The fluorescent treponemal antibody absorption (FTA-ABS) test is as specific as, and much more sensitive than, the Treponema pallidum immobilization test. The FTA-ABS test may detect syphilis earlier than the venereal disease research laboratories test for syphilis (VDRL), and it will rule out biologic false reactors with a high degree of accuracy. The FTA-ABS test likewise will permit the diagnosis of syphilis in many instances of late symptomatic syphilis which are nonreactive with routine reagin tests. Tests employing protein derived from the Reiter treponeme as antigen cause confusion because of lower sensitivity. The Kolmer test with Reiter protein (KRP) Reiter protein complement fixation test (RPCF) should be considered obsolete with the present availability of the FTA-ABS test.
Nicholas L. Serodiagnosis of Syphilis. Arch Dermatol. 1967;96(3):324-328. doi:10.1001/archderm.1967.01610030102016