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Sexually transmitted infections

False-Positive Serologic Test for Syphilis

False-Positive Serologic Test for Syphilis

Biologic false-positive reactions to nontreponemal tests range from 3% to 20%. They are defined as a positive nontreponemal antibody test result in patients for whom the FTA-ABS finding is negative. Acute or transient false-positive nontreponemal reaginic test reactions may occur whenever there is a strong immunologic stimulus, for example in acute bacterial or viral infection and early HIV infection. Positive reactions persisting for months occur with parenteral drug abuse; with autoimmune or connective tissue diseases, especially systemic lupus erythematosus; and with aging. Up to 10% of those older than 70 years of age and in patients with hypergammaglobulinemic states have a blas?positive test.

The illnesses that produce a false-positive nontreponemal reaginic test, such as systemic lupus erythematosus, may also result in a positive or borderline-positive FTA-abs test reaction. Also, the FTA-abs may be positive when the VDRL is negative. This false reaction can be identified by observing a beaded pattern of immunofluorescence on the treponemes. Infection with Borrelia burgdorferi that causes Lyme disease results in a positive FTA-abs test but does not cause a positive nontreponemal reaginic reaction (VDRL or RPR).