Case control studies

Question 1

Case control studies definition

Answer 1

Observational studies allowing researcher to be passive observer of natural events occurring in individuals with disease compared with people without disease

Question 2

Case control group assignments based on

Answer 2

Disease status

Question 3

Case control study useful for

Answer 3

Studying a rare disease or an outbreak

Question 4

Reasons to select case control study design

Answer 4

Unable to force group allocation
Limited resources
Disease of interest is rare
Prospective exposure data is difficult to obtain

Question 5

Case control studies are generally conducted in what fashion

Answer 5

Retrospective fashion

Question 6

Strengths of case control

Answer 6

Good for assessing multiple exposures of one outcome
Useful for rare diseases
Useful to determine associations (not causes)
Less expensive
Useful when ethical issues limit interventional studies
Useful when disease has a long induction/latent period

Question 7

Weakness of case control

Answer 7

Cant demonstrate causation
Can be impacted by unassessed confounders
Retrospective-cant control for other exposures
Can be impacted by various biases
Limited by available data (retrospective nature of design)

Question 8

Selection of cases in case control studies is

Answer 8

Defined by the investigator using accurate, medically reliable, efficient data sources

Question 9

Most difficult part of case control studies

Answer 9

Control selection

Question 10

Selecting controls for case control studies

Answer 10

Want the groups as equal as possible except the presence of the disease of interest
Controls must be selected irrespective of exposure status

Question 11

Control group can come from which several sources

Answer 11

Population (state/community/neighborhood)
Institutional/organizational/provider
Spouse/relative/friends

Question 12

T or F: Patients can function as both exposed and unexposed individual in the same study

Answer 12

True

-outbreak investigation with multiple exposures

Question 13

Nested case control studies

Answer 13

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

• subjects in cohort study that developed disease are defined as cases for the subsequent case control study
• -used to evaluate other exposures

Question 14

Selection of controls used for nested case control studies when sampling from previous cohort study

Answer 14

Survivor sampling- sample of non diseased individuals at end of study period
Base sampling- sampling of non diseased indiviuals at start of study period
Risk-set sampling- sample of non diseased individuals during study period at same time when case was diagnosed

Question 15

Common biases in case-control studies

Answer 15

Selection bias

Recall bias

Question 16

Case-crossover designs

Answer 16

Only case control design able to adequately attempt to address the issue of temporality
Patients act as their own control (exposed and unexposed)

Question 17

Individual matching

Answer 17

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

Question 18

Group matching

Answer 18

Proportion of cases and proportion of control with identical characteristics are matched
Requires cases to be selected first
Dont match on anything that might be a risk factor