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  1. Salmond, Susan W.


Practicing from an evidence-based paradigm requires the practitioner to integrate best available evidence with the patient's preference and values, the clinical context, and the practitioner's clinical expertise. However, the clinician is often at a loss for where to access best evidence. The 6S Model of evidence acquisition can guide the busy practitioner in efficient searching for best available evidence. The article explains the 6S model and the strengths and weaknesses of different types of evidence, while guiding readers with their role as clinicians in ensuring trustworthiness of evidence and relevance to their particular clinical context and patient population.


Article Content

It is impossible to pick up a professional journal without seeing reference to the importance of evidence-based practice (EBP). Professional nurses are expected to practice from an evidence-based perspective in which they integrate the best available evidence with patient preference, clinical expertise, and the clinical context itself (see Figure 1).

Figure 1 - Click to enlarge in new windowFigure 1. Components of evidence-based practice. From Com-prehensive Systematic Review for Advanced Nursing Practice, by C. Holly, S. Salmond & M. Saimbert, p. 5, Copyright 2012, by Springer Science+Business Media B.V. Used with permission.

The evidence-based approach to practice calls for practitioners to question why they do things in a particular fashion, whether there may be a better approach and what the evidence suggests may be best for a particular clinical context and patient population. This ongoing questioning stance or "informed skepticism" (Salmond, 2007) avoids the pitfalls of practice based on acceptance of tradition, hierarchy, or opinion (Holly, Salmond, & Saimbert, 2012; Stillwell, Fineout-Overholt, Melnyk, & Williamson, 2010). Nurses guided by an EBP approach question their practices (ASK) and seek to determine whether best practices are being used and whether these practices are resulting in the best outcomes for the patient (Holly et al., 2012; White & Dudley-Brown, 2012). Figure 2 describes the process of EBP with clinicians asking, acquiring evidence, appraising the strength of the evidence, applying the evidence, and then assessing the impact of the changed approach.

Figure 2 - Click to enlarge in new windowFigure 2. Evidence-based practice process.

Asking is a skill in itself. Models to guide questioning to facilitate acquisition of evidence typically follow a specified format (PICO) and are summarized in Table 1. This approach narrows the question and provides the outline for a search strategy using key words from the PICO mnemonic.

Table 1 - Click to enlarge in new windowTable 1. Asking Clinical Questions Using PICO Acronyms

Once the clinician identifies clinical questions, he or she must turn to evidence to inform practice. Evidence consists of practice-based or local evidence as well as research-based literature to seek the evidence to inform practice. Where is one to find the best evidence? How much evidence is enough evidence? How can one be sure of the quality of the evidence? This article will address the evidence of research-based literature as a component to EBP.


Before adoption of new knowledge, one must be assured that the evidence emerges from quality research. This requires critical appraisal, or the "careful and systematic examination of research to judge its trustworthiness, and its value and relevance in a particular context" ("Critical Appraisal Skills Programme," 2012). By assessing the balance of strengths and weaknesses in a study, decisions can be made to consider or not to consider the evidence so that ultimately practitioners rely on studies where the strengths outweigh the flaws. Fortunately since the start of the evidence-based movement, more sources have emerged where the work of appraisal has been done by experts. This is referred to as filtered evidence. Practitioners can efficiently access filtered evidence and is the preferred source for beginning the search (see Figure 3). Unfiltered evidence requires the practitioner to critically appraise the research before deciding to use it to inform practice.

Figure 3 - Click to enlarge in new windowFigure 3. The 6S pyramid.


The "6S" Pyramid of Evidence Resources (see Figure 3) provides a hierarchy the clinician can use as a guide to searching for the best information to manage and treat patients (DiCenso, Bayley, & Haynes, 2009). Start at the top of the pyramid when looking for evidence to guide clinical decision-making and work down until you find the evidence that matches your clinical question and applies to your patient population.



At the top of the pyramid is the clinical support system or electronic medical record that provides a smart system for linking patient problems or circumstances to best evidence or best practices. This smart computerized decision support system is updated continuously so that it can provide up-to-date summaries of relevant evidence on a clinical problem and alerts the practitioner as the system integrates patient characteristics and findings automatically with algorithms and care guidelines (DiCenso et al., 2009). Unfortunately, most clinicians do not have access to this type of evidence.



The next source of evidence that can efficiently provide answers to clinical questions are summaries. Summaries integrate the best available evidence from the lower tiers of the pyramid (synopses, syntheses, and studies) to compile a full range of evidence on the management of a given health problem (Haynes, 2006). This proves very valuable as evidence from the lower tiers typically targets narrow questions or one aspect of management (i.e., the effectiveness of tai chi in decreasing arthritic pain and improving balance among elders) and at the summary level the different aspects of management are integrated into a comprehensive evidence-based synopsis, so you would be able to access information on drugs, exercise, nutrition, etc.


