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

1. Searching for Trials for a
Systematic Review
US Cochrane Eyes and Vision Group
Completing a Cochrane Systematic Review Workshop
July 18, 2013

2.  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

3. 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!!!!

4. 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

5.  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

6. 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

7.  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

8. 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)

9.  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

10. 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

11. To develop simple search strategy,
start with your question
 Population
 Intervention(s)
 Comparison(s)
 Outcome

12. 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

13. 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

14. How do we find the
terms to use in the
search strategy?

16. macular degeneration AND lucentis AND avastin

20. Text wordsText words

22. Use the MH – MeSH terms
in known articles to build your
search strategy

23. 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

28. 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

29. 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

30. Use of all databases may be necessary to identify all reports
Lawrence et al Inj Prev 2008

31.  Registers of ongoing or completed trials
www.clinicaltrials.govwww.clinicaltrials.gov
www.controlled-trials.comwww.controlled-trials.com
www.who.int/ictrp/enwww.who.int/ictrp/en (WHO portal)
Clinical Trial registers

32. 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)

33.  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

34. Other sources of trial results
 FDA
 Pharmaceutical company registers
 Communication with experts in the field
 www.clinicaltrials.gov

35. 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

36. Use of all sources may be necessary
to 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 14
Citation databases 8 3 14
Other databases 8 2 9
Transport database 33 9 41
Internet search 10 3 14
Handsearch abstracts 6 2 9
Total 69 22 100
Ogilvie et al JECH 2005

37. 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

38. 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

39. 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

40. PRISMA Flow of Information
No. records identified
through database searching
No. additional records identified
through other sources
No. records
screened
No. studies included
in 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

41. 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