Fluorescent Treponemal Antibody, Absorbed (FTA-ABS) |
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The FTA-ABS is the most frequently used treponemal serologic test. It is more specific than the nontreponemal serologic tests and is used as a confirmatory test for syphilis after a reactive RPR is found. It is also useful in confirming the diagnosis in late stage syphilis in which the RPR is often negative.
The FTA ABS is highly sensitive in all stages of syphilis and becomes reactive earlier than the reagin tests. It will remain positive for many years with or without treatment, and therefore is a good indicator that a patient has previously had syphilis, but it does not indicate clinical activity or necessity of treatment (see Table in Rapid Plasma Reagin section). There is a 2% false positive rate which may be seen in a number of conditions including; autoimmune diseases, infectious mononucleosis, hypergammaglobulinemia, cirrhosis, diabetes mellitus, drug abuse, chronic infections, pregnancy and old age.
Results are reported as reactive or nonreactive. The reference value is nonreactive. State law requires that all positive reactions be reported.
The specimen requirement is one SST tube of blood.
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