Practical Tips for Literature Synthesis Cheryl Westlake, PhD, RN, ACNS-BC

The clinical nurse specialist (CNS), as an advancedpractice nurse, has the primary goal of continuousimprovement in patient outcomes and nursing care by creating clinical practice environments that reflect evidence-based practices and interventions.1 A synthesis of the literature may be needed to answer a clinical ques- tion for implementation in practice, serve as an indepen- dent paper for publication as a review, or be part of a larger project such as a research proposal, dissertation, or data-based publication. In order to achieve this goal, the CNS needs to be able to systematically review the lit- erature and synthesize the findings on issues related to patient outcomes and nursing care.

The synthesis of the literature is intended to do more than just document or summarize the relevant literature. Rather, the synthesis of the literature is intended to pro- vide a detailed analysis and yield conclusions about the current state of the science and the knowledge gaps about the topic of interest. An example of such a review created by Dumoulin and Hay-Smith2 on pelvic floor muscle training for urinary incontinence in women was published as a synopsis in the journal Clinical Nurse Specialist by McLoughlin and McAuley.3 The review serves as the example cited throughout this article.

While creating and writing a synthesis of the literature may seem like a daunting task to the CNS who has many demanding responsibilities and literature sources with which to maintain currency, the goal of this article is to provide a simple guide for the process that may be used easily by the CNS. Specifically, the purpose of this article is to provide a step-by-step process of how one might approach the literature synthesis. The specific topics covered in this article are the steps involved in a synthe- sis of the literature including recommendations about

how to analyze each individual paper for potential inclu- sion in the analysis and synthesis, specific processes for analyzing the collective papers, and suggestions for writ- ing the final product. Tools one might use to facilitate the process with examples using the Dumoulin and Hay- Smith’s2 article are provided to smooth the process and soothe the mind of the ambitious CNS.

A literature synthesis is a focused review, in-depth eval- uation, critical analysis, and creative compilation of infor- mation based on patterns, alternatives, or relationships gleaned from the process that allow one to come to a higher level of understanding or knowledge about a spe- cific topic. ‘‘It works very much like a jigsaw puzzle. The individual pieces (arguments) must be put together in or- der to reveal the whole (state of knowledge).’’4

CONSIDER AND REFINE THE QUESTION The first step in the synthesis of the literature is to care- fully consider and refine the question the CNS wishes to ask of the literature. Particular attention to the proposed concepts, research design, sample selection criteria and process, measures, and statistical analyses is warranted and recommended to ease the process. Refinement of the topic and clarity about the question are critical at the onset and is enhanced by the expert knowledge base of the CNS. The eventual quality of the synthesis of the literature is dependent, in part, on this important first step. Issues for consideration are provided in Figure 1.

Using the example of urinary incontinence, the posed question may have been: What is the difference in wom- en’s outcomes for different interventions for urinary in- continence including to pelvic floor muscle training?

LITERATURE SEARCH Next, the CNS needs to consider the focused question and describe the state of the science related to the CNS’s potential future as reflected in the available literature. In addition, the CNS needs to address the knowledge gaps and the areas where the available literature does not inform the CNS’s potential future project. The quality of

Author Affiliation: Professor and Associate Dean, International and Community Programs, School of Nursing, Azusa Pacific University, California. The author reports no conflicts of interest. Correspondence: Cheryl Westlake, PhD, RN, ACNS-BC, School of Nurs- ing, Azusa Pacific University, 720 E Foothill Blvd, Azusa CA 91702 (ccanary@apu.edu). DOI: 10.1097/NUR.0b013e318263d766

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Using Research to Advance Nursing Practice

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the literature search is dependent on the thoroughness and accuracy of the writer’s search. Thus, consultation with a librarian is recommended as librarians are expert in search methods and terms.

The refinement of the question and the review of the literature is an iterative process that is recursive in nature with the desired end point a fully refined and focused question with a matching review of the literature. This second step may require some consideration of the ques- tion, review and sorting of the literature, and reconsidera- tion and refinement of the question with another return to the literature (Figure 2).

