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How to Search for Literature More Effectively

Contents:


Before You Start: Your Topic, the Scope of Your Search, Where to Look

What causes disease?
How you conceptualize your topic affects how you search for relevant information. Consider first perhaps the interaction and interdependence of environmental factors (eg, pollution, disasters, outbreaks) and social factors (eg, smoking, obesity, drug use). You may also wish to consider other aspects of your topic.
Example:
  » Is exacerbation of asthma in West Oakland "caused" by air pollution and/or smoking?
    » Or, is it "caused" by inadequate regulation of transportation, energy production, and/or tobacco?
      » Or by historical racism in housing and neighborhood characteristics?
        » What about genetic factors? poverty? stress?
          » What about access to appropriate prescription drugs?
Think about the wider context of your topic. Do some preliminary exploration, both in the literature and in discussions with your teachers, advisors, and peers. What are the relevant scientific and policy circumstances?

Is your topic researchable?
You may need to broaden or narrow the focus of your topic.
This may become more apparent as you search for and find information. It may prove difficult to find research on very narrow topics, or to cope with the vast literature on an un-focused, broad topic.

How researchable do you think the following topics may be?
  1. "The harmful effects of domestic beer consumption among female students at Cal's Big Game"
  2. "Social factors contributing to binge drinking among college students in the United States"
  3. "Alcohol consumption by young adults"

What is the scope of your search?
Literature searching always involves balancing finding all relevant citations (which means you may also find many non-relevant citations) with finding only relevant citations (which means you may miss some relevant citations).


    » The search scope, as well as the purpose and audience of your literature search influences how you focus or limit your search when using online databases, as well as when you decide you have "enough."

Which disciplines are concerned with your topic?
Which aspect(s) - legal, political, environmental, behavioral etc. - of your topic is/are of interest?

» Answering these questions will help you decide which databases to search for literature.
Although PubMed may be the best place to start for most public health topics, you may miss key literature if you do not use other resources.
Use your question as the basis for deciding where to search. More information in the Beyond PubMed ... section, below.

The importance of indexing
» Do you want articles on labor (as in work) or articles on labor (as in giving birth)? Or is it labour?
Indexing facilitates more precise search statements, especially for topics that are vague or ambiguous.
Using index terms also helps you avoid the need to think of every possible synonym or alternate spelling of your search terms.
Indexing means the citations in the database are assigned terms from a controlled vocabulary; not all databases use a controlled vocabulary, however.
Index terms are sometimes called descriptors or thesaurus terms; in PubMed they are called Medical Subject Headings, or MeSH
» More information is in the database sections below.

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PubMed Tips

PubMed
Citations to over 21 million journal articles (and a small but growing number of books/book chapters),
with links to full text via

PubMed top tips for focusing your search:

  1. Combine terms with AND or OR
  2. Use Limits (Age group, Publication type, language, etc.)
  3. Search for your term as a word in the title or title or abstract (using Limits)
  4. Use MeSH, with subheadings
  5. Try PubMed's Clinical Queries or Topic-Specific Queries
  6. Use the Related Articles link, once you find a set of relevant citations
  » Information on these follows:

» PubMed Quick Guide: Basic search help.
» PubMed exercise set (Public Health Library): Use these to hone your PubMed skills.

» Combining search terms with Boolean operators (AND, OR, NOT - remember Venn diagrams?)

» Limits: Limit your search by language, age group, publication type, publication date, and more. Also use Limits search for words in the article title, abstract, or Medical Subject Heading (MeSH). Note that Limits stay in effect until you clear them.

» Use Medical Subject Headings (MeSH):


» Clinical Queries: You may especially be interested in finding systematics reviews on your topic. Also consider that etiology may be used for a "cause of disease" search, and that therapy encompasses any type of intervention.
» Topic-Specific Queries use "canned" search strategies to fetch a citation subset of PubMed. Some examples of topic-specific queries include:
» Saving citations temporarily using the Clipboard

» My NCBI:

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Beyond PubMed: Other Resources for Finding Journal Articles and More      

Remember those PubMed "Top Tips"? Most are applicable to many other online databases.

