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Evidence-Based Medicine (EBM) Timothy M. George, MD, FACS, FAAP.

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Presentation on theme: "Evidence-Based Medicine (EBM) Timothy M. George, MD, FACS, FAAP."— Presentation transcript:

1 Evidence-Based Medicine (EBM) Timothy M. George, MD, FACS, FAAP

2 Evidence-Based Medicine On the Need for Evidence-Based Medicine Rosenberg WMRosenberg WM, Sackett DL. Therapie. 51:212-7,1996Sackett DL “Doctors always seek to base their decisions on the best available evidence.” “Often this evidence represents extrapolations of pathophysiological principles and logic rather than established facts based on data derived from patients.” “The advent and proliferation of randomized controlled trials have led to a rapid increase in the quantity and quality of clinically valid evidence concerning clinical history taking and physical examination, issues of diagnosis, prognosis, therapy and other important health care issues.”

3 EBM uses techniques from science, engineering, statisticsscienceengineering statistics –the systematic review of medical literaturemedical literature –meta-analysismeta-analysis –risk-benefit analysisrisk-benefit analysis –randomized controlled trialsrandomized controlled trials EBM suggest that healthcare professionals should make "conscientious, explicit, and judicious use of current best evidence" in their everyday practice.healthcare Ex cathedra statements by the "medical expert" are considered to be least valid form of evidence. All "experts" are now expected to reference their pronouncements to scientific studies.Ex cathedraexpert

4 Yes, there’s an app for that

5 Evidence-Based Medicine How “Evidence” is uncovered Statistical measures Interpretation Clinical trials Limitations

6 Evidence-Based Medicine Statistical measures Evidence-based medicine attempts to express clinical benefits of tests and treatments using mathematical methods. Tools used by practitioners of evidence- based medicine include:

7 Evidence-Based Medicine Strength of the Association –Relative risk compares the risk or probability of one group having a particular outcome with the risk of another group having that outcome given the presence or absence of an exposure or experience. Statistical Significance –Statistical significance or inference testing deals with the characteristics of the larger population. Researchers infer what is happening in the larger group by examining a smaller sample. The measure of significance is the p value. Adjustment –Factors that create group differences and affect the study's results are called confounders. Researchers have several different types of tools to analyze confounders and determine if they biased the study. These techniques include stratification and regression analysis

8 Evidence-Based Medicine Interpretation concerns the conclusions made about the people in the study Causal Relationships –Several factors support a causal relationship. You can have more confidence assuming causation if: The risk factor occurs more often in people with the specific outcome. The risk factor being studied precedes the effect. Changes in the risk factor produce the effect.

9 Evidence-Based Medicine Other Supporting Evidence for Causation –Strength of the association between the factors such as LOS and hospital readmission, measured by the relative risk or other estimates. –Consistency of the association as demonstrated when similar outcomes are measured in different groups in different settings. –Biologic plausibility (in clinical studies) demonstrated by the scientific evidence that a particular factor can cause an outcome. Remember, however, that scientists may not be able to explain the physical foundations of a relationship that epidemiologists uncover! –Dose-response relationship which implies that higher levels of a risk factor will contribute more to the development of an outcome than a lower level. Evaluating dose-response relationships may be tricky, however, since some effects may increase at intermediate doses and decline at higher doses.

10 Evidence-Based Medicine Quality of clinical trials Evidence-based medicine attempts to objectively evaluate the quality of clinical research by critically assessing techniques reported by researchers in their publications.

11 LEVELS OF EVIDENCE AND GRADES OF RECOMMENDATION Levels of Evidence –Ia: Evidence obtained from meta-analysis of randomized controlled trials. –Ib: Evidence obtained from at least one randomized controlled trial. –IIa: Evidence obtained from at least one well-designed controlled study without randomization. –IIb: Evidence obtained from at least one other type of well- designed quasi-experimental study. –III: Evidence obtained from well-designed non-experimental descriptive studies, such as comparative studies, correlation studies and case studies –IV: Evidence obtained from expert committee reports or opinions and/or clinical experiences of respected authorities.

12 LEVELS OF EVIDENCE AND GRADES OF RECOMMENDATION Grades of Recommendation (Oxford Centre for Evidence-based Medicine) A: Evidence levels Ia, Ib. Requires at least one randomized controlled trial as part of the body of literature of overall good quality and consistency addressing the specific recommendation. B: Evidence levels IIa, IIb, III. Requires availability of well-conducted clinical studies but no randomized clinical trials on the topic of recommendation. C: Evidence level IV. Requires evidence obtained from expert committee reports or opinions and/or clinical experiences of respected authorities. Indicates absence of directly applicable clinical studies of good quality GPP: Good practice points. Requires evidence obtained from expert committee reports or opinions and/or clinical experiences of respected authorities. Indicates absence of directly applicable clinical studies of good quality D: At least fair scientific evidence suggests that the risks of the clinical service outweighs potential benefits. Clinicians should not routinely offer the service to asymptomatic patients. I: Scientific evidence is lacking, of poor quality, or conflicting, such that the risk versus benefit balance cannot be assessed. Clinicians should help patients understand the uncertainty surrounding the clinical service.

