From the Guidelines
Testing for syphilis involves a two-step process using blood tests, with the initial screening typically done with a non-treponemal test such as the Rapid Plasma Reagin (RPR) or Venereal Disease Research Laboratory (VDRL) test, followed by a confirmatory treponemal test like the Fluorescent Treponemal Antibody Absorption (FTA-ABS) or Treponema pallidum Particle Agglutination (TP-PA) if positive, as recommended by the most recent guidelines 1.
Diagnostic Tests for Syphilis
The diagnostic tests for syphilis include:
- Non-treponemal tests: Rapid Plasma Reagin (RPR) or Venereal Disease Research Laboratory (VDRL) test, which detect antibodies to cardiolipin
- Treponemal tests: Fluorescent Treponemal Antibody Absorption (FTA-ABS) or Treponema pallidum Particle Agglutination (TP-PA), which specifically identify antibodies against the syphilis bacterium
- Direct testing of lesion fluid using darkfield microscopy or PCR for suspected primary syphilis with visible chancres
Testing Algorithm
The testing algorithm for syphilis may vary, with some clinics using the traditional sequence of non-treponemal test followed by treponemal test, while others use the reverse sequence, starting with treponemal tests followed by non-treponemal tests if positive, as noted in 1 and 1.
Recommendations
Regular testing is recommended for:
- Sexually active individuals with multiple partners
- Men who have sex with men
- HIV-positive individuals
- Pregnant women Testing should occur 1-2 weeks after potential exposure, though antibodies may take up to 90 days to develop, as mentioned in 1 and 1.
Importance of Early Detection
Early detection is crucial as syphilis progresses through primary, secondary, latent, and tertiary stages if untreated, with increasing severity of complications including neurological and cardiovascular damage, highlighting the need for prompt diagnosis and treatment, as emphasized in 1 and 1.
From the Research
Diagnostic Tests for Syphilis
The diagnostic tests for syphilis can be divided into two main categories:
- Non-treponemal tests
- Treponemal tests
Non-Treponemal Tests
Non-treponemal tests detect antibodies that are not specifically directed against the bacteria that cause syphilis, but are produced in response to the infection. Examples of non-treponemal tests include:
- Venereal Disease Research Laboratory (VDRL) slide test 2
- Rapid Plasma Reagin (RPR) test 3, 4
- Macro-Vue RPR Card test 5
- HiSens Auto Rapid Plasma Reagin (AutoRPR) test 4
Treponemal Tests
Treponemal tests detect antibodies that are specifically directed against the bacteria that cause syphilis. Examples of treponemal tests include:
- Fluorescent Treponemal Antibody-Absorption (FTA-ABS) test 2, 3, 4
- Treponema Pallidum Hemagglutination (TPHA) test 3
- Treponema Pallidum Particle Agglutination (TPPA) test 3, 4
- TrepSure Anti-Treponema EIA Screen 5
- SeroDia TP-PA 5
- Liaison Treponema Screen 5
- Architect Syphilis TP 5
- AutoTPPA test 4
Reverse Sequence Screening Algorithms
In recent years, reverse sequence screening algorithms have been developed, where treponemal tests are performed before non-treponemal tests 5, 6. This approach has been shown to be effective in diagnosing syphilis, especially in populations with high prevalence of the disease.
Automated Tests
Automated tests, such as the HiSens Auto Rapid Plasma Reagin (AutoRPR) and Treponema Pallidum particle agglutination (AutoTPPA) tests, have been compared to conventional methods and shown to be reliable alternatives 4.
Point-of-Care Tests
Point-of-care tests, such as the Macro-Vue RPR Card test, can be used as supplementary tests to evaluate the activity of the syphilis infection 5.
Cerebrospinal Fluid (CSF) Parameters
For the diagnosis of neurosyphilis, CSF parameters such as the albumin quotient and IgG index can be used, as well as treponemal antibodies in CSF 3.