N494-M1

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Melnyk_PPT_Chapter_03.ppt

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Chapter 3

Finding Relevant Evidence to Answer Clinical Questions

Answering Clinical Questions

Searching for evidence that has already been appraised for validity and reliability decreases the amount of time needed to determine whether the information is reliable
Pre-appraised literature can include:
Systematic reviews and meta-analyses
Meta-syntheses
Integrative reviews
Synopses/critiques of single studies

Hierarchy of Information Resources

Databases Useful for Finding Individual Research Reports

MEDLINE®
CINAHL
PsycINFO®

Databases Useful for Finding
Pre-Appraised Evidence

Cochrane Database of Systematic Reviews
BMJ Clinical Evidence
Database of Reviews of Effects (DARE)
National Guideline Clearinghouse (NGC)
Physician’s Information and Education Resources (PIER)
American College of Physicians Journal Club (ACP)

Question

Which of the following sources of evidence would be the best evidence to use to suggest a clinical practice change?

A well-designed randomized controlled trial (RCT)
A systematic review that encompasses multiple studies
Expert opinion of experienced and educated nurses
A case study that addresses a similar clinical situation

Answer

b. A systematic review that encompasses multiple studies

Rationale: Systematic reviews are pre-appraised evidence, which are considered to be higher on the hierarchy of evidence than expert opinion, individual RCTs, or case studies.

Licensed Databases Versus Web- Based Search Engines

Licensed databases such as PubMed® list the journals indexed, which allows users to know which journals they are searching
Internet search engines such as Google and Google Scholar search the Internet, but there is no transparency as to what information is included in the search
Internet search engines include the grey literature, which include unpublished drug trials, reports, or conference proceedings. Because there is no peer review of this evidence, it should be appraised to ensure that the information is reliable.
Combining a licensed database with an Internet search engine may yield the best search results

Questions That Need to Be Asked About Databases Used for Searching Evidence

1. Is the evidence current?

2. Which search strategies are supported (e.g., are keywords, title searches, and subject heading searches all supported)?

3. How frequently is the database updated?

Three Commonly Used Search Strategies

Keyword searching uses words generated from each component of the PICOT question
All appropriate keywords, including common terms, synonyms, acronyms, phrases, coined phrases, and brand names, need to be used
Major strengths: Provides a quick snapshot of how helpful a database will be in finding relevant evidence
Major weaknesses: May miss studies that do not exactly match the authors’ keyword choices; may find many studies irrelevant to the PICOT question

Three Commonly Used Search Strategies—(cont.)

Subject headings searching uses a standardized set of preselected terms for the search
Also referred to as controlled vocabulary, subject terms, thesaurus, descriptors, or taxonomies
Major strengths: Searches can be broadened without considering every synonym for the chosen keyword; studies selected only if at least 25% relevant to the topic, thus decreasing the number of irrelevant hits
Major weaknesses: Newly developed technologies, phrases, and acronyms may not yet be linked in the database and thus be missed

Question

Is the following statement true or false?

Subject headings searching (also known as controlled vocabulary searches) may yield fewer hits than a keyword search, but these hits are more likely to be relevant to the clinical question.

Answer

True

Rationale: Controlled vocabulary systems exist to increase the relevance of search results while limiting the number of less relevant hits.

Three Commonly Used Search Strategies—(cont.)

Title searching uses keywords generated from the “P,” “I,” and “O” components of the PICOT question to search article titles with the same keywords
As with the use of keyword searches, all appropriate common terms, synonyms, acronyms, phrases, coined phrases, and brand names need to be used
Major strengths: Increases the chance of the article found being relevant to the PICOT question and is highly effective in finding relevant articles
Major weaknesses: Misses studies that do not contain the keywords in the title

Combining Searches

Placing several concepts from the PICOT question in one search allows a simultaneous search, but it cannot be determined which concept has the most available evidence
Running multiple single-word searches allows the number of “hits” to be seen for each. Then decisions can be made to possibly use Boolean operators.
Using the Boolean operator “AND” is useful when narrowing a search to combine two search results. BOTH terms need to be present or an article will not be included in the results.
Using “OR” will expand a search to include either one or both terms in the results

Combining Searches—(cont.)

