Validation of the INNO-LIA syphilis kit as a confirmatory assay for Treponema pallidum antibodies.

The commercially available diagnostic tests for syphilis are mostly based on the use of extracted antigens of Treponema pallidum. Pronounced cross-reactivities with other spirochete antigens are often reported. The aim of this study was to validate a novel multiparametric assay (the assay performed with the kit) INNO-LIA Syphilis for the confirmation of syphilis antibodies in a set of 840 documented human serum samples. All serum samples were previously tested at the French World Health Organization reference center for venereal diseases (Institute Alfred Fournier, Paris, France), with a consensus result provided for each sample. The study was conducted in two phases, with each phase involving a validation set (500 well-documented serum samples) and an exploratory set (340 serum samples) of serum samples, respectively. By measuring the sensitivity and specificity, we compared the result of the new assay with the consensus result on the basis of the results of a variable number of classical serological methods and clinical information when available. A sensitivity of 99.6% (95% confidence internal [CI], 98.5 to 99.9%) and a specificity of 99.5% (95% CI, 98.1 to 99.9%) were found for the new line immunoassay. Six of seven samples with indeterminate results by classical serology tested positive with the INNO-LIA Syphilis kit. This single multiparametric assay provides reliable confirmatory diagnostic information that must currently be obtained by the performance and interpretation of results of a combination of serological assays.