1. STDs
2. Syphilis
3. Testing

Syphilis Testing Singapore | Shim Clinic

Syphilis Diagnosis

During the primary stage, a test using a special microscope to identify the bacteria in the fluid obtained from the chancre is diagnostic. Experienced laboratory technicians are usually needed for this. Sometimes, this technique is the only way to diagnose primary syphilis because the blood test for VDRL (Venereal Disease Research Laboratory Slide Test) or RPR (Rapid Plasma Reagin) may not show up during this early phase or window period.

If a person presents with secondary symptoms, a blood test will usually confirm the diagnosis of secondary syphilis.

All latent and late syphilis are diagnosed by blood tests.

TORCH

Syphilis test is usually with

• Alere™ Determine™ Syphilis TP Test
• VDRL test / Venereal Disease Research Laboratory test
• RPR test / Rapid plasma reagin
• TPHA test
• FTA-Abs test

Laboratory Tests

The diagnosis of syphilis may be confirmed either by

• Darkfield microscopy to demonstrate T. pallidum in secretions from the primary chancre or moist lesions of secondary syphilis.

Serological Tests

i. Non-Treponemal Tests

The Rapid Plasma Reagin (RPR) test and the Venereal Disease Research Laboratory (VDRL) tests are monitored serially to assess the serological response to treatment. RPR titres are slightly higher than VDRL titres. A positive VDRL/RPR test needs to be confirmed by a treponemal test. VDRL/RPR may become negative if treatment is instituted early in the disease. However treatment of late infections often results in a persistently positive result – or a serological scar.

ii. Treponemal Tests

The Treponema Pallidum Haemagglutination Assay (TPHA), Treponema Pallidum Particle Agglutination (TPPA) test, the Line Immunoassay (LIA), the Fluorescent Treponomal Antibody Absorption (FTA-Abs) test, Rapid diagnotic tests (e.g. Abbott Determine Syphilis TP) and the treponemal EIA test are specific and can be used as screening tests. A positive result may need to be confirmed by another specific test, as well as a non treponemal test with a titre (eg RPR or VDRL).

Once positive, specific tests tend to remain positive even after the syphilis has been successfully treated. The titres of treponemal tests are not useful in monitoring treatment response.

The FTA-Abs test is the first test to become positive following infection, it is followed by the VDRL/RPR test, and then by the TPHA/TPPA test. In primary syphilis 85-90% of cases will have a reactive FTA-Abs test, but only 60% will have a reactive TPHA/TPPA. The FTA-Abs test is no longer routinely offered by laboratories in Singapore. The syphilis LIA test for both IgM and IgG can be done as an alternative confirmatory test, as well as to detect cases of early syphilis. There is evidence that the syphilis EIA test is also useful for detecting early infections.

Most cases of syphilis in HIV-infected persons will demonstrate typical serological responses. However there may be instances of an altered serological response (abnormally high, low or fluctuating titres).

Neurosyphilis is often difficult to diagnose, as there is no single test that is useful in all types of neurosyphilis.

Tests that are used to diagnose neurosyphilis include:
CSF – WBC count, protein and globulin levels, VDRL, LIA IgM and IgG, and TPHA.
A positive CSF VDRL in the absence of gross blood contamination is confirmatory for neurosyphilis. However there may be false negatives as the test is not very sensitive. The LIA is a more sensitive test. A negative CSF LIA result makes neurosyphilis very unlikely.

References

• Syphilis testing @ Wikipedia