13 Evidence-Based Medicine LIMITATIONS of Evidence-Based Medicine as the GOLD STANDARD Ethics –conducting randomized, placebo-controlled trials is commonly considered to be unethical, although observational studies may address these problems to some degree.observational studies Cost –The types of trials considered "gold standard" (i.e. large randomized double-blind placebo-controlled trials) are expensive, so that funding sources play a role in what gets investigated Generalizability –Furthermore, evidence-based guidelines do not remove the problem of extrapolation to different populations or longer timeframes. The quality of studies performed varies, making it difficult to compare them and generalize about the results.guidelines –Certain groups have been historically under-researched (racial minorities and people with many co-morbid diseases), and thus the literature is sparse in areas that do not allow for generalizing.

14 Evidence-Based Medicine More Limitations Publication bias –It is recognized that not all evidence is made accessible, that this can limit the effectiveness of any approach, and that efforts to reduce publication bias and retrieval bias is required.publication bias –Failure to publish negative trials is the most obvious gap, and moves to register all trials at the outset, and then to pursue their results, are underway. Changes in publication methods, particularly related to the Web, should reduce the difficulty of obtaining publication for a paper on a trial that concludes it did not prove anything new, including its starting hypothesis. –Treatment effectiveness reported from clinical studies may be higher than that achieved in later routine clinical practice due to the closer patient monitoring during trials that leads to much higher compliance rates. –The studies that are published in medical journals may not be representative of all the studies that are completed on a given topic (published and unpublished) or may be misleading due to conflicts of interest. –A 2004 statement by the International Committee of Medical Journal Editors (that they will refuse to publish clinical trial results if the trial was not recorded publicly at its outset) may help with this, although this has not yet been implemented. Populations, clinical experience, and dubious diagnoses –EBM applies to groups of people but this does not preclude clinicians from using their personal experience in deciding how to treat the person in front of them. In The limits of evidence-based medicine, Tonelli advises that "the knowledge gained from clinical research does not directly answer the primary clinical question of what is best for the patient at hand." and suggests that evidence-based medicine should not discount the value of clinical experience. –David Sackett writes that "the practice of evidence based medicine means integrating individual clinical expertise with the best available external clinical evidence from systematic research".

15 Evidence-Based Medicine Even More Limitations Ghost writers Political criticism –There is a good deal of criticism of evidence based medicine, which is suspected of being - as against what the phrase suggests - in essence a tool not so much for medical science as for health managers, who want to introduce managerialist techniques into medical administration. –Dr Michael Fitzpatrick writes: "To some of its critics, in its disparagement of theory and its crude number-crunching, EBM marks a return to 'empiricist quackery' in medical practice. –Its main appeal, as Singh and Ernst suggest, is to health economists, policymakers and managers, to whom it appears useful for measuring performance and rationing resources."

16 Evidence-Based Medicine Implementation of evidence-based medicine strategies requires: –learning evidence-based medicine –seeking and applying evidence-based medical summaries generated by others –accepting evidence-based protocols developed by others Two products of evidence-based medicine –Evidence-based guidelines (EBG) EBG is the practice of evidence-based medicine at the organizational or institutional level. Used in the production of guidelines, policy, and regulations. –Evidence-based individual decision making (EBID) Evidence-based medicine as practiced by the individual health care provider.

17 Evidence-Based Medicine GRADE Working Group observations from the implementation of EBG & EBID “Extrapolations" - data is used in a situation which has potentially clinically important differences than the original study situation. The quality of evidence to support a clinical decision is a combination of the quality of research data and the clinical 'directness' of the data.

18 Evidence in Chiari/Syringomyelia Evidence Class I Class II Class III (several large series pts) Class IV (almost all)

19 Recommendation in Chiari/Syringomyelia Grades of Recommendation A B Evidence levels IIa, IIb, III. Requires availability of well-conducted clinical studies but no randomised clinical trials on the topic of recommendation. C Evidence level IV. Requires evidence obtained from expert committee reports or opinions and/or clinical experiences of respected authorities. Indicates absence of directly applicable clinical studies of good quality GPP Good practice points. Requires evidence obtained from expert committee reports or opinions and/or clinical experiences of respected authorities. Indicates absence of directly applicable clinical studies of good quality

20 Evidence-Based Medicine Conclusions: EBM is important because there will be measurements in the future (outcome, cost, economic, lifestyle)


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