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Were participants picked by exposure, by outcome or by allocation, from data already collected?
More, if you want it
- Name an when exposure data exist only for groups.
How was the patient picked for the study?Tap a term: its definition, what you can do with it, and how often the exam asks it.
Definition: a design that picks people by exposure and follows them forward.
You can: Tell a cohort study from a case-control study by whether people were picked for exposure or for disease.
Definition: a cohort built from data already collected.
You can: Tell a retrospective cohort from a prospective cohort study by whether exposure and outcome were already recorded.
Definition: a design that picks people by disease and looks back at past exposure.
You can: Tell a cohort study from a case-control study by whether people were picked for exposure or for disease.
Definition: cases and matched controls taken out of an existing cohort or database.
Definition: a design that allocates people at random to drug or placebo.
Definition: a trial with predictable allocation, such as every alternate patient.
Definition: a design that compares exposure and outcome across whole groups.
You can: Name an ecological study when exposure data exist only for groups.
Each card is one term. The grey line is what the patient says, which is what the question stem gives.
Summary
A cohort study picks people by exposure status and follows them forward in time.
A cohort study picks people by exposure status and follows them forward in time. The study compares how often the outcome develops in the exposed and unexposed groups. A recruits a representative sample and keeps following the sample forward in time. Because the same people are followed over time, the design is longitudinal.
Cohort design is separate from case-control design. Children exposed to valproate in the womb had poorer language, attention and memory outcomes than children exposed to carbamazepine or lamotrigine. A longitudinal birth cohort follows the same people, so exposure is measured before the outcome appears. One study recruited people with several earlier depressive episodes and followed them forward for recurrence. An exposure is something a person has before the outcome, such as migraine or a drug.
Dr Priya Nair runs a research study in a headache clinic. Dr Nair says, "I recruited people with migraine and people without, and I will see who develops the outcome."
Candidates sometimes judge the design from the names of the groups. Groups chosen by exposure (migraine versus none) and followed forward make a cohort study, whatever the groups are called.
7 more sections on Study designs: cohort, case-control, nested case-control, controlled trials and more
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