literature search strategy

How to undertake a literature search: a step-by-step guide

Affiliation.

• 1 Literature Search Specialist, Library and Archive Service, Royal College of Nursing, London.
• PMID: 32279549
• DOI: 10.12968/bjon.2020.29.7.431

Undertaking a literature search can be a daunting prospect. Breaking the exercise down into smaller steps will make the process more manageable. This article suggests 10 steps that will help readers complete this task, from identifying key concepts to choosing databases for the search and saving the results and search strategy. It discusses each of the steps in a little more detail, with examples and suggestions on where to get help. This structured approach will help readers obtain a more focused set of results and, ultimately, save time and effort.

Keywords: Databases; Literature review; Literature search; Reference management software; Research questions; Search strategy.

• Databases, Bibliographic*
• Information Storage and Retrieval / methods*
• Nursing Research
• Review Literature as Topic*

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Dudley RA, Frolich A, Robinowitz DL, et al. Strategies To Support Quality-based Purchasing: A Review of the Evidence. Rockville (MD): Agency for Healthcare Research and Quality (US); 2004 Jul. (Technical Reviews, No. 10.)

Strategies To Support Quality-based Purchasing: A Review of the Evidence.

2 methods for literature search.

• Technical Expert Advisory Panel

For advice on the scope of the project, refinement of the key questions, and preparation of this technical review, we consulted technical experts in the following fields: employer purchasing strategies, provider performance assessment, consumer use of report cards and consumer preferences for health care information, risk adjustment, and economics. (See Appendix A , available at www.ahrq.gov/clinic/epcindex.htm .)

• Target Audiences and Population

The decisionmakers addressed in this technical review are purchasers (both private purchasers such as employers and public purchasers such as the Centers for Medicare & Medicaid Services and State Medicaid programs), executives in health plans that must negotiate incentive arrangements with provider organizations or individual providers, executives in provider organizations that must negotiate incentive arrangements with providers, public health officials and other organizations interested in creating health care performance reports for public release, and policymakers. For the purpose of this report, provider organizations include all clinical health providers such as physicians, nurses, and hospitals. Public health officials and policymakers include those at the local, State, Federal, and international levels.

The ultimate target population of this report is the U.S. population at risk for morbidity or mortality resulting from quality problems in the provision of health care. We are interested in QBP strategies that affect the entire U.S. population—all members of which are at risk for receiving poor quality care—including those of all racial and ethnic backgrounds, all ages, and both genders.

• Key Questions

We developed the key questions in collaboration with AHRQ, the Alliance (the nominating partner), and our Technical Expert Panel. The goal of these discussions was to identify the issues purchasers interested in QBP faced so that, if the available research offered conclusions about these aspects of QBP, the various stakeholders would be in a better position to select optimal approaches to QBP.

The key questions for which literature, ongoing research, or results from analyses were sought in preparation of this report were:

• What is the evidence on the extent to which health plans and employers use incentives to improve quality and efficiency?
• Does the use of financial incentives for quality and efficiency actually increase the probability that patients receive high quality, efficient care?
• The basis of the incentive (structure, process, outcome)?
• The nature of the incentive (bonus, penalties or holdback, tiering or patient steerage/referral)?
• To whom the incentive is targeted (plan vs. provider group vs. individual provider)?
• The payer of the incentive (purchaser vs. plan vs. medical group)?
• The magnitude of the incentive?
• Does the use of nonfinancial incentives for quality and efficiency actually increase the probability that patients receive high quality, efficient care?
• The nature of the incentive (public release of performance report vs. confidential performance report)?
• Does greater spending result in higher quality?
• What are the cost savings for the health care provider and purchaser as a result of the quality improvement?
• What are the cost savings associated with different approaches to preventing medical errors or otherwise improving quality?
• What specific processes and structures result in quantifiable cost savings? Who realizes the savings? How should they be shared?
• What contextual variables (e.g., provider supply, employer number and market share, health plan competition, organizational system/infrastructure, employee demographics) positively or negatively influence the effectiveness of financial and nonfinancial incentives for providers?
• Literature Review Methods

Based on input from our expert advisors, our conceptual model, and practical considerations, we developed literature review methods that included: inclusion and exclusion criteria to identify potentially relevant articles, search strategies to retrieve articles, abstract review protocols, and a system of scoring published studies for completeness.

