Differentiation of Late Latent Syphilis and False-Positive Serological Reactions: A Combination of ELISA and Discriminant Analysis.

The effectiveness of ELISA in combination with multivariate discriminant analysis (MDA) for differentiating late latent syphilis (LLS) and false positive reactions (FPR) for syphilis was assessed. ELISA was used to determine IgG levels in the sera of patients with confirmed LLS and FPR to five recombinant Treponema pallidum antigens: Tp319, Tp453, Tp684, Tp965, and Tp1038. The three most informative antigens Tp0453, Tp0684, and Tp1038 were identified by using stepwise discriminant analysis, and a discriminant function was constructed to distinguish the patient groups with LLS and FPR. The accuracy of differentiating the two nosologies was 90.3%. The Tp0684 antigen was the most substantial differentiating factor. The results demonstrate the promise of using a combination of ELISA and MDA to improve the diagnosis of latent forms of syphilis and reduce the frequency of erroneous interpretations of the serological tests.