Cochrane handbook for systematic reviews of interventions. Version 5.1.0 [updated March 2011]. The Cochrane Collaboration

abstracts can be used to eliminate clearly irrelevant reports, obviating the need to obtain the full text of those reports or to return to the bibliographic database at a later time. Accession number / unique identifier: it is advisable to allocate an unused field or fields to store the unique identifier(s) / accession number(s) of records downloaded, such as the PubMed ID number (PMID). This allows subsequent linkage to the full database record and also facilitates information management such as duplicate detection and removal (i.e. de-duplication). Copyright © 2019 The Cochrane Collaboration 75 Affiliation / address: may include the institutional affiliation and / or email address of the author / investigator. Article identifier / digital object identifier (DOI): can be used to cite and link to the full record. Author identifier: can be used to disambiguate authors with similar names. The identifier may be an ORCID (https://orcid.org/about/what-is-orcid/mission? lang=en_US), an International Standard Name Identifier (ISNI) http://www.isni. org/, or from the Virtual International Authority File (VIAF) http://viaf.org/. Clinical trial number: if the record contains a clinical trial number, such as those assigned by the ClinicalTrials.gov or ISRCTN schemes, or a number allocated by the sponsor of the trial, these should be downloaded to aid linking of trial reports to the original studies. In PubMed, the Secondary Source ID field [SI] contains information from secondary sources such as ClinicalTrials.gov and ISRCTN. Similarly, in Ovid MEDLINE, the Secondary Source Linking (SL) field contains the URL to ClinicalTrials.gov and ISRCTN resources where these are mentioned in MEDLINE records. In Embase, the Clinical Trial Number (CN) field contains clinical trial numbers associated with the record. Index terms / thesaurus terms / keywords: These help indicate why records were retrieved if the title and abstract lack detail. Investigator name: this field contains personal names of individuals (e.g. collaborators and investigators) who are not authors of the article but rather are listed in the article as members of a collective / corporate group that is an author of the article. Language: this is the language (or languages) of publication of the original document. Location identifier: this field may also contain a Digital Object Identifier (DOI). Original title: if the original title of the document is not in English and the original title is available, then both titles should be downloaded into separate database fields, to aid correct identification of the reference and de-duplication. See also Transliterated title below. Other term: this field contains largely non-MeSH subject terms (also referred to as Keywords) that describe the content of the article. Author-supplied keywords are included here in PubMed (since 2013). Registry Number / EC Number and Substance Name: these fields provide supplementary subject information regarding substances (chemicals, drugs and enzymes). Transliterated title: in PubMed, this field contains the original title (or, where available, the transliterated title) of each record originally published in a non-English language. This field can be useful for de-duplication. Copyright © 2019 The Cochrane Collaboration 76 Comments, corrections, errata, retractions and updates: It is mandatory, for Cochrane reviews of interventions, to examine any relevant retraction statements and errata for information (MECIR C48). All fields that relate to subsequently published comments, corrections, errata, retractions and updates should be selected for inclusion in the download, so that any impact of these subsequent publications can be taken into account. The MECIR standard specifies: “Care should be taken to ensure that this information is retrieved in all database searches by downloading the appropriate fields, together with the citation data”. For example, the most important fields to consider, in relation to comments, errata etc, together with their field labels in PubMed, are provided in Box 4.a. Box 4.a Important field labels in PubMed in relation to comments, retractions etc CIN: ‘Comment in’ CON: ‘Comment on’ CRI: ‘Corrected and republished in’ CRF: ‘Corrected and republished from’ EIN: ‘Erratum in’ EFR: ‘Erratum for’ ECI: Expression Of Concern In ECF: Expression Of Concern For RIN: ‘Retraction in’ ROF: ‘Retraction of’ RPI: ‘Republished in’ RPF: ‘Republished from’ UIN: ‘Update in’ UOF: ‘Update of’ See: https://www.nlm. nih.gov/bsd/mms/medlineelements.html The above list is provided as an example of the relevant fields in PubMed and as an indicator of the equivalent fields in other databases and service providers. Copyright © 2019 The Cochrane Collaboration 77 4.3 De-duplicating references Because searching to inform systematic reviews is intended to be extensive, thousands of records may be retrieved from multiple sources. References to the same article may be downloaded multiple times from different sources and duplicates can even be found within individual databases. The identification and elimination of duplicate records (de-duplication) reduces unnecessary work during the screening phase. Removing duplicate records from the pool of retrieved references is also necessary if the total number of records identified through database searching (in addition to the total number of additional records identified through other sources) is to be reported correctly in the PRISMA flow diagram together with the total number of records after the duplicates have been removed (Liberati et al 2009). Many Cochrane Information Specialists de-duplicate records so that review authors see only search results that have already been de-duplicated. Formatting of citation information often varies across sources, and automated identification of duplicate references from within reference management software may lead to false positives (removing non-duplicate records) and false negatives (retaining duplicate records). Meanwhile, de-duplication through visual examination of each record is time-consuming and often impractical. Several strategies have been developed to address these issues. Methods for modifying duplicate detection algorithms within reference management software have been developed and tested (Kwon et al 2015, Bramer et al 2016b). An online method to identify search results that are duplicates of PubMed citations has been reported (Sampson et al 2006). Open-source software programs for online duplicate detection have also been developed (Jiang et al 2014, Rathbone et al 2015). There is no consensus on the optimal method for duplicate detection, and the most appropriate method will most likely depend upon the size of the combined dataset, the number and output format of the resources searched, and the skill and comfort level of the operator. A combination of automated methods and visual inspection is often used. After de-duplication of search results, records may be screened for inclusion from within the reference management database. Alternatively, the records may be exported into dedicated screening software or into systematic review production software that includes screening capabilities. If screening is carried out within the reference management database, records for the included and excluded studies can be exported and uploaded into systematic review software such as RevMan. Instructions for importing references into RevMan can be found at: https://community.cochrane. org/help/tools-and-software/revman-5/support-revman5/revman-5-faq. The decision whether to screen within reference management software or within dedicated screening or review production software will most likely depend upon the number of retrieved references, access to various tools and review author preference. Copyright © 2019 The Cochrane Collaboration 78 4.4 Summary points • Cochrane review authors should seek advice from their Cochrane Information Specialist on managing references. • Authors of non-Cochrane reviews should seek advice from their medical / healthcare librarian or information specialist, with experience of managing references for systematic reviews. • Use of reference management software is recommended. • Ensure that all the necessary fields are downloaded. • Remove duplicate references before screening. • Either screen references within the reference management software and export references for the included and excluded studies into systematic review software, or export references to specialized screening software. 5 Supplement information Authors: Carol Lefebvre, Julie Glanville, Simon Briscoe, Anne Littlewood, Chris Marshall, MariaInti Metzendorf, Anna Noel-Storr, Tamara Rader, Farhad Shokraneh, James Thomas and L. Susan Wieland on behalf of the Cochrane Information Retrieval Methods Group