Case-Control Studies

Question 1

What are Case-Control Studies?

Answer 1

• Observational studies that allow the researcher to be a passive observer in individuals with disease/condition of interest (cases) who are compared with people who do not have the condition of interest (controls)

Question 2

What are the group assignments based on?

Answer 2

• Disease Status

Question 3

When are case-control studies useful?

Answer 3

When studying a rare disease or investigating an outbreak

Question 4

What are the reasons to select a case-control design?

Answer 4

• Unable to force group allocation
• Limited resources (time, money, subjects)
• The disease of interest is rare in occurrence and little is known about its associations/causes
• Prospective exposure data is difficult/expensive to obtain and/or very time inappropriate

Question 5

Which perspective are case-control studied customarily conducted in?

Answer 5

• Retrospective

Question 6

What are the general strengths of case-control studies?

Answer 6

• Good for assessing multiple exposures of one outcome
• Useful when diseases are rare
• Useful in determining Associations
• Less expensive than interventional and prospective cohort studies
• Useful when ethical issues limit interventional studies
• Useful when Disease has a long induction/latent period

Question 7

Who defines the selection of cases?

Answer 7

The investigator, hopefully using accurate, medically reliable, efficient data sources

Question 8

What is the difficult part of a case-control study?

Answer 8

• Control selection

Question 9

How do you select control population?

Answer 9

• Want them to be as equal as possible to case group except for exposure.
• Must be selected irrespective of exposure status

Question 10

What sources can the control group come from?

Answer 10

• Population
• Institutional/Organizational/Provider
• Spouse/Relatives/Friends

Question 11

Case-Crossover design

Answer 11

• When an individual can function as both an exposed individual and and unexposed individual in the same study

Question 12

Nested Case-Control Studies

Answer 12

• case-control studies conducted after, or out of, a prospective previous study type (cohort or interventional)

Question 13

Where can the control for Nested Case-Control study come from?

Answer 13

• Survivor sampling
• Base sampling
• Risk-Set sampling

Question 14

Survivor Sampling

Answer 14

• Sample of non-diseased individuals at the end of study period

Question 15

Base Sampling

Answer 15

• Sample of non-diseased individuals at the start of study period

Question 16

Risk-Set Sampling

Answer 16

• Sample of non-diseases individuals during the study period at the same time when case was diagnosed

Question 17

What are the most common biases associated with case-control studies?

Answer 17

• Selection

- Recall

Question 18

Individual Matching

Answer 18

• Matches individuals based on specific patient-based characteristics

Question 19

Group matching

Answer 19

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

• requires the cases to be selected first