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Syphilis: an enzyme immunoassay method for the diagnosis of syphilis
Medical expert of the article
Last reviewed: 04.07.2025
Treponemal antibodies of the IgM class are not detected in the blood serum of healthy people.
Of all the serological methods for diagnosing syphilis, the ELISA method is the most sensitive (over 95%) and specific (100%). When used, specific (treponemal) antibodies of the IgM and IgG classes are detected. IgM antibodies are of great importance for diagnosing primary, secondary and congenital syphilis. Detection of IgM antibodies indicates that the patient has primary, secondary or congenital syphilis. IgM antibodies are detected in the blood serum starting from the 2nd week after infection. During treatment, the content of IgM antibodies in the patient decreases. Their number can be used to monitor the effectiveness of the treatment. After successful treatment, the content of IgM antibodies decreases to negative results. Determination of IgM antibodies is of great importance for diagnosing early forms of congenital syphilis, differential diagnosis of relapses, and reinfection. The IgM antibody test may be negative in some cases of late latent syphilis and neurosyphilis. IgM antibody detection by ELISA has a very high sensitivity in congenital syphilis (100%) and lower sensitivity in primary syphilis (82%), secondary (60%), latent (53%), neurosyphilis (34%) and tertiary syphilis (11%) and a very high specificity.
IgG antibodies appear during the acute period of the disease and can persist in cured patients for life.
The ELISA method is used to diagnose syphilis, differentiate false positive results obtained in MR, and monitor the effectiveness of treatment.