Medical Studies What Can You Believe


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How do you know what to believe when it comes to medical research studies? What sources of information should you trust? What about statistics? Is evidence based medicine the sollution?

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  • The costs of medical care are rising sharply, yet we know that not all common or expensive procedures are necessary, and some may be harmful. Wide variations in the outcomes of medical care have been observed between different centres and different individual clinicians. Patients and their advocates are becoming more informed, more aware that they have (or should have) choices, and more vocal in seeking to make informed choices. Clinicians, health care managers, and, increasingly, lawyers, acknowledge that decision making in health care should involve the patient and be based on best evidence of effectiveness and harm. Comprehensive lists of published research papers, indexed electronically and accessible via standard search techniques, have become available at little or no cost over the internet. Statistical tools, especially those of meta-analysis, are better understood and more widely used. Hence, precise and cumulative estimates of effectiveness and harm tend now to be published soon after the relevant trials are complete. The discipline of critical appraisal (evaluating research papers for their validity and relevance) has evolved and become both more rigorous and more accessible to the non-expert through the publication of basic guides and structured checklists.
  • Assignment of individuals is randomized RCT: Individuals similar at the beginning RCOT: Prospective analytical, susceptible to bias if carry over effects occur Observational: allocation or assignement is not under investigator control; weaker potential evidence; potential for large confounding variables Cohort: prospective, follow-up period to determine effect of exposure and outcome, stronger than case-control but more expensive Case-Control: retrospective, secondary data from chart review, useful for rare conditions, inexpensive, many forms of bias Cross-Sectional: descriptive study of relationship between factors at one point in time Case-Series: series of cases, lack of comparability, source of hypothesis, most common study type Case-Report: anecdotal evidence,
  • Scientific enquiry has never been, and never will be, independent of prevailing political, ideological, economic and technological forces
  • Medical Studies What Can You Believe

    1. 1. How to Evaluate New Medical Treatments Mark Perloe, M.D.
    2. 2. Mass-Media Influence <ul><li>Discoveries and innovations characterized by </li></ul><ul><ul><li>unjustifiable degree of certainty </li></ul></ul><ul><ul><li>Immediate promise of reducing the burden of illness or increasing life expectancy </li></ul></ul><ul><li>Technical detail and scientific jargon are boring </li></ul><ul><li>Exaggerates the risks posed by putative health hazards </li></ul><ul><li>Pharmaceutical company advertising </li></ul>
    3. 3. Internet Medicine <ul><li>Where to find information </li></ul><ul><ul><li>National Library of Medicine Medline, Grateful Med, PubMed </li></ul></ul><ul><ul><li>Expert Chats </li></ul></ul><ul><ul><li>Organization Websites </li></ul></ul><ul><ul><li>Mailing Lists </li></ul></ul><ul><li>Limitations </li></ul><ul><ul><li>Credentials not evident </li></ul></ul><ul><ul><li>Financial bias </li></ul></ul><ul><ul><li>Self promotion </li></ul></ul>
    4. 4. Rationale for Evidence-based Medicine <ul><li>Cost of medical care rising sharply </li></ul><ul><li>Wide variations in outcomes of medical care </li></ul><ul><li>Patients are better informed and more vocal seeking to make informed choices </li></ul><ul><li>Health-care decision making should involve the patient and be based on best evidence </li></ul><ul><li>Statistical tools (meta-analysis) are better understood </li></ul><ul><li>Evaluation of research papers for validity and relevance </li></ul>
    5. 5. Evidence-based Medicine <ul><li>Incorporation of relevant scientific information into the clinical decision making process </li></ul><ul><li>Provides the impetus to gather, review and summarize evidence on effective and cost of health-care interventions (meta-analysis) </li></ul><ul><li>Optimizes the utilization of health-care resources by avoiding ineffective and medical & surgical therapies </li></ul>
    6. 6. Clinical Study Types <ul><li>Experimental Studies </li></ul><ul><ul><li>Randomized Control Trials (RCT) </li></ul></ul><ul><ul><li>Randomized Cross-Over Trial </li></ul></ul><ul><li>Observational Studies </li></ul><ul><ul><li>Cohort (Incidence, Longitudinal) </li></ul></ul><ul><ul><li>Case-Control </li></ul></ul><ul><ul><li>Cross-Sectional (Prevalence) </li></ul></ul><ul><ul><li>Case Series </li></ul></ul><ul><ul><li>Case Report </li></ul></ul>
    7. 7. Statistics <ul><li>ANOVA, Student’s t -test, Chi-square </li></ul><ul><li>P < 0.05 </li></ul><ul><li>Power Calculations </li></ul><ul><li>Clinical vs. biological significance </li></ul>
    8. 8. Evaluating Medical Studies <ul><li>Validity: Truth </li></ul><ul><ul><li>External Validity: Can the study be generalized to the population of the reader </li></ul></ul><ul><ul><li>Internal Validity: Study is well designed. Results not due to chance, bias or confounding factors </li></ul></ul><ul><ul><li>Symmetry Principle: Groups are similar </li></ul></ul>
    9. 9. Evaluating Medical Studies <ul><li>Confounding: distortion of the effect of one risk factor by the presence of another </li></ul><ul><li>Bias: Any effect from design, execution, & interpretation that shifts or influences results </li></ul><ul><ul><li>Confounding bias: failure to account for the effect of one or more variables that are not distributed equally </li></ul></ul><ul><ul><li>Measurement bias: measurement methods differ between groups, lack of blinding </li></ul></ul><ul><ul><li>Sampling (selection) bias: design and execution errors in sampling </li></ul></ul><ul><ul><li>Reader/Investigator bias: human tendency to accept information that supports pre-conceived opinions and reject studies that don’t </li></ul></ul><ul><ul><li>Sponsorship bias: studies designed to support sponsors views </li></ul></ul>
    10. 10. What’s a Meta-analysis? <ul><li>Met-analysis provides an overview of clinical trials </li></ul><ul><li>Meta-analysis is a set of statistical procedures designed to accumulate experimental and correlational results across independent studies that address a related set of research questions. </li></ul>
    11. 11. Meta-Analysis <ul><li>Variability in populations </li></ul><ul><li>Variability in study design </li></ul><ul><ul><li>Study quality </li></ul></ul><ul><ul><li>Endpoint reportage </li></ul></ul><ul><ul><li>Availability of data </li></ul></ul><ul><li>Variability in interventions </li></ul>
    12. 12. Limitations of EBM <ul><li>Impact of prevailing political, ideological, economic and technological forces </li></ul><ul><ul><li>NIH research often politically directed (stem cell) </li></ul></ul><ul><ul><li>Pharmaceutical industry financing limits comparative studies of alternative therapies </li></ul></ul><ul><li>Homogenous population required for studies </li></ul><ul><li>Limited evaluation of co-therapies </li></ul><ul><li>Lack of evidence does not equal lack of effectiveness </li></ul>
    13. 13. Clinical Decision-making <ul><li>What is my patient’s RISK ? </li></ul><ul><ul><li>of the event the treatment strives to prevent? </li></ul></ul><ul><ul><li>of the side-effect of treatment? </li></ul></ul><ul><li>What is my patient’s RESPONSIVENESS? </li></ul><ul><li>What is the treatment’s FEASIBILITY in my practice/setting? </li></ul><ul><li>What are my patient’s VALUES ? </li></ul>