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Epidemiology > [2] Class 20-21: Case-control Studies > Flashcards

[2] Class 20-21: Case-control Studies Flashcards

1
Q

Why are observational studies lower on pyramid than interventional?

A

They cant prove causation like interventional can

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2
Q

Increasing evidence for obs study

A 
Case reports/series->
Ecological->
Cross-sectional->
Case-control->
Cohort
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3
Q

Obs studies allowing researcher to be a passive observer of natural events occurring in individuals w/ the Dz/ condition of interest

A

Case-control studies

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4
Q

People who don’t have the Dz of interest

A

Control

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5
Q

Supplies info. About the expected baseline risk-factor profile in the population from which the cases are drawn

A

The control group

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6
Q

How are group-assignments made?

A

Based on Disease Status

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7
Q

When is a case control study useful?

A

When studying a rare disease or investigating an outbreak

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8
Q

What type of randomization is used in case control studies?

A

IT’s not! Subjects are randomly selected but they’re not randomized!

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9
Q

Obs studies and random selection:

A

Sometimes the Dz population is so high that you only need a fraction of the population. Randomly pick from that population.

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10
Q

Case-controls commonly generate an ____________ for each, then an _____________ as a measure of asso.

A

Odds of exposure; odds ratio (OR)

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11
Q

2x2 table Where is Dz

A

On top of the column

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12
Q

What conclusion can be drawn from case-control studies?

A

Strong, weak, no association

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13
Q

Know how to calculate an odds ratio

A

Odds-exp. of interest / odds-placebo

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14
Q

Reasons to use case-control design (4):

A
  • Unable to force group allocation [randomize]
  • limited resources
  • rare Dz of interest/little known
  • can be retrospective/prospective
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15
Q

Case-control design retro or prospective?

Interventional?

A

Both;

Interventional can only be prospective

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16
Q

Case-control studies are typically conducted in a ______________ fashion

A

Retrospective

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17
Q

Strengths of case-control study (in general) [6]:

A
  • can assess multiple exposures of one outcome
  • useful w/ rare Dz
  • Determining asso.
  • Less expensive
  • useful for ethical limitation w/ interventional
  • useful for long induction/latent period of Dz
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18
Q

Determining selection of cases :

A

Objectively, consistently, accurately, and w/ validity

Best: clinically-supportable/definable criteria

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19
Q

WHo determines selection of cases?

A

The investigator

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20
Q

Labeling patients _________ is ideal

A

Correctly

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21
Q

The risk of ________________ subjects into wrong group is always present

A

Misclassifying

22
Q

All else being =[same grp] the outcome if something didn’t occur

Counterfactual outcome for smokers estimated by non-smokers

Req’s assumption of exchangeability

Comparability w/ respect to all other determinants of outcome.

A

Counterfactual theory

23
Q

What is the only thing investigators want to be different about the 2 groups?

A

Dz of interest

24
Q

What is the most difficult part of selection of cases?

A

The control selection

25
To assess for the presence of an asso btw exposure and known condition of interest by selecting non-Dz ppl from the sample population which produces cases.
Goal of control selection
26
What is a major determinant in whether any conclusion is valid?
The way the controls are selected
27
The way the controls are selected can affect(2):
Internal validity Selection bias
28
Best way to select the control study population:
Make the groups as close as possible except the presence of the Dz
29
If the exposure has no effect, what is the odds ratio:
1
30
Controls must be selected irrespective of:
Exposure status
31
Why would you select control irrespective of exposure status?
You could accidentally cause or mask an asso. If you get that involved
32
Control group can come from several sources (3):
Population Institutional/organizational/provider Spouse/relative/friends
33
Illnesses of control should be:
Unr/t exposure being studied
34
Why study relatives?
Genetic/environmental, socio-economic
35
Why were neighbors selected for control in MO heat wave of 1980? What other factors were accounted for and should be for this and other controls?
They were good pick b/c theyre in the same climate; Gender, +/- 5 years of age Systematic 'control-search' pattern
36
An easier way to select controls; Participated in same event and 'at-risk' What is this termed in control selection?
Outbreak-sources of controls:
37
Study in which we only know the outcome and we're looking for an association w/ the exposure
Case-control study
38
An individual can actually function as both an exposed individual AND an unexposed individual in the SAME study. Subjects are their own controls during the other times they don't have the acute change in risk
Case-crossover
39
What is the only case-control design able to adequately ate,pt to address the issue of temporality
Case-crossover design
40
Case-control studies that are conducted after or as a subsequent study to a prospective cohort study. Can take ppl from that study and use in either control or case categories
Nested Case-control
41
3 techniques to selecting controls for nested case-control studies
Survivor Base Risk-set
42
Selection from Sample of non-diseased individuals at the END of the study period for nested case-control studies
Survivor sampling
43
Selection from Sample of non-diseased individuals at the START of the study period for nested case-control studies
Base sampling
44
Selection from Sample of non-diseased individuals DURING the study period at the SAME TIME when case was diagnosed for nested case-control studies
Risk-set
45
R/t to the way subjects are chosen for study- usually more concerning for control group, but less concerning for case-crossover Common bias in case-control studies
Selection bias
46
2 Common bias types in case-control studies
Selection bias Recall bias
47
R/t the amount / specificity that cases or controls recall past events DIFFERENTLY More commonly cases more likely to recall past exposures and levels of exposure
Recall bias
48
Cases can be matched to controls at ratios from 1:1-5:1 Can be done on individual or group
Matching
49
Matches subjects based on specific patient-based characteristics Useful for controlling confounding characteristics
Individual matching
50
Proportion of cases and proportion of controls w/ identical characteristics are matched Req's cases be selected 1st Ex: 41% cases are male=41% of controls will be male
Group matching
51
What is something that we want to be careful not to match?
Anything that might be a risk factor should not be matched

Epidemiology (12 decks)

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