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