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Updated: Jul 17, 2026
10:41
Detection of Toxin Translocation into the Host Cytosol by Surface Plasmon Resonance
Published on: January 3, 2012
Summary
In individuals with initially reactive fluorescent treponemal antibody absorption (FTA-ABS) tests and negative VDRL tests, repeat testing is recommended. Many cases resolve spontaneously, particularly those with low fluorescence intensity.
Area of Science:
- Infectious Diseases
- Immunology
- Clinical Diagnostics
Background:
- Syphilis diagnosis relies on serological tests like VDRL and FTA-ABS.
- Discordant results (VDRL-negative, FTA-ABS-reactive) can occur in clinically healthy individuals.
- Understanding the natural course of these discordant results is crucial for accurate diagnosis.
Purpose of the Study:
- To investigate the serological evolution of clinically healthy individuals with reactive FTA-ABS and negative VDRL tests.
- To determine the rate of spontaneous seroreversion in this population.
- To assess the utility of fluorescence intensity in predicting serological outcomes.
Main Methods:
- Prospective study of 56 clinically healthy individuals with negative VDRL and reactive FTA-ABS tests.
- Serial serological testing (VDRL and FTA-ABS) over a period of up to eight months.
- Quantification of FTA-ABS fluorescence intensity (e.g., 2+ or less).
Main Results:
- Twenty out of 56 individuals (35.7%) showed spontaneous conversion to nonreactive FTA-ABS tests within eight months.
- Most spontaneous conversions (all but one) were associated with low fluorescence intensity (2+ or less).
- The VDRL test remained consistently nonreactive in all participants.
Conclusions:
- A reactive FTA-ABS test with a negative VDRL test in healthy individuals may not indicate active syphilis.
- Serial testing for up to one year is advised before diagnosing syphilis in such cases.
- Reporting FTA-ABS fluorescence intensity can aid in differentiating true positives from resolving or false-positive reactions.
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