Syphilis serology: Seroprevalence in a selected population and considerations on the Euroline WB test

Introduction: The clinical diagnosis of syphilis is always supported by appropriate laboratory tests and the test results are interpreted with reference to the patient’s history. In the diagnosis of syphilis, the use of tests based on antibody search that recognize both treponemal and reaginic antigens increases the diagnostic chances. Our study discusses the various serological and alternative tests currently available along with their limitations, and relates their results to the likely corresponding clinical stage of the disease. Methods: in our laboratory were analyzed 264 sera and 4 liquor (123 Females, 145 Males). 187 patients are subject at low risk for luetic infection, including pregnant woman, patient with organ transplant, outpatients or hospitalized undergoing routine serological, and 81 from patients with confirmed syphilis including 4 pregnant women in antibiotic treatment, patients with suspected disease, HIV positive and patients with autoimmune diseases with Cardiolipin positive. All sera were tested with ELISA Anti-Treponema pallidum Screen (IgG / IgM) and in parallel with agglutination tests VDRL and TPHA. On all positive sera was tested Euroline-WB EUROIMMUN and reading done with the program EuroLineScan. Results: by ELISA Anti-Treponema pallidum Screen IgG / IgM 162 sera were negative and 106 sera positive (39.5%), distributed as follows: 45 (42%) with a value greater than 200 RU / ml, 43 (41% ) with a value> 22 RU / ml and 18 (17%) with a borderline value between> 16 to <22 RU / ml. The execution of the Blot IgG showed: 18 negative sera, 6 with borderline value with one only band of specific antigens (p15, p45, p47 or p17), while 82, including 4 liquor (neurolue), were certainly positive showing more than one band antibody to the treponemal antigens. Only one patient had in place at the time of screening, an initial infection; in fact, there was a single clear positivity in the IgM protein bands, while 7 sera was uncertain values. It is reported 11 positivity for IgM Cardiolipin, while Cardiolipin IgG was detected with a high positivity in 34 sera. The presence of borderline values and / or positivity for a single protein band can be attributed to a unspecific reaction caused by autoimmune diseases or related cross-reactions with other Spirochete or to other Borrelia. Conclusions: The immunoblot test gave useful information at epidemiological and clinical level. The deepening with a confirmation test with proteic antigens and cardiolipin identifies false reactivity, but also indicates the specific reactivity to past infection and a better characteriation in the different stages of disease. In our study in the latent forms there are relevant discrepancies among the various tests. Compare to traditional methods, anti-cardiolipin antibodies positivity in our confirmatory test has the advantage of providing non subjective interpretation, being based upon the EuroLineScan program.