Objectives:
1. Establish baseline characteristics of a snapshot of Clinical Evidence topics that had substantial changes or new evidence, which will allow future comparisons and analyses.
2. Determine the nature of new evidence incorporated into Clinical Evidence, and how this varies between topics and sections
3. Describe the impact of new evidence in the categorisation and certainty of interventions.
4. Describe what has driven changes in categorisation in issue 13 of Clinical Evidence.
5. Identify occasions in which a question had been answered but new data addressing that specific question emerged, which will prepare the ground for future research into the reasons why this additional research was done.

Methods: Clinical Evidence Issue 13 will be our reference. We will list all updated topics and those with new evidence or substantial changes. For those with new evidence, we will describe the nature of the evidence. We will look at variations in these figures across different areas of knowledge and healthcare disciplines (e.g. surgical, medical, paramedical)

Results: Of the one hundred and ninety six topics in Clinical Evidence issue 13, sixty seven were updated for this issue. Thirty two of these had one or more changes that were deemed to be substantive (either by new evidence or a reassessment of previous evidence that changed our conclusions on the effectiveness of a treatment). Thirteen categorisation changes were made for issue 13. Seven were based on reassessment of old evidence and six were based on new evidence.

Conclusion: We will assess the impact of new evidence on Clinical Evidence topics in the latest issue. This will provide baseline data that will support future studies, and provide valuable information for scientists and researchers working in evidence-based health care