20-21 Case Control Studies Flashcards
Define case.
A person with a disease of interest.
What are case control studies?
observational and analytical
allows researchers to be a passive observer of natural events occurring in cases compared with controls
group assignments are based on disease status
useful when studying a rare disease or investigating an outbreak
study differences in exposure
List reasons not to select a case-control study.
Unable to randomize
limited resources
the disease of interest is rare in occurrence and little is known about its associations/causes
prospective exposure data is difficult to obtain and/or very time inappropriate
List the strengths of case control studies.
good for assessing multiple exposures of one outcome
useful when diseases are rare
useful in calculating odds and odds ratios (associations)
less expensive than interventional trials and prospective cohort studies
useful when ethical issues limit interventional studies
useful for dynamic populations
useful when diseases has a long induction/latent period
How are cases selected?
by the investigator using accurate, medically-reliable, and efficient data sources
How does the researcher apply the selection process to the study participants?
objectively, consistently, accurately, and with validity
What is the best criteria for case selection?
clinically supportable and definable
What do we worry about with case selection?
misclassification
True or False, control selection is easier than case selection.
False, control selection is harder than case selection.
True or False, the way the controls are selected is a major determinant in whether any conclusion is valid.
True
What sources can the control group come from?
population
institutional/organizational/provider
spouse/relatives/friends
outbreak: other participants of the event
True or False, an individual can actually function as both a case and a control in the same study.
True
How can an individual can actually function as both a case and a control in the same study?
Can be associated with an outbreak investigation with multiple exposures
in a situation of a brief (acute) change in risk of the outcome in interest (hazard period)
What are nested case control studies?
These are case control studies conducted after, or out of a prospective cohort study.
What are the different types of sampling of controls?
Survivor, base, and risk-set sampling
What is survivor sampling of controls?
Sample of non-diseased individuals at the end of the study period.
What is base sampling of controls?
sample of non-diseased individuals at the start of the study period.
What is risk-set sampling of controls?
sample of non-diseased individuals during the study period at the same time when the case was diagnosed.
What is selection bias?
related to the way subjects are chosen for study
What is recall bias?
related to the amount/specificity that cases or controls recall past events differently
List and describe the 2 matching schemes for case control studies.
Individual: matches individuals based on a specific patient-based characteristics
Group: proportion of cases & proportion of controls with identical characteristics are matched
Where does nested case-control studies get their controls?
They go back to the cohort study and pull their controls from there.
How are case-control studies setup?
based on outcome, looking for exposure
Define bias.
any factor in the design/execution of a study that causes study groups to different which ultimately leads to a spurious association between variables
True or false, selection bias is less of, or not, a significant issue during Case-Crossover study designs.
True
