Searches for studies

The "Search methods for identification of studies" is part of every Cochrane protocol. Review authors should describe in detail in the protocol the elctronic database sources they are going to search and must provide the span of search for each one of them.

An example of how this should be reported in the protocol is provided below:

"We will search search the The Cochrane Hepato-Biliary Group Controlled Trials Register (Gluud 2013), Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE (1950 to present), EMBASE (Excerpta Medica Database) (1980 to present), the Science Citation Index Expanded (1945 to present) (Royle 2003), and the Conference Proceedings Citation Index (1990 to present)."

In addition, any other resources must also be specified. Eg, "We will also search the Clinicaltrials.gov website (http://clinicaltrials.gov) and World Health Organization International Clinical Trials Registry Platform (ICTRP 2011) for ongoing trials.

No language limitations will be applied.

All search strategies are provided in Appendix 1*."

*Appendix 1 is a table with three columns, designed to show the Database source, the Date of search, and the third column is to provide the Search strategy developed for the search of the respective database.

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Royle 2003 
Royle P, Milne R. Literature searching for randomized controlled trials used in Cochrane reviews: rapid versus exhaustive searches. International Journal of Technology Assessment in Health Care 2003;19(4):591-603.
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Review authors cannot search on their own The Cochrane Hepato-Biliary Group Specialised Register or The Diagnostic Test of Accuracy Studies Register as these databases are maintained locally at the CHBG Editorial Team offices. They contain bibliographic details on more than 22,000 publications and multiple searches of these databases will be performed by The Information Specialist, Sarah Louise Klingenberg, after a title for a systematic review is registered, after a protocol is approved for publication, when the search results have become outdated, when the protocol or the review needs to be updated, or when there is a request from interested authors. Authors receive the results of the searches (a bibliographic list in text format) by e-mail. Key words are suggested either by the authors or the Trials Search Co-ordinator. The finally designed search strategies should be a common effort between the authors and the Trials Search Co-ordiantor.

Almost all of the publications are coded for study design. The greatest number of references are randomised clinical trials. There are also a substantial number of controlled clinical trials, studies with uncertain design, meta-analyses, and miscellaneous references on publications that may serve as a background material for the protocols and the reviews.

The CHBG Diagnostic Test of Accuracy Studies Register contains references on 92 diagnostic test accuracy studies. This latter register is in the process of being built.

Additional search strategies
Authors should also search the citations and reference lists of the publications retrieved with the searches for additional trials or studies (eg, of diagnostic test accuracy) that might fulfil the inclusion criteria of their review. Authors should strive to identify published or unpublished studies in the form of abstracts, letters, etc. by contacting pharmaceutical industry, approach investigators of clinical trials or similar. Authors may also run their own searches in The Cochrane Library and any other databases (MEDLINE, EMBASE, Science Citation Index Expanded, LILACS, etc) that they have access to. If authors do not have access to any of these databases or their access is limited to some, then The CHBG will assist with searching the databases as well. Authors, while preparing their systematic review, are also requested to contact authors of studies as well as manufacturers of drugs for additional or missing information. No language limitations should be applied. Abstracts from EASL and AASLD conference meetings should be provided by The CHBG, and that is why authors should in general only search conference meetings from th emost recent years.

Throughout the review process, authors must follow the latest version of the Cochrane Handbook for Systematic Reviews of Interventions, ie, the Handbook

Study selection
Generally, The CHBG recommends inclusion of randomised clinical trials only for the assessment of benefit. As adverse events may not be caught in small or even large randomised clinical trials, The CHBG encourages also the inclusion of quasi-randomised studies, cohort studies, and case-control studies when dealing with reports of harmful effects of interventions. Authors must follow the guidelines in Chapter 14 of the Cochrane Handbook for Systematic Reviews of Interventions about adverse effects. Two authors should generally perform the selection of trials and data extraction independently. Therefore, the Editorial Team encourages at least two authors to work on a systematic review.