During the mid-20th century, in many jurisdictions, including most US states, applicants for a marriage license were required by law to undergo a Wassermann test.

A sample of blood or cerebrospinal fluid is taken and introduced to the antigen – cardiolipin extracted from bovine muscle or heart.

[citation needed] The Wassermann test is ineffective at identifying primary syphilis as sufficient reagin has not yet been produced from tissue destruction at this stage.

[2] The antibody test was developed by Wassermann, Julius Citron, and Albert Neisser at the Robert Koch Institute for Infectious Diseases in 1906.

[citation needed] Indeed, the "biologic false positives" of modern tests usually indicate a serious alternate condition, often an autoimmune disease.