Agricola
Subjects include all aspects of agriculture: agricultural economics, nutrition, hunger, food production, agricultural chemicals, etc.
» Agricola does not use a controlled vocabulary. Use the subject descriptor index to find terms, or focus your search by using title words.
» What's not in PubMed?
    Nutritionally induced diseases, WIC program, women in rural development ...

BIOSIS Previews
The most comprehensive database for life science research. Coverage includes traditional areas of biology, such as botany, zoology and microbiology, as well as related fields such as biomedicine, agriculture, pharmacology and ecology. Interdisciplinary fields such as medicine, biochemistry, biophysics, bioengineering and biotechnology are also included, as well as instrumentation and methods. Includes journal article citations, books and meeting abstracts, papers and posters.
» Use Concept Codes, Taxonomic Data, and more to focus your BIOSIS Previews search.
» What's not in PubMed?
    Better searching by taxonomic data, includes meeting abstracts ...
» Guide to BIOSIS previews:  html  |  pdf

Business Source Complete
Marketing, management, economics, finance, accounting, and more. Besides journal literature, BSC includes financial data, conference proceedings, case studies, investment research reports, industry reports, market research reports, country reports, company profiles, SWOT analyses, and more.
» BSC does use a controlled vocabulary. Click Subjects on the right side to browse the thesaurus.
» What's not in PubMed?
    Search by company or industry, public health topics form a marketing point of view ...

Embase
Broad biomedical scope with strong coverage in pharmaceutical and toxicological research, including economic evaluations. Useful for clinical medicine, genetics, biochemistry, molecular biology, microbiology, infectious diseases, healthcare policy & management, biomedical engineering & medical devices, and more. Embase is a primary resource for conducting systematic reviews and researching evidence-based medicine. Includes abstracts of over 2,000 conferences.
» Embase does use a controlled vocabulary. Click Emtree above the search box to search or browse for terms.
» What's not in PubMed?
    Exceptional coverage of drug/toxicology topics, more European literature, sophisticated indexing scheme ("Emtree"'), search by CAS Registry Number ...

Global Health
Citations in environmental and occupational health, food safety and hygiene, infectious diseases, medical microbiology, nutrition, public health, toxicology, zoonoses, and more. Sources include journals, books, reports, conference proceedings, patents, theses, and electronic only publications. Significantly more international coverage than PubMed.
» Global Health does use a controlled vocabulary. Use the drop-down menu and select Descriptors then click to browse the thesaurus.
» What's not in PubMed?
    Search by (relatively narrow) geographic locations (ie, setting), or country in which work published.
» Global Health Help

PsycINFO
Citations in psychology, behavior, and related disciplines; includes citations of journal articles, conference proceedings, books and book chapters, reports and dissertations.
» PsycINFO does use a controlled vocabulary. Click Search Tools then Thesaurus to browse for terms.
» What's not in PubMed?
    Economic security, community attitudes, socioeconomic class attitudes, labeling, test/measurement index ...
» PsycINFO Quick Guide (PDF)

Social Work Abstracts
Citations on topics such as homelessness, HIV/AIDS, child and family welfare, aging, substance abuse, legislation, community organization, and more.
» Social Work Abstracts does not use a controlled vocabulary. Use the subject term index to find terms: click Indexes and choose Subjects to browse for terms, or use title words.
» What's not in PubMed?
    Age bias, family functioning, resiliency, ...
» Social Work Abstracts Help

Sociological Abstracts
Citations in demography, education, law, social psychology, and sociology. Sources include journals, books, conferences and meetings, and dissertations.
» Sociological Abstracts does use a controlled vocabulary. Click Search Tools then Thesaurus to browse for terms.
» What's not in PubMed?
    Cultural capital, peer relations, victimization, family structure, strategies, neighborhoods, social constructionism, ...
» Sociological Abstracts Exercise
» Sociological Abstracts Fact Sheet

Web of Science
Large, multidisciplinary database; links to cited articles and times cited are provided for retrieved articles.
» Web of Science does not use a controlled vocabulary; it uses author keywords and keywords assigned algorithmically.
» What's not in PubMed?
    Scope of database is broad; best resources for cited reference searching; can sort search results by times cited.
» Search Tips for Web of Science
» Cited Reference Searching

   


The above are but a sample of the many databases available to find article and other citations.
See the Public Health Library's Indexes and Databases web page for more.
Ask a librarian for help if you are having trouble with your topic.

