Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Medical Studies What Can You Believe


Published on

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?

  • Be the first to comment

  • Be the first to like this

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>