Inclusion and Exclusion Criteria

To be considered an article that provided evidence regarding one of the key questions above, the article had to address one of the predictor variables and either quality (as measured by processes or outcomes) or cost. In addition, the intervention in the trial had to be a strategy that could plausibly be introduced by a purchaser. Our focus was on articles that provided definitive primary data from randomized, controlled trials, but we also included systematic reviews to determine whether these contained any additional information not covered by the primary randomized, controlled trial reports.

We excluded articles that did not meet specific criteria in terms of the quality of the research and reporting. These were:

• Intervention randomized
• Inclusion/exclusion criteria clear and appropriate
• Greater than 75% follow-up
• Note: two criteria usually used to judge the quality of a randomized, controlled trial—provision of placebo to the control group and blinding of the subjects—are not applicable in this situation
• Information source appropriate
• Information source adequately searched
• Data abstraction performed by at least 2 independent reviewers
• Principal measures of effect and the methods of combining results appropriate

Search Strategy

The objective of our search strategy was to identify all published QBP randomized trials and all ongoing research into QBP strategies. For the literature review, we used standard search strategies involving the querying of two online databases (MEDLINE ® and Cochrane) using key words, followed by evaluation of the bibliographies of relevant articles, Web sites of relevant organizations (especially of funding agencies providing project summaries and of employer organizations pursuing QBP), and reference lists provided by our Technical Expert Panel ( Table 1 ).

Table 1. Information sources for literature review and catalog of ongoing research.

Database Searches

To identify potentially relevant articles in the medical literature, we searched MEDLINE ® and Cochrane databases and references provided by our Expert Advisors.

MEDLINE ® search strategies. We searched MEDLINE ® (January 1980 to December 15, 2003) for English language articles using the search terms described in Table 2 . Some citations were reviewed and articles were retrieved in more than one of the searches listed below.

Table 2. MEDLINE ® searches to identify potentially relevant primary data.

Cochrane search strategies. We searched the Cochrane databases from January 1, 1990 through December 15, 2003 (OVID, Evidence Based Medicine Reviews Multifile) using the search terms described in Table 3 .

Table 3. Search terms and citations for Cochrane databases.

Abstract Review

To identify potentially relevant articles for focused searching, at least two investigators (to ensure consistent application of the inclusion and exclusion criteria) reviewed each citation and, whenever an abstract was available, the abstract. Discrepancies in inclusion were resolved by discussion and re-review.

Evaluating Published Articles for Completeness of Reporting

We assessed each of the published articles for their completeness in reporting the factors we identified in our conceptual model that could influence a provider's response to incentives. Specifically, we scored them for the inclusion (or not) of descriptions of the elements in Table 4 . We also recorded the type of care (preventive care, acute care, or chronic care) to which the quality measured pertained.

Table 4. Evaluating randomized controlled trials for completeness of reporting.

• Identifying Ongoing Research

Based on input from our expert advisors, our conceptual model, and practical considerations, we developed methods to catalog ongoing research into QBP that involved specifying: inclusion and exclusion criteria to identify potentially relevant research projects, search strategies to retrieve project abstracts, abstract review protocols, and a system of describing the study design of ongoing research projects.

Since the search for ongoing research focused on projects not yet reported in the literature, the criteria for identifying relevant projects focused on the planned intervention. Two types of research potentially met our inclusion criteria: projects designed as randomized controlled trials, or projects with interventions using QBP methods as described above (i.e., payment or performance reporting strategies) and applied at the community level (or in a broader geographic region, such as a State) that included historical or contemporaneous non-randomized control groups.

