A retrospective observational study designed to determine whether there is a link between a given parameter (e.g. a disease or a health determinant) and a specified cause.
Note: Investigators select a group of subjects presenting the parameter of interest (cases) and a group not presenting the parameter (controls). Then they compare the histories of the cases and controls to determine whether there is an association between the parameter and the cause being studied.
Note: The term “case-control study” is often, incorrectly, considered a synonym of “retrospective study.” Although, in both cases, it is necessary to look into the past for the chain of events, the term “retrospective study” does not necessarily include the element of comparison of two or more groups defined at the start of the study, an element that characterizes case-control studies. The qualifier “retrospective” simply indicates the temporal direction of the study.