Practical Tips for Literature SynthesisCheryl 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 reflectevidence-based practices and interventions.1 A synthesisof 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 alarger 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 topatient outcomes and nursing care.

The synthesis of the literature is intended to do morethan 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 thecurrent state of the science and the knowledge gapsabout the topic of interest. An example of such a reviewcreated by Dumoulin and Hay-Smith2 on pelvic floormuscle training for urinary incontinence in women waspublished as a synopsis in the journal Clinical NurseSpecialist by McLoughlin and McAuley.3 The review servesas the example cited throughout this article.

While creating and writing a synthesis of the literaturemay seem like a daunting task to the CNS who has manydemanding responsibilities and literature sources withwhich to maintain currency, the goal of this article is toprovide a simple guide for the process that may be usedeasily by the CNS. Specifically, the purpose of this articleis to provide a step-by-step process of how one mightapproach the literature synthesis. The specific topicscovered 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 foranalyzing the collective papers, and suggestions for writ-ing the final product. Tools one might use to facilitate theprocess with examples using the Dumoulin and Hay-Smith’s2 article are provided to smooth the process andsoothe 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 relationshipsgleaned from the process that allow one to come to ahigher level of understanding or knowledge about a spe-cific topic. ‘‘It works very much like a jigsaw puzzle. Theindividual pieces (arguments) must be put together in or-der to reveal the whole (state of knowledge).’’4

CONSIDER AND REFINE THE QUESTIONThe first step in the synthesis of the literature is to care-fully consider and refine the question the CNS wishes toask of the literature. Particular attention to the proposedconcepts, research design, sample selection criteria andprocess, measures, and statistical analyses is warrantedand recommended to ease the process. Refinement of thetopic and clarity about the question are critical at the onsetand is enhanced by the expert knowledge base of theCNS. The eventual quality of the synthesis of the literatureis dependent, in part, on this important first step. Issuesfor consideration are provided in Figure 1.

Using the example of urinary incontinence, the posedquestion 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 SEARCHNext, the CNS needs to consider the focused questionand describe the state of the science related to the CNS’spotential future as reflected in the available literature. Inaddition, the CNS needs to address the knowledge gapsand the areas where the available literature does notinform the CNS’s potential future project. The quality of

Author Affiliation: Professor and Associate Dean, International andCommunity 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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the literature search is dependent on the thoroughnessand accuracy of the writer’s search. Thus, consultationwith a librarian is recommended as librarians are expertin search methods and terms.

The refinement of the question and the review of theliterature is an iterative process that is recursive in naturewith the desired end point a fully refined and focusedquestion with a matching review of the literature. Thissecond 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 returnto the literature (Figure 2).

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

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

outset, the following might be offered regarding thesearch. A search in CINAHL plus full text, Health Source:Nursing/Academic Edition, and MEDLINE with full textof English-language, peer-reviewed, research articles ofadult (919 years of age) women using the search termspelvic floor muscle training yielded 51 results for from2002 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 inthe final review of the literature. Three were deemed in-appropriate on the basis of the population,5Y7 a fourthbecause the study was an economic evaluation nota clinical evaluation,8 and 2 additional articles as theywere not clinical research studies.9,10 Thus, 26 articleswere included for the next stet.

ANALYZE INDIVIDUAL, RETAINED PAPERSNow that the articles for inclusion in the review of theliterature have been identified in a cursory fashion, theCNS must critically appraise the quality of the selectedempirical 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 willbe retained for the review of the literature.

REVIEW AND ORGANIZE THE LITERATUREOnce 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 toanalyze 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 researchcourses is to compile the individual articles into a tableof evidence or matrix table.12,13

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

STRUCTURE AND SUMMARIZE THE LITERATURENow, the CNS is ready to reflect about the studies in thetable for the purpose of structuring and summarizing theinformation. Review the studies, take notes, sort, and or-ganize your concepts and their relationships. Seek thecommon points or themes that allow the individual arti-cles to be grouped into specific categories. The createdsimilarity heuristic will facilitate the development of a ta-ble of these common points or themes that will serve asan organizing framework for analyzing, and synthesizingof the individual articles into a whole. These categoriesmay be used later to organize the article.

