unit 9 pt 1 - Causal Hierarchy Causal Hierarchy Unit 9...

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Unit 9. Introduction to Experimental Studies/ Experimental Studies/ Intervention Studies ± Randomized Clinical Trials Community Trials ± Dr. Aurora Sanchez-Anguiano Epidemiology 6000 Causal Hierarchy ² Epidemiologists evaluate evidence to determine whether an exposure is directly responsible for an outcome. ² Studies follow a hierarchy in terms of the quality of evidence that they can the quality of evidence that they can provide. ² Strongest study is the RCT (randomized clinical trial). Observational vs. Experimental Design ± Observational: investigators observe and record exposures ± Experimental: investigators control the degree of exposure. ± Experimental studies are called intervention studies. The investigator intervene into the lives of the subjects manipulating the exposure. Two major types of planned experimental studies ± Two major types of experimental studies. ± Randomized controlled trials RCTs (clinical trials) ± Community trials (community intervention trials) ± Basic difference between them is the unit of analysis ± RCTs: individual ± Community trials: group Experimental Studies ± Just a note. Natural Experiments ± There is a third type of experimental study that is unplanned : ± Natural Experiment ± Rare situation in nature ± Levels of exposure differ in a population (s) ± Relatively unaffected by other factors ± So, it resembles a planned experiment ± Examples: ± Sn …. ± Chernobyl ± Fluoride (from observational to experimental) Intervention Studies Intervention Studies application. ² Intervention studies. Employed to test the efficacy of a preventive or therapeutic measure (individuals or populations) therapeutic measure (individuals or populations). Detection by screening (high lipid level, high blood pressure) Detection by surveillance (high adolescence mortality alcohol related) ³ Preventive (primary prevention) ² Participants are healthy ² Preventive therapies are tested ² Individuals or populations (polio vacc-field trial; fluoride-community trial) ³ Therapeutic (secondary or tertiary prevention; CT) ² Participants have a disease or condition ² Therapies are tested for benefit (efficacy) ³ Medical (new vs. old diet and complications DM; cancer treatment). ³ Surgical vs. Medical (coronary bypass vs. drug treatment) ³ Surgical vs. surgical (Breast Ca radical vs. limited mastectomy) Introduction to Clinical Trials ² Definition ² Keywords ² Randomized ² Placebo Controlled ² Blinded Clinical Trial Designs ² ² Parallel ² Crossover ² Strengths and Limitations ² Some Community/Intervention trials
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Randomized Controlled Trials ± Consider the “gold standard” of epidemiologic studies. Well designed, provide the strongest possible evidence of causation. If not well Gold Standard provide the strongest possible evidence of causation. If not well designed… ± DEFINITION ± Type of prospective study (analytical study) ± Investigator selects exposure of interest (therapeutic regimen) ± Subjects are assigned at random to the exposure (Rx) ±
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unit 9 pt 1 - Causal Hierarchy Causal Hierarchy Unit 9...

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