Searching Workshop - Evidence Based Dentistry

Incorporating Evidence: Searching for Studies Anne Littlewood Trials Search Co-ordinator Cochrane Collaboration Oral Health Group University of Manchester

Which databases should I search?
How do I construct a search?
How do I test the strategy?
What are search filters?
Do I need to do handsearching as well?
Searching for evidence… http://www.flickr.com/photos/jakebouma/3345296623/

Why is a good search strategy important?
Ensures that a variety of sources of information are included
Makes sure that all relevant studies are identified
Reduces the risk of bias
Ensures that others can replicate your study

Which database?
Selection of databases is very important and depends on topic
MEDLINE should always be used for medical / dental searches
EMBASE is an alternative
CENTRAL at the Cochrane Library should be searched for systematic reviews or studies involving controlled trials (RCTs/CCTs)

Other sources
CINAHL: for topics involving nursing or care
PsycINFO: for topics involving psychology (eg Dental Anxiety)
LILACs: database of health care in Latin America – useful for non-English language references
Cochrane Review Groups and their specialized registers

Grey Literature
Grey literature: that which cannot be obtained readily from normal book/journal channels
Sources:
OpenSIGLE (System for Information on Grey Literature in Europe)
ZETOC: Free search of conference proceedings
ClinicalTrials.gov: access to ongoing trials in the USA
Meta Register of Controlled Clinical Trials (mRCT): www.controlled-trials.com

Which platform?
Databases are often available from more than one source, e.g.
MEDLINE is available via:
OVID
PubMed
EBSCO
Etc...
Make sure you check which are available to you from your librarian

Remember…
A search designed for one database or platform will not work in another!
For example, a search designed to be used in PubMed will not work in the Cochrane Library
A search designed to work in MEDLINE via PubMed will not work in MEDLINE via EBSCO
For each database/platform, check the help pages to see how you should conduct your search
See your librarian / Trials Search Co-ordinator for advice!

Controlled Vocabulary
The National Library of Medicine in the US has developed an indexing system: Medical Subject Headings (MeSH)
Some databases use subject headings that are arranged in a hierarchy, or tree
Broader concepts come near the top, more specific terms lower down
Subject headings are assigned according to the subject of an article by experienced indexers at the National Library of Medicine
MEDLINE, EMBASE and CINAHL all use MeSH

Example of a MeSH Tree
Stomatognathic Diseases
Tooth Diseases
Tooth Demineralization
Dental Caries
Dental Fissures
Root Caries

How do I find the MeSH for my topic? Go to: http:// www.nlm.nih.gov/mesh/MBrowser.html

To explode or not to explode?
MeSH can be “exploded” to include all the terms that are included in that subject heading on the tree
eg exploding the term “Dental Caries” will make your search include “Dental Caries”, “Dental Fissures” and “Root Caries”
If you want to focus your search to just dental caries without including the terms dental fissures and root caries, use the specific unexploded term “Dental Caries”

Free-text searching (1)
Searching for MeSH terms limits the search to only include those terms in the keyword field of a record
Free-text or keyword searching can be applied anywhere in the record – title, abstract, author, keywords or even full-text
You can add a single word, or a phrase: for example: “dental caries”

Free-text searching (2)
Can I just search using free-text and ignore MeSH? Remember: if you just use free-text, the search will be limited to just the phrases you have entered
For example: a search for “maxillofacial abnormalities” as free-text will only pick up records with this phrase
The same phrase exploded in MeSH will also pick up these articles, but also the articles containing subordinate terms on the MeSH tree (example: cherubism, jaw abnormalities)

Boolean operators (1)
Most databases work using Boolean operators:
AND, OR, NOT
AND is used when the article must contain both terms
OR is used when a paper may contain either search term
NOT is used when the search should retrieve the first term and not the second

Boolean Operators (2) Cars The AND operator: cars AND buses Buses

Boolean Operators (3) The OR operator: cars OR buses Cars Buses

Boolean Operators (4) The NOT operator: cars NOT buses Cars Buses

Boolean Operators (5)
“ dental caries ” AND chlorhexidine will retrieve all articles containing these two terms when they appear together
“ dental caries ” OR “ tooth decay ” will retrieve all articles containing these two terms regardless of whether they appear together or not
AND will REDUCE the number of hits in your search
OR will INCREASE the number of hits in your search

“ Cancer NOT children ” is designed to retrieve those articles about cancer but not cancer in children
NOT should be used with caution

For example, if the opening sentence of the abstract is:
“ This article looks at cancer but exclusively cancer in adults and not cancer in children”
The search “cancer NOT children” will not pick up this potentially relevant paper, as you have asked the database to search for cancer but not children, and both of these terms are in the opening sentence of the abstract

