Levels of Evidence 2

Jeremy Howick

The Levels of Evidence 2 table was created by Jeremy Howick PhD, PGCert, MSc, BA.

One day workshop on Evidence-Based Health Care
26th June 2013 (1 day)
More Information

Click here to download the new Levels of Evidence 2 Table
(PDF Version)

BMJ Editorial

BMJ Editorial on the OCEBM Levels II: Martin Dawes claims: "These new levels of evidence are an important tool for scientific reasoning. They appear easier to use, more practical, and should have a positive effect on healthcare as we deal with the increasing complexity and volume of evidence."

Read Editorial (subscription required)

OCEBM Levels of Evidence System

Introduction

Click here for the OCEBM Levels Table. NB: the table is intended to be used alongside the Introductory Document and Background Document. Please do not read the table separately but rather read the Introductory Document and Table together.

Hierarchies of evidence have been somewhat inflexibly used, and criticised, for some decades. The CEBM "levels of evidence" were first produced in 1998 for Evidence-Based On Call to make the process of finding appropriate evidence feasible and its results explicit. We have revised the "levels" in light of new concepts and data, and we would like to hear your feedback.

There are two different ways to interpret Level 1 evidence for treatment benefits as it is currently stated. The intended interpretation is: "either N-of-1 randomized trials or systematic reviews of randomized trials". The wrong interpretation is: "either systematic reviews of randomized trials or systematic reviews of n-of-1 trials".

Click here to see the OCEBM Table of Evidence Glossary of Terms

Table: results of a PubMed search for "atrial fibrillation AND warfarin" with some filters

Type	Term used	Number of articles
All articles	(no filter)	2175
RCT	"random allocation" [MeSH]	7
cohort	"cohort studies" [MeSH]	366
Case-control	"Case-Control Studies"[Mesh]	234
Case report	Case Reports [Publication Type]	196

(search done Jan 7th 2010)

Citing Levels of Evidence 2

If you intend to cite this table and/or the accompanying text please use one of the following citation examples.

How to cite the Levels of Evidence 2 Table - Download - French Translation

OCEBM Levels of Evidence Working Group*. "The Oxford Levels of Evidence 2".
Oxford Centre for Evidence-Based Medicine. http://www.cebm.net/index.aspx?o=5653

* OCEBM Levels of Evidence Working Group = Jeremy Howick, Iain Chalmers (James Lind Library), Paul Glasziou, Trish Greenhalgh, Carl Heneghan, Alessandro Liberati, Ivan Moschetti, Bob Phillips, Hazel Thornton, Olive Goddard and Mary Hodgkinson

How to cite the Introductory Document - Download - French Translation

Jeremy Howick, Iain Chalmers, Paul Glasziou, Trish Greenhalgh, Carl Heneghan, Alessandro Liberati, Ivan Moschetti, Bob Phillips, and Hazel Thornton. "The 2011 Oxford CEBM Levels of Evidence (Introductory Document)".
Oxford Centre for Evidence-Based Medicine. http://www.cebm.net/index.aspx?o=5653

How to cite the Background Document - Download - French Translation

Jeremy Howick, Iain Chalmers, Paul Glasziou, Trish Greenhalgh, Carl Heneghan, Alessandro Liberati, Ivan Moschetti, Bob Phillips, and Hazel Thornton. "Explanation of the 2011 Oxford Centre for Evidence-Based Medicine (OCEBM) Levels of Evidence (Background Document)".
Oxford Centre for Evidence-Based Medicine. http://www.cebm.net/index.aspx?o=5653

Click here to download the new Levels of Evidence 2 Table (PDF Version)

French Translation (PDF Version) - Nancy Durieux, Francoise Pasleau

References

Ball CM, Phillips RS. Evidence-Based On-Call. Churchill Livingstone: Edinburgh, 2001.

Guyatt, G.H., et al., GRADE: an emerging consensus on rating quality of evidence and strength of recommendations. BMJ, 2008. 336(7650): p. 924-6.

Page last edited: 30 April 2013