Evidence-Based Clinical Practice: Dispelling the Myths 
* Department of Dietetics and Nutrition,
University of Kansas Medical Center, Kansas City, Kansas; the Correspondence: Mary E. Hise, The University of Kansas Medical Center, Department of Dietetics and Nutrition, 3901 Rainbow Blvd., Mail Stop 4013, Kansas City, KS 66160-7250. Electronic mail may be sent to mhise{at}kumc.edu. Evidence-based practice merges the best and most relevant clinical research data with clinician experience, pathophysiology of disease state, and the specifics of individual patient care. Currently, there is a significant gap between the best research evidence in healthcare and application of this evidence to clinician practices. Consistent with this finding, nutrition support is not always applied effectively or consistently, despite available scientific evidence that could be used to enhance a given treatment protocol. Cited obstacles that prevent the incorporation of research evidence into daily practice include lack of time, inadequate research skills, and information overload. Identification and application of the most valid primary research and evidence summaries (clinical guides to practice and meta-analyses) should, however, be an integral part of appropriate nutrition care. Consequently, it is important that clinicians develop and improve upon the basic skills required to allow efficient and accurate searches and evaluations of the literature. This review describes the basic and practical components of evidence-based medicine and provides tools to determine whether current nutrition practices are based upon an analysis of valid clinical evidence or anecdotal nutrition traditions and myths.
I have no data yet. It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. —Arthur Conan Doyle, 1891 A 2001 Institute of Medicine report concluded that the most appropriate medical care is not always applied effectively, routinely, or consistently in daily practice.1 Clarkson2 has reported that there is a significant lag time before outcome-based research is adopted into clinical practice. Various reasons that have been cited as barriers to integration of current best evidence with clinical practice include the following: extent of belief in the validity of the data, the presumed importance of the data to one's own clinical population, organization structure, data interpretation difficulties, and information overload.3 In a survey of Australian physicians, 74% identified insufficient time and 41% listed limited literature search skills as obstacles to making better use of evidence data.3 Additionally, in a recent survey of pediatric dietitians, although 90% believed in the tenets of evidenced-based medicine, 73% did not engage in evidence-based nutrition practice or rated themselves as beginners.4 Regardless of these constraints to best evidence and practice integration, there are changes that have occurred within the nutrition support field that can make such integration significantly easier. One recent change is the increased emphasis throughout the field on outcomes-based research, with the concomitant emphasis upon assessment of the data that the research generates. Additionally, technological advances associated with electronic literature databases and online publications have significantly improved the ease with which one may access data and interpret the data more precisely and with more certainty. Such advances increase one's ability to subsequently apply data that are efficacious in the area of nutrition support. Traditionally, in order to provide appropriate patient nutrition care in their respective practices, physicians, nurses, dietitians, and pharmacists rely heavily upon the skill and knowledge each developed and learned in focused educational programs. In addition to these formal education venues, consultations with local experts and colleagues also serve to provide an "authority based" approach to nutrition care. These classic approaches have been characterized to contain the following elements: analysis of the patient and diagnosis of the problem with subsequent planned resolution of the problem based upon personal knowledge, disease pathophysiology, and clinical experience. Application of these elements of classic medical practice provides a mechanism by which nutrition therapy is recommended. This traditional approach to nutrition care can, however, be subject to limitations whenever evidence-based data are not included among the clinical practice elements.5 The practice of evidence-based nutrition support shifts clinical practice from one that relies more heavily upon tradition and individual experiences to one that relies more heavily upon integration of individual experiences with the best and most currently available clinical evidence. Thus, in the evidence-based nutrition support practice model, clinical practice is strengthened by the synergistic combination of time-tested individual knowledge with evidence-based clinical data. Personal experiences, knowledge of disease states, and patient preferences are balanced and considered with best clinical evidence. Evidence-based medicine is most frequently defined as the conscientious, explicit, and judicious use of current best evidence in making decisions about care of the individual patients.6 This shift from an authority-based or customary approach to a more evidence-based approach emphasizes the examination of relevant clinical research as the primary guide to treatment recommendations. This approach therefore initially requires that clinicians first pose specific questions to gather the needed information. A search of the clinical literature for clinical guides, systematic reviews, or primary research is then undertaken. If practice guides or systematic reviews are unavailable, the clinician is required to examine the primary article(s) for the level of evidence the article provides, and the applicability of the data to the patient. For many, new skill sets may be required to appropriately search the literature, evaluate systematic reviews, and apply the fundamental rules of evidence evaluation to clinical research. Within the context of the above information, the objectives of the present article are to examine the basic and practical components of evidence-based medicine and to provide tools to determine whether current nutrition practices are based upon an analysis of best available evidence or upon nutrition traditions and myths. With the significant current clinical emphasis upon improved patient outcomes, and a mandate to improve the quality of patient care while reducing cost, the use of evidence-based medicine becomes an important vehicle to manage information overload and improve healthcare delivery to patients.
