Searching workshop   new york 2011
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  • We’re going to give you a taster so that you understand how the searching element of the review works – how we go about developing a search at Cochrane. Anyone who goes on to do a Cochrane systematic review will get full support from the Editorial Base – developing the search strategy, running the electronic searches, advising on content for the search methods section
  • The presentation today will cover the following.
  • Should be searching more than one database It should be a sensitive search to identify all the available studies – review could be biased if an RCT is missed A well reported search strategy means that others can replicate your study – Cochrane advice is to make sure they appear AS RUN in the appendix of your review
  • MEDLINE via PubMed – one of the biggest biomedical databases, based in US. Contains over 21 million citations. EMBASE via OVID at NYU – European database with pharmacological focus, also now a good source for conference proceedings Access to the Cochrane Library is available at NYU – via the library. The Cochrane Library is where all the Cochrane systematic reviews are published, also contains a database of RCTs/CCTs. This includes records from MEDLINE and EMBASE, but also the many records that have been found by handsearching journals (more about this later)
  • CINAHL via EBSCO – examples – Oral hygiene for nursing home residents PsycINFO is via Proquest – example – Interventions for reducing dental anxiety in children and adolescents LILACs – large number of dental schools in South America, so there are a number of dental journals on here, dates back to early 1980s Each cochrane group keeps a specialized register of RCTs/CCTs in their particular field, OHG’s register is substantial with 26,000 citations. It can only be searched for authors of Cochrane reviews.
  • OpenGrey has been relaunched and is now a resource that’s free to use and features grey literature (mainly European) I wouldn’t search web of knowledge as a general rule as it’s not the best source for RCTs, but it can be useful for discovering conference proceedings. There are other trials register platforms also – for example, World Health Organization have one, although it’s future is a little uncertain at the moment. There are some national trials registers which are freely available and also can provide you with access to unpublished studies.
  • As we’ve already discussed in the workshop, a well constructed question is the place to start. The better the question, the clearer the concepts, the easier the search is to construct.
  • So we’ve already seen this… Some more examples…
  • Searching is a trade off between sensitivity (picking up all studies that might be out there) and precision (picking up only studies of interest to your question). Cochrane systematic reviews aim for maximum sensitivity in order to pick up every trial on the topic. It’s not uncommon to get 1000s of references to screen (the most I’ve seen was 16,000 for the review on Oral Mucositis). This is an extreme example: search results are likely to be in the 100s!
  • Pt 1: So if you search for a particular subject heading, for example, Toothbrushing, you’ll retrieve all articles with the subject heading of toothbrushing. Pt 4: MEDLINE uses MeSH, as does CINAHL. EMBASE has a controlled vocabulary called EMTREE. We’ll be concentrating on MeSH and PubMed today.
  • So this is an example of the hierarchy – within tooth diseases you have tooth demineralization, and within that dental caries. Tooth diseases itself lies within stomatognathic diseases. It’s a bit like a Russian doll, inside each heading are more headings, each retrieving a smaller subset of results.
  • Demo – follow the link. Look up dental caries – explain scope notes, entry terms – how entry terms can be used to build up free text search.
  • Cochrane searches are systematic, and use both free text and controlled vocabulary.
  • You have to be careful not to exclude things from your search. Databases are not intuitive.
  • PubMed (which we’re using today) does not.
  • Now we’re going to discuss how to put all of this together to create the search – example I’m going to use is a systematic review on chlorhexidine for the prevention and treatment of dental caries in children. Our participants are children with caries. Back to task 1 – here are the synonyms I found for caries…
  • And the synonyms for the intervention: chlorhexidine. Note: some of these are trade names. That is allowed in a systematic search.
  • We should take a decision on whether to add these terms to the search or not. Will it be too restrictive? Need to test to find out, and talk to the authors about which groups of children to target.
  • Specific groups: children, elderley, even things like smokers? Caution against using limits generally, because indexers are human and make mistakes! But could be used in the testing process.
  • Different ways of saying caries!
  • Remember databases are not especially intuitive!
  • So you would start to enter your search in the box, and click “preview” to keep track of how many hits as you go along. If you want to check the results at any point, click through on the number to the results to see what is being retrieved.
  • This is especially true of older citations.

Searching workshop   new york 2011 Searching workshop new york 2011 Presentation Transcript

  • Searching for Studies Anne Littlewood Sue Furness Trials Search Co-ordinator Editor/Methodological Support Cochrane Collaboration Oral Health Group University of Manchester, UK
    • 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
  • 1. 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 Specialized Registers: OHG Register has over 26,000 citations (RCTS, CCTs and systematic reviews)
  • Grey Literature
    • Grey literature: that which cannot be obtained readily from normal book/journal channels
    • Sources:
      • OpenGrey - open access to 700,000 bibliographical references of grey literature (paper) produced in Europe and allows you to export records and locate the documents
      • Web of Knowledge: allows searching 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
        • Silverplatter
        • 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!