The CNS may wish to organize all the individual articlesusing 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 muscletraining example and the article of Borello-France et al,13

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

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

Another variation on the similarity heuristic table maybe to create the table using only the interventions as thecommon points across which the literature is reviewed.Now, the CNS might complete the table as indicatedin Table 3 and synthesize the literature by intervention.The article by Borello-France et al13 is included in thesample (Table 3). As the original question posed in thepelvic floor muscle training was about a comparison ofinterventions, such a table may be most useful. Similar toTable 2, all retained articles would be included in the fi-nal version of Table 3.

Another strategy to synthesize the collective literaturethe CNS may wish to consider is the use of a concept map.Concept maps are tools for organizing and graphically re-presenting knowledge. The concepts are usually indicatedby circles or boxes, and the relationships among conceptsby colors and between concepts by lines or arrows, if thedirection is known. Words or symbols such as +,j, &, and% may be placed on the line to describe the relationshipsbetween concepts. Such an organizing tool may provide theCNS with a tool to visualize the relationships between andamong the concepts. Concept maps have been describedas particularly useful for organizing complex scientific in-formation14 and creating a literature review (Figure 3).15Y18

Table 1. Table of Evidence

MethodSample (Age; UI,SI, UrI, or Mixed)

Treatment (PFMT, None,Sham, PL, or Other)

Outcome(SC, SxI, QOL) Risk Bias

& 2-Arm RCT, parallel design & N = 44 & PFMT supine (n = 22) & Primary end pointat 9Y12 wk

& Random sequencegenerationa& Comparison: supine

PFMT vs supine andupright PFMT

& SI & PFMT alternate exercisebetween supine, sitting,and standing positions(n = 22)

& Primary outcome: notstated

& Allocationconcealmenta

& No a priori powercalculation

& 1 US site

& Other outcomemeasures & Blindingb& 38Y70 y old

) QOL (IIQ) & Incompleteoutcome datac

& Not pregnant

) Urinary diary& Selective reportingd

& Ambulatory

) Modified 1-h pad test& Symptoms of SI Q1/wk

) Digital PFMassessment(Brink scale)

& Mean age: 51.7 T 8.9 yvs 53.6 T 8.1 y

Abbreviations: IIQ, Incontinence Impact Questionnaire; PFM, pelvic floor muscle; PFMT, pelvic floor muscle training; PL, placebo; QOL, quality of life; RCT, random-ized controlled trial; SC, symptomatic cure; SI, stress incontinence; SxI, symptomatic improvement; UI, urinary incontinence; UrI, urge incontinence.aSelection bias.bPerformance bias and detection bias.cAttrition bias.dReporting bias.Borello-France et al.13

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The literature review as a concept map for the pelvic floormuscle training is represented as an example in Figure 4.

The concept map may be created as a rough hand-drawn diagram, on a computer using a simple documentformat or concept mapping software (www.SmartDraw.comfor personal computer users or Inspiration Maps for theiPadhttp://www.inspiration.com/ipad), or online-developedsticky notes or note cards.

SYNTHESIZE THE LITERATUREAt this step, the CNS is challenged with drawing conclu-sions about the concepts and their relationship. Note re-peated words, concepts, and instruments, and conceptual,methodological, and analytical conflicts or contradictionswithin and between studies. The identification of the pat-terns, trends, strengths, and weaknesses of the reviewedliterature may be accomplished by examining the similar-ities and differences between and among the concepts.The state of the science about the topic must be de-scribed, the knowledge gaps illuminated, and the clinicalimplications delineated. Keep the original question in theforefront as the synthesis is conducted and later written.The synthesis will describe these concepts and their rela-tionships in a way that is novel and creative and may laythe foundation for future work or study.

