[Analysis of positive results in mediace rapid plasma reagin and Treponema pallidum latex agglutination as the automated syphilis test].

BACKGROUND

We compared the results of automated and quantitative methods for the diagnosis of syphilis, Mediace Rapid Plasma Reagin (RPR) and Mediace Treponema pallidum Latex Agglutination (TPLA) (Sekisui Chemical Co., Ltd, Japan) with those of conventional methods.

METHODS

Sera from 3,896 persons who had health checkups between December 2005 and November 2006 were included in the evaluation of positive rates and biological false positives (BFP) for Mediace RPR and TPLA. In addition, 134 patients' sera positive for automated Mediace RPR or TPLA were tested for VDRL and TPHA. Discrepancies between TPLA and TPHA results were confirmed by the RecomBlot Treponemal IgG/IgM (Mikrogen GmbH, Germany). Automated Mediace RPR and TPLA were performed using the Hitachi 7600 chemistry autoanalyzer (Hitachi, Japan). Samples with positive Mediace RPR and negative TPLA results were defined as BFP.

RESULTS

Positive rate of automated Mediace RPR was 0.23% (9/3,896). BFP of the Mediace RPR was 0.18%. Positive rate of automated TPLA was 1.62% (37/2,284). Among the 134 patients' sera, 33 (24.6%) showed a discrepancy between conventional VDRL and automated Mediace RPR results: Among 31 Mediace RPR(+)/VDRL(-) sera, 13 were positive and 18 were negative for TPLA. The remaining 2 sera of discrepancy with Mediace RPR(-)/VDRL(+) were all positive for TPLA. There were seven sera that showed a discrepancy between automated TPLA and TPHA results: Two sera with Mediace RPR(+)/TPLA(-)/TPHA(+) showed negative recomBlot Treponemal IgG/IgM results, and among five sera with TPLA(+)/TPHA(-), three demonstrated IgG or IgM by recomBlot Treponemal IgG/IgM.

CONCLUSIONS

The results of comparison data demonstrated that automated TPLA results had a high concordance with recomBlot Treponemal IgG/IgM results. Moreover, there are additional advantages of automated methods such as quantitative detection, low infection risk, and no influence by human handling.