Box 113 Methods to identify and locate RCTs

♦ Search Cochrane Controlled Trials Register (CENTRAL)


♦ If appropriate, search other bibliographic databases [43]

e.g. Allied and Alternative Medicine, Biological Abstracts (BIOSIS) CAB Health, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Derwent Drug File, Phychological Abstracts, Science Citation Index/Current Contents

♦ Hand search relevant un-indexed journals

♦ Hand search meeting proceedings

♦ Cross check bibliographies of identified trials

♦ Consult general registers

♦ Consult relevant specialist registers

♦ Consult pharmaceutical industry if appropriate

♦ Consult authors of identified trials citations. At the end of 2001 it contained records of over 250,000 reports of controlled trials and it is the first place that many reviewers seek trials. At present, others prefer to use MEDLINE (or other commercial databases) as it has more sophisticated searching facilities and does not contain duplicate citations.

Even if CENTRAL is consulted as the primary source of trials, it is recommended that MEDLINE should also be searched for recent publications [43]. This is because RCTs are downloaded to CENTRAL from MEDLINE and other bibliographic databases by searching for those with the indexing term RCT. Recent trials will not have benefited from the additional safety net of the re-tagging exercise. Consequently, some RCTs may not be tagged appropriately and will therefore not be downloaded to CENTRAL. For the same reason reviewers should employ the Cochrane Collaboration search strategies [43] rather than rely on selection by the RCT index term. A free version of MEDLINE is available at

To gain a fuller coverage of journals, EMBASE should also be searched, the overlap with MEDLINE in indexed journals is only 34 per cent [44] and whereas MEDLINE indexes mostly journals published in the US, EMBASE has more of a European focus and includes a large number of non-English language journals. It also has a good coverage of pharmaceutical journals. Although searching bibliographic databases is often seen as a straightforward task, it requires both skill and experience to obtain the best results and inexperienced searchers should seek expert help. As an example, a modified (simplified) version of the Cochrane Collaboration search strategy for locating RCTs, combined with specific terms to locate trials of chemotherapy, radiotherapy or surgery in lung cancer is shown in Box 11.4.

Appropriate journals and meeting abstracts that are not indexed by the bibliographic databases selected and have not already been searched by a Cochrane group (in which

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