Diagnosis of syphilis

For the diagnosis of syphilis , the most widely used serological methods allow detecting immune disorders( the emergence of antisyphilitic antibodies) in the patient's body in response to the multiplication of the causative agent of the disease.

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

Syphilitic antibodies can be nonspecific( reactive) and specific( anti-treponemal).

For sero and liquorodiagnosis of syphilis, the following methods can be used.

• Microsequence of precipitation( MR) with cardiolipin Ag is a screening test used for population screening for syphilis. The MP is performed with plasma or inactivated blood serum. Foreign tests VDRL( VDRL), RPR( RPR) and others are similar to MR, both on the principle of setting the reaction, and on sensitivity and specificity.
• ELISA( using Ar from cultured or pathogenic pale trepanemia).
• Passive hemagglutination reaction( RPHA).Ar from cultured or pathogenic pale treponemes.
• The reaction of immunofluorescence( RIF) in the following modifications: RIF-abs, RIF-c, RIF with capillary blood from the finger.
• A complex of serological reactions to syphilis, consisting of RSK with treponemal and cardiolipin Ag, and MR.Since treponemal Ar is specific, the complex of serological reactions is referred to as diagnostic tests. In connection with the development of more sensitive, specific and less time-consuming reactions, it became possible to replace the DSC with IFA or RPGA( also in combination with MR).
• The reaction of immobilization of pale treponemes in which pathogenic pale treponema of the Nichols strain is used as Ag.

Treponemal AT-class IgM in serum is not determined in healthy people.

Of all serological diagnostic methods for syphilis, the ELISA method is the most sensitive( over 95%) and specific( 100%).When it is used, specific( treponemal) AT classes of IgM and IgG are detected. AT class IgM are of great importance for diagnosis of primary, secondary and congenital syphilis. The detection of IgM AT indicates that the patient has primary, secondary or congenital syphilis.АТ class IgM is detected in serum from the 2nd week after infection. In the course of treatment, the content of AT-class IgM in a patient decreases. By their number, you can monitor the effectiveness of the treatment. After successful treatment, the content of AT-class IgM is reduced to negative results. The determination of ATM class IgM is of great importance for diagnosis of early forms of congenital syphilis, differential diagnosis of relapses, reinfection. The test for determining Ig IgM may be negative in some cases of late latent syphilis and neurosyphilis. Determination of IgM IgM by ELISA has a very high sensitivity for congenital syphilis( 100%) and a lower sensitivity for primary syphilis( 82%), secondary( 60%), latent( 53%), neurosyphilis( 34%) and tertiary syphilis( 11%) and very high specificity [Rich RR et al., 2001].

AT-class IgG appear in the acute period of the disease and can persist for cured patients for life. According to the order of the Ministry of Health of the Russian Federation No. 286 "On Improving Control over Sexually Transmitted Diseases" of December 7, 1993, it is recommended to use ELISA as a specific test for confirmation of syphilis instead of the reaction of immobilization of pale treponemes and RIF.

The ELISA method is used to diagnose syphilis, differentiate false positive results obtained in MP, control the effectiveness of treatment.