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General medicine
Refining the E in EBM
  1. Tom Jefferson
  1. Centre for Evidence Based Medicine, University of Oxford Centre for Evidence-Based Medicine, Oxford, UK
  1. Correspondence to Dr Tom Jefferson, Centre for Evidence Based Medicine, University of Oxford Centre for Evidence-Based Medicine, Oxford OX3 7LF, UK; jefferson{at}

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This is the second in a series of notes addressing the need to change our evidence sources for assessing the effects of pharmaceuticals and biologics because of the danger of unrecognised reporting bias. In this note I shall discuss the possibility of using a shorter way of redefining the E than using clinical study reports.

In the first note—‘Redefining the ‘E’ in EBM’— I made the point that trial publications (if they exist) are the tip of the data iceberg.1 The ‘iceberg’ is made up of a complex and massive reality of thousands of pages of clinical study reports, manuals, forms and slides of meetings invisible below the waterline. The submerged part is likely to represent anything between 1 and 8000 pages of published material.2 Even more importantly, the submerged material has the potential to change the conclusions of systematic reviews. To prove this point we have presented a list of references in our first editorial1 and at the Restoring Invisible and …

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  • Contributors TJ is the sole author.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests TJ has provided a link to a webpage with extensive disclosure in the manuscript.

  • Patient consent for publication Not required.

  • Provenance and peer review Commissioned; internally peer reviewed.

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