Flashcards
Week 10
Cards in this deck (16)
- 1What is a case control study?When you compare people with disease to people without disease. Subjects with the disease are called cases and subjects without are called controls. Both disease and exposure have already occurred (not sure which one came first).
- 2Designing a Case Control StudyDefinition and selection of cases. Selection of controls (trickiest - no motivation to be in the study) and Compare exposure levels between cases and controls.
- 3Sources for selecting casesHospital based case control studies and population based case control studies
- 4Sources for controlsHospitals, Populations or Friends
- 5How many controls per case?1:1 ratio is good if the number of cases is adequate. when the sample size is limited, up to 4 controls per case
- 6Most important factors when choosing a control group?The risk factors of the control patients should be representative of those in the population at risk of becoming cases (controls would have been included as cases if they had the disease). Exposures measurable with the same accuracy as cases.
- 7Selection of control group criteriaMake sure info from cases & controls on factors obtained in similar manner. Consider whether or not to match the controls so they are similar to cases with respect to confounding variables. Desirable controls from population similar to cases. Take into account Practical and economic considerations
- 8What is Matching?Selecting controls that are similar to the cases in certain characteristics e.g. age, sex, race, SES, occupation
- 9Disadvantages of matching?Difficulty to get controls
- 10Nested Case control studyObtains its cases and controls from a cohort that has been followed for a period of time
- 11Analysing Case control studiesCan't calculate IR therefore can't use RR and thus uses OR.
- 12Advantages of Case ControlCheaper & Faster. Use for studying disease for long latent periods. Use for studying rare diseases. Allows investigation of multiple exposures at the same time
- 13What is latent period?Time between exposure and development of disease
- 14Disadvantages of case controlNot suitable to evaluate rare exposures unless study is very large or exposure is common among those with the disease. Susceptible to bias (info & selection) since disease & exposure have occurred. The temporal rx b/w exposure & disease cant always be established
- 15Case control vs Cohort -> Case ControlStudy group: with disease. Comparison group: without disease. Measures of risk: OR. Temporal sequence: sometimes hard. Multiple Asso: disease with several exposures. Time req: short. Cost: inexpensive. Population: small. Best when: disease rare, exposure freq. Problems: selection controls, incomplete info.
- 16Case control vs Cohort -> CohortStudy group: with exposure. Comparison group: without exposure. Measures of risk: OR, RR, AR. Temporal sequence: easy. Multiple Asso: exposure with several diseases. Time req: long. Cost: expensive. Population: large. Best when: exposure rare, disease freq. Problems: selection non exposed, changes over time in methods.
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- Epidemiology Flashcards on Week 10, created by Indah on 17/10/2013.
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- Indah
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