  • 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:
    • Participants
    eg children with caries, smokers with periodontal disease
    • Intervention
    eg antibiotics, physiotherapy, powered toothbrushes
    • Comparison
    What the intervention is to be compared to: eg another intervention, placebo
    • Outcomes
    eg longevity of restorations, pain reduction, quality of life
  • Example research question
    • Chlorhexidine for the management of childhood caries
    Participants: Children with caries Intervention: Chlorhexidine Comparison: Placebo/no treatment Outcome: management of caries (fewer restorations for example)
  • For the search…
    • Take the first two elements of the research question:
      • Participants
      • Interventions
    • List as many synonyms for each as you can
    • Cochrane systematic reviews aim for MAXIMUM SENSITIVITY, to pick up ALL relevant RCTs
  • Why not… ?
    • Why not comparison?
      • Only in certain circumstances: eg one treatment versus another
      • Not necessary if placebo or no treatment
    • Why not outcomes?
      • Entering outcomes in your search will limit it to studies containing only those outcomes
      • These may not be in the abstract, and you may risk limiting the search as a result
  • Task 1 (10 mins)
    • Use a research question of your own, or use an example research question below to develop a search strategy. List the participants and intervention and find as many synonyms as you can for each term. Use the internet to help you, and try and find an article on the topic that might give you additional keywords. 
    • Example Research Questions:
      • Alendronate for preventing tooth loss in postmenopausal women
      • Hypnosis for anxious children undergoing dental treatment
      • Occlusal adjustment for treating and preventing temporomandibular joint disorders in adults
  • 2. Constructing a search
    • Cochrane searches are a combination of controlled vocabulary and key words
      • Controlled vocabulary – what it is and where to find it.
      • Key word or free text searching
        • Boolean operators
        • Truncation and proximity operators
        • Putting it all together
  • Controlled Vocabulary
    • Some databases use subject headings that are arranged in a hierarchy, or tree allowing articles to be collected, labelled and searched using the heading
    • Subject headings are assigned according to the subject of an article by experienced indexers
    • The National Library of Medicine in the US has developed an indexing system: Medical Subject Headings (MeSH)
    • Broader concepts come near the top of the tree, more specific terms lower down
  • 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 or keyword searching (1)
    • Searching for MeSH terms limits the search to only include those terms in the subject heading 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 freetext searches in databases work using Boolean operators:
    • AND, OR, NOT
    • AND is used when the article must contain both search 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) dental floss The AND operator: dental floss AND toothbrushing toothbrushing
  • Boolean Operators (3) The OR operator: dental floss OR toothbrushing dental floss toothbrushing
  • Boolean Operators (4) The NOT operator: dental floss NOT toothbrushing dental floss toothbrushing
  • 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
  • Boolean Operators (6)
    • “ Cancer NOT children ” is designed to retrieve those articles about cancer but not cancer in children
    • NOT should be used with caution
  • Boolean Operators (7)
    • 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 (8)
    • 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
  • Putting it all together: p articipants
    • Synonyms for Dental Caries
      • Tooth/teeth decay
      • Tooth/teeth demineralization
      • Tooth/teeth remineralization
      • Tooth/teeth cavities
      • Tooth/teeth lesions
      • Enamel/dentin decay
      • Root caries
  • Putting it all together: intervention
    • Synonyms for Chlorhexidine
      • Chlorohex
      • Eludril
      • Corsodyl
      • PerioChip
      • CHX
      • MK-412a
      • Nolvasan
      • Sebidin
      • Tubulicid
      • Cervitec
      • Chlorzoin
  • Putting it all together: adding more (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
  • Adding more (2) – with caution!
    • 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 (could be “patients” or “participants”)
    • Search terms for participants should therefore be used with caution!
    • Most helpful when there are specific groups
    • PubMed has search limits that can be added and tested as part of the search
  • Next steps: MeSH
    • Take identified synonyms for the participants 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?
