The Cochrane Oral Health Group has been reviewing it’s policies and procedures for searching for studies for a systematic review. Here’s what authors need to know…
Searches: how and when
One of the first stages of undertaking a systematic review is to develop a comprehensive search strategy.
A search strategy will be developed for MEDLINE by the Oral Health Group’s Trials Search Co-ordinator, Anne Littlewood, in consultation with the authors at the very beginning of the review process. In order to do this, she will need some background information on the population, interventions, comparisons and outcomes. A relevant RCT or systematic review is also helpful at this stage for testing the search. The agreed search strategy will be presented in the protocol as an appendix.
A full set of searches will normally take place after the publication of the protocol, once the search strategy and databases to be searched have been subject to peer review. The search strategy is NOT considered to be final until the protocol has been published.
All electronic searches will take place at the editorial base. Results can be provided either in a text file, or in a file for import into reference management software (eg EndNote, Reference Manager, RefWorks).
Anne can also advise on:
- Databases to search. The Oral Health Group policy is to search the Oral Health Group Trials Register, CENTRAL, MEDLINE and EMBASE as a minimum. Additional databases may also be required depending on topic (for example, PsycINFO if the topic was dental anxiety). Other databases can be searched on request, providing the access required is available at the Editorial Base (for example, AMED, LILACS, Web of Science Conference Proceedings, ClinicalTrials.gov).
- RCT filters. An RCT filter may be required if the yield from the search is large (>500). An RCT filter is a search strategy which is added to the main search strategy so that the majority of the studies retrieved are randomized controlled trials or controlled clinical trials. A filter has been developed for MEDLINE, and this is published in the Cochrane Handbook, Section 188.8.131.52). RCT filters have been developed at the Editorial Base for other databases, such as EMBASE and AMED. The Brazilian Cochrane Center has developed a filter for LILACS.
Searches must be no more than 12 months old when the review is published, so it is likely that the searches will have to be updated before publication.
(A definition from the Cochrane Handbook, Section 184.108.40.206) “Handsearching involves a manual page-by-page examination of the entire contents of a journal issue or conference proceedings to identify all eligible reports of trials”
The Cochrane Collaboration has been undertaking a worldwide handsearching programme to identify randomized and controlled clinical trials from the literature. The process has been managed by the US Cochrane Center, who maintain files of all handsearching activity in a Master List of Journals. Over 3,000 journals have been, or are being, searched within the Collaboration.
Authors are NOT routinely expected to handsearch journals for their reviews but they should contact Anne to see whether in their particular case handsearching of any journals or conference proceedings might be beneficial. She can advise on whether the journal of interest has already been handsearched and to which dates.
Search methods section of the review
Anne can help authors to complete the search methods section of the review. We have standard copy to add to this section. All search dates, search platforms and databases searched should be documented in the abstract and full text, so that the searches are replicable and the methodology is transparent. The search strategies for all databases should be presented as appendices. If the Cochrane Collaboration’s RCT filter has been used, this should be correctly referenced.
More on screening for eligibility soon…