Case control study:
- is a retrospective comparison between representative samples of people who get a disease and people who do not
- is a type of observational study in which characteristics of subjects with a disease are compared with a selected group of control subjects without the disease. The validity of this type of study depends on the appropriate selection of control subjects. Can show associations, but cannot establish causality
- the objective of a case control study is to validate an aetiological hypothesis or to suggest mechanisms of causation for a disease. In a case control study the comparison between groups is with respect to EXPOSURE whereas a cohort study is compared with respect to DISEASE e.g.
Establish proportion with past exposure to HRT <--------- cases of DVT/PE past exposure in menopausal women
Establish proportion with no past exposure <--------- cases of DVT/PE in menopausal women
HRT users -----------> incidence of breast cancer
non-HRT users -----------> incidence of breast cancer
- MeReC Briefing (2005);30 (supplement):1-7.