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Searching the Literature: Concepts, Resources & Searching Skills. Victoria H. Goode, MLIS Clinical Informationist Welch Medical Library Search process overview Important Database features

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searching the literature concepts resources searching skills

Searching the Literature: Concepts, Resources & Searching Skills

Victoria H. Goode, MLIS

Clinical Informationist

Welch Medical Library

today s agenda

Search process overview

Important Database features

Some major databases other than PubMed – esp. important to include in systematic review searching

Why controlled vocabulary searching is key

Controlled vocabulary searching in PubMed

PubMed searching techniques and mechanics

Clinical Queries and Google Scholar

Reminders – final thoughts

Today’s agenda
effective literature searching the steps
Effective Literature Searching: the steps
  • Identify your topic (and write it down!)
  • Identify applicable resources
  • Create a list of controlled vocabulary terms, synonyms and related terms
  • Conduct your search
  • Record you findings
  • Critically evaluate the information
literature searching process overview


Define the purpose of your search

Form your question

Write it down!

Now identify relevant databases and resources

Create a search query from your question – for use within a specific database!

Identify the key concepts (often 2-3 sometimes more) in your question

Find searchable terms for those concepts: most specific controlled vocabulary terms as well as keyword phrases

Group into distinct sets the terms that represent/describe each main concept with Boolean “OR”

Combine sets with Boolean “AND”

Literature searching - process overview
literature searching process overview cont

Run your search query

Revise the query until you are satisfied

Remember, a good search query usually incorporates controlled vocabulary terms from the database, when there is a controlled vocab., as well as keywords/phrases.

Record and store your findings

Strategy can be saved in MyNCBI & in Word Documents – good for making notes to self; citations can be saved in RefWorks or other citation management programs.

Revisit/revise the search query for each distinct database you search

Evaluate the findings

Critically appraise the articles

Literature searching - process overview (cont.)
get to know your databases features

Does a database include/allow:

automatic term mapping?

a controlled vocabulary for use in searching?

vocabulary designated as major focus?

Boolean operators (AND, OR, NOT)

adjacency or proximity searching?

required special syntax – e.g.“around keyword phrases” in PubMed to override automapping; ‘around keyword phrases’in EMBASE.

field tag searching? -- e.g. [tiab] in Pubmed

Get to know your databases’ features
database specific controlled vocabularies

Some major databases:Has controlled vocabulary?

PubMed MeSH

Cochrane Library MeSH


Web of Science No


PsycInfo YES – “Thesaurus”

Global Health YES – “Thesaurus”


ERIC YES – “Descriptors”

Database-specific Controlled Vocabularies
what s the big deal with controlled vocabulary

It provides a consistent, precise way to retrieve information when different natural language words/phrases (synonyms) are used for the same concept, or when the same natural language is used for different concepts! (e.g. “cold” Which meaning?)

Controlled vocabulary terms control for spelling variations (think British v. Am. English), plurals, acronyms.

Why do we say cont. vocab. searching is precise? – because only articles indexed with that vocabulary term are retrieved.

Select the most specific cont. vocab. term available for your concept; that’s how indexers apply them!

What’s the big deal with controlled vocabulary?
controlled vocabulary in pubmed

MeSH (Medical Subject Headings)

NLM’s controlled vocabulary to search Medline (PubMed)

Over 22,000 terms

Don’t guess – check the MeSH Database for what the controlled vocabulary term is for your concept.

Natural language:MeSH Term:

Health screening Mass Screening [MeSH]

Emergency department Emergency Services, Hospital [MeSH]

Computed tomography Tomography, X-Ray Computed [MeSH]

SARS SARS Virus [MeSH]; Severe Acute Respiratory Syndrome [MeSH]

Reproductive health Reproductive Medicine [MesH]; Reproductive Health Services [MeSH]

Controlled vocabulary in PubMed
pubmed searching specifics

Always look at the “Details” box:

Find out what the automatic mapping behind the scenes did to the keywords/phrases you put in the search box.

What’s in the details is the query.

You can amend the query in this view – but…

It’s often easier to just override the mapping by selecting your own “building blocks” – a combo of MeSH headings & possibly keyword phrases -- and then combining them in Advanced Search.

But first…

PubMed searching specifics
one method might be to use pico format
One method might be to use PICO format
  • PICO is a format to organize your thoughts:

What is the Patient, Intervention, Comparison, Intervention, Outcome(s) of interest to me?

or you can write out your question and circle your main concepts

E.g. “What are the treatment margins being used in stereotactic body radiotherapy for lung cancer?”

Identify main concepts:

(Concept 1) (Concept 2) (Concept 3)

margins stereotactic body lung cancer


Or you can write out your question and circle your main concepts
concepts to query

(Concept 1) (Concept 2) (Concept 3)

margins stereotactic body lung cancer





(Radiosurgery [MeSH] OR “stereotactic body radiotherapy” OR “SBRT” OR “body radiosurgery” OR “extracranialradiosurgery”)


(lung neoplasms [MeSH] OR “lung cancer”)

Concepts to Query
now let s walk through the mechanics of how to do that in pubmed

How to force keyword strings – double quotes

How to send terms from MeSH database to PubMed and run the search

How to combine concept sets with Boolean operators

Open a MyNCBI account (important for saving searches AND NIH Public Access Policy Compliance – Bibliography Management)

Now let’s walk through the mechanics of how to do that in PubMed…
a quick bit on pubmed clinical queries interface

Great for clinical questions. Quickly connect to evidence-based literature within PubMed.

Can search by clinical study category or search for systematic reviews.

It’s called an evidence-based resource due to the behind-the-scenes “filters” or search algorithms; developed by librarian/physician teams at McMaster – and tested in information retrieval studies.

Using MeSH in this interface is more precise, too.

A quick bit on PubMed Clinical Queries interface
a word on google scholar

Has no controlled vocabulary – if Google changes its algorithm, there’s no guarantee you’ll get the same results when you search.

No unique identifier (like a PMID) for each record: you might get different version of an item/article if you repeat your search at another time.

Can’t sort results by date.

The full-text you find depends on to what your institution subscribes, so what you find will vary depending on where you do your search (on campus or through VPN vs. at another university, hospital, Internet café in Thailand).

Scientific methods, including your SEARCHING METHODS, must be reproduceable.

Donot use Google Scholar for formal searching.

A word on Google Scholar
reminders final thoughts

Testing/revising your search strategy:

It’s not about the number of hits per se.

It’s whether the strategy captured on-topic target articles – but not too many off-topic articles. It’s a trade-off: precision v. recall (kind of like specificity v. sensitivity)

Read a random sample of abstracts from your results.

Investigate why you got outlier articles.

Review the record for an on-topic article from your results to see the controlled vocabulary terms (e.g. in “Medline” display in PubMed) that were applied.

Reminders -- final thoughts
reminders final thoughts cont

Continue to review your question – has it changed/evolved?

Write it down

Break out searchable concepts to create sets of terms

Consult an expert searcher* -- your department’s assigned informationist for your literature searches.

Invite her or him to be a team member, esp. on systematic reviews and content analyses, where the search results are the critical “inputs” for the project.

Reminders -- final thoughts (cont.)

"As a statistician, I've often told clinicians that "We are the experts at analyzing data, please come to us for help, or let us do it for you. Don't just do it yourself, you might miss something."

It was nice to hear the librarians tell me the same thing. They are the experts at searching the literature; we should go to them for help and not do it ourselves.”

Marta Marsh Gilson, PhD, Assistant Professor,

SOM, Surgery