“Evidence-based” is a popular phrase used throughout many journal articles today. As a relatively new concept, some confusion exists as to what evidence-based means and what skills are needed for evidence-based decision making and practice.
Using evidence from the medical literature to answer questions, direct clinical action, and guide practice was pioneered at McMaster University in Ontario, Canada, in the 1980s. As clinical research and the publication of findings increased, so did the need to use medical literature to guide practice. The old clinical problem-solving model based on individual experience or information gained by consulting authorities (colleagues or textbooks) gave way to a new methodology for practice. The new methodology was termed evidence-based medicine (EBM)1 and is defined as “the integration of the best research evidence with clinical expertise and patient values.”2 Inherent in this definition is the recognition that research evidence is a valued component of the clinical decision making process. Yet, the use of current best evidence does not replace clinical skills, judgment, or experience but instead provides another dimension to the decision making process that also considers the patient’s preferences (Figure 1).3-5 It is this decision making process that is termed evidence-based decision making (EBDM).
Evidence vs Research
Evidence is distinguished from research in that a single research study does not constitute evidence but, rather, contributes to an overall body of knowledge derived from multiple studies investigating the same area.6 Therefore, evidence is the synthesis of all valid research studies that answer a specific question. Once synthesized, this evidence can help determine whether a method of diagnosis or a treatment is effective as compared to other methods of diagnoses or to other treatments and under what circumstances.
The use of evidence in practice is not new. However, the nature of clinical evidence itself is new in terms of how evidence is gathered (randomized controlled trials [RCTs] and other well-designed methods), the statistical tools for synthesizing and analyzing it (systematic reviews [SRs] and meta-analysis), and the ways for accessing and applying it (electronic databases and EBDM).7 In other words, evidence-based practice is not just a new term for an old concept. As a result of these advances, practitioners now need more efficient and effective online searching skills to find relevant evidence as well as the critical appraisal skills to rapidly evaluate and sort out what is useful.8
Evidence-based Decision Making Process
EBDM requires understanding new concepts and developing new skills, such as asking good clinical questions, conducting an efficient computerized search, critically appraising the evidence, applying the results in clinical practice, and evaluating the outcomes. Translating these requirements into action requires the following five steps:2
- Convert information needs/problems into clinical questions so they can be answered,
- Conduct a computerized search with maximum efficiency for finding the best external evidence with which to answer the question,
- Critically appraise the evidence for its validity and usefulness (clinical applicability),
- Apply the results of the appraisal or evidence in clinical practice, and
- Evaluate the process, your performance, and outcomes of care.
The following procedures provide an overview of the five steps and skills involved in establishing an evidence-based practice.
Regarding step one, asking the right question is a difficult skill to learn, yet it is fundamental to evidence-based practice. The process almost always begins with a patient question or problem. A well-built question should include four parts, referred to as PICO, that identify the patient problem or population (P), intervention (I), comparison (C), and outcome(s) (O).2
Once these four components are clearly identified, the following format can be used to structure the question:
“For a patient with _____(P), will _____(I) as compared to _____(C) increase/ decrease/provide better/be more effective in doing _____(O)?”
Step two involves finding relevant evidence that requires conducting a very focused search of the peer reviewed professional literature. The first step—formulating the PICO question—provides the foundation for the search terms used in the database. By using PICO, a set of citations that will potentially provide an answer to the question is quickly pinpointed.
Where Do I Look?
To assist professionals in keeping up with the literature, online access to MEDLINE, the National Library of Medicine’s premier bibliographic database covering the fields of medicine, nursing, dentistry, veterinary medicine, and the health care system is available. PubMed (http://pubmed.gov) provides free access to MEDLINE and has an excellent tutorial that can help new users learn how to conduct a good search.
The Cochrane Library Database of Systematic Reviews is another valuable resource. To date, the Cochrane Collaboration Oral Health Group has produced 106 SRs and protocols covering specific questions related to disease prevention interventions and different general dentistry and dental specialty topics. A complete listing of topics and their abstracts can be accessed free of charge from the Cochrane Library at www.cochrane.org/reviews/index.htm.
Levels of Evidence
EBDM is about solving clinical problems and involves two fundamental principles:
- Evidence alone is never sufficient to make a clinical decision.
- A hierarchy of evidence exists to guide clinical decision making.9
EBDM is a structured process that incorporates a formal set of rules for interpreting the results of clinical research and places a lower value on authority or custom.10
The hierarchy of evidence is based on the notion of causation and the need to control bias.11 The highest level of evidence is called level 1 and includes the SR, meta-analysis, which is more than one human RCT, and RCTs. These are followed respectively by cohort studies (level 2); case-control studies (level 3); case series (level 4); traditional narrative reviews without critical appraisal (level 5); and finally studies that do not involve human subjects. Figure 2 depicts the general characteristics of SRs and literature reviews. Although each level may contribute to the total body of knowledge, “…not all levels are equally useful for making patient care decisions.”12 As you progress up the pyramid, the number of studies and, correspondingly, the amount of available literature decreases, while at the same time their relevance to answering clinical questions increases.
Knowing which segment of the literature is appropriate for clinical decision making and how to quickly retrieve this information is important to evidence-based practice. A short and graphic review of each of the levels of evidence and research study design can be found on the SUNY Downstate Medical Research Library of Brooklyn’s website at http://library.downstate.edu/ebm/2100.htm featuring the Guide to Research Methods, The Evidence Pyramid.13
Once you have found the most current evidence, step three is to understand what you have and its relevance to your patient and PICO question. However, for many practitioners the skills for evaluating research studies are not straightforward. Fortunately, appraisal forms have been developed by international evidence-based groups to assist in this process and are available online at no charge.14-16 For example, the Critical Appraisal Skills Programme (CASP) has checklists consisting of a structured series of yes or no questions:15
- Are the results of the study valid?
