Tests for syphilis (syphilis) are divided into non-specific (reagin) and specific (spirochetal) serological tests. The first ones, incl. VDRL and USR tests are screening and are used to make an initial diagnosis. If the reagin test is positive, further testing is required for the presence of antibodies against the syphilis bacterial antigens. See when to get tested for syphilis so that the result is reliable.

Testing for syphilisis most often performed by performing a blood test for antibodies against the antigens of syphilis bacteria (an antigen is a molecule that comes from a microorganism or something similar to it). However, for their results to be reliable, tests should be performed at least 3-4 weeks after infection, and for even greater certainty - after 6 weeks. This is the time when the syphilitic bacteria enter the blood. If the serological test is performed sooner, the result may be false-negative.

It is also possible to perform a microscopic test that detects the presence of pale spirochetes in the discharge from skin lesions. It is performed when disturbing symptoms are noticed up to 6 weeks after syphilis infection.

Microscopic examination to detect syphilis bacteria

The first stage of infection with syphilis, i.e. primary syphilis (up to 9 weeks after infection), is divided into a sero-negative period (up to week 3-6) and a serum-positive period (week 6-9). During the serum negative period, the syphilis bacteria are not yet present in the blood and the only sure way to detect them is to collect the secretion from the lesions. The doctor examines the collected material under a microscope in a dark field of view - against this background, it is easy to recognize pale spirochetes as bright, glowing spirals. The test gives almost 100% confidence that syphilis has been infected.

Microscopic examinations are rarely performed. Usually, for a complete diagnosis, it is necessary to carry out serological tests, i.e. blood tests.

Non-specific (reagin) tests for syphilis

Syphilis reagin tests can be performed at the earliest 3-4 weeks after infection.

Diagnostics begins with screening tests, i.e. non-specific reagin serological tests.They are designed to detect reagin antibodies in the blood against the lipid components of the bacteria. On their basis, it cannot be clearly stated that the patient has syphilis, because similar antibodies are present in the serum in many other diseases, e.g. lupus erythematosus, pneumonia, chickenpox, measles, thyroid diseases, liver, anemia, neoplasms, malaria, Lyme disease. , in drug addicts and people over 70 years of age. So if the reagin test result is positive, it is necessary to perform specific tests.

Among non-specific reagin studies for syphilis:

  • Wassermann's reaction- the so-called a classic test involving the addition of a sick serum developer in the form of an ox heart extract. If this causes a complement fixation reaction, there are antibodies (reagins) in the blood. Nowadays, the WR test is no longer performed because it has a limited specificity and sensitivity - its results are subject to a considerable risk of error;
  • VDRL test ( Veneral Disease Research Laboratory )- microscopic fluff test. Its sensitivity is 70-80% for primary (first period) syphilis and almost 100% for secondary (second period) syphilis. It uses a cardiolipid antigen similar to the syphilis antigen, which in contact with antibodies in the patient's blood leads to precipitation of the preparation - as a result, characteristic flocs appear in it, which is evidence of the presence of bacteria. The VDRL test is used both to detect syphilis and to control its course in the later stages of the disease;
  • USR test ( Unheated Serum Reagin )- macroscopic flocculation test with unheated serum. The basic and most frequently used test for the presence of pale spirochete. Currently, it is standard to carry it out in the first place when there is a suspicion of infection. A positive result is confirmed by VDRL test and specific tests.
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How to prepare for syphilis screening?

Research for syphilis does not require any special preparation. Blood is drawn in the same way as for normal morphological examinations. You should be fasting before the test. Possible complications include slight bleeding from the site where the blood was taken and the possibility of a hematoma.

Specific tests for syphilis

Specific tests for people who have had syphilis infection remain positive for the rest of their lives. Therefore, in the event of a recurrence, only reagin tests are performed.

These tests are performed when the reagin test is positive. They serveconfirmation of infection. They only detect syphilis bacteria, so it is not possible for them to be positive for any other disease. They are performed with the use of antigens from the spirochete, Reiter and Nichols.

Among the syphilis-specific tests, the following are distinguished:

  • FTA ( Fluoroscent Treponemal Antibody Test )- test using the Reiter and Nichols spirochete antigen. In addition, it uses fluorescein, which helps in the detection of complexes formed after contact of antigens with antibodies;
  • FTA-ABS ( Fluoroscent Treponemal Antibody Absorbent Test )- an improved FTA test, in which to increase the sensitivity and better detection of antibodies against keel, special filters are used to absorb the remaining antibodies common to all spirochetes;
  • TPHA ( Treponema Pallidum Hemagglutination Assay )- test of hemagglutination, i.e. the clumping of red blood cells. It is carried out with the use of ram blood cells coated with the spirochete antigen;
  • TPI ( Treponema Pallidum Immobilization Test )- spirochetal immobilization test called the Nelson test. Infection with syphilis is detected by placing pale spirochetes on an artificial substrate and observing whether they become immobilized in combination with the patient's antibodies. Antibodies detected in this way are immobilisins, which appear after about 50 days from the moment of infection.
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Order of syphilis tests

Usually the first test performed when syphilis is suspected is the USR. If the result is positive, it is confirmed by the VDRL test and the specific FTA-ABS test. When the results are inconclusive (plus and minus), it is necessary to perform an additional TPH test. If TPH also gives questionable results, TPI spirochetal immobilization test should ultimately be performed.

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