FTA-ABS

Alternative names:

fluorescent treponemal antibody absorption test

What the risks are:

• excessive bleeding
• fainting or feeling lightheaded
• hematoma (blood accumulating under the skin)
• infection (a slight risk any time the skin is broken)
• multiple punctures to locate veins

Special considerations:

Excessive hemolysis and gross lipemia can affect test results.

Many conditions cause false positive results with the VDRL and RPR tests including mycoplasma pneumonia, malaria, acute bacterial and viral infections, and autoimmune disorders.

Syphilis results from infection by Treponema pallidum. Early infections are associated with an antibody to some substance produced by the body in response to the infection. This antibody also appears in other infections so the tests which measure it (VDRL and RPR) are not specific for syphilis (i.e., there is a high false positive rate). Later in the infection, an antibody specific to the organism appears. This antibody can be detected by the FTA-ABS test.

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.