An observational study to find out the possible cause(s) of a disease or condition. This is done by comparing a group of patients who have the disease or condition (cases) with a group of people who d [..]

Studies that use people who already have a disease or other condition to see whether there are characteristics of these individuals that differ from matched partners who don’t have the disease.

Studies which start with the identification of persons with a disease of interest and a control (comparison, referent) group without the disease. The relationship of an attribute to the disease is exa [..]

Retrospective studies beginning with people who have a disease and controls who are similar but do not have the disease. The investigator then looks retrospectively to see what proportion in each grou [..]