Intended for healthcare professionals


Putting evidence into practice

BMJ 2011; 342 doi: (Published 11 April 2011) Cite this as: BMJ 2011;342:d2072
  1. Martin Dawes, Royal Canadian Legion professor and head of department
  1. 1University of British Columbia Department of Family Practice, Vancouver, BC, Canada V6T 1Z3
  1. martin.dawes{at}

Revised levels of evidence help to find the best evidence, in real time

In 1998 the Centre for Evidence Based Medicine (CEBM) published its levels of evidence, which were designed to help clinicians and decision makers have a clearer understanding of bias within clinical research and be able to look at the fewer articles with higher validity. Recently the levels of evidence were revised in light of new concepts and data (table 1).1

View this table:

Oxford Centre for Evidence Based Medicine 2011 levels of evidence1

Not all that is published is true. Although this may not matter too much for some publications, when it comes to clinically relevant ones it can be a matter of life or death. Consequently, there is a clear need for a scientific approach to clinical evidence. Not every test or treatment will be completely accurate or effective in every person. Moreover, study results usually come with confidence intervals that provide a range of possibilities for what happens in a wider population and can help clinicians explain uncertainty when making decisions with individual patients.2 In addition to the confidence interval …

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