Fluorescent treponemal antibody absorption test

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The fluorescent treponemal antibody absorption (FTA-ABS) test is a diagnostic test for syphilis. Using antibodies specific for the Treponema pallidum species, such tests would be assumed to be more specific than non-treponemal testing such as VDRL but have been shown repeatedly to be sensitive but not specific for the diagnosis of neurosyphilis in cerebrospinal fluid (CSF). In addition, FTA-ABS turns positive earlier and remains positive longer than VDRL. Other treponemes, such as T. pertenue, may also produce a positive FTA-ABS. The ABS suffix refers particularly to a processing step used to remove nonspecific antispirochetal antibodies present in normal serum.

In general, the test has two roles:

1. As a confirmatory test for a positive result from a serum screening test (RPR for example).
2. Since the test has high negative predictive value it is very useful in both serum or CSF to exclude/rule out neurosyphilis if the FTA test result is negative. " A negative FTA in serum excludes neurosyphilis".