The first and fundamentally important step in clinical evidence analysis begins with a clearly formulated question. Each question should be carefully structured to accurately access and evaluate the relevant literature. The question should be framed to focus upon a specific patient population, and should include a predictor (intervention treatment), an outcome variable (expected result of the intervention treatment), and the comparator (population without intervention treatment or with a different intervention treatment, ie, the control group). When possible, questions should be based upon important patient outcomes in a clinically relevant setting and should avoid surrogate outcomes (ie, laboratory-based and physiologic measures) because surrogate outcome variables alone may not always correspond with patient benefit.7 For example, we could ask: "In an intensive care unit patient population, does feeding by the enteral route (predictor) reduce morbidity or mortality (outcome variables) when compared with parenteral nutrition (comparator)?" The next step in the evidence-based process is to access the best available evidence to answer the question posed. In the following paragraphs, we will examine primary and secondary evidence sources and provide the reader with tools to identify and examine data sources. After evidence sources have been identified, the clinician will be required to examine the quality and clinical relevance of the published papers reviewed. Critical appraisal of published reports is vital because it has been estimated that poor quality studies tend to overestimate treatment benefit by 30%.8 Together, consideration of the consistency and strength of the association, the size of the intervention effect, and the relevancy to one's patients provide the steps initial for appraisal of the literature.9–10 The last step in this process is the application of the best available evidence to clinical decision making. Once at the decision stage of this process, it is important to integrate clinical expertise and patient-specific needs and circumstances with the published evidence. The use of a tally sheet that lists the potential benefits and harms that the evidence suggests allows one to consider and evaluate all potential influences of a specific intervention. Consequently, any decision based upon this evaluative process should always be balanced and influenced by clinical expertise and patient-specific needs.10–11
Currently, there are several different evidence appraisal systems frequently used to evaluate the nutrition support literature. These distinct appraisal systems each utilize a different grading system to establish a level of confidence (strength of the data) associated with healthcare recommendations. Grading systems for the American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.), the American Dietetics Association (ADA), and the Canadian Critical Care Practice Guidelines Committee may be the most commonly utilized by the nutrition support practitioner. Below, each of the aforementioned evidence appraisal systems will be examined in regard to interpretation and use. The A.S.P.E.N. Clinical Guidelines Task Force adopted a modified version of the method used by the Agency for Healthcare Research and Quality (AHRQ), an agency within the U.S. Department of Health and Human Services, to assess the strength of evidence supporting guideline development. As a result, conclusion statements were assessed on the type of clinical trial supporting the evidence (ie, randomized trials, well-designed studies without randomization, or expert opinion). At the time of the evidence appraisal, the quality of the trials themselves was not evaluated; thus, the evaluation of evidence quality is left to the user. After review of the selected references, the task force established the following letter grade classification system to grade the strength of the evidence in support of each guideline statement:
The advantage of the A.S.P.E.N. evidence appraisal and subsequent recommendations is the inclusion of pertinent data derived from several different types of studies (ie, randomized trials, well-designed studies without randomization, expert opinion, and editorial consensus). This inclusive approach to recommendation formulation allows an important breadth of studies upon which to base recommendations. The limitations of the A.S.P.E.N. recommendations database are: 1) the inability of the user to identify and connect specific evidence with conclusion statements because there is not a clear link from graded conclusion statements to specific references; and 2) the lack of quality assessment of primary source studies used to generate recommendations. Therefore, the specific data sources linked to conclusion statements and quality assessment methodology are not transparent to the user. The Healthcare Research and Quality Act of 1999, Part B, Title IX, Section 911(a) mandated that AHRQ, in collaboration with experts from the public and private sectors, identify methods or systems to assess health care research results. Therefore, the AHRQ commissioned the University of North Carolina Evidence-based Practice Center to evaluate systems that rated the strength of the scientific evidence, including evaluation of the quality of individual articles that represented the body of evidence associated with a specific scientific question in health care. Based upon the findings, the clinical data grading system developed