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11 Cards in this Set
- Front
- Back
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What are the 3 types of observational study?
What is a cohort study? |
Cohort, Case control, cross sectional
Cohort - Investigator recruits disease free population. Looks for development of disease. Groups individuals by exposure |
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What are the advantages of a cohort study?
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1) powerful
2) can explore outcomes of rare exposures 3) can explore multiple outcomes of the exposure 4) can explore harmful exposures 5) less susceptible to selection bias |
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What are the disadvantages of a cohort study?
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1) They are prospective studies and are therefore time consuming and expensive
2) Prone to information bias 3) Patients may be lost to follow-up 4) Channeling bias may occur 5) Susceptible to confounding 6) Requires more patients than a case control study |
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When does a prospective cohort study begin?
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After the exposure has occurred but before the outcome appears
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When does a retrospective study begin?
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After the exposure and the outcome have occurred
Groups are identified by antecedent conditions which makes it a cohort study. |
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What is a case control study?
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You work backward from the outcome to the exposure. You take the cases with and without disease and see if they were exposed to a drug in the past year.
Groups made by outcome. |
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What are the advantages of Case-Control Studies? (3)
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They are efficient for assessment of rare events and long exposure events because they require fewer patients than cohort studies.
They are inexpensive and easy to conduct Can be completed quickly |
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What are the disadvantages of Case-Control Studies? (6)
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1) Retrospective - depends on historical data
2) Most susceptible to selection and information bias 3) selection of controls is complicated 4) difficult to sort out the temporal relationship between exposure and outcome since both are collected at same time 5) Cannot calculate incidence of the condition, only the odds of occurrence 6) Can only evaluate one outcome at a time |
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What is a cross sectional design?
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You recruit a study population, group them into having or not having a disease and then look at whether they have a particular risk factor
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What are the advantages (5) of Cross sectional design?
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Inexpensive and easy to conduct
Can complete quickly Can study many potential exposures Can examine many subgroup variables Can study harmful exposures |
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What are the disadvantages of cross sectional design?
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Susceptible to bias
Relies on non-verified, self reported information Often uses a survey methodology Susceptible to cause and effect conclusions Can have errors in data collection |
