Clinical Research - Cochrane Collaboration in review

Cochrane Collaboration in review

The Cochrane Collaboration contributes up to 20% of the global output of systematic reviews of the effects of healthcare interventions. Mike Clarke looks at the work of the world's largest organisation in this field

Many tens of thousands of clinical trials are currently ongoing around the world, and reports for tens of thousands of closed trials will be published between now and the end of 2010. Health practitioners, policymakers and other health and healthcare decision makers can be forgiven for feeling overwhelmed by the sheer volume of this research. Increasingly, these healthcare professionals are turning to the work of systematic reviewers who have identified the evidence relevant to a particular topic, appraised and summarised it, and presented it in a structured, up-to-date report that can be used as one piece of the evidence base.

Yet, systematic reviews should not be seen simply as the means by which the findings of long-finished research are made more accessible; they should form the basis for the design of the study, and then its interpretation when it is being analysed.

A growing literature

A search of the World Health Organisation's International Clinical Trials Registry Platform reveals that more than 30,000 trials are currently recruiting, and this is known to be an underestimate of the total amount of ongoing research. Indeed, the healthcare literature is growing at a rate of upwards of 25,000 reports per year based on the contents of the Cochrane Central Register of Controlled Trials. Systematic reviews are struggling to keep pace.

An audit of PubMed reveals that around 2,500 systematic reviews were published in 2004. A few hundred of these were contributed by Cochrane. In 2009, detailed guidance was published aimed at improving the quality of the reports of systematic reviews, including a call for a prospective register of this type of research.¹

A collaborative effort

So how does the Cochrane Collaboration work? The Collaboration is a global organisation dedicated to the preparation and maintenance of systematic reviews of the effects of healthcare interventions. It began within the NHS's Research and Development Programme, with the establishment of the UK Cochrane Centre in 1992 - now part of the National Institute of Health Research, which continues to be a major funder of the work of The Collaboration. This work now covers more than 100 countries and involves more than 24,000 people. The Collaboration covers all areas of health and all aspects of care, including screening, treatment, prevention and rehabilitation.

There are now 4,000 Cochrane systematic reviews published in full in The Cochrane Library (www.thecochranelibrary.com), and they are free at the point of use in many parts of the world through national and regional provisions.² The Collaboration also produces Cochrane methodology reviews, providing a unique collection of systematic reviews of the methods for systematic reviews and other evaluations of health and social care.³

All Cochrane reviews have editorial input and oversight from one of the 51 Cochrane Review Groups, under the Editor-in-Chief, David Tovey. These Groups cover specific areas of health, such as pregnancy and childbirth, dementia, skin diseases, stroke and lung cancer. Between them, they produce around 400 new reviews each year, as well as updating hundreds of existing reviews, sometimes with the addition of evidence that will lead to changes to their conclusions. The Collaboration works closely with both practitioners and consumers to ensure the relevance of its work, while a Cochrane Consumer Network helps to promote the involvement of users of healthcare and services in the production, and use, of Cochrane reviews.

Every review is published in the Cochrane Database of Systematic Reviews, which is part of The Cochrane Library. They are also indexed in MEDLINE and included in Thomson Reuters Impact Factor, with an impact factor of 5.182 in 2008.

To ensure the accessibility of the reviews, they have a standard structure, and include a plain language summary aimed at a lay audience, a structured abstract, and a Summary of Findings table to provide the main numerical results of the review and an indication of the strength of this evidence. The main text covers the background and objectives, eligibility criteria, search strategy, methods of the review, description of the studies and their methodological quality, results, discussion, and the authors' conclusions, divided into implications for practice and implications for research. Each review is preceded by a refereed, published protocol setting out the proposed methods for the review. There are currently 1,900 protocols in The Cochrane Library, and these will be upgraded into full reviews over the coming years.

Cochrane reviews are widely used in decision making and guidelines. A survey in 2008, for example, found that 54 guidelines from the National Institute of Health and Clinical Excellence (NICE) included a total of 572 citations to Cochrane reviews, and the recent guideline on schizophrenia cited 24.

Improving access

There are also initiatives underway to improve access to the findings of Cochrane reviews. Recent developments include the introduction of short, audio podcasts in which the authors of reviews summarise the findings of their research in an evidence pod (www.cochrane.org/podcasts) and a monthly, web-based Journal Club highlighting the reviews' clinical and methodological aspects (www.CochraneJournalClub.com).

While Cochrane reviews cover the whole range of healthcare, much work still remains to cover all areas for which reliable evidence is needed. This would be made easier if the researchers responsible for clinical trials used systematic reviews to show the scientific and ethical justification for their new studies and interpreted their findings in the light of an updated systematic review.

For more information about The Cochrane Collaboration or systematic reviews contact the author at mclarke@cochrane.ac.uk, or visit the UK Cochrane Centre's website at www.cochrane.ac.uk.

References

1. Liberati A, Altman DG, Tetzlaff J, Mulrow C, G?tzsche PC, Ioannidis JPA, Clarke M, Devereaux PJ, Kleijnen J, Moher D, and the PRISMA Group. The PRISMA Statement for reporting systematic reviews and meta-analyses of studies that evaluate health care interventions: explanation and elaboration. PLoS Medicine 2009; 6: e1000100.
2. Allen C, Clarke M, Tharyan P. International activity in The Cochrane Collaboration with particular reference to India. National Medical Journal of India 2007; 20: 250-255.
3. Tricco AC, Tetzlaff J, Sampson M, Fergusson D, Cogo E, Horsley T, Moher D. Few systematic reviews exist documenting the extent of bias: a systematic review. Journal of Clinical Epidemiology 2008; 61: 422-434.

Mike Clarke is director of the UK Cochrane Centre National Institute for Health Research in Oxford