Syphilis test

Syphilis is a sexually transmitted disease caused by the pale spirochete ( Treponema pallidum ). The disease begins with the appearance of a painless ulcer at the site of introduction of the pathogen (hard chancre ) and regional lymphadenitis. After some time, the infection becomes generalized: secondary and then tertiary syphilis develops. The classification of syphilis is given below.

Classification of syphilis

• Primary - develops 10-90 days (on average 21 days) after infection.
• Secondary - develops 2-6 months after infection or 2-10 weeks after the appearance of hard chancre.
• Latent (hidden) - a stage of the disease in which serological reactions are positive, and any signs of damage to the skin, mucous membranes and internal organs are absent:
  • early latent - less than 2 years from the onset of the disease;
  • late latent - more than 2 years from the onset of the disease;
  • unspecified latent.
• Tertiary - develops 3-7 years after the onset of the disease (from 2 to 60 years), gummas appear after 15 years.
• Congenital.

Test for syphilis

Serological methods are most widely used to diagnose syphilis, allowing the detection of immune disorders (the appearance of anti-syphilitic antibodies) in the patient’s body in response to the reproduction of the pathogen in it.

The development of antisyphilitic antibodies during the disease occurs in accordance with the general patterns of the immune response: first, IgM antibodies are synthesized, and as the disease progresses, IgG synthesis begins to predominate. IgM antibodies appear 2-4 weeks after infection and disappear in untreated patients after approximately 18 months; during treatment of early syphilis - after 3-6 months; late - after 1 year. IgG antibodies usually appear on the 4th week after infection and reach higher titers than IgM. They can persist for a long time even after clinical recovery of the patient.

Syphilitic antibodies can be non-specific (reagins) and specific (antitreponemal).

The following methods can be used for sero- and cerebrospinal fluid diagnostics of syphilis.

• Microprecipitation reaction (MP) with cardiolipin antigen is a screening test used in population screening for syphilis. MP is performed with plasma or inactivated blood serum. Foreign tests VDRL, RPR and others are similar to MP both in the principle of reaction setting and in sensitivity and specificity.
• ELISA (uses antigen from cultured or pathogenic pale treponemas).
• Passive hemagglutination assay (PHA). Antigens from cultural or pathogenic pale treponemas.
• Immunofluorescence reaction (IF) in the following modifications: IF-abs, IF-c, IF with capillary blood from a finger.
• A set of serological reactions for syphilis, consisting of the CSC with treponemal and cardiolipin antigen, and MR. Since the treponemal antigen is specific, the set of serological reactions is classified as diagnostic tests. Due to the development of more sensitive, specific and less labor-intensive reactions, it became possible to replace the CSC with ELISA or RPGA (also in combination with MR).
• Treponema pallidum immobilization reaction, in which pathogenic Treponema pallidum of the Nichols strain is used as an antigen.

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