BMJ 2000;320:1720-1723 ( 24 June )

Education and debate

Seeing what you want to see in randomised controlled trials: versions and perversions of UKPDS data

James McCormack, associate professor ^a, Trisha Greenhalgh, senior lecturer ^b. 

^a Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, Canada V6T 1W5, ^b Department of Primary Care and Population Sciences, Royal Free and University College Medical School, London N19 3UA

Correspondence to: J McCormack jmccorma@interchange.ubc.ca

The first 150 words of the full text of this article appear below.

Randomised controlled trials are objective, free of bias, and produce robust conclusions about the benefits and risks of treatment, and clinicians should be trained to rely on them; so says the gospel of evidence based practice. In this article we argue, using the United Kingdom prospective diabetes study (UKPDS) as an example, that there is one stage in the conduct of a randomised controlled trialthe interpretation and dissemination of resultsthat is open to several biases that can seriously distort the conclusions. By bias, we mean the epidemiological definition: anything that systematically distorts the comparisons between groups. We will argue that certain biases arise when different stakeholders assign their individual values to the interpretation of the final results of randomised controlled trials.

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	Marketing the UK prospective diabetes study results

Until 1998, type 2 diabetes had been treated for over 25 years with drugs such as the sulphonylureas, insulin, and metformin. Only one well designed, prospective clinical trial had evaluated . . . [Full text of this article]

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Rapid Responses:

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Is This Any Different?

B M Hegde
bmj.com, 24 Jun 2000 [Full text]

Math and medicine: chaos, butterflies and RCT's

Vivian S Rambihar
bmj.com, 27 Jun 2000 [Full text]

Another bias for consideration:

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bmj.com, 26 Jun 2000 [Full text]

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bmj.com, 28 Jun 2000 [Full text]

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bmj.com, 30 Jun 2000 [Full text]

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bmj.com, 5 Jul 2000 [Full text]

Transparency is important

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bmj.com, 7 Jul 2000 [Full text]

Ill informed choice

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bmj.com, 11 Jul 2000 [Full text]

Also meta-analyses may have interpretation bias.

Morten Lindbaek
bmj.com, 16 Jul 2000 [Full text]

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bmj.com, 19 Jul 2000 [Full text]

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bmj.com, 31 Aug 2005 [Full text]

To obtain the true findings of the UKPDS unintentional bias in it should be further analyzed

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