In this evaluation of the fluorescent treponemal antibody-absorption (FTA-ABS) test, special emphasis is placed on its specificity as opposed to sensitivity. Among a total of 827 persons tested, there were five with a reactive FTAABS test confirmed by the Control Laboratory, and a non-reactive Treponema pallidum immobilization test accompanied by no clinical or historical evidence of syphilis. These five persons represent 0.6% of the total tested and 1.4% of those with a reactive FTA-ABS test. Three of these patients had diseases in which abnormal globulins frequently are found—rheumatoid arthritis, autoimmune hemolytic anemia due to lymphosarcoma, and alcoholic cirrhosis; two had no recorded evidence of disease. All were more than 50 years of age. Whether these cases represent old syphilis or false positive reactions to the FTA-ABS test is problematical.
Mackey DM, Price EV, Knox JM, Scotti A. Specificity of the FTA-ABS Test for Syphilis: An Evaluation. JAMA. 1969;207(9):1683–1685. doi:10.1001/jama.1969.03150220099011
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