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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
Q

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.

A

Goal of control selection

26
Q

What is a major determinant in whether any conclusion is valid?

A

The way the controls are selected

27
Q

The way the controls are selected can affect(2):

A

Internal validity

Selection bias

28
Q

Best way to select the control study population:

A

Make the groups as close as possible except the presence of the Dz

29
Q

If the exposure has no effect, what is the odds ratio:

A

1

30
Q

Controls must be selected irrespective of:

A

Exposure status

31
Q

Why would you select control irrespective of exposure status?

A

You could accidentally cause or mask an asso. If you get that involved

32
Q

Control group can come from several sources (3):

A

Population

Institutional/organizational/provider

Spouse/relative/friends

33
Q

Illnesses of control should be:

A

Unr/t exposure being studied

34
Q

Why study relatives?

A

Genetic/environmental, socio-economic

35
Q

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?

A

They were good pick b/c theyre in the same climate;

Gender, +/- 5 years of age
Systematic ‘control-search’ pattern

36
Q

An easier way to select controls;
Participated in same event and ‘at-risk’

What is this termed in control selection?

A

Outbreak-sources of controls:

37
Q

Study in which we only know the outcome and we’re looking for an association w/ the exposure

A

Case-control study

38
Q

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

A

Case-crossover

39
Q

What is the only case-control design able to adequately ate,pt to address the issue of temporality

A

Case-crossover design

40
Q

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

A

Nested Case-control

41
Q

3 techniques to selecting controls for nested case-control studies

A

Survivor
Base
Risk-set

42
Q

Selection from Sample of non-diseased individuals at the END of the study period for nested case-control studies

A

Survivor sampling

43
Q

Selection from Sample of non-diseased individuals at the START of the study period for nested case-control studies

A

Base sampling

44
Q

Selection from Sample of non-diseased individuals DURING the study period at the SAME TIME when case was diagnosed for nested case-control studies

A

Risk-set

45
Q

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

A

Selection bias

46
Q

2 Common bias types in case-control studies

A

Selection bias

Recall bias

47
Q

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

A

Recall bias

48
Q

Cases can be matched to controls at ratios from 1:1-5:1

Can be done on individual or group

A

Matching

49
Q

Matches subjects based on specific patient-based characteristics

Useful for controlling confounding characteristics

A

Individual matching

50
Q

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

A

Group matching

51
Q

What is something that we want to be careful not to match?

A

Anything that might be a risk factor should not be matched

Epidemiology (12 decks)

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