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Describe the major available electronic resources Describe how to build a search strategy Describe some alternate sources for finding trials Describe what to do once you get your search results
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Searching for Trials for a Systematic Review
US Cochrane Eyes and Vision GroupCompleting a Cochrane Systematic Review Workshop
July 18, 2013
Describe the major available electronic resources
Describe how to build a search strategy Describe some alternate sources for finding
trials Describe what to do once you get your
search results
Objectives
OK, I Have a Title- What next?
If you are doing a Cochrane review, work with the Trials Search Coordinator for the relevant Cochrane review group.
Work with an information specialist trained in searching for systematic reviews
Use Chapter 6 in the Cochrane Handbook as a guide Include the search protocol in your protocol (strategy
and sources) Document everything you do and when you do it!!!!
Identification of evidence
Develop your protocol for conducting the search: What sources
• Databases• Hand searching
How – search strategies How to make decisions (duplicate screening?) How to document – dates, numbers included,
excluded
Cochrane Central Register of Controlled Trials (CENTRAL) (www.thecochranelibrary.com)
Includes about 650,000 citations Includes MEDLINE and EMBASE searches Includes Cochrane group specialized registers
MEDLINE/PubMED (www.ncbi.nlm.nih.gov/sites/entrez)
Includes 22 million citations; > 5,600 journals in 39 languages Citations fully indexed from 1966 forward PubMed has most recent – but non-indexed articles
EMBASE (www.embase.com) Includes 25 million citations > 7,600 journals Includes MEDLINE Includes > 6 million conference abstracts
Major electronic databases used to search for clinical trials
Other important databases National and regional databases (often local language)
LILACS (bases.bireme.br)
Subject-specific databases CINAHL (www.cinahl.com) PsycINFO (www.apa.org/psycinfo/) OTSeeker (www.otseeker.com)
Citation databases Web of Science (www.thomsonreuters.com) Scopus (www.scopus.com)
Dissertations, thesis databases ProQuest (www.Proquest.com)
Grey literature databases Opengrey (www.opengrey.eu) – formerly SIGLE
Will review be limited to RCTs or will it include other study designs?
Will adverse events be included?
Is there any geographic consideration?
Is there a limited time period when the intervention was used?
Other issues to consider
Add to search strategy
Plurals - (acuity, acuities) Abbreviations - (e.g., CNV for choroidal neovascularization) Synonyms -
Lucentis, ranibiuzumab Avastin, bevacizumab
Spelling variations - (randomized/randomised) Truncation – (antibod* for antibody or antibodies)
Medical Subject Headings (MeSH) - Descriptors (with thesaurus) - Most specific term used
Textword searching - titles for all records, abstracts since 1975 - truncation useful
Publication type Sensitivity (recall) vs Specificity (precision)
- no gold standard available
Searching trials on PubMed
1. Start with simple search strategy
2. Run search and retrieve reports
3. Analyze MeSH and text words of studies fitting your criteria
4. Re-run search with revised strategy
5. Repeat steps 2 – 4 if necessary
6. Run optimal search strategy
7. Retrieve reports identified with optimal search strategy
Development of MEDLINE search strategy
To develop simple search strategy, start with your question
Population Intervention(s) Comparison(s) Outcome
P
I
C
O
For patients with choroidal neovascularization associated with age-related macular degeneration, do intravitreal injections of Lucentis, when compared with Avastin, prevent vision loss?
Individuals with choroidal neovascularization associated with age-related macular degeneration
Lucentis, ranibizumab
Avastin, bevacizumab
Change in visual acuity or visual field
Searching PubMED Start with the general format:
(Population OR synonym# 1 OR synonym #2) AND (Intervention OR synonym # 1 OR synonym#2) AND
(Comparator OR synonym#1 OR synonym#2) AND
(Outcome OR synonym# 1 OR synonym # 2) AND
Add study type filter terms
How do we find the terms to use in the search strategy?
