Confessions of a Quackbuster

This blog deals with healthcare consumer protection, and is therefore about quackery, healthfraud, chiropractic, and other forms of so-Called "Alternative" Medicine (sCAM).

Monday, November 22, 2004

CEBM - Levels of Evidence and Grades of Recommendation

CEBM - Centre for Evidence Based Medicine:

Levels of Evidence and Grades of Recommendation

Levels of Evidence
Footnotes & References
Recent Comments
Related material on Study Designs and Critical Appraisal
Frequently-Asked Questions about these levels
Download these Levels as an RTF document


What are we to do when the irresistible force of the need to offer clinical advice meets with the immovable object of flawed evidence? All we can do is our best: give the advice, but alert the advisees to the flaws in the evidence on which it is based.

The ancestor of this set of pages was created by Suzanne Fletcher and Dave Sackett 20 years ago when they were working for the Canadian Task Force on the Periodic Health Examination [1]. They generated 'levels of evidence' for ranking the validity of evidence about the value of preventive manoeuvres, and then tied them as 'grades of recommendations' to the advice given in the report.

The levels have evolved over the ensuing years, most notably as the basis for recommendations about the use of anti-thrombotic agents [2], have grown increasingly sophisticated [3], and have even started to appear in a new generation of evidence-based textbooks that announce, in bold marginal icons, the grade of each recommendation that appears in the texts [4] in bold icons.

However, their orientation remained therapeutic/preventive, and when a group of members of the Centre embarked on creating a new-wave house officers� manual (see the EBOC page), the need for levels and grades for diagnosis, prognosis, and harm became overwhelming and the current version of their efforts appears here. They are the work of Chris Ball, Dave Sackett, Bob Phillips, Brian Haynes, Sharon Straus, and Martin Dawes with lots of encouragement and advice from their colleagues.

Comments to this latest version are available. More are welcome as these continue to develop.

Periodic updates will appear here, and surfers are invited to suggest ways that they might be improved or further developed.

A final, cautionary note: these levels and grades speak only to the validity of evidence about prevention, diagnosis, prognosis, therapy, and harm. Other strategies, described elsewhere in the Centre’s pages, must be applied to the evidence in order to generate clinically useful measures of its potential clinical implications and to incorporate vital patient-values into the ultimate decisions.

Oxford Centre for Evidence-based Medicine Levels of Evidence (May 2001)

(Large chart)