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Evidence-Based Medicine: A Basic Primer


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  • 1. Evidence-Based Medicine: A Basic Primer Kevin Bradford, M.L.S. Clinical Information Librarian Instructor Medical College of Georgia April 2007
  • 2. EBM Defined  Evidence-based medicine (EBM) has been defined as "the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients. The practice of evidence based medicine means integrating individual clinical expertise with the best available external clinical evidence from systematic research."(1)  More recently, EBM has been described as the "integration of best research evidence with clinical expertise and patient values."(2) 1. David Sackett, et al. "Evidence Based Medicine: What It Is and What It Isn't," BMJ 312, no. 7023 (1996) 2. David Sackett, et al. Evidence-Based Medicine: How to Practice and Teach EBM (New York: Churchill Livingstone, 2000)
  • 3. EBM Defined A total process beginning with knowing:  what clinical questions to ask  how to find the best practice  how to critically appraise the evidence for validity and applicability to the particular care situation.  the best evidence and applying it with expertise in considering the patient's unique values and needs, and  how to evaluate the effectiveness of care and the continual improvement of the process
  • 4. What EBM Is Not  “Cookbook” medicine  A tool for administrators and insurers  Restricted to randomized trials and systematic reviews  Opposed to patient centered medicine
  • 5. EBM: The Literature  Archie Cochrane  Effectiveness and Efficiency: Random Reflections on Health Services (1972)  Because resources would always be limited, they should be used to provide equitably those forms of health care which had been shown in properly designed evaluations to be effective.
  • 6. The base of the steps in the illustration is where information usually starts with an idea or laboratory research. As these ideas turn into drugs and diagnostic tools they are tested in laboratory models, then in animals, and finally in humans. The human testing may begin with volunteers and go through several phases of clinical trials before the drug or diagnostic tool can be authorized for use within the general population. As you move up the steps, the amount of available literature decreases--but increases in its relevance to the clinical setting. EBM: Steps to Success
  • 7. EBM: The Literature  Systematic Reviews usually focus on a clinical topic and answer a specific question. An extensive literature search is conducted to identify all studies with sound methodology. The studies are reviewed, assessed, and the results summarized according to the predetermined criteria of the review question. The Cochrane Collaboration has done considerable work in the area of systematic reviews.  Meta-analyses will thoroughly examine a number of valid studies on a topic and combine the results using accepted statistical methodology as if they were from one large study. Some clinicians put Meta-analyses at the top of the pyramid because part of the methodology includes critical appraisal of the selected RCTs for analysis.  Randomized controlled clinical trials are carefully planned projects that study the effect of particular therapies on actual patients. These include methodologies that reduce the potential for bias (randomization and blinding) and allow for comparison between intervention groups and control groups (no intervention).
  • 8. EBM: The Literature  Cohort Studies take a large population and follow patients who have a specific condition or receive a particular treatment over time and compare them with another group that has not been affected by the condition or treatment being studied. Cohort studies are observational and not as reliable as randomized controlled studies, since the two groups may differ in ways other than in the variable under study.  Case Control Studies are studies in which patients who already have a specific condition are compared with people who do not. They often rely on medical records and patient recall for data collection. These types of studies are often less reliable than randomized controlled trials and cohort studies because showing a statistical relationship does not mean than one factor necessarily caused the other.  Case series and Case reports consist of collections of reports on the treatment of individual patients or a report on a single patient. Because they are reports of cases and use no control groups with which to compare outcomes, they have no statistical validity.
  • 9. How To Structure Clinical Questions P – Patient population / problem What are you trying to address Does gender/age influence clinical care I - Intervention / Area of interest What will you do for the patient? Drugs, surgery, diet, exercise C – Comparison intervention / status Alternatives to your chosen intervention? Against other interventions, gold standard, or no treatment O – Measurable outcome of interest What will be improved for the patient? Less risk of fracture, fewer hospitalizations, etc. “Asking answerable clinical questions” in D.L. Sackett, S.E. Straus, W.S. Richardson, W. Rosenberg, R.B. Haynes. Evidence-Based Medicine: How to Practice and Teach EBM. New York: Churchill Livingstone, 2000. p. 13-27
  • 10. How To Structure Clinical Questions Filtering the Evidence: The “Big Four”  Therapy  Does it do more good than harm?  Diagnosis  How well does it confirm or exclude a diagnosis?  Prognosis  How well does it predict clinical course over time?  Etiology  How well does it identify a cause for a disease?