Boolean operators can be used together with brackets
For example: ( tooth OR teeth ) AND caries
This search will retrieve all articles containing the terms tooth and caries, and teeth and caries

Truncation
Databases can support truncation or enable you to search for the stem of a word e.g.
PubMed:
child * will retrieve child , or children or child’s
Some databases also support wildcard searches e.g.
wom ? n will retrieve women or woman
Symbol for truncation / wildcard can vary
* or $ or ?
Use the help pages of databases to check symbol

Proximity Operators (1)
Some databases allow you to search terms that are in close proximity to each other
This is a more precise way of searching than just using AND
For example, in the Cochrane Library, you can use the operator NEAR

Proximity Operators (2)
“ dental near/6 anxiety”
will retrieve any references where the term dental appears within 6 words of the term anxiety
Not all databases support proximity searching
Operator used in different databases can vary
e.g. in OVID databases, you use “ adj ” (adjacent to) instead of “ near ”
Use help pages of any electronic databases to find out if search method is supported

Building a Strategy
A well constructed research question is the place to start

Research Questions
A medical research question could contain four elements that can be broken down as:
eg longevity of restorations, pain reduction, quality of life
Outcomes
eg caries, temporomandibular joint disorders, halitosis
Condition
eg antibiotics, physiotherapy, powered toothbrushes, education programme
Intervention
eg children, adults, smokers
Participants

Example research question
Chlorhexidine for the management of childhood caries
management of caries (fewer restorations for example) Outcome: caries Condition: chlorhexidine Intervention: children Participants:

Next steps
Take three elements of the research question
participants
interventions
condition
List as many synonyms for each as you can
Why don’t we use outcomes for searching?
Entering outcomes in your search will limit it to studies containing only those outcomes.

Condition
Synonyms for Dental Caries
Tooth/teeth decay
Tooth/teeth demineralization
Tooth/teeth remineralization
Tooth/teeth cavities
Tooth/teeth lesions
Enamel/dentin decay
Root caries

Intervention
Synonyms for Chlorhexidine
Chlorohex
Eludril
Corsodyl
PerioChip
CHX
MK-412a
Nolvasan
Sebidin
Tubulicid
Cervitec
Chlorzoin

Participants (1)
Synonyms for children
Possibilities:
infant(s)
toddler(s)
child / children
baby / babies
pre-school child(ren)
adolescent(s)
teenager(s)
under 5(s) / under 10(s) / under 16(s)
More information needed to decide which to use

Participants (2)
Searching for participant information can be difficult e.g.
if you are looking for adults rather than children, putting the term “adults” in will not necessarily help as “adult” might not be in all the articles you want to retrieve
Search terms for participants should therefore be used with caution!

Next steps: MeSH
Take identified synonyms for the condition and intervention
Check whether any of them have a Medical Subject Heading by going to http://www.nlm.nih.gov/mesh/MBrowser.html
Are there any other synonyms in the MeSH tree that could be useful that you can add to your search?

Next steps: free-text
Look at your identified synonyms
Can any of them be truncated?
Are there any alternative spellings?
Are there any hyphens?
e.g. “tooth deminerali s ation” OR “tooth deminerali z ation”
“ mk-412a ” OR “ mk 412a ” OR “ mk412a ”

Condition: Dental Caries
MeSH terms available:
Dental Caries (exploded)
Tooth Demineralization (not exploded)

First part of PubMed strategy using MeSH:
#1 Dental Caries [mh:exp]
#2 Tooth Demineralization [mh:noexp]
[mh] is the way to indicate to PubMed that you are looking for a MeSH term

Now begin to build the free-text search:
#3 (teeth AND (cavit* or caries or carious or decay* or lesion or deminerali* or reminerali*))
#4 (tooth AND (cavit* or caries or carious or decay* or lesion or deminerali* or reminerali*))
#5 (dental AND (cavit* or caries or carious or decay* or lesion or deminerali* or reminerali*))
#6 (dentin AND (cavit* or caries or carious or decay* or lesion or deminerali* or reminerali*))
#7 (enamel AND (cavit* or caries or carious or decay* or lesion or deminerali* or reminerali*))
#8 (root* AND (cavit* or caries or carious or decay* or lesion or deminerali* or reminerali*))

Once all the MeSH and free-text terms have been added, you need to tell the database to search for all the terms
Line 9 should read:
#1 or #2 or #3 or #4 or #5 or #6 or #7 or #8
This tells PubMed to retrieve all of these search terms

