Evidence derived from medical (or lay) histories, unsupported by objective data. Anecdotal evidence can be an important indicator of need for further study. This may be an anecdotal study, such as the medical histories of a series of cases of a rare condition, and may in turn suggest further investigation, such as a case control study. Examples include the case history series that preceded the first epidemiological studies of malignant neoplasm of the vagina in young women caused by prenatal exposure to diethylstilbestrol (DES) and of hemangiosarcoma of the liver in workers exposed to vinyl chloride. Anecdotal evidence influences policy making when politicians play on emotions aroused by publicizing a single case to promote a particular cause, such as investing in costly diagnostic equipment.
Subjects: Public Health and Epidemiology.