Evidence-based health care

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The 'Wedge' of Best Evidence - Start at the top
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See also Evidence-based web 2.0, Point of care decision-making tools - Overview and Systematic review searching

According to the Centre for Evidence-Based Medicine (CEBM) and David Sackett: "Evidence-based medicine is the conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients". The term Evidence-based medicine often includes the synonymous terms evidence-based health care and evidence-based practice and can be extended to nursing, pharmacy, physiotherapy, and allied health. EBHC may also refer to evidence-based management of health services, programs and people (ie. Health Services Research) as well as technologies used to aid health care practice (ie. Health Technology Assessment). Evidence-based practice is known throughout the world but the study of health services research and health technology assessment is relatively unknown. When health professionals refer to best evidence they are referring to major clinical studies & trial types that use explicit and reproducible methodologies.

In biomedicine, the scholarly communication cycle begins with new ideas about how to treat patients (ie. using new drugs) or clinical problems. Researchers start by writing grant proposals and making formal application to funding agencies. Often, the key to funding stems from gathering the evidence, identifying new areas or 'gaps' in medical knowledge and formulating clear research questions. After these questions are posed, identifiable goals and objectives in research are developed. Once research funding is secured and the research itself conducted, the researcher engages in the formal sharing of findings by publishing articles in peer-reviewed journals or scholarly monographs. Research publications provide the foundation from which future scholarship is carried out and directed, commencing once again in the process described above.

EBM Explained by Dr. Marc Ebell



Evidence-based practice (EBP)

See also Evidence-based medicine - history

The phrase evidence-based medicine dates back to a 1992 article by Gordon Guyatt et al. EBM is now a worldwide movement that affects all areas of clinical medicine including education and management. Simply put, EBM seeks to locate and apply evidence from the published medical literature to guide physicians in their decision-making. Some synonyms for EBM include evidence-based practice (EBP) and evidence-based health care (EBHC). There are three distinct but interdependent areas of evidence-based practice; the treatment of individual patients, supported by scientifically valid studies in the literature; practitioners should select treatment options based on the best available scientific research; the second area is a systematic review of literature to evaluate the best studies. This process is human-centered, but also involves computers for information retrieval and statistical analysis. The ability to judge the quality of the medical literature on finding it is central to EBM including what facts can be inferred from it, to appreciate the strength of those inferences, and to apply them to particular patients. As medicine has continued to grow and become more specialized, the number of medical specialties has increased. At the same time, the amount and complexity of the medical literature has also grown. In this sense, evidenced-based medicine can be considered a burgeoning medical specialty, with the medical literature itself - and its efficient retrieval, and appraisal - the object of study. Two of the other scientific issues that have an impact in EBM: 1) the generalizability of research (extent to which results of a study are applicable to other populations); and 2) was the research done using rigorous methods and is it reproducible? Finally, EBM may be understood as a "movement" where advocates popularize its methods and usefulness for patient communities, educational institutions and practicing professionals.

Five (5) steps of EBM - see [1]

  1. Formulate a sensible, focused clinical question.
  2. Search the medical literature for evidence related to the focused, clinical question.
  3. Rate the quality of the available studies.
  4. Apply the evidence to a particular patient or clinical situation.
  5. Assess outcomes of decisions.

EBM and librarians

  • In the first step, clinicians decide explicitly what patient population they are studying, what tests, treatments, and alternatives are under consideration, and what outcomes are to be measured. The acronym PICO - Patient, Intervention, Comparison and Outcome is often used to remember these steps, and questions.
  • The second step of EBM is searching the medical literature. Health librarians must therefore have an understanding of the methods, strengths, and weaknesses of search strategies/ tools as they strive to find the highest levels of evidence. In general, systematic reviews (not to be confused with general reviews) are considered the highest level of evidence, followed by randomized controlled trials (RCTs), then case-control studies, followed by expert opinions, and anecdotal evidence.
  • The third step - rating the quality of the available studies - involves a knowledge of research methodologies in order to make valid conclusions. For example (with RCTs): was a control group used? Was assignment to an experimental vs. control group truly random? Were patients, treatment providers, and outcome assessors blinded to assignments? What is the risk of a Type I or Type II error? What is the effect size? In systematic reviews (involving health librarians), was the literature review truly comprehensive? Was the assessment of study quality done with rigour, and was it subjectively graded? Can numerical assessments be statistically combined (a "meta-analysis") to increase statistical power? Answers to these questions often depends on the particular parameters decided in step one.
  • The fourth and fifth steps involve translating findings of controlled studies to the less-ideal and less-controlled situation of particular patients. What are the risks and benefits for this patient? What are his or her preferences? What are the costs, alternatives and availability of treatments? Even for a statistically significant finding is the effect size practically significant? Do practitioners have the skills or resources to deliver treatments or to monitor outcomes? The final step involves reassessment of the clinical question and outcomes where the whole process may begin again by returning to the patient.

PICO - sensible, focused questions

The PICO acronym (patient/population; intervention; comparison; outcome) is used by health professionals and librarians in providing direction for step one of EBM. The PICO framework - diagram guides EBM as it combines elements of the clinical scenario in an orderly fashion. The goal, of course, is to build a focused, answerable clinical question:

  • P - patient, population of patients, problem
  • I - intervention (a therapy or test)
  • C - comparison (another therapy or placebo)
  • O - outcome

Generally speaking, health librarians use the most relevant terms, keywords and concepts from PICO to find the best evidence. Several resources are available to introduce EBM concepts and to guide you through the process of shaping your information need into a clinical question.

For other examples, see:

Randomized controlled trials

See Major clinical studies & trial types

A randomized controlled trial (RCT) is a clinical trial or scientific study used in the testing of the efficacy of medicines or medical procedures. The RCT is widely considered the most reliable form of scientific evidence because it is the best known study design for eliminating a variety of biases that regularly compromise the validity of medical research.

Systematic reviews (SRs)

Systematic reviews are generally viewed as the highest level of medical evidence for they bring together major randomized controlled trials in a given area, pool results (which may include a meta-analysis) and review their efficacy. An understanding of SRs and how to implement them in practice is mandatory for all health professionals. SRs are summaries of the literature based on expert searching. A literature review is followed by an in-depth critical appraisal of individual studies to identify the most valid and applicable evidence. Finally, appropriate techniques are applied to combine these valid studies in the SR. Many SRs are based on an explicit quantitative meta-analysis of data, but there are qualitative reviews which adhere to the standards for gathering, analyzing and reporting evidence. Many healthcare journals now publish SRs, but the best-known source is the Cochrane Collaboration, a group of over 6,000 specialists who systematically review biomedical trials and the results of other research. Cochrane reviews, based on explicit meta-analyses, are published in the Cochrane Database of Systematic Reviews section of the Cochrane Library, which has over 3000 complete reviews. The Cochrane Group provides a handbook for systematic reviewers where guidelines indicate appropriate content. The Alberta Research Centre for Child Health Evidence provides an overview of EBM terms taken from the Cochrane Reviewer's Handbook.

Canadian context

McMaster University in Ontario, Canada is arguably the birthplace of evidence-based medicine. Several major figures meet there every summer for a series of workshops including Gordon Guyatt, Deborah Cook, Victor Montori, Scott Richardson, Holger Schünemann and others. Many health librarians have attended this annual pilgrimage but there are a number of McMaster health librarians who help to integrate guest health librarians into the How to teach EBCP workshop - they are Liz Bayley, Neera Bhatnagar and others.

See also


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