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Syphilis: Immunofluorescence reaction
Last reviewed: 19.10.2021
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Treponemal antibodies of IgG class in serum do not normally determine.
The reaction of immunofluorescence (FTA-ABS IgG) is referred to as treponemal tests of syphilis diagnosis, it allows to detect specific treponemal AT-class IgG in the blood. Sensitivity and specificity of the test for primary syphilis are 85% and 97% respectively, in the secondary case 99% and 97%, in the late 95% and 97%, in the latent 95% and 97%. FTA-ABS IgG is used to confirm the diagnosis, if there is a suspicion of late syphilis of any type, it is necessary to carry out this test even in the case when MR is negative. Antibody titers in the RIF do not correlate with the clinical activity of the disease and remain elevated indefinitely for 95% of patients, reflecting the presence of infection in the past. FTA-ABS IgG is not used to evaluate ongoing treatment, as the test remains positive for 2 years after adequate treatment in 80% of cases of seropositive early syphilis. Currently, the FTA-ABS IgG test is not recommended for the diagnosis of congenital syphilis in newborns.