Using Limits in Searches

Using the “limit” function pares down a large results list
Options for limiting the results vary by database
Limiting to RCTs or meta-analysis first can help determine the highest level of evidence that is available
Limiting the search may result in missing relevant evidence (e.g., limiting the search to “full-text only” eliminates all publications that the database does not subscribe to in full text)

Using Reference Management Software Systems (RMS) in Searches

Often referred to as citation managers
Used to save, search, sort, share, and continuously add, delete, and organize promising citations
Web-based proprietary examples include RefWorks and Endnote®
Open-source options include Mendeley ( http://www.mendeley.com) and Zotero ( http://www.zotero.org)

Examples of Evidence Databases

SH, subject heading; FT, full text; KW, keyword; KP, key phrase; TI, title.

Database	Document and Resources	Search Strategies
CINAHL	+ Journal article citation and abstract of primary studies, reviews, and synopses + FT (with FT subscription)	KW, KP, TI SH (i.e., CINAHL headings)
Cochrane Databases	+ CDSR—FT systematic review + CENTRAL—citation and abstract of clinical trials Note: Only two of the five Cochrane databases are described here	KW, SH (i.e., MeSH if you know the heading)

Examples of Evidence Databases—(cont.)

SH, subject heading; FT, full text; KW, keyword; KP, key phrase; TI, title.

Database	Document and Resources	Search Strategies
EMBASE	+ Journal article citation and abstract of primary studies, reviews, and synopses + conference coverage	KW, KP, TI, SH
MEDLINE	+ Journal article citation and abstract of primary studies, reviews, and synopses + FT (varies on PubMed; other vendors with FT subscription)	KW, KP, TI, SH, clinical queries

Examples of Evidence Databases—(cont.)

SH, subject heading; FT, full text; KW, keyword; KP, key phrase; TI, title.

Database	Document and Resources	Search Strategies
National Guideline Clearinghouse	+Clinical practice guidelines + syntheses of selected guidelines + FT	KW, category
PsycINFO	++ Journal article citation and abstract of primary studies, reviews, and synopses + FT (with FT subscription)	KW, KP, TI, SH

Examples of Evidence Databases—(cont.)

SH, subject heading; FT, full text; KW, keyword; KP, key phrase; TI, title.

Database	Document and Resources	Search Strategies
Trip	+Journal article citation and abstract of primary studies, reviews, and synopses + guidelines + linkout to FT when available	KW, KP, TI, PICOT search builder, proximity

Question

Which of the following online evidence sources is most likely to provide pre-appraised evidence?

CINAHL
MEDLINE
PubMed
The Cochrane Library

Answer

d. The Cochrane Library

Rationale: The Cochrane Databases include the Cochrane Database of Systematic Reviews (CDSR), which is a collection of systematic reviews that synthesize RCTs from multiple peer-reviewed sources. CINAHL, MEDLINE, and PubMed may contain evidence at a synthesis level, but most of the sources are individual research articles that must be appraised by the user.

PubMed®: A Unique Resource

PubMed®: Database produced and maintained by the National Center for Biotechnology Information (NCBI) at the National Library of Medicine

Contains >19 million citations from >5,600 journals of biomedical sciences, nursing, dentistry, and pharmacy
Free and committed to providing access to all evidence
Provides free online access to the MEDLINE® database
Includes automatic term mapping that uses the keywords entered to map them to appropriate MeSH® terms

PubMed®: A Unique Resource—(cont.)

Search results appear in the order in which they were added to the database. To find the most recently published article, use the “Sort by Pub Date” option.

PubMed®: A Unique Resource—(cont.)

Automatic term mapping uses a three-step process to search keywords entered in the search box and to map them to appropriate MeSH® terms:

Step 1—MeSH® term: Looks for a match between keywords entered and a list of MeSH® terms. If a match is found, MeSH® term plus the keyword is used to run the search.
Step 2—Journal title: If no MeSH® term match, keywords are compared with a list of journal titles. If a match is found, the journal title is used to run the search.

PubMed®: A Unique Resource—(cont.)

Step 3—Author name: If no match is found in steps 1 and 2, words in the search box are then compared with a list of author names. If there is a match, author’s name is used to run the search.

If no match is found after step 3, search engine will drop the keyword farthest to the right in the search string and will repeat the three-step process

If a match is found, then automatic term mapping will use the match (MeSH® term, journal title, or author name) plus the keyword as part of the search and return to process the term that was previously dropped to begin a separate search

PubMed®: A Unique Resource—(cont.)

Final Tips to an Efficient Search

Begin with PICOT question to generate keywords
Use subject headings when available
If search results are sparse, expand it using the explode option (if not automatic)
Use available search engine mechanisms to focus the search so that the topic of interest is the main point of the article
Establish inclusion/exclusion criteria before searching so that the studies that answer the question are easily identifiable. Apply these criteria after search strategy is complete.