by the Institute for Clinical Systems Improvement (ICSI)12 met all of the criteria to best evaluate the strength of evidence. These criteria included: 1) quality assessment, which represents the aggregate of quality ratings for individual studies, predicted on the extent to which bias was minimized; 2) quantity assessment, which represents the magnitude effect, numbers of studies, and sample size or power; and 3) consistency assessment, which represents the extent to which similar findings are reported using similar and different study designs. In addition to the grading of the conclusion statements, the studies upon which the conclusion statements are based are rated for quality. The use of this grading system provides a transparent evaluation of the evidence. Transparency is developed through the use of a conclusion grading worksheet for each clinical question. The worksheet includes the grade for the conclusion statement, each literature reference supporting the conclusion statement, each literature citation, design type, class of research report, quality score for the report, information about the population studied, results from the study, and the authors' conclusions. The ADA has a grading system13 based upon the grading system developed by the ICSI.12 In the ADA Evidence Analysis process, focused answerable questions are developed and appropriate data sources are identified. The evidence articles are classified by type:
Reports that synthesize collections of primary reports are designated as M (meta-analysis or systematic review, decision analysis, cost-benefit analysis, cost-effectiveness study), R (review, consensus statement, consensus report), or X (medical opinion). Quality of studies are evaluated based on specific validity and reliability criteria with final assessment in grades of strong, neutral, or poor, as outlined in the ADA Evidence Analysis Guide. Conclusion statements are developed by group consensus and assigned conclusion grades I–IV, based on the strength of the evidence.13 A Conclusion grade I indicates that the conclusion is supported by GOOD EVIDENCE from studies of strong design to answer the question addressed, and the results are both clinically important and consistent with, at most, minor exceptions. The results are free of any significant doubts with respect to generalization, bias, and flaws in research design. Studies with negative results have sufficient sample size to be adequately statistically powered. A Conclusion grade II indicates that the conclusion is supported by FAIR EVIDENCE from studies of strong design to answer the question addressed. However, THERE IS SOME UNCERTAINTY attached to the conclusion because of inconsistencies among the results from the studies or because of minor doubts about generalization, bias, research design flaws, or adequacy of sample size. Alternatively, the evidence consists solely of results from weaker designs to examine the question addressed, but the results have been confirmed in separate studies and are consistent with, at most, minor exceptions. A Conclusion grade III indicates that the conclusion is supported by LIMITED EVIDENCE from studies of strong design to answer the question. However, THERE IS SUBSTANTIAL UNCERTAINTY attached to the conclusion because of inconsistencies among the results from different studies or because of serious doubts about generalization, bias, research design flaws, or adequacy of sample size. Additionally, the evidence may solely consist of results from a limited number of studies of weak design to answer the question. A Conclusion grade IV statement is SUPPORTED BY EXPERT OPINION but is not substantiated by the results of research studies. A No Conclusion Grade indicates that research data are available to form the basis for a recommendation, but no clinical trial data are found that address a specific question. A statement to that effect is made, but no conclusion grade is given. The advantages of the ADA evidence appraisal and subsequent recommendations are the breadth of evidence data inclusion that may be beneficial and necessary to clearly understand the strength of the evidence for treatment options, the assessment of data quality, and the transparency of information upon which the recommendations are based. Limitations of the ADA evidence appraisal system include the possible risk of redundancy when primary research is considered for its contribution to the literature and additionally included for consideration with meta-analysis when evaluating the evidential base for focused clinical questions. The Canadian Critical Care Practice Guidelines Committee recently developed the "Canadian Clinical Practice Guidelines for Nutrition Support in Mechanically Ventilated, Critically Ill Adult Patients," using an appraisal process that focused guideline development on systematic reviews and meta-analyses of RCTs.14 Consistent with the previously described appraisal systems, conclusion statements were developed by committee using an explicit appraisal process. Search strategies, study selection criteria, quality of evidence, and data extraction processes are clearly outlined, and therefore provide a relatively transparent process. In this appraisal system, the quality of the trials are grouped into 2 levels as follows: Level 1 represents trials of high quality in that randomization was concealed, outcome adjudication was blinded, and intention-to-treat analysis was performed; and Level 2 represents the rating for all other trials if one of the Level 1 characteristics was omitted. Additionally, the language of the summary recommendations is linked to the strength of the evidence. The grading language of the Canadian Clinical Critical Care Practice Guidelines Committee summary recommendations is as follows:
