J Infect Dis. 1997 Nov;176(5):1397-400. Unique Identifier : AIDSLINE
Injection drug users were assessed serologically for human
immunodeficiency virus infection and syphilis every 6 months. Treatment
histories were reviewed for any high-titer biologic false-positive (BFP)
reactors, that is, persons with rapid plasma reagin (RPR) titers > or =
1:4 and negative results for fluorescent treponemal antibody absorption
(FTA-ABS) tests. Selected sera were analyzed further by immunoblotting
for the presence of antibodies reactive with specific Treponema pallidum
antigens. Of 112 BFP reactors, 35 (31%) had at least one RPR test
reactive at a dilution >1:8 while the FTA-ABS test remained nonreactive.
Five reactors (4.5%) converted from nonreactive to reactive by FTA-ABS
test; 4 (3.6%) were reactive by FTA-ABS tests but later became
nonreactive. Antibodies to T. pallidum membrane antigens were detected
in some samples that were persistently nonreactive by FTA-ABS test.
Serologic patterns over time, along with very high-titer BFP reactions
and reactivity with T. pallidum-specific antigens, suggest that some BFP
reactions may represent FTA-negative syphilis.
*Antibodies, Bacterial/BLOOD *HIV Infections/IMMUNOLOGY *Substance
Abuse, Intravenous/COMPLICATIONS *Syphilis/DIAGNOSIS *Treponema