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Evidence-Based Medicine 1. Knowledge and Skills for Critical Reading Karen Schetzina, MD, MPH. Overall Objective.
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Evidence-Based Medicine 1 Knowledge and Skills for Critical Reading Karen Schetzina, MD, MPH
Overall Objective • Become familiar with research methods and explore issues that may lead to future research interests, community service activities, advocacy projects, or focuses of study in your career.
Epidemiology • The study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems
Assumptions • Disease does not occur at random but is related to environmental and /or personal characteristics • Causal and preventive factors for disease can be identified; knowledge of these factors can then be used to improve health of populations
Purposes of Epidemiologic Studies • Identify new diseases • Identify populations at risk for a disease • Identify possible causative agents of a disease • Identify factors or behaviors that increase risk of disease and their relative importance
Purposes of Epidemiologic Studies (continued) • Rule out factors or behaviors as contributing to a disease • Evaluate therapies for a disease • Guide in the development of effective public health measures and preventive strategies
Reading Epidemiologic Studies • Become familiar with medical terminology (but you don’t need to know every word) • Have some prior knowledge of the pathophysiology of the disease of interest • Understand principles of study design, analysis, and interpretation
Pneumocystis Pneumonia--- Los Angeles • Background Info/Definition of Terms • Opportunistic infections – occur only in persons with abnormal immune systems • Pneumocystis carinii pneumonia • Cytomegalovirus (CMV) infection • Candidiasis/candida mucosal infection – yeast infection • Leukopenia / neutropenia – low white blood cell count • Viruria – virus detected in urine • Titre – antibody count • Neoplasia - cancer • Hodgkins Disease – a type of lymphoma (cancer)
Clinical Correlations “Pneumocystis Pneumonia– Los Angeles” “First Report of AIDS”
Pneumocystis carinii pneumonia (PCP) • Caused by a microorganism • Frequently seen in persons with compromised immune systems: • AIDS patients • Elderly • Premature babies • Presentation • Fever • Shortness of breath • Nonproductive cough • (Bilateral infiltrates- chest x-ray)
Cytomegalovirus (CMV) • Group of herpesviruses • Often infections are asymptomatic • If symptoms present: • Mononucleosis-like illness
Pneumocystis Pneumonia--- Los Angeles • What type of article is this? • What do you think is/are the purpose(s) of the article? • From what population are the subjects of this report derived? • What similarities between the cases were mentioned in the article? • What conclusions did the editor reach? • What are the limitations of this type of report in terms of the information it provides? • What are the public health implications of this report? • What questions arise after reading this report? What future research is needed?
Anatomy of a Journal Article • Abstract • Introduction / statement of the problem • Methods • Results • Discussion • References
Definitions • Hypothesis or research question • Population – Collection of units from which a sample may be drawn • Sample – A selected subset of a population • Variable - “Any quantity that varies. Any attribute, phenomenon, or event that can have different values.” • Predictor Variable – Risk factor • Outcome Variable – Disease or condition of interest • Association or Correlation – Degree to which variables change together
Definitions • Estimate – Incorporates some degree of error • Prevalence - “The number of events in a given population at a designated time” • Incidence – “The number of new events in a defined population within a specified period of time” • Mean – average • Variance – A measure of dispersion or variation • Standard Deviation/Error – Square root of the variance
Study Designs • Observational, Descriptive • Observational, Analytic • Experimental
Study Designs • Observational, Descriptive • Describe the amount and distribution of disease • Useful for generating hypotheses • Observational, Analytic • Designed to test one or more specific hypotheses • Experimental • The exposure and the persons to be exposed are determined by the investigator
Study Designs • Observational, descriptive • Case reports, case series • Ecological • Cross-sectional • Observational, analytical • Case control • Cohort • Experimental • Randomized clinical trial • Community Intervention Trial