Design of a case-control study
Case-control studies
In most outbreaks the population is large or not well defined, and so cohort studies are
not feasible. In these instances, you would use the case-control study design. Case-control
studies can be matched or unmatched, where matching is used as one way to control confounding
by selecting study participants so as to ensure that potential confounding variables (such as
age and sex) are evenly distributed in the two groups being compared (refer to Legionnaires' Disease Outbreak Study protocol).
Definition: epidemiological study of persons with the disease (or other outcome
variable) of interest and a suitable control group of persons without the disease. Potential
relationship of a suspected risk factor or an attribute to the disease is examined by
comparing the diseased and non-diseased subjects with regard to how frequently the factor or
attribute is present in each of the groups.
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