The advantages of the Canadian Critical Care Practice Guideline Committee recommendations are the strict use of only RCT data upon which to base recommendations, the assessment of data quality, and the transparency of information upon which the recommendations are based. Additionally, the applicability of meta-analysis to nutrition support literature is especially relevant due to the abundance of small, underpowered clinical trials. Such analyses can clearly provide a robust approach to evidence review. The limitations for the appraisal system used by the Committee are those discussed routinely in association with meta-analysis, including the possible heterogeneity among studies, underlying study design limitations, and the absence of recommendations for pertinent questions that have not been examined by RCT. For example, the question as to the efficacy of use of blue dye to assess aspiration events is not addressed because no RCT has been performed to address this issue.
Primary and Secondary Evidence Primary evidence sources used to evaluate treatment decisions are often categorized by study design. Randomized, controlled trials and observational studies (cohort, case control, cross-sectional) may serve to provide the basis for primary research reports that are used to evaluate treatment recommendations. Primary research sources may also be organized into secondary evidence sources by the use of systematic reviews and evidence-based practice guidelines. For treatment questions in nutrition support, systematic reviews collate data synthesized from RCTs and report the findings with a single summary of evidence. The randomized, blinded clinical trial is considered the best design to determine treatment intervention effects. Observational studies are descriptive in nature and may explore health-related characteristics or distribution of disease states. Cohort, case control, and cross-sectional studies are also considered primary evidence sources, but these types of studies may provide less robust evidence for treatment recommendations.
Meta-Analyses and Systematic Reviews To help overcome these obstacles in determining best treatment practices, results from similar, individual randomized trials may be assembled and collated as a single study and the grouped data analyzed. In a systematic review using meta-analysis, clinical trial results are assessed by stringent protocols and those results determined to be of high quality can be combined to produce both a more statistically reliable result and one that may, in certain circumstances, be applied to other settings. Through data pooling, this form of systematic review increases the statistical power of smaller, poorly-powered studies. This retrospective analysis combines outcomes from a series of different investigations using a statistically-dependent weighting process for individual studies, such that those studies with less variance are given more emphasis.15 The basic steps required to undertake a meta-analysis include: 1) develop a specific question in regard to the patient population to be examined; 2) identify the type of research design to sufficiently answer the question; 3) develop criteria for a thorough and explicit literature search; 4) design the protocol for data abstraction related to specific outcome variables of interest; 5) appraise the quality of studies selected; and 6) make decisions in regard to data analysis that include subgroup analysis and data combination.11,15 Meta-analysis, as with any statistical procedure, has both strengths and weaknesses. Because metaanalyses are retrospective, these analyses are considered by many to be more observational than experimental and more hypothesis-generating than hypothesis-testing. Indeed, some investigators/clinicians believe that meta-analysis should primarily be used as a tool to plan definitive trials and only used as a primary decision tool in the absence of definitive trials.16 This particular use of meta-analysis information is supported clinically when data are pooled from small studies to generate hypotheses and to calculate the estimated sample size necessary for an adequately powered clinical trial. However, the medical literature, including the nutrition support literature, has increasingly endorsed the use of meta-analysis of RCTs to guide treatment decisions.14,17–21 When completed appropriately, this quantitative method may in fact provide a robust evaluation of pooled data that produces clinical conclusions. These conclusions have been shown to be useful in evaluation of the efficacy of nutrition interventions.15 Clearly, the use of meta-analyses has demonstrated great potential with respect to the transfer of research evidence to clinical practice. Although evidence suggests that meta-analyses are an extremely valuable guide for the practitioner and should be used to evaluate treatment recommendations, it is important that the clinician evaluate the rigor used in the development of meta-analysis studies when considering applying results to their clinical practice. Large, well-designed trials and metaanalyses should be complementary with respect to evaluation of best evidence.
