Searching the medical literature aug 2010

Searching the Medical Literature

Robin FeatherstoneClinical Medicine LibrarianUWOrfeathe@uwo.ca

http://www.slideshare.net/featherr

Selinda BergClinical Medicine LibrarianWindsorsberg@uwindsor.ca

Objectives

• List four categories of information resources• Apply selection criteria to identify appropriate

information resource• List five databases to find primary studies• Strategize and execute a systematic, explicit and

reproducible search of the biomedical literature

Level of Evidence Pyramid

Qualitative Studies

Systems, Synopses & Summaries

Systems Synopses SummariesFew exist Number in the thousands Fewer than 50,000

Textbook-like; integrate clinical evidence with other types of info; directed at clinical practice decisions

Summaries of studies and systematic reviews; includes guides or advice from expert clinicians

Systematic reviews of articles and guidelines; you assess and make decisions

Very easy to use Easy to use May require searching

Criteria for Selecting a Resource

1. Soundness of evidence-based approach2. Comprehensiveness and specificity3. Ease of use4. Availability

Questions to Ask

• Bias? Conflict of interest? • Evidence grading or ranking applied? • Links? • Discipline coverage? • Consistent and quick to search? • Cost? • Available in my location?

Studies

• Number in the millions• No processing of evidence – must individually

assess• Require searching large databases

Available from Western Libraries (or for free)Systems Synopses Syntheses Studies

• ACP PIER

• DynaMed

• Clinical Evidence

• UpToDate

• Micromedex

• ACP Journal Club

• InfoPOEMS (Essential Evidence Plus)

• DARE (Database of Reviews of Effects)

Centre for Reviews and Dissemination

• Cochrane Database of Systematic Reviews

Cochrane Library

• US National Guidelines Clearinghouse

• MEDLINE PubMed Ovid Pubget

• EMBASE• SCOPUS• Cochrane Controlled Trials Registry (CCTR)

Cochrane Library

• CINAHL• PsycINFO• Web of Science

•TRIP Database

Find at: www.lib.uwo.ca/programs/undergraduatemedicaleducation/

HOW TO SEARCH STUDIES

A Comprehensive Search is...

• Systematic• Explicit• Reproducible

7 tasks in a comprehensive search

1. Develop a search statement or question2. Select a source 3. Choose search terms4. Run the search5. Apply practical screens (limits)6. Apply methodological screens7. Synthesize the results

How questions influence search results

Relevancy

Retrieval(# of search results)

Broad Questions

Narrow Questions

High = lots of articles

Low = very few articles

High = directly relevant articles

Low = mostly irrelevant articles

Sample Search Statements• I am looking for articles about osteoarthritis of the

knee.– 13,886 articles in PubMed

• I am looking for RCTs on arthroscopic surgery for osteoarthritis of the knee that include placebo surgery as a control.

– 9 articles in PubMed

• I am looking for RCTs on arthroscopic surgery conducted in latino females with type 1 diabetes mellitus.

– 0 articles in PubMed

Turn your statement into a strategy

1. Break you question into concepts2. Identify subject headings for each concept3. Identify keywords for each concept

• Tips: – Use a “target article” to help identify search terms– Use a strategy worksheet to keep track of your terms:http://www.lib.uwo.ca/files/taylor/grad/

Search_Strategy_Worksheet.pdf

Does hand washing prevent MRSA? in the ICU?Hand washing MRSA ICU Prevention

Handwashing [MeSH]

Methicillin-Resistant Staphylococcus aureus [MeSH]

Intensive care units [MeSH] +

Handwash$.mp. Methicillin resistant staphylococcus aureus.mp.

Intensive care unit$.mp.

Prevent$.mp.

Hand wash$.mp. MRSA.mp. ICU.mp.

Hand disinfect$.mp.

Critical care unit$.mp.

Surgical scrub$.mp.

Hand clean$.mp.

