Case Control Studies

Question 1

When might I use a case-control study ?

Answer 1

Useful when investigating cause of disease, because it helps determining if an exposure (risk factor) is associated with an outcome (disease, condition of interest)
Useful to study conditions with low incidence rate e.g.<5%
acute outbreaks,
rare diseases,
long latency diseases (time-lag between exposure & outcome)
When it might be unethical to expose the patient or do nothing following exposure

An example of a case-control study would be interviewing a group of mothers of children born with birth defects (cases, with the outcome of interest) to mothers of children born without birth defects (controls, without outcome the interest) and comparing their dietary and supplemental intakes of folic acid just prior to and during their pregnancies (exposure).
If a lower level of exposure to folic acid is found in the case group as compared to the control group, the hypothesis that lower levels of folic acid are related to certain birth defects can be supported.

Question 2

Benefit of Case Control Study ?

Answer 2

• Relatively low cost
• Short duration as events have already occurred.
• Useful in uncommon or long latency diseases where it is impossible to await an event’s development.
• It is possible to study several exposure factors simultaneously.
• Risk approximation by calculating the odds ratio.

Question 3

Disadvantages of Case - Control Studies?

Answer 3

The magnitude of the association can be affected by the characteristics of those selected for the control group.

• Based on previously recorded information, thus, susceptible to memory or registry bias when retrieving data.
• They require proper control groups, which are often hard to obtain.
• Does not calculate relative rusk on account of being unable to estimate event incidence, among groups.

Question 4

How to work oout the odds ration ?

Answer 4