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Evidence-Based Medicine: EBM & Cochrane

Welcome to Evidence-Based Medicine (EBM) guide that is intended to provide basic information about EBM with special emphasis on searching and evaluating studies retrieved using Medline, PubMed, Cochrane and other Internet resources.

EBM & Cochrane

Cochrane is an international organization that started in 1993.  It was developed after Archie Cochrane, a UK epidemiologist who noticed that health-care is not always based on good evidence.  It prepares, maintains and promotes the accessibility of systematic reviews of the effects of health care intervention.  It has more than 15 centers worldwide, with 8000 members.  Each subject area in health care is covered by a Specialized Cochrane Review Group.

Cochrane reviews are high quality, up-to-date systematic reviews across a broad range of health topics, intended to help decision makers to cope with the large volume of literature by summarizing the reliable evidence of the benefits and risks of healthcare. Systematic reviews limit bias and reduce chance effects, thus providing more reliable results for drawing decisions about health care.   Cochrane contains a number of high-quality evidence databases the most important being:

  • Cochrane Database of Systematic Reviews (CDSR): are full text documents reviewing effects of health care.  These are highly structured and systematic and have the highest level of evidence.

  • Database of Abstracts of Reviews of Effects (DARE): provides structured abstracts of systematic reviews that have been initially appraised by reviewers giving comment on the quality of methodology.  It complements CDSR by offering a selection of high-quality assessed reviews in those subjects where there is currently no Cochrane review.

  • Cochrane Central Register of Controlled Trials (CENTRAL): is a bibliography of controlled trials, it also includes reports published in conference proceedings and other sources not indexed in Medline or other bibliographic databases.

  • Cochrane Methodology Register (CDMR): contains articles on research synthesis and systematic reviews.

  • Health Technology Assessment Database ( HTA ): contains information on healthcare technology assessment, including details of ongoing projects and publications from health technology assessment organizations.

  • NHS Economic Evaluation Database (NHS EED)


Cochrane Collaboration Logo:

Cochrane Logo illustrates a systematic review of data from 7 randomized controlled trials (RCT) comparing one health care treatment with a placebo.   Each horizontal line represents results of one trial.  The shorter the line means the more certain the result.  The diamond is the combined result, if it is to the left then treatment is beneficial.  If a horizontal line touches the vertical one then the trial found no clear difference between the treatments.  If the horizontal line is to the right or the diamond is to the right of the vertical line then the treatment in not good, and may do more harm than good. 


A Cochrane systematic review consists of:

  • Title of review, name and addresses of reviewers & editorial team.
  • Structured report of review consisting of an abstract, background information, objective, materials & methods, results of review,discussion & conclusions about implications for practice & research.
  • Full citations of studies incorporated in review.
  • Tabulation of the characteristics of trials included in review including information on assessment of the methodological quality of each of the studies included.
  • Sometime there is also tabulation of the results of the review with presentation of statistical syntheses (meta-analyses).

The first stage in preparing a review is the development of a protocol which includes an introduction, objectives, inclusion criteria, and methods (including search, strategy). It takes about 12 -18 months for a protocol to become a full review.  If it remains as a protocol for 2 years, it is removed from the database. Updating reviews is very essential, this may be done in light of comments from others or as new evidence shows up. 


Cochrane Search Options

Below are some Cochrane search options:

◦Default is Boolean AND; use OR and parenthesis ( ).

◦May 2000 abstracts were added to Medline/PubMed.

◦Many  records in Cochrane are not indexed using  MeSH.  So search using   MeSH “OR”ed with textwords.

◦Protocols are not yet indexed by MeSH, so use textwords. Two thirds of CENTRAL  records are indexed by MeSH, and some of the DARE database.

.Truncation(*), could be internal, external or at beginning of word.

◦NEXT ( is adjacent ); NEAR ( is maximum 6 words)

◦Allows "Phrase Search"