Locating Systematic Reviews and Other Evidence Sources Additionally, the database of systematic reviews maintained by the Cochrane Collaboration23 may also be used as an excellent secondary database source. The Cochrane Collaboration is the largest organization in the world involved in the production and maintenance of systematic reviews. Systematic reviews listed within the Cochrane Collaboration database are considered to employ some of the most rigorous standards for scientific merit and analyses.24 In a study by Jadad et al,24 Cochrane reviews were more frequently updated than those published in peer review journals and often had more explicit development of protocol criteria for meta-analyses. The Cochrane Library is a subscription service via CD-ROM or the Internet, and although it is provided at no cost as a "national provision" in numerous countries, smaller institutions in the United States may not have the monetary ability to subscribe and thus lack access. Fortunately, the clinician may browse, search, and obtain abstracts of Cochrane Reviews free of charge at http://www.cochrane.org, and full reviews may be ordered online.
Clinical Practice Guidelines The terms clinical practice guidelines and evidence-based medicine have often been used interchangeably. However, clinical guidelines to practice and evidence-based medicine are not synonymous. Although the vast majority of clinical practice guidelines are now directed by evidence-based methodologies, subjective consensus-based guidelines may still be found in the literature. Guidelines and position statements for nutrition clinical practices have been published by numerous countries, societies, and organizations.14,18,26–27 Multiple guidelines for specific nutrition conditions may be found and leave the reader facing the dilemma of which set of guidelines to adopt for consideration and inclusion into their clinical practices. Given the abundance of nutrition-associated controversies, it is to be expected that knowledgeable, respected professional groups may differ on therapy and treatment issues for clinical nutrition topics. An additional complicating factor in decision making is that development of the focused clinical questions may also influence guideline recommendations. Therefore, although clinical questions may be very similar in topic, due to the specific nature of the question posed (population of interest, intervention, outcome variable) and evidence appraisal system used, the answer to each question may yield different results. There are several reliable Internet sources for clinical practice guidelines. A useful Internet website to examine and compare existing guidelines is The National Guideline Clearinghouse (NGC, www.guideline.gov). NGC is an initiative of the AHRQ and the U.S. Department of Health and Human Services. This website offers a comprehensive database of evidence-based clinical practice guidelines and related documents that include search mechanisms for structured abstracts and summaries, evidence tables, personal data assistant (PDA) downloads, and other useful tools. The National Guideline Clearinghouse requires that all guidelines included in the NGC website be considered current only if the guidelines were generated within the last 5 years. An additional site available for dietitians to examine graded conclusion statements to aid in directing clinical practice is the American Dietetic Association Evidence Library. The review of evidence on specific topics (ie, critical care nutrition) is currently provided as a members-only benefit of the American Dietetic Association. However, when the evidence is incorporated into comprehensive clinical practice guides, it is routinely available in published journals, by purchase or by accessing the NGC. Currently, there are 4 evidenced-based guidelines developed by the ADA or in conjunction with other organizations listed on the NGC website. Eight additional guides may be found as part of the Nutrition Screening Initiative, an initiative developed in the more traditional consensus process of analysis. Lastly, A.S.P.E.N.'s clinical guidelines provide an inclusive review of graded conclusion statements to help guide treatment decision in pediatric and adult nutrition support patients.26 These guidelines are organized into 3 sections: 1) a broad comprehensive section concerning issues required by most adult and pediatric nutrition support patients (assessment, nutrient requirements); 2) disease-specific sections for adults; and 3) disease-specific sections for pediatrics. These guidelines are available in publication, as a member benefit of A.S.P.E.N. and also through the NGC website. Where there is disagreement among recommendations or significant conflict with institutional practice, it is important that the clinician, where possible, examines the original source literature sufficiently to carefully evaluate the data provided. Regardless of the approach, one should always maintain focus upon the patient and the best patient care that may be delivered. Table 1 provides a review of advantages and disadvantages of primary and secondary evidence sources that may be used in clinical decision making.
The following case scenario provides an example of how evidence-based nutrition support practice may be employed in one's day-to-day work routine.