- What are the results and are they important?
- Will the results help in caring for my patient?
The fourth step is applying the results of the appraisal or evidence in clinical practice. A key component is determining whether the findings are relevant to the patient, problem, or question. A question to consider is, “Would your patient have met the inclusion criteria for the study?”
After making a decision and implementing a course of treatment, evaluating the outcome is the final step. Evaluating the process may include a range of activities such as examining outcomes related to the health/function of the patient, patient satisfaction and input into the decision making process, and a self-evaluation of how well each step of the EBDM process was conducted.
With an understanding of how to effectively use EBDM, you can quickly and conveniently stay current with scientific findings on topics that are important to you and your patients.
Identifying EBDM Publications
The five steps in the EBDM systematic process should be reflected in evidence-based publications. Typically, a structured abstract describes the methods used to conduct the review in enough detail so that the reader understands exactly what was completed and how decisions were made. Table 1 illustrates how the five steps are reflected in an evidence-based publication.
The most confusion regarding evidence-based publications is between SRs and literature reviews. With the growing popularity of evidence-based practice, many articles and literature reviews are inappropriately using the phrase “evidence-based” in the title of articles. Major distinctions between SRs and literature reviews are the focus of the topic, the selection of studies to include, and the methods used to synthesize results. For example, SRs concentrate on answering a specific, clinically focused question, making them narrower in scope than a literature review. Typically, a multidisciplinary team of experts conducts the review using formal and explicit methods and specifies criteria for including or excluding studies, which is designed to reduce bias.12
In contrast to SRs, literature reviews are generally conducted by an individual using personal experience to define the hypothesis or research question, and select and summarize the literature on a broad range of issues on a given topic rather than answering a specific question in depth. Also, it is less systematic, more subjective, and personal bias may influence the literature selected based on the support for the hypothesis being investigated (see Table 1).17
Evidence-based journals were established to simplify and streamline the evidence-based process for practitioners by publishing 1 to 2 page summaries of valid research studies from the scientific literature to answer a specific clinical question. Two journals specific to dentistry are published: the Journal of Evidence Based Dental Practice (JEBDP) and Evidence Based Dentistry. Both strive to notify practitioners of current evidence with the goal of providing a time and cost-effective method of staying current with clinically important advances in practice. For example, JEBDP scans the top dental journals, identifies articles that reported on research conducted on at least 100 patients, and then has them reviewed for clinical relevance to practice.
EBDM recognizes that clinicians can never be completely current with all aspects of patient care and provides a mechanism for learning the skills and assimilating current research findings into everyday practice in order to stay current and provide the best possible care. Understanding how evidence is reported allows the clinician to better judge the validity and relevance of findings in making decisions about patient care and in developing an evidence-based practice.
- Evidence-based medicine. A new approach to teaching the practice of medicine. Evidence-based Medicine Working Group. JAMA. 1992;268:2420-2425.
- Sackett D, Straus S, Richardson W. Evidence-Based Medicine: How to Practice & Teach EBM. London: Churchill Livingstone; 2000:1.
- Hearings on Health Care Quality Before the House Subcommittee on Health and the Environment. 105th Cong, (October 28, 1997) (statement of John M. Eisenberg, MD, MBA). Available at: www.ahcpr.gov/news/test1028.htm. Accessed August 9, 2005.
- Institute of Medicine. Dental Education at the Crossroads, Challenges and Change. Washington, DC: National Academy Press; 1995.
- Haynes RB. Some problems in applying evidence in clinical practice. Ann N Y Acad Sci. 1993;703:210-224.
- Greenhalgh T. “Is my practice evidence-based?” BMJ. 1996;313:957-958.
- Davidoff F, Case K, Fried PW. Evidence-based medicine: why all the fuss? Ann Intern Med. 1995;122:727.
- Palmer J, Lusher A, Snowball R. Searching for the evidence. Genitournin Med. 1997;73:70-72.
- Evidence-based Medicine Working Group. Users’ Guides to the Medical Literature, a Manual for EB Clinical Practice. Chicago: American Medical Association; 2002:5-8.
- NHS Centre for Reviews and Dissemination. Undertaking Systematic Reviews of Research on Effectiveness. Available at: www.york.ac.uk/inst/crd/ report4.htm. Accessed June 5, 2005.
- Long A, Harrison S, Cole A. Evidence-based decision making. Health Serv J. 1996;106(suppl):S1-S2.
- McKibbon A, Eady A, Marks S. PDQ, Evidence-Based Principles and Practice. Hamilton, Ontario: Decker Inc; 1999:1-13.
- SUNY Health Sciences. Guide to Research Methods, the Evidence Pyramid. Available at: http://library.downstate.edu/ebm/2100.htm. Accessed June 5, 2005.
- Altman DG, Schulz KF, Moher D, et al. The Revised CONSORT statement for reporting randomized trials: explanation and elaboration. Ann Intern Med. 2001;134:663-694.
- Critical Appraisal Skills Programme. Ten questions to help make sense of the literature. Available at: www.phru.nhs.uk/casp/appraisa.htm. Accessed June 5, 2005.
- Moher D, Cook DJ, Eastwood S, Olkin I, Rennie D, Stroup DE. Improving the quality of reports of meta-analyses of randomised controlled trials: the QUOROM statement. Quality of Reporting of Meta-analyses. Lancet. 1999;354:1896-1900.
- Chalmer I, Altman DG. Systematic Reviews. London: BMJ Publishing Group; 1995:vii-16.1995.
From Dimensions of Dental Hygiene. September 2005;3(9):12.