We searched online health services research databases (HSRProj and AHRQ's Grants-On-Line Database or GOLD). We also searched the Web sites of other funders or coordinators of projects (e.g., the Leapfrog Group at www.leapfroggroup.org/RewardingResults/ ). Finally, we inquired of staff at AHRQ, the Robert Wood Johnson Foundation, the California HealthCare Foundation, and the Commonwealth Fund whether there was ongoing research that met our inclusion criteria being funded by those organizations. Table 5 lists our information sources for this aspect of the report.

Table 5. Information sources for the catalog of ongoing research.

We searched the two available databases for ongoing health services research, using a similar search strategy for each ( Tables 6 and 7 ). We accessed HSRProj through the National Library of Medicine's Gateway database at gateway.nlm.nih.gov/gw/Cmd and GOLD at www.gold.ahrq.gov .

Table 6. Search terms and citations for GOLD.

Table 7. Search terms and citations for HSRProj database.

GOLD search strategies . We searched GOLD through February 15, 2004 for grants funded by AHRQ using the categories described in Table 6 . Through our combination of searches, we eventually evaluated all projects in GOLD.

HSRProj search strategies . We searched the HSRProj database through February 15, 2004 using the categories described in Table 7 .

Grant Abstract Review

Two investigators reviewed the abstracts of projects identified from the database searches to assess relevance to the technical review. Discrepancies in inclusion were resolved by discussion and re-review and by discussion with project officers at funding agencies or with the principal investigator of the project under consideration.

Describing the Study Design of Ongoing Research

For each research project, we interviewed either project staff (usually the principal investigator) or the project officer to determine the study design. We obtained information about the intervention—performance measures and incentives used—and the control group. The information sought is described in Table 8 .

Table 8. Design information sought about ongoing research.

• Cite this Page Dudley RA, Frolich A, Robinowitz DL, et al. Strategies To Support Quality-based Purchasing: A Review of the Evidence. Rockville (MD): Agency for Healthcare Research and Quality (US); 2004 Jul. (Technical Reviews, No. 10.) 2, Methods for Literature Search.
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Learning Objectives

(1) Explain steps in conducting a literature search

(2) Identify resources to utilize in a literature search

(3) Perform an online literature search using U of U Health resources

Valentina is a third year pediatric resident who notices that many of the teenagers she sees in clinic use their phones to play games and connect with friends and family members. She wonders if there could be an app for teenagers to manage their chronic diseases, specifically type 1 diabetes. But where does she begin? 

What is a literature search?

iterature search is a comprehensive exploration of published literature with the purpose of finding scholarly articles on a specific topic . Managing and organizing selected scholarly works can also be useful.

Why do a literature search?

Literature search is a critical component for any evidence-based project. It helps you to understand the complexity of a clinical issue, gives you insight into the scope of a problem, and provides you with best treatment approaches and the best available evidence on the topic. Without this step, your evidence-based practice project cannot move forward.

Five steps for literature search success

There are several steps involved in conducting a literature search. You may discover more along the way, but these steps will provide a good foundation. 

Plan using PICO(T) to develop your clinical question and formulate a search strategy.

Identify a database to search.

Conduct your search in one or more databases.

Select relevant articles .

Organize your results . Remember that searching the literature is a process.

#1: Plan using PICO(T)

The PICO(T) question framework is a formula for developing answerable, researchable questions. Using PICO(T) guides you in your search for evidence and may even help you be more efficient in the process ( Click here to learn all about PICO(T) ). 

Once you have your PICO(T) question you can formulate a search strategy by identifying key words, synonyms and subject headings. These can help you determine which databases to use. 

#2: Identify a database

For your search, you will need to consult a variety of resources to find information on your topic. While some of these resources will overlap, each also contains unique information that you won’t find in other databases.  

The "Big 3" databases: Embase, PubMed, and Scopus are always important to search because they contain large numbers of citations and have a fairly broad scope. ( Click here to access these databases and others in the library's A to Z database.) 

In addition to searching these expansive databases, try one that is more topic specific.

We are here to help.

If you are conducting a literature search and are not certain of the details, don't panic! U of U Health has a wealth of resources, including experienced librarians, to help you through the process. Learn more here. 

Utah’s Epic-embedded librarian support

Did you know you can request evidence-based information from the library directly through Epic?  Contact us through Epic’s Message Basket.

