We can help you to...
- Register a proposed systematic review with us.
- Define research questions and refine search strategies.
- Get access to electronic bibliographic databases.
- Prepare and maintain Cochrane Systematic Reviews.
- Transform meta-analyses and reviews published elsewhere into systematic reviews for the Cochrane Library.
- Get in touch with our collaborators around the world.
- Find people to help with guideline development.
Here are some useful guides:
Cochrane Handbook for Systematic Reviews of Interventions: the official guide to producing Cochrane systematic reviews.
Introduction to the Heart Group Editorial Process: guide to develop your Cochrane Heart Group protocol and review.
Guidelines for updating a Heart Group's review: the process of updating your Cochrane Heart Group review (every 2 years).
RevMan homepage: the software authors must use to produce and maintain their Cochrane systematic review. Download the latest version of RevMan (RevMan 5), along with user guide, support and FAQs.
Training and support: this page contains information about Cochrane Collaboration workshops and provides access to open learning materials.
Handling continuous variables: please read this document for guidance on how to calculate the difference in the means (or weighted mean differences) for continuous variables.
Cochrane style resource: compare your review against the official style document.
PRISMA: please note that all draft reviews submitted to the Cochrane Heart Group must be accompanied by a PRISMA flowchart, which records the flow of papers through your review. If you need help with your PRISMA statement please contact the editorial base.
Permission to republish your review form: this form must be completed and returned to the Permissions Department at Wiley if you wish to re-publish your Cochrane systematic review in another scientific journal. Please see clarification from Wiley regarding permission to re-publish material.
Methods used in reviews
Authors should contact the Trials Search Coordinator BEFORE they begin their search. We will provide detailed and specific assistance in the preparation of your search strategy and work with you to develop it.
Access to specialised register by reviewers
Authors can search the Cochrane Library with the search term SR-VASC this will identify records on our specialist trials register. For further information please contact the Trials Search Co-ordinator.
Additional search strategies
The Trials Search Co-ordinator will assist authors in preparing search strategies, including advising which databases, or other sources, should be searched for their review.
Once you have done your searching it is helpful to manage your records by downloading them into a reference management package such as Reference Manager, Procite or Endnote. We ask all authors to keep track of what happens to these records, and how many are discarded/used in the review. To keep track of your records please use a flow diagram, as suggested in the PRISMA statement.
We ask authors to read and to use the Cochrane Handbook for Systematic Reviews of Interventions and encourage the use of randomised controlled trials as these represent the best available evidence for effects of health care interventions. All authors must provide a PRISMA statement with their Review (Moher 1999). We encourage authors to focus on questions of clinical relevance and consequently trials with clinical event outcomes and suitable follow-up times are preferred. We ask authors to use forms to record eligibility and to help them decide whether a study is included or excluded. The editorial base can provide authors with examples of these forms. Ideally two authors should independently select trial reports for inclusion using the eligibility forms and differences should be resolved by discussion. These forms are useful to record why specific trial reports were excluded from the systematic review.
Assessment of risk of bias
We ask authors to follow the methods for assessing the risk of bias in included studies in the Cochrane Handbook for Systematic Reviews of Interventions (www.cochrane-handbook.org). Standard scales are not recommended. We advise authors to collect informationon sequence generation, allocation concealment, blinding of participants, personnel and outcome assessors, incomplete outcome data and selective outcome reporting. Effects of methodological quality of included studies may be examined depending on the authors' views. As yet there is no consensus on the optimum method to assess the methodological quality of randomised controlled trials. Scoring the quality of RCTs can be disadvantageous and is viewed withs ome controversy (Juni 1999).
The Cochrane Heart Group recommend authors address the following criteria intheir assessment of quality of RCTs:
1 Was the allocation sequence adequately generated?
2 Was allocation adequately concealed?
3 Was knowledge of the allocated intervention adequatelyprevented during the study?
4 Were incomplete outcome data adequately addressed?
5 Are reports of the study free of suggestion of selectiveoutcome reporting?
6 Was the study apparently free of other problems that couldput it at a high risk of bias?
We ask authors to use a form on which to record the data they will use from each study for their systematic review. These are called "data extraction forms". The editorial base can provide authors with examples of these forms. Ideally two authors should independently complete data extraction forms and then resolve differences by discussion and re-examination of study reports. These forms are helpful for inputting data for the systematic review and, if included in the review, meta-analysis.
Verification of data is the responsibility of the authors.
Unpublished data should be sought where feasible. For drug trials, rare adverse events should be commented upon in the discussion of the Review and evidence from case reports and large post-marketing surveillance case series cited as appropriate.
We request that authors abstract data on all clinical event outcomes and also on risk factor changes (where appropriate). Physiological, pathological, psychological, quality of life or radiological outcomes may be abstracted depending on the nature of the question the review seeks to answer.
We ask authors to follow the methods of analysis in the Cochrane Handbook for Systematic Reviews of Interventions. Analysis should be performed in RevMan. Statistical support is available in the form of the Cochrane Handbook for Systematic Reviews of Interventions, from the Cochrane Heart Group editorial office and from statistical advisors to the group. Please restrict the number of analyses to those which are clinically appropriate, as if many analyses are prepared some could reach cut offs for statistical significant by chance. Please take care not to pool data from heterogeneous trials - or where data itself are too varied to merit pooling.
Statistical methods for the comparison of clinical events recommended are Odds ratios, Peto odds ratios or Risk ratios (relative risk) and for continuous data difference in means. 95% confidence intervals and, where possible, precise P values should be reported for all effect size estimates for both individual trials and pooled estimates. Heterogeneity between trials should always be explored by considering the clinical setting, patients involved and the intervention. Sub-group and sensitivity analyses may be appropriate. We recommend to those who want to include cross over trials in their systematic reviews the analytical methods described by Elbourne et al (Elborune 2002). For information on any aspects of analysis or for statistical assistance please contact the Cochrane Heart Group editoral office.
Reporting of reviews
We encourage authors to publish their reviews in other journals. We ask that authors contact the Cochrane Heart Group office when considering publishing in another journal. Many other journals allow dual publication of systematic reviews in The Cochrane Library and their journal. We ask all authors to publish their review on The Cochrane Library (the Cochrane Database of Systematic Reviews) before publishing in another journal or to arrange "simultaneous" publication. Authors must complete a Permissions request form which is available from the website of the Heart Group or the Collaboration's website. This form must be sent to the permissions office of Wiley and sons. Commentaries describing Cochrane systematic reviews may be published in other journals and similarly a permission request form is required for this.
Elbourne DR, Altman DA, Higgins JPT, Curtin F, Worthington HV, Vail A. Meta-analyses involving cross-over trials: methodological issues. International Journal of Epidemiology 2002; 31: 140-149
Juni P, Witschi A, Bloch R, Egger M. The hazards of scoring the quality of clinical trials for meta-analysis. 1999. JAMA, 282, 11, 1054-1060.
Moher D, Cook DJ, Eastwood S, Olkin I, Rennie D, Stroup DF, for the Quorom Group. Improving the quality of reports of meta-analyses of randomised controlled trials: the Quorom Statement. The Lancet, 1999, Vol 354, 1896-1900.)