  • 11. How To Structure Clinical Questions  Levels of Clinical Evidence in the Primary Literature:
  • 12. How To Structure Clinical Questions  MEDLINE  Contains over 12 million citations to research articles, case reports, letters, editorials, and animal studies published in biomedical journals. However, many of these articles and reports are not clinically relevant.  Search Filters for  Therapy, Diagnosis, Prognosis, Etiology  Recommended: “Optimized” choice  Restrict results to specific:  Population, Gender, Language  Age Group, Publication Type
  • 13. Evaluating the Evidence  Background/Literature review  Study Design  Control group or comparison group  Randomization & Blinding  Population (size, traits) & time frame  Follow-up (>80%)  Results of study  Well defined outcome criteria  Applicable to patients  Purpose & problem clearly stated  Data Collection Procedures  Method & time frame specified  Organization & analysis of data  Study Participants  Selection Process & Number of participants  Nature of setting(s) utilized  Results of study  Impact on clinical practice  Suggestions for future research
  • 14. Evaluating the Evidence  Are the results of this study appropriate for my patients?  Do my patients meet the inclusion and exclusion criteria?  Is there any reason to believe that these results would not apply to my patients?  Does the study include all of the outcomes I find clinically important?  Do the treatment benefits outweigh the potential harm and/or costs?
  • 15. EBM Resources: Bibliographic Databases  Cochrane Database of Systematic Reviews “A well-conducted, scientifically rigorous, systematic review on a clearly defined clinical topic is invaluable in the development of evidence-based practice because it [1] summarizes existing research, [2] defines the boundaries of what is known and what is not known, and [3] helps us resolve inconsistencies among diverse pieces of research evidence.” Cook D, Mulrow C, & Haynes R. (1997). Systematic reviews: synthesis of best evidence for clinical decisions. Ann Intern Med., 126(5), 376–380  Summarizes literature on key clinical topics  Exhaustive searching (controlled trials, meta-analyses, protocols for in-process reviews)  Analysis of all results for clinical impact  Focus on questions related to therapy or treatment
  • 16. EBM Resources: Bibliographic Databases  Database of Abstracts of Reviews of Effectiveness (DARE)  Structured abstracts of systematic reviews  Commentary on clinical usefulness  ACP Journal Club  Methodologically sound & clinically relevant study  Value of article in clinical practice  AHRQ Guidelines (National Guideline Clearinghouse)  Comprehensive database of evidence-based clinical practice guidelines and related documents
  • 17. EBM Resources: Bibliographic Databases  PubMed Clinical Queries  A user-friendly approach to evidence- based searching of the Medline database.  Pre-set research methodology filters enable the searcher to quickly locate the relevant literature on etiology, prognosis, diagnosis and therapy of diseases and diagnostics.  The utilities in Clinical Queries are not intended to supply a comprehensive literature search, but are designed to provide information on those few "good" articles which will help the clinician make informed decisions.  Divided into three sections:  Clinical Studies  Systematic Reviews  Medical Genetics
  • 18. Selected Point-of-Care Tools  ACP’s PIER (Physician’s Information and Education Resources)  Grades clinical recommendations based on the strength of the evidence available (via STAT!Ref)  Over 300 modules focusing on the diagnosis and treatment of diseases  Evidence indicators and standard tables  Quarterly updates
  • 19. Selected Point-of-Care Tools  DynaMed  Contains more than 2,000 disease summaries. Diseases represented in the database reflect those most commonly seen in primary care.  Levels of evidence included with every topic summary.