Estudios de casos y controles

Case-control studies are analytical observational epidemiological studies generally devoted to evaluate factors associated with infrequent diseases. Its hierarchy within the pyramid of evidence lies in an intermediate place between cross sectional and cohort studies. The measure of association used for these studies is the Odds Ratio. Some variants of this design, such as incident and nested case studies and nested case-control studies (within a cohort) can reduce the risk of selection bias. The basic concepts related to this type of studies are reviewed.