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Chapter 5: Literature Reviews: Finding and
Critically Appraising Evidence
Purposes of Research Literal Reviews
โ A narrative literature review is one where the findings from the studies under review are integrated using the judgements of the reviewers, rather than through statistical integration- as in a meta-analysis. Until meta-analytic techniques were developed, all reviews were narrative reviews โ Literature reviews provide researchers with information to guide a high-quality study, such as information about the following โ The scope and complexity of the identified research problem (for the argument) โ What other researchers have found in relation to the research question โ The quality and quantity of existing evidence โ The contexts and locales in which research has been conducted โ The characteristics of the people who have served as study participants โ Theoretical underpinnings of completed studies โ Methodologic strategies that have been used to address the question โ Gaps in the existing evidence base- the type of new evidence that is needed โ Reviewing literature: process of identifying, locating, and reading relevant sources of research evidence. โ Written narrative literature reviews may take the following forms โ A review embedded in a research report โ A review in a research proposal โ A review in a thesis or dissertation
Literature Reviews in Qualitative Research
โ Grounded theory researchers often collect and analyze their data before reviewing the literature. โ Phenomenologists often undertake a search for relevant materials at the outset of a study โ Upfront literature review is necessary
Sources for a Research Review
โ Rely mostly on primary research reports โ Study protocol are an additional type of primary source - they are descriptions of the design and methods for studies that are underway but have not yet been completed โ Secondary Sources: descriptions of studies prepared by someone other than the original researcher โ Literature reviews
Major Steps and Strategies in a Narrative Literature Review
โ First the review must be comprehensive, thorough, and up to date โ Second a high-quality review is systematic โ Reviewers should strive for a review that is insightful and is more than the sum of its parts
Search Strategy Options
โ Database searches are used to search for key variables โ Ancestry approach: using references cited in recent, relevant studies to track down earlier research on the same topic. โ Descendancy approach: to find a pivotal early study and to search forward in indexes to find more recent studies
Eligibility Criteria Specifications
โ Search limits are most often managed in databases through filters โ Be sure not to limit your search exclusively in the nursing literature
Identifying Keywords
โ An early task is to identify and make a list of the keywords that will be used to search bibliographic databases. โ Many people utilize the PICO formulation as keywords for a literature search โ Important to think about synonyms for words
Searching Bibliographic Databases
โ Two major strategies for searching โ Search for standardized subject heading that are assigned by indexers โ Enter your own key words into the search fields (words are mentioned in the abstract not the entire article) โ Boolean operators: expands or delimits a search โ Include AND, OR, am dMPT/ โ AND delimits a search โ OR expands the search โ NOT narrows the search โ Be careful using NOT because you run the risk of inadvertently removing relevant articles โ Truncation symbol (often an asterisk) expands a search term to include all forms of a root word โ Some databases allow for a wildcard symbol (often ?) that can be inserted into the middle of a search term to allow for alternative spellings
Key Electronic Databases for Nurse Researchers
โ Two bibliographic databases that are useful are CINAHL and MEDLINE (accessed through pubmed) โ CINAHL: โ Provides abstracts for most citations โ Helps you find other relevant references once a good one has been found. โ Use find similar results link โ MEDLINE โ You can launch a clinical query search, which is particularly useful for searching for evidence in the context of an EBP inquiry โ Has a similar articles tab โ Google Scholar โ Does not order the retrieved references by publication date
Literature Review Summary Tables
โ Include: title, authors, year it was published, country, study design, independent variables, dependent variables, sample size and characteristics
Critical Appraisal of Evidence
โ A distinction is sometimes made between a research critique and a critical appraisal. The latter term is favored by those focusing on the evaluation of evidence for nursing practice โ Appraisals of Individual Studies โ A research critique is an appraisal of the strengths and weaknesses of a study. โ Good critique identifies areas of adequacy and inadequacy in an unbiased manner โ https://casp-uk.net/casp-tools-checklists/ โ Lists of checklists for article appraisals
Preparing a Written Literature Review
โ Organizing Review: โ Having an outline helps structure narrative flow โ Outline should list the main topics or themes to be discussed and the order of presentation โ Writing literature review โ Provide readers with an objective, organized synthesis of evidence on a topic. โ A review should be neither a series of quotes nor a series of abstracts โ When describing study findings you should use phrases suggesting that results are tentative such as โ Several studies have found โ Findings thus far suggest โ The study results support the hypothesis โ There appears to be good evidence that
Summary Points
โ A research literature review is a written synthesis of evidence on a research problem โ Major steps in preparing a written research review including formulating a question, devising a search strategy, developing a plan to organize and document review activities, conducting a search, screening and retrieving relevant sources, extracting key data from the sources, appraising studies, analyzing aggregated information for important themes, and writing a synthesis โ Research articles are the major focus of research reviews. Information in nonresearch references-such as case reports and editorials- may broaden understanding of research problem but has limited utility in summarizing research evidence โ A primary source is the description of a study prepared by the researcher who conducted it; a secondary source is a description of the study written by someone else. Literature reviews should be based on primary source material. โ Strategies for finding studies on a topic include the use of bibliographic databases โ Electronic searches of bibliographic databases are a key method of locating references. For nurses, the CINAHL and MEDLINE databases are especially useful
โ In searching a database, users can perform a keyword search that looks for searcher-specified terms in text fields of a data base record, or they search according to subject heading codes themselves โ Access to many journal articles is becoming easier through online resources โ References must be screened for relevance, and then pertinent information must be extracted for analysis. Two dimensional evidence summary tables facilitate the extraction and organization of data from the studies, as does a good coding scheme. โ A research critique or critical appraisal is a careful evaluation of a studyโs strengths and weaknesses. Critical appraisals for a research review tend to focus on the methodologic aspects and findings of retrieved studies โ The analysis of information from a literature search involves the identification of important themes-regularities and inconsistencies in the information. Themes can take many forms including substantive, methodologic, and theoretic themes โ In preparing a written review, it is important to organize material logically. The reviewers role is to describe study findings, the dependability of the evidence, evidence gaps, and contributions that the new study would make