Eccles Health Sciences medical librarians are able to provide expertise in articulating the clinical question, identifying appropriate data sources, and locating the best evidence in the shortest amount of time. You can also send a message to ASK EHSL .

#3: Conduct your search

Now that you have identified pertinent databases, it is time to begin the search!

Use the key words that you’ve identified from your PICO(T) question to start searching. You might start your search broadly, with just a few key words, and then add more once you see the scope of the literature. If the initial search doesn't produce many results, you can play with removing some key words and adding more granular detail.

In our intro case study, Valentina’s population is teenagers with type 1 diabetes and her intervention is a mobile app. Watch the video below to see how Valentina uses the powerful Embase PICO search feature to identify synonyms for type 1 diabetes, mobile apps, and teenagers.

Example of   Embase using PICO Why use Embase? This search casts a wider net than most databases for more results.

Common Search Terms and Symbols

AND Includes both keywords Narrows search OR Either keyword/concept Combine synonyms and similar concepts Expands search "Double quotes"  Specific phrase Wildcard* Any word ending variants (singular, plural, etc.) Example: nurs* = nurse, nurses, nursing, etc.

Controlled Vocabulary

Want to help make your search more accurate? Try using the controlled vocabulary, or main words or phrases that describe the main themes in an article, within databases. Controlled vocabulary is a standardized hierarchical system. For example, PubMed uses Medical Subject Headings or MeSH terms to “map” keywords to the controlled vocabulary. Not all databases use a controlled vocabulary, but many do. Embase’s controlled vocabulary is called Emtree, and CINAHL’s  controlled vocabulary is called CINAHL Headings. Consider focusing the controlled vocabulary as the major topic when using MeSH, Emtree, or CINAHL Headings. 

For Valentina’s question, there are MeSH terms for Adolescent, Diabetes Mellitus, Type 1, and Mobile Applications.

Example of  PubMed using MeSH MeSH helps focus your PubMed search

Talk with your librarians for more help with searching with controlled vocabularies. 

Every database uses filters to help you narrow your search. There are different filters in each database, but they tend to work in similar ways. Use filters to help you refine your search, rather than adding those keywords to the search. Filters include article/publication type, age, language, publication years, and species.

Using filters can help return the most accurate results for your search.

Article/publication types, such as randomized controlled trial, systematic reviews, can be used as filters.

Use an Age Filter, rather than adding “pediatric” or “geriatric” to your search.

Valentina uses the age filter for her question rather than as a keyword in the video below.

Example of a PubMed keyword search using filters PubMed is the most common search because it is the most widely available.

#4: Select relevant articles

Once you have completed your search, you’ll select articles that are relevant to your question. Some databases also include a “similar articles” feature which recommends other articles similar to the article you’re reviewing—this can also be a helpful tool.

When you’ve identified an article that appears relevant to your topic, use the “Snowballing” technique to find additional articles. Snowballing involves reviewing the reference lists of articles from your search. 

In other words, look at your key articles and review their reference list for additional key or seminal articles to aid in your search.

#5: Organize your results

As you begin to collect articles during your literature search, it is important to store them in an organized fashion. Most research databases include personalized accounts for storing selected references and search strategies. 

Reference managers are a great way to not only keep articles organized, but they also generate in-text citations and bibliographies when writing manuscripts, and provide a platform for sharing references with others working on your project.

A number of reference managers—such as Zotero , EndNote , RefWorks, Mendeley , and Papers are available. EndNote Basic (web-based) is freely available to U of U faculty, staff and students. If you need help with this process, contact a librarian to help you select the reference manager  that will best suit your needs.

Using these steps, you’re ready to start your literature search. It is important to remember that there is not a right or wrong way to do the search. Literature searches are an iterative process—it will take some time and negotiation to find what you are looking for. You can always change your approach, or the information resource you are using. The important thing is to just keep trying. And before you get frustrated or give up, contact a librarian . They are here to help!

This article originally appeared May 12, 2020. It was updated to reflect current practice on March 14, 2021.

Tallie Casucci

Barbara wilson.

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