  • Participants: Dental Caries
    • MeSH terms available :
      • Tooth demineralization (exploded)
    • First part of PubMed strategy using MeSH:
      • #1 Tooth demineralization [mh:exp]
        • [mh] is the way to indicate to PubMed that you are looking for a MeSH term
        • exp is the way to indicate that the term should be exploded
  • Participants: Dental Caries
    • Now begin to build the free-text search:
      • #2 (teeth AND (cavit* or caries or carious or decay* or lesion* or deminerali* or reminerali*))
      • #3 (tooth AND (cavit* or caries or carious or decay* or lesion* or deminerali* or reminerali*))
      • #4 (dental AND (cavit* or caries or carious or decay* or lesion* or deminerali* or reminerali*))
      • #5 (dentin AND (cavit* or caries or carious or decay* or lesion* or deminerali* or reminerali*))
      • #6 (enamel AND (cavit* or caries or carious or decay* or lesion* or deminerali* or reminerali*))
      • #7 (root* AND (cavit* or caries or carious or decay* or lesion or deminerali* or reminerali*))
  • Participants: Dental Caries
    • Once all the MeSH and free-text terms have been added, you need to tell the database to search for all the terms together
    • Line 8 should read:
      • #1 or #2 or #3 or #4 or #5 or #6 or #7
    • This tells PubMed to retrieve all of these search terms
  • Intervention: Chlorhexidine
    • Now the search for the participants is complete, Line 9 of your search should move to the intervention
    • Using the same process, find appropriate MeSH and build a free-text search
  • Intervention: chlorhexidine
    • #9 Chlorhexidine [mh:noexp]
    • #10 (chlorhexidine or chlorohex* or eludril* or corsodyl* or PerioChip*)
    • #11 (“mk 412a” or mk412a)
    • #12 (nolvasan* or sebidin* or tubulicid* or cervitec* or chlorzoin*)
    • #13 chx [tiab]
    • #14 #9 or #10 or #11 or #12 or #13
  • Intervention: chlorhexidine
    • A word about line 13:
    • #13 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 participants and intervention together by using the AND command
    • In this case: #8 AND #14
    • 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 participants will be retrieved
  • 3. 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?
      • Try out the search limits: are these helpful?
  • Task 2 (20 mins)
    • 1. Find the MeSH terms for your chosen topic.
    • Go to the National Library of Medicine MeSH browser: http://www.nlm.nih.gov/mesh/MBrowser.html
    • Enter the search terms and synonyms and make a note of the MeSH terms for your topic. Do any need to be exploded?
    • 2. Look at your identified synonyms and think about how to build a free-text search:  
    • Can any of the terms be truncated? Are there any alternative spellings? (for example, think about US English v British English spelling: -ize versus -ise or -ization versus -isation.) Are there any terms that can be represented by initials alone? How should these be represented in the search?
    • 3. Now test your search in PubMed (use Advanced Search)
    • http://www.ncbi.nlm.nih.gov/pubmed
  •  
  •  
  • 4. What are search filters?
    • There are standardised methodological search filters available if you are searching for a particular kind of study
      • the Cochrane Collaboration has developed a filter to retrieve randomized controlled trials and controlled clinical trials
      • Search filters can be added to your search to make them more precise
      • There are search limits in PubMed, but the Cochrane filter has been rigorously tested against a gold standard
  • 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]
    • #11 #9 NOT #10
    • Reference: The Cochrane Handbook for Systematic Reviews of Interventions, Version 5.1.0, [updated March 2011], 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 (participants/interventions) 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, plus information on how they were developed and tested:
    • http://www.york.ac.uk/inst/crd/intertasc/
  • Task 3: Adding a Filter (10 mins)
    • Add a methodological search filter to the search you built in Task 2.
    • Check your worksheet for the Cochrane Highly Sensitive Search Strategy for identifying RCTs in PubMed and enter the terms
    • Join the subject search from Task 2 and the Filter by using the “AND” command
  • 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
  • Task 4: Translating the strategy (10 mins)
    • Translate your search for use in the Cochrane Library.
    • Go to http://www.cochrane.org and click on the “Cochrane Library” (top right)
    • Click Advanced Search
    • Check the tips on your worksheet and translate your PubMed Search to the correct search syntax for the Cochrane Library
  •  
  •  
  •  
  • 5. Do I need to handsearch as well?
    • 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
      • Hopewell S, Clarke MJ, Lefebvre C, Scherer RW. Handsearching versus electronic searching to identify reports of randomized trials. Cochrane Database of Systematic Reviews 2007, Issue 2. Art. No.: MR000001. DOI: 10.1002/14651858.MR000001.pub2.
  • 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
  • Any questions?
    • Contact for help with any aspect of literature searching for a Cochrane systematic review:
    • Anne Littlewood, Trials Search Co-ordinator, Cochrane Oral Health Group
      • Email: [email_address] Tel: +44 161 275 7814