Case Control Studies

Question 1

What statistical test is used when doing a case control study?

Answer 1

Odds Ratio

Question 2

How is an odds ratio different to an incidence rate ratio?

Answer 2

An OR is affected by the number of controls as well as the number of cases.

Question 3

Describe a ‘conventional’ case control study

Answer 3

There is a retrospective collection of data

Question 4

Define a ‘nested’ case study

Answer 4

Data is collected from the evolving outcome and exposure database of a cohort study.

Question 5

Why is a nested case control study advantageous?

Answer 5

Incidence rates can be calculated
The sampling of controls is already defined- less bias
More detailed information of the participants is obtained

Question 6

How can selection bias occur in a case control study?

Answer 6

When the people in the study are not representative of the population. There will be an underestimate of the odds ratio

Question 7

How can information bias occur in a case control study?

Answer 7

There can be randomly inaccurate measurements or systematic bias

Question 8

How can confounding factors be minimised in a case control study?

Answer 8

Adjust for confounders using logistic regression. Eg. make sure the control group and the case group have the same median age

Question 9

Outline the basis of a case control study

Answer 9

2 groups of people with and without a specific outcome are studies to see if they have been exposed to a specific factor in the past