Different databases have different subject headings

• Tips:– Complete a concept map for each database that you search– Select subject headings that are the closest match for your concept

(remember: systematic, explicit and reproducible)– Pay attention to “explode” commands – some databases will search related

headings by default, others will not

Database Subject Headings

Medline MeSH

EMBASE EMTREE

CINAHL CINAHL Headings

Cochrane Library MeSH

Web of Science N/A

Scopus N/A

Some key operators in OvidOperator Command

$ Truncation (finds alternate endings)

? Wildcard (finds alternate spellings)

.mp. Mapping Alias (tells Ovid to search for your term in the Title, Abstract, Subject Headings, Table of Contents and Key Phrase Identifier fields) – useful for lit. reviews because it is broad

() Parentheses control the order of search operations

Adj Adjacency operator (can be followed by a number) tells Ovid terms must appear adjacent to one another

AND all terms must appear in results

OR any terms will appear in results

Note: These are recommended operators for research lit reviews. There are many, many more operators... Use Ovid‘s Help menu to locate them.

Or see: http://content.library.utoronto.ca/gerstein/subjectguides/ovidmedline_shortcuts.pdf

How does patient adherence to medication regimens influence outcomes following surgery

for myocardial infarction?

Source: Practical Screens:

Running your search

Running your search(es)• Start with your first concept

– Search for the subject headings first– Then search keywords– Combine these synonymous searches with OR using

your search history

• Repeat for your second, third, and subsequent concepts

• Finally, combine large search results set with AND

Running your search(es)

Search #2 =

Search #3 =

Search #4 =

Search #5 = #1 OR #2 OR #3 OR #4

Search #1 =

Concept 1

Search #6 =

Search #7 =

Search #8 =

Search #9 =

Concept 2

Search #10 = #6 OR #7 OR #8 OR #9

Search #11 = #5 AND #10

Results

Applying practical & methodological screening criteria

Screening

• Two kinds: practical and methodological • Why?

– Use practical screening to identify a broad range of potentially useful studies

– Use methodological screening to identify the best available studies

Practical Screening Criteria – some examples

1. Date of publication – only studies conducted between 2005 and 2010

2. Participants of subjects – only children 6 to 12 years of age

3. Publication language – only materials written in English

4. Research design – only clinical trials

Methodological Screening Criteria - some questions to ask

• Is the study’s research design internally & externally valid?

• Are the data sources used in the study reliable & valid?

• Are the analytic methods appropriate? • Are the results meaningful in practical &

statistical terms?* *Fink, A. (2005). Conducting Research Literature Reviews. London: Sage.

Applying Screens (or limits)

• Apply practical screens by using “limits” (may also be called “search options”)

• Apply methodological screens by reading through the articles

Next steps

Moving to another source

• Retain as much of your original strategy as possible

• Recognize that subject headings will be different (or non-existent)

• Keep track of your search terms using a new concept map

Working with your results

• Export search results from each database or website into a citation manager (i.e., RefWorks)

• Remove duplicates• Remove inappropriate studies by applying

methodological screens

Synthesizing the results

Look for Patterns

• What conclusions did these studies reach? • Which studies agreed/disagreed with the

consensus?

• Consider using a synthesis matrix:www.ncsu.edu/tutorial_center/writespeak/download/Synthesis.pdf

Use your results to...

1. Describe current knowledge about your research topic

2. Support the need for and significance of new research

3. Explain research findings4. Describe the quality of a body of research*

*Fink, A. (2005). Conducting Research Literature Reviews. London: Sage.

Recap1. What is a quality search? 2. Develop a research question that’s ________3. Which boolean operator do you use to

combine synonymous search terms?4. What screens should you apply to your

results?

Questions

Robin FeatherstoneClinical Medicine LibrarianUWOrfeathe@uwo.ca

Selinda BergClinical Medicine LibrarianWindsorsberg@uwindsor.ca