Gram Negative Spiral
Most specific test of syphilis (AIIMS 10)
a. FTA Abs- Fluorescent Treponemal antibody test- this is a treponemal antibody test which uses virulent T. pallidum, maintained by serial passage in rabbit testis since 1912, called Nichol’s strain.
b. It is an indirect fluorescent antibody test. It is a modification of the original FTA test, in which the test serum is preabsorbed with a sonicate of Reiter’s treponemes to eliminate group specific reactions.
c. It is the first serological test to become positive following infection, i.e and one of the most specific, i.e false positives are minimal.
d. It can’t be used for assessment of treatment as the specific treponemal tests remain positive inspite of treatment.