Last update:

   20-Apr-2012
 

Arch Hellen Med, 29(2), March-April 2012, 240-247

APPLIED MEDICAL RESEARCH

"Case-control" studies
A brief history from the "abstain from beans" of Pythagoras to the present

P. Galanis
Center for Health Services Management and Evaluation, Department of Nursing, National and Kapodistrian University of Athens, Athens, Greece

Epidemiological studies include experimental and non experimental studies. Experimental studies include clinical trials, field trials and community intervention trials, while non experimental studies include quasi experimental studies, follow-up studies (in which subjects are selected with reference to their determinant status), "case-control" studies (in which subjects are selected in reference to their illness status), cross-sectional studies and ecological studies. The "case-control" study aims at achieving the same goals as a follow-up study but more efficiently, using "sampling". Properly carried out, "case-control" studies provide information that mirrors what could be learned from a follow-up study, usually at considerably less cost and time. In "case-control" studies, the source population is the population that gives rise to the cases included in the study. The control series should be sampled from the person-time of the source population so that the determinant distribution of the controls sampled mirrors the determinant distribution of the person-time in the source population. There are a number of options in "case-control" studies for selecting a control series: (a) Population controls, (b) random-digit dialing, (c) neighborhood controls, (d) friends controls, (e) hospital- or clinic-based controls and (f ) dead people, among others. In a "case-control" study, one can calculate the quasi incidence-densities ratio which is a valid estimation of the real incidence-densities ratio in a population without having to obtain individual information on every person in the source population.

Key words: "Case-control" studies, Incidence-densities ratio, Matching, Source population, Study population.


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