term meta-analysis
• The statistical analysis of a large
  collection of analysis results from individual
  studies for the purpose of integrating the
  findings

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Systematic reviews and meta-analyses in medicine

• Interest began in the late 1970s
• In 1979, the first overview (meta-analysis) of
  perinatal trials was published
• (Chalmers 1979)

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Development of meta-analyses in
hepatogastroentrology (1997)
Auperin et al (1997 ). Aliment Pharmacol Ther 11,
215-25
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The Cochrane Collaboration (1993-)

• 1993
• Formal launch of the Cochrane Collaboration at
  the 1st Cochrane Colloquium, in Oxford, UK
• Update Software releases, version 1 RevMan
• 1996
• The Cochrane Library launched as a quarterly
  publication on CD
• 1998
• The Cochrane Library became available online

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Protocols for reviews and systematic reviews on
The Cochrane Library
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Development of systematic reviews(2009)
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Methodological quality of Cochrane systematic
reviews versus reviews in Medline

• Jadad et al found that more Cochrane reviews
• Included a description of the inclusion and
  exclusion criteria
• Assessed trial quality
• No language restrictions
• Regularly updated
• Jadad et al (1998). JAMA 280 278-80

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Methodological quality of Cochrane systematic
reviews

• Olsen et al assessed the quality of 53
  Cochrane systematic reviews. The scores given in
  the independent assessments were
• no problems (n 24)
• minor problems (n 31)
• major problems (n 19)
• Olsen (2001). BMJ 323 829-32

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Quality of 809 Cochrane systematic reviews
versus 156 paper-based reviews

• Moja (2005). BMJ 330 1053

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24 Cochrane versus other meta-analyses of the
same drugs

• Industry supported reviews
• poorer quality
• less transparent
• included trials with higher risk of bias
• always recommend the experimental drug
• Reviews with undeclared/not for profit/no support
  
• similar cautious conclusions to matched Cochrane
  reviews Jørgensen et al. BMJ  2006333782

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Systematic reviews, now

• Quantity
• - more non-Cochrane reviews
• Quality
• - but are these non-Cochrane reviews
• systematic?
• none of the non-Cochrane reviews have a
  
• published protocol
• several other methodological shortcomings

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Systematic reviews, are we there yet?

• Increase quantity
• Improve quality

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Thank you