Screening is performed on a 24/7 basis with automatic release of screen negative results. TPHA and RPR tests are performed 3 times per week (M, W, F) on screen reactive sera.
All serum syphilis serology are screened using an ECL (electrochemiluminescence) - based assay.
Reactive (i.e. abnormal) EIA screens will be tested by TPHA (Treponemal-specific test) and RPR (Non-Treponemal Specific Test).
Syphilis is a venereal disease, usually sexually transmitted, caused by the spirochete organism Treponema pallidum . Infection is systemic from the outset and the disease is characterised by periods of latency, often in excess of 20 years. These features, together with the fact that T.pallidum cannot be cultured, means that serological techniques play a major role in the diagnosis of syphilis and treatment follow-up.
There are 2 important groups of tests:
- Non-Treponemal Specific (RPR, VDRL)
- Treponemal Specific (Roche Syphilis Screen, TPHA)
Non-Treponemal Specific
This group looks for antibody responses stimulated by Lipoidal antigens (The Reagin Test). The end point values from sequentially obtained serum samples decline following successful treatment until after a period of several months the patient will usually become reagin test non-reactive.
The VDRL test is the only syphilis serological assay that can be used on CSF specimen type to assist in the diagnosis of cases of presumptive neurosyphilis.
Treponemal Specific
Clinical diagnostic serum specimens which are reactive in reagin tests are typically confirmed using treponemal tests. In contrast to the nontreponemal tests, treponemal test reactivity will persist following treatment in approximately 85% of the cases often for the life of the patient.
NOTE: Serological testing does not distinguish between infections by the different treponemal species (i.e. Syphilis and Yaws). It should be noted that Yaws has been eradicated from most areas of the South Pacific since 1961 with occasional cases now seen in the Solomon Islands, P.N.G and parts of Indonesia. Patients born after this date with positive syphilis serology are most likely to have syphilis and should be managed as such.
For further information contact the laboratory (contact via Lablink: 22000 or (09) 307-8995 or 0800 522 7587) ,or:
the Virology team
virology@adhb.govt.nz