2020 Volume 69 Issue 3 Pages 323-328
The serological test for syphilis (STS) for the diagnosis of syphilis has recently been simplified with an automatic analyzer; however, the linearity of a high concentration range and the reduction of the prozone effect due to high concentrations of the target antigen in samples pose a problem. Here, we report the performance evaluation of Accuras-auto RPR, a new reagent-based latex agglutination turbidimetric assay, which eliminates these issues. The repeat accuracy was good. The dilution linearities determined using a high-RPR-concentration sample were 22.4 R.U. for Accuras-auto RPR and 8.1 R.U. for Mediace RPR. Evaluation of the prozone revealed a trend of decreasing RPR in both Accuras-auto RPR and Mediace RPR measurements. The addition of 3000 F.T.U resulted in 1.3 R.U. and 1.0 R.U. positive errors in Accuras-auto RPR and Mediace RPR, respectively, in the chyle sample. The detection limit of Accuras-auto RPR was 0.30 R.U. and that of Mediace RPR was 0.57 R.U. A confirmation test of the correlation using sera from 100 patients revealed that the judgment agreement rate was 93% (24 patients with positive results and 69 patients with negative results); the difference in results could be attributed to differences in reactivities. Accuras-auto RPR demonstrated an improved measurement range compared with the conventional reagent. Moreover, the prozone effect was mild, and thus, usage of Accuras-auto RPR could reduce the retest rate of high-RPR-concentration samples, and it is considered to be a useful reagent for a routine diagnostic test.