In recent years, evidence summarization services and clinical electronic textbooks that provide clinical pathways, clinical summaries of evidence-based information, and regularly updates information for clinicians have become available. These sites are sources of evidence for screening and prevention, treatment, ethical and legal issues, quality measures, and alternative therapy (Holly et al., 2012) and have processes for updating that include thorough searches and appraisal of the literature. The clinician accessing these sources will be informed of the best available evidence from systematic reviews (SRs) and other primary research studies and is a valuable source of evidence to answer clinical questions at the point of care. The level of evidence is noted and the clinician will be advised if there is no good evidence to answer the question. Examples of summaries include Clinical Evidence (, the Physicians' Information and Education Resource (, Dynamed (, and UpToDate (


As new summary sources become available clinicians should validate whether the site provides information about its review and appraisal process to assure confidenence in the truthfulness of the data. Failure to post this transparency in approach makes the site questionable. Although summaries are clearly the optimal source of evidence for most clinicians, these sites are limited by the number of conditions that can be included as there is constant attention needed in keeping the site regularly up-to-date.


Another source of summary-level data are clinical practice guidelines (CPGs). Clinical practice guidelines are "systematically developed statements to assist both the practitioner and patient in decision making about appropriate health care for specific clinical circumstances" (DiCenso et al., 2009, p. JC2-2). As not all clinical guidelines meet the same rigor criteria, it is important to assess the quality of the CPG by ensuring that it is based on comprehensive searches and appraisal of the literature (ideally current SRs if available) and for all recommendations, levels of evidence are specified (DiCenso et al., 2009, p. JC2-2). The standard for appraising the methodological rigor and transparency in which a guideline was developed is to use the AGREE tool (the Appraisal of Guidelines for Research and Evaluation), which can be accessed along with tutorials available at


A common source of CPGs is the National Guidelines Clearinghouse (; however, because it is a clearinghouse for many sources of guidelines, ranging from expert opinion to high levels of evidence, the clinician should be assured that the CPG being reviewed is current and evidence-based. Other sources for guidelines include the American Academy of Orthopaedic Surgeons (, Centers for Disease Control and Prevention (, the Scottish Intercollegiate Guidelines Network (, and The Registered Nurses Association of Ontario (, to name just a few.


Synopses of Syntheses

A synopses article of an SR is a source of preappraised or filtered information that presents the critical appraisal of an SR (see information on syntheses below) along with a short, generally one-page, concise, user-friendly assessment, and summary of the evidence. Synopses that are published meet the screening criteria for "study strengths being greater than study flaws." This type of article is generally published in evidence-based abstraction journals such as Evidence Based Nursing, International Journal of Evidence-Based Healthcare, Evidence-Based Mental Health, and ACP Journal Club.



Syntheses refer to research approaches (SRs) that provide comprehensive summaries of all the related research for a given focused clinical question. Generally speaking, individual studies, no matter how rigorous or scientific, are not a sufficient evidence base from which to make informed policy and practice decisions. Rather, the strength of the evidence is increased when multiple studies have been done on a specific question. In reality, when one pulls these multiple studies, it is common to find that there are often differing results. Systematic reviews are an approach to dealing with multiple studies and varying results.


Systematic reviews are a form of secondary research, pool data from primary research studies on a defined topic, and through different approaches synthesize these often-differing findings providing an unbiased summary of evidence. There is an assumption by many that only studies of effectiveness where randomized controlled trials have been used can be part of an SR. In fact, the type of question (see Table 2) determines the best research design. In some cases, studies with the preferred research design may not be available and the SR approach may then be to summarize the "best available" literature on the topic. No matter what the level of evidence used, the SR will report the particular approach to pooling the data (and the accompanying limitations of the approach) and provide an explanation not only of the summary of the findings but of the strengths and limitation of the evidence used in the SR. It is knowledge of these two distinct components, the summary of the state of the science and the strength of this science, that the clinician considers in whether to adopt the evidence in practice.

Table 2 - Click to enlarge in new windowTable 2. Types of Systematic Review Questions, Preferred Study Types, and Examples

An SR is not a review of the literature. An SR "comprehensively locates and synthesizes the research on a particular question using organized, transparent and replicable procedures" (Hall & Rousell, 2014, p. 18). Guidelines established by Joanna Briggs Institute, Cochrane Institute, and Campbell Collaboration, all organizations focused on generating SRs for practice, require that an SR be done by at least two persons to introduce greater reliability of the findings and proposals and final reviews are peer reviewed prior to publication. Table 3 summarizes the defined, transparent steps used in an SR.

