More precisely, VDRL and TPHA are screening tests; as such, they are used to identify those individuals who most likely have contracted the disease, but who need further tests for diagnostic confirmation.
VDRL and TPHA have different clinical significance, and are often performed jointly.
TPHA has the disadvantage of becoming positive around the 10th week of infection; as such, it is of little value in the early stages and tends to remain positive throughout life, regardless of therapy.
The VDRL is positivized between the eighth and the fifteenth day from the onset of primary syphiloma (initial stage, which occurs after about three weeks of incubation, manifesting itself with a small painless wound that appears on the area where the infection occurred).
The VDRL, while being a fairly sensitive test, is poorly specific. Indeed, VDRL values may appear elevated even in the absence of syphilis, for example in conditions such as pregnancy, autoimmune diseases (Lupus, Rheumatoid arthritis), drug addiction and other viral infectious diseases (acute hepatitis, chicken pox, Epstein-Barr, measles) or chronic bacterial diseases (leprosy, tuberculosis, malaria). As shown in the table, sensitivity decreases in early primary syphilis and in latent and late congenital syphilis, phases in which it is around 75%; instead it is maximum (100%) in the secondary forms. Since it is negativized after adequate therapy, the VDRL is also used as a test to evaluate the efficacy of the treatment.
, if the pregnant woman is affected by it or contracts the infection during pregnancy (congenital form).
During acute infection, the subject shows the presence of specific antibodies against syphilis of the IgM type, followed later by that of the IgG type, which remain throughout life.
VDRL and TPHA are serological tests that involve the search for antibodies in the blood and, sometimes, in the cerebrospinal fluid (CSF).
- VDRL is a non-treponemal test, i.e. it is capable of detecting antibodies not specifically directed against T. pallidum. This test is very sensitive, but not very specific: antibodies can be produced in the context of syphilis, but also in the presence of other pathologies. In case of positivity, before making the diagnosis, another treponemal test must always be performed.
- TPHA is a treponemal test, capable of detecting specific antibodies directed against the antigens of the T. pallidum.
If the result of these serological tests is positive, further investigations should be performed for confirmation of active disease.
they are absent to indicate the lack of exposure to Treponema pallidum.Attention! A negative result indicates that there is no evidence of the disease at the time of the examination. Recall that specific antibodies against syphilis are detectable only a few weeks after exposure to the pathogen. Therefore, if a person is certain that they have been exposed or in any case if the suspicion persists, a repeat of the test is required after a few weeks.
in case of:
- Pregnancy;
- Autoimmune Disorders (SLE, Rheumatoid Arthritis);
- Drug addiction;
- Other infections (including acute hepatitis, chickenpox, Lyme disease, measles, leprosy, tuberculosis, and malaria).
Therefore, a positive result must be confirmed with the use of more specific tests.
If the patient is treated appropriately, the non-treponemal antibodies generally disappear after three years.
TPHA
- A positive TPHA result confirms the screening test result, hence the diagnosis of syphilis.
- A negative result, on the other hand, indicates that the VDRL test gave a false positive result and further tests are needed to investigate the causes.
interfere with the result. During this period, a moderate amount of water is allowed.
. In this regard, pregnant women are divided into two groups, depending on the presence or absence of risk factors for the disease.If these risk factors are present:
- 3 serological controls (VDRL - TPHA):
- at the first visit during pregnancy
- at the second trimester (28 weeks)
- at the time of delivery
if they are absent:
- 2 serological controls:
- at the first visit during pregnancy
- at the time of delivery.
