Leccture 18 - Case-Control Studies

Question 1

What is a case-control study?

Answer 1

• observational study
• those with the disease of interest are the cases and those without are the controls
• group-assignment is based on disease status
• useful in studying rare diseases or outbreaks
• generates odds ratio

Question 2

What type of ratio is a case-control study most useful for generating?

Answer 2

-odds ratio

Question 3

What is the scenario where the phrase “randomly selected” can be used but not indicate an interventional study?

Answer 3

-in a case-control study where there are more cases or controls than needed for the study so those observed are randomly selected

Question 4

What are the strengths of case-control studies?

Answer 4

• good for assessing multiple exposures of one outcome
• useful in rare diseases
• useful in determining associations
• less expensive and time consuming
• avoid ethical issues

Question 5

What should be taken into account when selecting controls for case-control studies?

Answer 5

• controls should be as equal as possible to cases but without disease
• should be picked regardless to exposure status

Question 6

What is a case-crossover study design?

Answer 6

• case control study where subjects act as their own control
• look at patient before they were a case and assess what exposures they had in between that may be responsible for the change

Question 7

What is a nested case-control study?

Answer 7

-a case-control study that comes out of a prospective study (such as cohort or interventional)

Question 8

What are the types of sampling of controls in nested case-control studies?

Answer 8

Survivor sampling:
-sample non-diseased individuals (survivors) AT THE END of a study

Base sampling:
-sample non-diseased individuals AT THE START of a study

Risk-set sampling:
-sample non-diseased individuals DURING STUDY period AT SAME TIME case was diagnosed

Question 9

What are the common types of bias affecting case-control studies?

Answer 9

• selection bias

- recall bias

Question 10

What method is commonly used to control for bias in case-control studies?

Answer 10

Individual matching:
-individuals are matched based on criteria making them similar

Group matching:
-proportional matching of cases and controls to make the groups similar (ie. % of gender)