With each iteration, the CNS is wise to document the changes, additions, or deletions made in the search terms and databases. These changes may be made by hand in a paper notebook at the side one’s computer, online in a notebook such as Notepad (http://www.google.com/ notebook/#b=BDQmGSgoQl92H_PAm) Evernote (http://www .evernote.com/ for personal computer users, or Evernote for Mac users http://www.evernote.com/), or Notes on the iPad, or in a simple word document, or using an applica- tion such as StickyNotes (http://www.sticky-notes.net/ for personal computer users and stickynotesapp.com for Mac users). Whatever the method, the CNS is now well poised to move forward, and the documented changes will serve to streamline the third step.

LITERATURE SEARCH METHODS A complete and comprehensive description of the liter- ature search in very specific, concrete terms is required next. Begin with an introduction that outlines the empir- ical literature reviewed explaining the methods used in your literature search. Remember to include the search strategies, keywords used, databases and periods searched, a description of articles that were excluded and the ra- tionale for the exclusion. For example, considering the question about pelvic floor muscle training posed at the

outset, the following might be offered regarding the search. A search in CINAHL plus full text, Health Source: Nursing/Academic Edition, and MEDLINE with full text of English-language, peer-reviewed, research articles of adult (919 years of age) women using the search terms pelvic floor muscle training yielded 51 results for from 2002 to 2012 that reduced to 38 by adding urinary incon- tinence andwas further reduced to 32 by adding women. All articles were read. Six articles were not included in the final review of the literature. Three were deemed in- appropriate on the basis of the population,5Y7 a fourth because the study was an economic evaluation not a clinical evaluation,8 and 2 additional articles as they were not clinical research studies.9,10 Thus, 26 articles were included for the next stet.

ANALYZE INDIVIDUAL, RETAINED PAPERS Now that the articles for inclusion in the review of the literature have been identified in a cursory fashion, the CNS must critically appraise the quality of the selected empirical studies. Based on the internal (instrument re- liability and statistics, equivalence of participant charac- teristics, and control of experience/environment variables) and external validity characteristics (operations and instru- ment validity, population validity, and ecological validity) by Cook and Campbell,11 evaluate each study that re- mains for consideration in the review of the literature. This review may be done by the CNS and another col- league or two or by an external judge panel. Those arti- cles that are evaluated as being of sufficient quality will be retained for the review of the literature.

REVIEW AND ORGANIZE THE LITERATURE Once the relevant, high quality papers have been iden- tified and located, one needs to read, analyze, and or- ganize them to begin the synthesis. The first step is to analyze each individual article and then organize all the

FIGURE 1. Define your research question.

FIGURE 2. Question refinement and literature review.

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articles into a usable format for review and synthesis col- lectively. The method frequently used in nursing research courses is to compile the individual articles into a table of evidence or matrix table.12,13

An example of a single entry in a table of evidence using an article from our pelvic floor muscle training muscle re- view of literature is provided in Table 1.13 The table of evidence would include an entry with the associated data included for each of the retained studies.

STRUCTURE AND SUMMARIZE THE LITERATURE Now, the CNS is ready to reflect about the studies in the table for the purpose of structuring and summarizing the information. Review the studies, take notes, sort, and or- ganize your concepts and their relationships. Seek the common points or themes that allow the individual arti- cles to be grouped into specific categories. The created similarity heuristic will facilitate the development of a ta- ble of these common points or themes that will serve as an organizing framework for analyzing, and synthesizing of the individual articles into a whole. These categories may be used later to organize the article.

The CNS may wish to organize all the individual articles using a single table with all the potential relationships in- dicated and the studies supporting or refuting the relation- ships cited in the table. Using our pelvic floor muscle training example and the article of Borello-France et al,13

the table might be constructed as in Table 2. The final table would include all articles retained in the review of the literature.

Into each of the boxes where a relationship is de- scribed in the table of evidence, a plus or minus sign and the authors/date may be written to indicate studies where the relationship is supported or refuted. Notes and thoughts may be written in the margins for reflection in order for conclusions to be drawn.