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24 Cards in this Set
- Front
- Back
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What is analytic epidemiology?
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An analytic study attempts to answer WHY and HOW A HEALTH-RELATED STATE or event occured
-Tests specific a priori hypotheses (qirhour peioe knowledge, educated guess) |
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Case-Control Study
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-Retrospective (backwards, know outcome)
-The outcome is always identified prior to the exposure 1. Identify cases 2. Identify controls 3. Investigate whether the cases are more or less likely than controls to have had past experiences, lifestyle behaviors, or exposures |
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Selection bias
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-Cases and controls being slected into the study based in some way on the exposure
-The relationship between exposure and disease among participants in the study differs from what the relationship would have been among individuals in the population of interest |
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Two types of selection bias
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1. Berkson's bias - obtain controls from the general
2. Prevalence-incidence bias (Neyman bias) - take steps to assure the mild, clinically resolved, or fatal cases are represented in the case group |
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Missclassification
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1. Differential - non-random
-May arise if exposure classification influences differential accuracy in ascertaining outcome information 2. Non-differential - random, equal levels of not accurate results -May arise by inaccuracies in classifying exposure status of individuals, but these misclassifications occur similarly between exposed and unexposed groups |
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Confounding
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Occurs when an extrinsic factor is associated with a disease outcome and, independent of that association is also associated with the exposure
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Case-crossover Study Design
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-Compared the exposure status of a case immidiately before its occurence with that of the same case at a prior time
-The case-cross over study design is especially appropriate where individual exposures are intermittent, wherein the disease occurs abruptly and the incubation period for detection and the induction period are short |
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Nested Case-Control Study Design
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-AKA case-cohort study
-A case control study "nested" within a cohort study |
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Cohort Studies
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-Refers to a group of persons being studied who were born in the same year or time period
-As time passes, the group moves through different and successive time periods of life; as the group ages, changes can be seen in the health and vital statistics of the group -NEVER add to a cohort study, loss to follow up is common |
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Experimental studies may be what?
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1. Between-group design
2. Within-group design |
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Between-group design
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The STRONGEST method design
-Where the outcoms are compared between two or more groups of people receiving different levels of the intervention |
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Within-group design
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May be used where the outcome in a single group is compared before and after the assignment of an intervention
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Within-group strengths
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Individual characteristics that might confound an association are control
Ex: gender, race |
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Within-group strengths
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Susceptible to confounding from time-related factors such as the media but may be adjusted for in the analysis
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Random Assignment
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-Makes intervention and control groups look as similar as possible
-Chance is the only factor that determines group assignment -Neither the patient or the physician know in advance which prevention program or therapy will be assigned -Confounding and sample size |
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What are the three levels of blinding
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1. Single blind
2. Double blind 3. Triple blind |
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Single-blinded Study
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The EASIEST study
-Placebo controlled study, the subjects are blinded but investigators are aware of who is receiving the active treatment |
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Double-blinded Study
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Neither the subjects nor the investigators know who is receiving the active treatment
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Triple-blinded Study
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The MOST EFFECTIVE
-Not only are the treatment and research approaches kept a secret from the subjects and investigators, but the analyses are completed in a manner that is removed from the investigators |
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Why blind patients?
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-Patients try to get well/please physicians
-To minimize potential bias from a placebo effect |
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Placebo Effect
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The effect on patient outcomes (improved or worsened) that may occur due to the expectation by a patient that a particular intervention will have an effect
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What are problems with blinding?
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-For non-drug studies it may be impossible or unethical to blind
-May also be problematic to blind in drug studies where a treatment has characteristic side effects |
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Summary of ethical principles
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-Benefits > Maximize good
-Risks > Avoid doing harm -Subject > Respect for all persons -Society > Fairness to all -Is consent necessary? -Is it necessary to disclose to the subject the fact that they will be determined by chance? -Should subject be compensated for injury? -Who should be permitted to participate in clinical research? -When and how should a clinical trial be stopped? |
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Summary of Ethical Principles
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Competent investigators and good research design lead to a greater likelihood of benefits, protect subjects from harm, ensure that peoples' time is not wasted and their desire to participate in a meaningful activity not frustrated
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