Case-Control Studies Flashcards

1
Q

case-control studies

A

observational studies allowing researcher to be a passive observer of natural events occurring in individuals with the disease of interest compared to people who do not have the disease

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2
Q

group assignments of case-control studies

A

group assignments are based upon your disease status

diseased = group of interest
no disease = control

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3
Q

case-control studies are useful when …..

A

studying a rare disease or investigating an outbreak

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4
Q

case-control: randomization

A

do not randomize people into groups

take the population and just randomly select people to include but their group allocation is decided by their disease state

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5
Q

in case-control we are looking at…….. (data)

A

odds of exposure for each group and an odds ratio

commonly use a 2x2 table to compare the data

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6
Q

reasons to select a case-control design

A
  1. unable to force group allocation
  2. limited resources
  3. disease of interest is rare
  4. prospective exposure data is hard to obtain
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7
Q

unable to force group allocation

A

unethical

not feasible

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8
Q

limited resources

A

time
money
subjects

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9
Q

disease of interest is rare

A

in occurrence

little is known about it’s associations or causes

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10
Q

prospective exposure data is difficult to obtain

A

expensive

time inappropriate

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11
Q

case-control studies are classically _______ studies

A

retrospective studies
data is already collected, all has happened in the past
ex. any long term cancer

typically know the outcome of interest

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12
Q

strengths of case-control studies

A
  • good for assessing multiple exposures of one outcome
  • good for rare diseases
  • good for determining associations (not causes)
  • less expensive than interventional/prospective studies
  • less ethical issues
  • good for diseases w/ long induction/latent periods
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13
Q

weaknesses of case-control studies

A
  1. can’t determine causes
  2. impacted by confounders
  3. retrospective-cannot control for variables or contamination
  4. impacted by biases - selection and recall bias
  5. may only have limited data available due to being retrospective
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14
Q

selection of cases is defined by _______

A

the investigator using accurate, medically reliable data sources

classifying patients correctly is ideal but misclassification is present

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15
Q

new term for case definition

A

diagnostic criteria

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16
Q

all else being equal, the outcome if something didn’t occur

A

recall counterfactual theory

requires assumption of exchangeability to allow comparability

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17
Q

most difficult part of case-control studies is

A

picking the controls

18
Q

goals of control selection

A

to assess for the presence of an association between exposure and known condition of interest by selecting non-diseased individuals from the same population which produces the cases

19
Q

expectation of the controls

A

that they represent the baseline risk of exposure in the population

20
Q

control subjects cannot be selected upon

A

because of their exposure

researcher cannot look at a subjects exposure before allocating them as a control

21
Q

the way controls are selected is a major determinant of …….

A
  1. validity of conclusions
  2. internal validity
  3. selection bias
22
Q

differences between case and control groups

A

want the groups to be as equal as possible except that the control subjects do not have the disease

23
Q

if the exposure truly has no effect, then ……

A

the odds will be exactly the same for both groups

OR = 1.0

24
Q

controls must be selected ……

A

irrespective of exposure status

25
selection of controls can come from several sources:
1. randomly obtained from the population 2. institutional/ organization/ provider of care 3. spouse/ relatives/ friends
26
how to select the control group for studies on an outbreak
people who participated in the same event that caused the outbreak but did not get the actual illness
27
an individual can function as both an exposed individual and an unexposed individual in the same study
the case-crossover design because they are looking at different exposures
28
the only case-control design able to adequately attempt to address the issue of ______ .
case-crossover design issue of temporality
29
case-crossover study
a case-control study (observational) finds people who are cases and finds a temporally close earlier time period in their life when they weren't doing the exposure so didn't have the event
30
nested case-control study
a case-control study nested/comes from a study that is already done. from a cohort or interventional study. comes from another study but set up as a normal case-control study can be used to evaluate other exposures
31
selection of controls used for nested case-control studies
1. survivor sampling 2. base sampling 3. risk-set sampling
32
survivor sampling
sample of non-diseased individuals at end of the study period for control subjects in nested case-control studies
33
base sampling
sample of non-diseased individuals at start of study period for control subjects in nested case-control studies
34
risk-set sampling
sample of non-diseased individuals during study period at same time when case subjects were diagnosed for control subjects of nested case-control studies
35
another term for risk-set sampling
risk-analysis sampling
36
common biases in case-control studies
1. selection bias --- how subjects were chosen | 2. recall bias --- is subjects are required to recall information that will effect the study
37
matching
1:1 typically in case:control but can be higher can be individual or group matching
38
individual matching
matching individuals based on specific patient-based characteristics
39
what is individual matching useful for?
controlling confounding characteristics
40
group matching
proportion of cases and proportion of controls with identical characteristics are matched this requires cases to be selected first
41
what does group matching require
case subjects to be selected first
42
when matching, never match anything that ____ .
could be a risk factor