Case Scenario Searching the Literature in Real Time. The dietitian recalled that a visiting gastroenterologist had given a Grand Round presentation the previous year at her institution on the benefits of enteral nutrition support in acute pancreatitis patients. She remembered that the speaker discussed a research article on the subject and the fact that clinical outcomes were improved with enteral nutrition support. The use of enteral support for acute pancreatitis patients was not a common practice at her institution and was considered only for patients that exhibited less severe symptoms. While waiting for a call-back from a team member, she attempted to identify the article with a quick MEDLINE search (www.pubmed.org) using a computer terminal at the nurses' station. By using the search terms "acute pancreatitis" and "enteral nutrition" and limiting the search of articles to randomized clinical trials, 21 clinical trials were rapidly identified. After briefly reading 4 abstracts, she was able to identify several relevant articles. Within a few minutes, she was able to download PDF (Adobe Portable Document Format) files of 2 articles and print each for review. After reading the articles at the end of the day and considering the best route to provide the information, she left the articles on the chart for the attending physician, planning to discuss the papers' limitations and benefits the following morning during rounds. The next day on rounds, the physician was reluctant to try postpyloric enteral feeding on this patient even in light of the published clinical trials demonstrating benefit. He questioned the sample size and the overall quality of the studies, and thought the patient populations studied were too different with respect to his current patient. Parenteral nutrition was ordered. Several weeks later another acute pancreatitis patient was admitted and the topic of nutrition support was again considered. Because of the previous discussions, the pharmacist on the nutrition support service decided to search the Cochrane Collaboration website for any systematic reviews in this area and the dietitian again searched the PubMed site, but this time she limited her search to published meta-analyses using the same search terms. The pharmacist was able to quickly obtain an appropriate abstract from the Cochrane Library by using the search term "pancreatitis." He reviewed the main results from the meta-analysis (2 trials, n = 70) and considered the reviewers' conclusions indicating a trend toward a reduction in adverse outcomes with enteral nutrition when compared with parenteral nutrition. Reviewers noted at the time that there were insufficient data to draw firm and definitive conclusions about the effectiveness and safety of enteral nutrition and that larger patient-number clinical trials were needed.28 He noted that the review had been updated in October 2002. An additional meta-analysis was quickly identified by the dietitian using the PubMed search system. In this 2004 publication, 6 studies were used for metaanalysis (n = 263) and the authors concluded that enteral nutrition should be the preferred route in acute pancreatitis.17 Both the limitations and overall quality of these systematic reviews were discussed with the physician on rounds. The metaanalyses results alleviated some of his reservations and he agreed to attempt a trial of enteral nutrition in the patient. Case Study Comment. As clinicians, we must always attempt to introduce and incorporate best evidence in the care of our individual patients. Considerations for the feasibility of proposed treatments, potential harm and benefits, and patient considerations must be evaluated on a case-by-case basis (Table 2). It is well documented that evidence-based healthcare changes occur slowly.1 In this case study, a collaborative approach to patient care allows the introduction of best available scientific knowledge and gives opportunities for change. Easy access to best evidence sources becomes a necessity to influence treatment decisions in real time daily practice.
The evidence base of nutrition support must continue to expand in both scope and quality of clinical trials. For some treatment decisions, such as use of parenteral nutrition, a relatively large research base is available both in guideline development and meta-analysis.20–21,26 However, for numerous nutrition support practices, many important questions remain unanswered and for those questions that have some evidential base, quality of studies is often lacking. Importantly, daily employment of evidence-based methods helps clinicians determine when no satisfactory evidence is available and provides a firm basis for the necessity of implementing outcomes-based research. Evidence-based medicine fosters skills to improve the location, appraisal, and implementation of evidence-based practice in our daily patient care. Evidence-based nutrition support is often best served by multidisciplinary teams whose collaborative approach to patient care lends itself to the introduction of new knowledge. Additionally, using evidence-based medicine to direct nutrition care gives one's career a structural framework to continue formal education and self-directed learning. All varieties of nutrition support teams and nutrition support clinicians may benefit from inclusion of these basic skills into daily practice.
Nutrition in Clinical Practice, Vol. 20, No. 3,
294-302 (2005) This article has been cited by other articles:
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Basic Components of Evidence...
Evidence Appraisal