Table 3 - Click to enlarge in new windowTable 3. Process of Systematic review

The comprehensiveness of the search, the critical appraisal process, and the approaches to synthesis all set the SR above the typical literature review as a source of evidence to guide practice. The search for studies on the specified topic is indeed more comprehensive than a traditional literature review capturing both published and unpublished literature as well as gray literature. This targeted search eliminates some of the bias found in published work that often favorably publishes articles where statistical significance has been found. By searching abstracts from national and regional conferences, it is possible to access additional research that may not have been published but has examined the clinical question of interest. Moreover, gray literature, or literature not indexed by commercial publishers, may have valuable work that has been published on an organization website or in text form but not referenced in a broad base database such as MEDLINE or CINAHL. Scientific gray literature may include newsletters, reports, working papers, government documents, fact sheets, and conference proceedings (Holly et al., 2012). Examples of gray literature include the Institute of Medicine reports and the reports and fact sheets developed through the Decade of the Joint.


In addition to the broad and comprehensive search for relevant studies, the SR research process calls for critical appraisal of all of the relevant studies to determine whether the design is strong enough to warrant inclusion in the SR. Studies where the flaws outweigh the strengths of the study are not included in the final pooling so that ultimately the clinician can be confident that the recommendations for practice emerge from science that can be considered valid and trustworthy. The findings from those articles included for final review are extracted and pooled, and these pooled findings are synthesized quantitatively (in the form of meta-analysis), qualitatively (in the form of metasynthesis), or nonquantitatively in a narrative review when the study does not allow for statistical pooling. Clinicians should become familiar with how to read and interpret these types of syntheses.


Through pooling of data from individual, smaller studies, SRs are more precise and more powerful and have more convincing conclusions (Cook, Mulrow, & Hanes, 1997). The "strength and generalizability/transferability of the findings is increased because data is derived from a broader range of populations, settings, circumstances, treatment variations and study designs" (Holly et al., 2012, p. 14). This summary of the state of the science makes it usable to clinicians and policy makers to inform decision making. It is also valuable to researchers as it provides an overview of the levels of evidence and gaps revealing the need for additional primary research.


An SR should use a transparent, rigorous process as outlined in Table 3. Being published does not assure quality. An SR that is not summarized as a synopsis requires critical appraisal to ensure that the study has the necessary rigor for findings to be used in practice. There are many standard tools that can be used to guide the clinician in critical appraisal. The Critical Appraisal Skills Programme ( provides a standard tool for appraising SRs.


Table 4 summarizes sources for locating SRs. Accessing the websites for organizations whose mission is to generate synthesized evidence to guide practice is a good starting point. Many specialty organizations also post links to SRs relevant to their specialty area with many associations providing synopses of these reviews, thereby providing preappraised critique and summary of the information. In addition, SRs are now published in a variety of journals and can be searched for in standard databases such as CINAHL, MEDLINE, and PsychInfo. Using PubMed Clinical Queries, it is possible to search specifically for SRs (

Table 4 - Click to enlarge in new windowTable 4. Sources for Systematic Reviews

Synopses of Single Studies

In the absence of systems, summaries, synopses of syntheses, or syntheses, the next source to search is for a synopsis of a single study. If published in an evidence-abstraction journal such as Evidence-Based Nursing, its publication itself attests to the assurance that the study is of sufficient high quality. Also provided in the synopsis will be a brief summary of the study, an appraisal summarizing strengths and weaknesses, and a commentary that speaks to the clinical applicability of the study findings.



Nonappraised or nonfiltered evidence can be located through traditional databases such as PubMed (, MEDLINE, CINAHL, PsychInfo, and EMBASE. These databases have approaches to searching that allows for specification not only of key words (drawn from the PICO question) but also for querying of specific research designs including SRs.


As this literature has not been preappraised, it is incumbent upon the reader to appraise the strength of the evidence before considering it as evidence to change practice. Using standardized review tools for the specific type of research design, the reader is taken through specific criteria where they judge the criteria to be present or absence. There are many sources of critical appraisal tools including the Joanna Briggs Institute ( and the Critical Appraisal Skills Programme (


Expert Opinion

The lowest rung of evidence is that from anecdotal articles (not empirical) or from expert opinion. Clearly clinicians have a vast wealth of knowledge that is of value, but there are limitations to knowledge that has been continued through tradition and expert sources. Generic textbooks are considered a source of expert opinion in contrast to some of the newer electronic textbooks that are updated regularly and presenting summaries of the evidence. Expert opinion is a good source for background knowledge on a condition, but for specific questions (foreground knowledge) turning to higher-level evidence-based sources is recommended.



Practicing from an evidence-based perspective is the expectation of clinicians today. This requires being able to ask clinical questions and access the best available evidence to guide practice. Using the "6S" model of evidence acquisition is an efficient approach to first search for filtered evidence that has been critically appraised and can be considered for practice if congruent with patient values, the clinical context, and one's clinical expertise. In the absence of filtered evidence, clinicians must retrieve and appraise the research evidence to consider it for practice. Whether filtered or unfiltered evidence, the ideal evidence emerges from SRs that provide summaries of evidence from a number of individual studies on a given topic (Khan, Kunz, Kleijnen, & Antes, 2003).




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For 12 additional continuing nursing education articles on evidence-based practice, go to