macular degeneration AND lucentis AND avastin
Text wordsText words
Use the MH – MeSH termsin known articles to build your search strategy
Angiogenesis Inhibitors/
Administra-tion & dosage/
Antibodies Monoclonal/ Administra-tion & dosage
Choroidal neovascularization /drug therapy
Macular degeneration/ complications/ drug therapy/ physiotherapy
Visual acuity/ physiology
Visual fields/ drug effects
CATT X X
Paper 2 X X X
Paper 3 X
Paper 4 X x X X
Paper 5 X X
MeSH Analysis
Completed search strategy(this is added to the Cochrane “highly sensitive search strategy”)
#1 exp macular degeneration/#2 exp retinal degeneration/#3 exp retinal neovascularization/ #4 exp choroidal neovascularization/#5 exp macula lutea/#6 maculopath$.tw.#7 ((macul$ or retina$ or choroid$*) adj3 degener$).tw.)#8 ((macul$ or retina$ or choroid$*) adj3 neovasc$).tw.) #9 ((macula$ adj2 lutea.tw#10 or/1-9#11 exp angiogenesis inhibitors/#12 exp angiogenesis inducing agents/#13 exp vascular endothelial growth factors/#14 (lucentis$ or avastin$ or ranibizumab$ or bevacizumab$).tw#15 (anti adj2 VEGF$).tw.#16 (endothelial adj2 growth adj2 factor$).tw.#17 or/ 11-16#18 10 AND 17
P
I, C
Add study filter terms to identify study type
Common errors in search strategies
Spelling errors Missed spelling variant (randomized instead of random) Truncation error (methods* instead of method*) Logical operator error (using NOT instead of AND) Wrong line number (when combining lines) MeSH and free text terms on same line Irrelevant MeSH term Missed MeSH term Unwarranted explosion of MeSH terms Redundancy without rationale Search strategy not tailored for other databases
Sampson et al, J Clin Epi 2006
Use of all databases may be necessary to identify all reports
Lawrence et al Inj Prev 2008
Registers of ongoing or completed trials
www.clinicaltrials.govwww.clinicaltrials.gov
www.controlled-trials.comwww.controlled-trials.com
www.who.int/ictrp/en www.who.int/ictrp/en (WHO portal)
Clinical Trial registers
Google Scholar vs PubMed
Search engine No citations
Mean (SD) Median (IQR)
Google scholar 2211 (3999) 1040 (339,1958)
PubMed 44 (47) 35 (20,53)
Identified 22 Drug Information Rounds review articles Searched PubMed or Google Scholar with 2 keywords (MeSH) or text
Google presented “older” literature first compared with PubMed - Freeman et al Pharmacotherapy 2009
Similar results reported using clinical query (PubMed) and advanced scholar search (Google scholar)
- Anders et al (Resp. Care 2010)
Journals in topic area
Conference proceedings in area
Bibliographies of related systematic reviews
More efficient and more accurate to use SCOPUS to download all references in a review than to review them manually - Chapman et al, Health Information and Libraries J 2010)
Handsearching
Other sources of trial results
FDA Pharmaceutical company registers Communication with experts in the field www.clinicaltrials.gov
Systematic Snowballing
Use included articles as a source to identify missing studies:
Reference lists - check cited articles = backward searching
Web of Science, SCOPUS - check citing articles = forward searching
(“Related articles”/ “Find Similar”) in MEDLINE, EMBASE) – also could use to find new terms to expand your search strategy
Use of all sources may be necessaryto identify all reports
Sources of studies for a systematic review for studies promoting a shift from use of cars to walking or cycling
Source Total No. No. in review %Health databases 4 3 14Citation databases 8 3 14Other databases 8 2 9Transport database 33 9 41Internet search 10 3 14Handsearch abstracts 6 2 9Total 69 22 100
Ogilvie et al JECH 2005
Screening search results Full record citations downloaded from electronic databases
into an electronic file – either a text file or a reference manager file
Files distributed to two team members for screening Yes, Maybe, No Systematic reviews - obtain full copy for review of references
Disagreements resolved by consensus or by third team member
Electronic documentation Reference manager – use new field to enter yes/no/maybe/ref Word – identify using highlighted text, comment box, copy/paste to
new file Excel – possible, but difficult to manage
Screening full text articles Develop and use a data collection form (paper or electronic)
Query inclusion/exclusion criteria Duplicate screening - Yes, no, unclear Disagreements resolved by consensus or by third team member
Responses for excluded studies provide “reason for exclusion” in RevMan
Articles with unclear designation usually need author contact –go into “awaiting assessment” in RevMan
Start to identify multiple articles from same trial Authors Numbers of randomized participants Interventions
Document your findings
When you searched (month/year) Where you searched
Electronic databases Handsearches Trial registers Communications with experts, industry Bibliographies, etc. Internet
How you searched Search strategies
What you found PRISMA flow diagram
PRISMA Flow of InformationNo. records identified
through database searchingNo. additional records identified
through other sources
No. recordsscreened
No. studies includedin qualitative synthesis
No. full-length articles assessed for eligibility
No. records after duplicates removed
No. records excluded
No. full-length articles excluded, with reasons
No. studies included in quantitative synthesis
Conclusions
Develop a search strategy for electronic database searching using an iterative approach, starting with your question
Make sure to perform searches from all additional sources (adapting strategy as necessary)
Document when, where, and how you searched and what you found