WRITE THE LITERATURE SYNTHESIS PAPERThe final step is for the CNS to write the paper describingthe synthesis of the literature. Begin with the question inmind and provide the reader with the rationale aboutwhy the synthesis is needed. The background and ratio-nale for the synthesis of the literature may assist the readerin understanding the scope of the concepts, literature, syn-thesis, and implications. Use the steps as the outline for thewritten work. Tables and figures created by the CNS mayserve to communicate the process and elucidate the relation-ships between and among concepts. Describe the similaritiesand differences, methods and limitations, and strengths andweaknesses of the literature as a whole. Use headings andsubheadings to allow the reader to track and facilitate greaterunderstanding of the synthesis of the literature. Focus onthe question the synthesis addresses and the totality ofthe literature rather than on the individual papers. Finishyour paper with a concluding paragraph that summarizesthe critical findings offered. The use of bullet points maymake your key findings abundantly obvious.19 Finally, pro-vide the reader with the important clinical and researchimplications of the synthesis in a few sentences. Usingthe example of our pelvic floor muscle training question,Dumoulin and Hay-Smith2 offered:

Table 3. Table Matrix Alternate Form

UI SI UrI

PFMT SC

SxI

QOL Borello-France et al13

& Effect of exercise position (supineor supine and upright positions)- IIQ at baseline and aftertreatment

& Exercise position j

& PFMT +

Sham SC

SxI

QOL

Placebo SC

SxI

QOL

Other SC

SxI

QOL

Abbreviations: IIQ, Incontinence Impact Questionnaire; QOL, quality of life;PFM, pelvic floor muscle; PFMT, pelvic floor muscle training; SC, symptomaticcure; SI, stress incontinence; SxI, symptomatic improvement; UI, urinaryincontinence; UrI, urge incontinence.

Table 2. Literature Matrix

Age PFMT

SHAM,Placebo,Other SC SxI QOL

UI

SI Borello-Franceet al13j +;no effect ofposition

UrI

Age X

PFMT X Borello-Franceet al13 + IIQ;no effect ofposition

Sham,placebo,other

X

SC X

SxI X

QOL X

Abbreviations: IIQ, Incontinence Impact Questionnaire; QOL, quality of life;PFM, pelvic floor muscle; PFMT, pelvic floor muscle training; SC, symptomaticcure; SI, stress incontinence; SxI, symptomatic improvement; UI, urinaryincontinence; UrI, urge incontinence.

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The review provides support for the widespreadrecommendation that PFMT be included infirst-line conservative management programsfor women with stress, urge, or mixed urinaryincontinence. Statistical heterogeneity reflectingvariation in incontinence type, training, andoutcome measurement made interpretation difficult.The treatment effect seems greater in women withstress urinary incontinence alone, who participatein a supervised PFMT program for at least 3 months,but these and other uncertainties require testingin further trials.2(p2)

In summary, a synthesis of the literature is a high-levelskill needed often by the CNS in achieving the goals ofcontinuous improvement in patient outcomes and nurs-

ing care through evidence-based practices and interven-tions. The skill may be described in a 7-step process:

1. consider and refine the question to be addressed inthe synthesis of the literature;

2. search the literature for relevant studies;3. analyze the quality of the individual articles;4. review and organize the literature into a manage-

able form;5. structure and summarize the collective literature;6. synthesize the literature addressing the state of the

science and knowledge gaps regarding the originalquestion; and

7. write the synthesis of the literature.Tools the CNS might use to facilitate the process such

as a table of evidence, literature matrix, or concept map

FIGURE 3. Concept mapVsorting relevant information. From Steinerova.19

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were offered, and examples of each provided. Hopefully,the individual CNS reader will feel more empowered togenerate and publish these important literature synthesesin order that all CNSs might benefit and use the review inthe quest to improve patient outcome\s and nursing care.

ResourcesLiterature Review: Synthesizing Multiple Sources. http://www.iupui

.edu/~uwc/pdf/Literature%20Review%20and%20Synthesis.pdf.Writing A Literature Review and Using a Synthesis Matrix. http://

www.ncsu.edu/tutorial_center/writespeak/PDF%20Handouts/synthesis%20matrix.pdf.

The Use of Mapping in Literature Review. http://sites.google.com/site/andycoverdale/texts/the-use-of-mapping-in-literature-review.

Galvan J. Writing Literature Reviews: A Guide for Students of the Be-

havioral Sciences. 3rd ed. Glendale, CA: Pyrczak Publishing; 2006.

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FIGURE 4. Concept mapVpelvic floor muscle training.Abbreviations: PFMT, pelvic floor muscle training; SI, stressincontinence; UI, urinary incontinence; UrI, urge incontinence.

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