Intervention: chlorhexidine
Now the search for the condition is complete, Line 10 of your search should move to the intervention
Using the same process, find appropriate MeSH and build a free-text search

#10 Chlorhexidine [mh:noexp]
#11 (chlorhexidine or chlorohex* or eludril* or corsodyl* or PerioChip*)
#12 (mk-412a or “mk 412a” or mk412a)
#13 (nolvasan* or sebidin* or tubulicid* or cervitec* or chlorzoin*)
#14 chx [tiab]
#15 #10 or #11 or #12 or #13 or #14

A word about line 14:
#14 chx [tiab]
Initials should be used in a search with caution: although unlikely in this case, your search could potentially pick up an author’s initials: eg C.H.X. Smith
The search here has been limited to just the title and abstract: [tiab] so that the author field is not searched

Condition and intervention
The final line of your strategy should bring the condition and intervention together by using the AND command
In this case: #9 AND #15
This means that all the terms you have entered are included in the search, but only those articles which include the terms for the intervention PLUS the terms for the condition will be retrieved

Testing the strategy
The next step is to have a test run of the strategy in PubMed Advanced Search
Is the number of hits manageable?
Are any lines retrieving no hits?
Have you spelled everything correctly?
Have you truncated everything correctly?
Check the keywords that relevant articles have been indexed with: can any of them be added to the search?

Search filters
There are standardised search filters available if you are searching for a particular kind of study e.g.
the Cochrane Collaboration has developed a filter to isolate randomized controlled trials and controlled clinical trials
Search filters can be added to your search to make them more precise

Cochrane Highly Sensitive Search Strategy for identifying randomized controlled trials in MEDLINE:
#1 randomized controlled trial [pt]
#2 controlled clinical trial [pt]
#3 randomized [tiab]
#4 placebo [tiab]
#5 drug therapy [sh]
#6 randomly [tiab]
#7 trial [tiab]
#8 groups [tiab]
#9 #1 or #2 or #3 or #4 or #5 or #6 or #7 or #8
#10 animals [mh] not (humans [mh] and animals [mh])
#11 #9 not #10
Reference: The Cochrane Handbook for Systematic Reviews of Interventions, Version 5.0.1, [updated September 2008], box 6.4a

Adding a search filter
To add a search filter to your search to make the search more precise:
Enter your subject search into PubMed
Enter the search filter, exactly as written
Add an “ AND ” command line to link the last line of the search filter with the last line of the subject search

Search filters
Other search filters are available for
Systematic Reviews
Observational studies
Outcome studies
Therapy studies
Diagnostic studies
The InterTASC website has examples of all of these and more:
http://www.york.ac.uk/inst/crd/intertasc/

Translating the strategy
Once you are happy with the PubMed strategy, you need to translate it for other databases you intend to search
Check the database help pages / try running the strategy to make sure that you are using:
the correct symbols to truncate
the correct search terminology
(eg is there a different way of searching for title/abstract keywords?)
the correct MeSH terms
If a line of your search retrieves less hits than expected, you may have to change it

Handsearching (1)
Handsearching requires the searcher to read/scan a journal page by page to identify relevant studies, including abstracts and correspondence
A Cochrane Systematic review has demonstrated that handsearching in addition to electronic searching is the best technique for retrieving all relevant studies

Handsearching (2)
Why do handsearching? Isn’t electronic searching enough?
Electronic searching will only pick up records in which the subject and study design information is given in either the title, abstract or keywords assigned to the paper
Many citations do not have abstracts – leaving only the title - publication type - and keywords to be searched electronically

Handsearching (3)
The Cochrane Collaboration runs a handsearching programme to identify randomized and controlled clinical trials in the literature
These are then added to the Cochrane Library
Before handsearching, check with your Trials Search Co-ordinator which journals have already been searched – it may not be necessary

Documenting your search
Writing up the search is an important part of doing a systematic review
All search strategies should be included in your review AS RUN in the database – the idea being that another researcher could easily replicate them
For Cochrane Reviews, all search strategies should be put in appendices along with search filters and number of references retrieved

Documenting your search
In the text of your review
List the electronic databases you have searched and the dates you have searched from and to
Reference any search filters you have used
Comment on any language restrictions
List the journals you have handsearched

Any questions?
Contact for help:
Anne Littlewood, Trials Search Co-ordinator, Cochrane Oral Health Group
Email: [email_address] Tel: 0161 275 7814
I can conduct searches for Cochrane systematic reviewers, or advise on any part of your search strategy

Searching Workshop - Evidence Based Dentistry

by Anne Littlewood

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