3.1 Sources of biomedical literature

Core databases

1. MEDLINE contains records from 5600 journals (39 languages) in the of biomedical field, from 1946 onwards (Access for KCE | Free access through PubMed).
2. EMBASE: Records from 7600 journals (70 countries, 2000 not covered by Medline) in biomedical field, from 1974 onwards (Access for KCE).
3. CENTRAL - The Cochrane Controlled Trials Register, part of the Cochrane Library: Records of randomised controlled trials and controlled clinical trials in healthcare identified through the work of the Cochrane Collaboration including large numbers of records from MEDLINE and EMBASE as well as much material not covered by these databases (Dickersin, 2002). (Access for KCE through CDLH | Free access to abstracts)

Databases for systematic reviews

1. CRD Database of reviews of effectiveness (DARE) contains structured abstracts, including critical appraisal, of systematic reviews identified by regular searching of bibliographic databases, and handsearching of key journals. [the update of CRD DARE has ceased March 2015]
2. Cochrane Database of Systematic Reviews (CDSR, part of the Cochrane Library) lists the results of systematic reviews (full text) conducted by Cochrane groups, but also ongoing projects (Access for KCE through CDLH | Free access to abstracts)
3. Special queries exist for Medline or Embase to limit the identified records to articles identified as Systematic reviews. See appendix.

Databases for HTA reports

1. The INAHTA HTA database is a bibliographical database of published HTA reports; it also lists ongoing HTA projects. Members of INAHTA are regularly invited to update their information on the HTA database, informaiton from the main HTA producers is also collected by the database maintainer. Access is free, records of the HTA database are also searchable via the Cochrane Library.
2. HTA reports can also be found at individual agencies’ sites, the HTAi vortal lists HTA organisations, it also provides a custom Web search engine that limits the Google results to pages published on the website of HTA organisations listed on the HTAi vortal.

Databases for specific topics

• Nursing: CINAHL (Cumulative Index to Nursing and Allied Health Literature), British Nursing Index (BNI) (Access for KCE through CDLH)
• Physiotherapy: PEDro (contains records of RCTs, systematic reviews and evidence-based clinical practice guidelines in physiotherapy, from 1929 onwards; most trials in the database have been rated for quality to quickly discriminate between trials that are likely to be valid and interpretable and those that are not; free access)
• Psychology and Psychiatry: PsycInfo (Access for KCE)
• More bibliographic databases are listed on the KCE library catalogue (e.g. CAM, ageing, ...)

3.2 Sources of economic literature

Core database

• NHS Economic Evaluation Database (NHS EED) contains over 7000 abstracts of quality assessed economic evaluations. The database aims to assist decision-makers by systematically identifying and describing economic evaluations, appraising their quality and highlighting their relative strengths and weaknesses. [the update of CRD NHS EED has ceased March 2015]
• Some of the search filters for Medline or Embase limit the records to articles related to Costs, Economic evaluations, Economics

Complementary databases

• EconLit:database of economics publications including peer-reviewed journal articles, working papers from leading universities, PhD dissertations, books, collective volume articles, conference proceedings, and book reviews  (Access for KCE)

3.3 Sources of clinical practice guidelines

Often, specific guidelines can only be retrieved through local websites of scientific associations or government agencies. It is therefore recommended to combine a Medline search (with specific filters for guidelines) with a search of the following:

• National Guideline Clearinghouse (NGC): a US-based database of clinical practice guidelines primarily in the English language; free access
• International Guideline Library (G-I-N): database of the Guideline International Network (KCE is member of GIN and has full access to the records)
• EBMpracticenet: DUODECIM guidelines, free access in Belgium, funded by RIZIV-INAMI, translation in Dutch and French; adaptation to Belgian context ongoing
• More sources of guidelines are available on BIBKCE under Databases, Practice Guidelines or  Practice Guideline, Publishers' catalogue

3.4 Sources of ongoing clinical trials

Ongoing trials may have limited use as a means of identifying studies relevant to systematic reviews, but may be important so that when a review is later updated, these studies can be assessed for possible inclusion. Several initiatives have been taken recently to register ongoing trials:

• International Clinical Trials Registry Platform (ICTRP)
• EU Clinical Trials Register
• ClinicalTrials.gov
• Current Controlled Trials
• More clinical trials register are listed on the KCE library catalogue

3.5. Sources of grey literature

More and more electronic sources describe "grey literature" (results of scientific research not published in scientific journals; e.g. reports, working papers, thesis, conference papers, ...)

Institutional repositories

• OAIster
• Base
• OpenAIRE
• EconPapers (REPEC)
• More repositories are listed on the KCE library catalogue

3.6 Building a search strategy

For each database, search terms defined in the preparation phase will be mapped to the Thesaurus terms of the database (when available). Mapping can be achieved using the built-in functionality of the search interface, or manually by looking at the indexation of previously identified pertinent articles. Attention will need to be paid to the explosion tool (sometimes selected by default linke in PubMed, sometimes not like in OVID Medline).

The most important synonyms of the Thesaurus terms identified for each facet will also be added to the search strategy as text word. Advanced functionalities of the search interfaces will be used (see below: truncation, wildcard, proximity operators).

The terms within a specific facet will be combined with the Boolean operator ‘OR’ in order to group all articles dealing with this facet. For some concepts, special queries (also called search filters) have been developed (see below). The resulting groups of articles will then be combined using the Boolean operator ‘AND’.

It is recommended to validate each search strategy by a second reviewer.

3.7 Documenting a search strategy

The search strategy for electronic databases should be described in sufficient detail to allow that

• the process could be replicated
• an explanation could be provided regarding any study not included in the final report (identified by electronic sources search or not)

The template required by KCE to describe a search strategy is provided in attachment.

All identified references must be exported, preferably in a text file to be imported in a Reference Management Software (see appendix for technical description).