Case Control Studies
Definition
Studying infrequent events, such as death from cancer,
using randomized clinical trials or other controlled
prospective studies requires that large populations be
tracked for long periods in order to observe disease
development. Case-control studies use patients who
already have a disease or other condition and look back
to see if there are characteristics of these patients that
differ from those who don’t have the disease. The casecontrol
study provides a much cheaper and quicker
study of risk factors. If the evidence found is convincing
enough, then resources can be allocated to more “credible”
and comprehensive studies. The case-control study
begins with the identification of an outcome or effect
and a number of potential causative factors. A group
of cases which exhibit the outcome under investigation
is selected. A number of control subjects (or controls)
who do not exhibit the outcome or effect under investigation
are then chosen. These controls should match the
cases as closely as possible with respect to the non-risk
variables; this allows the proposed non-risk variables to
be ignored in the analysis. Sometimes more than one
control group is used. The case and control groups are
then compared for the proposed causal factors, and statistical
analysis is used to estimate the strength of association
of each factor with the studied outcome.
Case-control studies are a valuable investigative tool,
providing rapid results at low cost, but caution should
be exercised unless results are confirmed by other, more
robust evidence.
Tags: cancer, case control studies, case control study, causal factors, causative factors, caution, control group, control groups, control subjects, infrequent events, investigative tool, long periods, populations, prospective studies, randomized clinical trials, rapid results, risk factors, risk variables, robust evidence, statistical analysis