Use the library catalogs to find books, reports, etc. on your topic.
Books, while not often where original research is published, can often provide an overview of a topic and get you started with some key articles.

Sources of systematic and other reviews
"Systematic reviews seek to collate all evidence that fits pre-specified eligibility criteria in order to address a specific research question. They aim to minimize bias by using explicit, systematic methods." (from Higgins JPT, Green S (editors). Cochrane Handbook for Systematic Reviews of Interventions Version 5.1.0 [updated March 2011]. The Cochrane Collaboration, 2011. Available from www.cochrane-handbook.org).

Grey Literature
Grey Literature generally refers to publications not produced by commercial publishers, including reports (pre-prints, preliminary progress and advanced reports, technical reports, market research reports, etc.), theses, conference proceedings, and other documents. They are often produced by government entities, research institutions, or NGOs/IGOs.

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Critically Evaluating What You Find

What is evidence?

All research is (potentially) "evidence" and there are no "perfect" studies.
Critically evaluating articles, books, etc. will help any unearth biases or methodological shortcomings that may be present.

Reliability and validity
Adopted from Chapter 3, Conducting research literature reviews : from the Internet to paper, by Arlene Fink; Sage, 2010.
Reliable data collection: relatively free from "measurement error."
  » Is the survey written at a reading level too high for the people completing it?
  » If I measure something today, then measure it again tomorrow using the same scale, will it vary? Why?
Validity refers to how well a measure assesses what it claims to measure
  » If the survey is supposed to measure "quality of life," how is that concept defined? Is it measurable?
Extensive discussions of reliability and validity are available in several texts, such as Textbook in Psychiatric Epidemiology (3rd Ed.; M. Tsuang et al. Wiley. 2011; See chapters 5 and 7).

What to consider when looking at survey or estimated data:
Adopted from information on the UCSF Family Health Outcomes Project web site

Critical Appraisal Tools
Critical Appraisal of Intervention Studies is a free online learning module from Canada's National Collaborating Centre for Methods and Tools. It demonstrates how to assess the quality of an intervention study and to develop skill in applying the criteria for critical appraisal of an intervention study to enable you to determine whether that intervention can be applied to your own public health situation.

The Critical Appraisal Skills Programme (UK) links to a set of brief PDF checklist documents on critically evaluating different types of studies (eg, systematic reviews, cohort studies, RCTs, qualitative studies, etc.).

Critical appraisal of epidemiological studies and clinical trials (J. M. Elwood. Oxford University Press, 2007) has several chapters that provide detailed information on critically evaluating different kinds of studies. This book is available both online and in the Public Health Library:

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Organize Your Citations and Search Strategy

Organizing Your Literature Search/Search Results
Charts like this Literature Review Matrix (.doc) help you organize what you find in your literature search.
(This is a simplified version of the matrix presented in Health sciences literature review made easy: the matrix method, J. Garrard; Sudbury, MA: Jones and Bartlett Learning, 2011, available in the Public Health Library, call number R118.6 .G37 2011; Reference Section)
  » You can adapt RefWorks, EndNote, Zotero, or Mendeley to be used with a matrix like this by using notes or custom fields in your database.
      » Take a class to learn how to use these programs, all of which greatly simplify keeping track of citations you find.
      » This EndNote custom style was created for use with a literature review matrix; download it to the Styles folder in your EndNote program.

Save your search strategies: Nearly all the databases you use to find articles, etc., retain your search history. Literature reviews, like epidemiological research, should be rigorous and reproducible. Save or print your search history to help document your search strategy, which will include:

Using PubMed's Clipboard and My NCBI can help with both saving your search strategy and the citations you find;
See links in the PubMed section, above.

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