Exam 2 : Lecture Case-Control Studies

Question 1

Case-control, observational or interventional?

Answer 1

Observational

Question 2

How are groups assigned?

Answer 2

Based on diseased status

Question 3

When is it good to use a case-control study?

Answer 3

When studying a rare disease or investigating an outbreak

Question 4

What biases could there be in an observational study?

Answer 4

Recall

Interviewer

Question 5

Reasons to use a case-control design

Answer 5

1. Unable to force group allocation (cant give disease)
2. Limited resources
3. Dishes of interest is rare
4. Prospective exposure dates is difficult/ expensive to obtain and/or very time inappropriate

Question 6

How are case-control studies customarily conducted?

Answer 6

Retrospectively

Question 7

Strengths of case control?

Answer 7

1. Good for assessing multiple exposures of one outcome
2. Useful when disease is rare
3. Useful in determining association
4. Less expensive
5. Useful when ethical issues limit interventional studies
6. Useful when disease has a long induction/later period

Question 8

All else being equal, the outcome if something didn’t occur
Requires assumption of exchangability
Exchangability = comparability

Answer 8

Recall counter factual theory

Question 9

What is the most difficult thing about case-control studies?

Answer 9

Control selection

Question 10

What is the goal with control selection?

Answer 10

Assess for presence of an association between exposure and known condition of interest by selecting non diseased individuals

Question 11

How to select control:

Answer 11

Groups needs to be equal
Controls must be selected irrespective of exposure status
Outbreak-sources of control (participated in same event)

Question 12

Where can controlled group come from

Answer 12

Population
Institutional
Spouse/releatives/friends

Question 13

Can a person function as both an exposed and unexposed in this type of study?

Answer 13

Yes
Can be associated with an outbreak investigation with multiple exposures or
In an situation of a brief change in risk of the outcome in interest

Question 14

Case control studies conduced after, or out of , a prospective previous study type

Answer 14

Nested case control

Question 15

What type of sampling of controls does nesting case control have?

Answer 15

Survivor sampling
Base sampling
Risk-set sampling

Question 16

Survivor sampling

Answer 16

Non-diseased individuals at end of study period

Question 17

Non-diseased individuals at start of study period

Answer 17

Base

Question 18

Risk-set sampling

Answer 18

Sample of non-diseased individuals during study period at same time when case is diagnosed

Question 19

What is the only case-control design able to adequately attempt to address issue of temporality?

Answer 19

Cross-over case- control study

Question 20

Matches individuals based on specific patient based characteristics
Useful for controlling confounding

Answer 20

Individual matching

Question 21

Proportion of cases and proportion of controls with identical characteristics are matched

Answer 21

Group matching

Question 22

Can we match on anything in a case-control study?

Answer 22

No. DON’T match on anything that might be a risk factor