ABSTRACT
Objective The emerging reverse sequence on syphilis screening program generates special discordant results,characterized with the appearance of both positive treponemal test and negative nontreponemal test at the same time.The aim of this study was to analyze the characteristics of the discordant results among low syphilis prevalence population in China,to provide evidence for improving the process of reverse sequence syphilis screening program.Methods Laboratory data was retrospectively analyzed,under reverse sequence screening algorithm selecting ELISA as the initial screening test for syphilis.All the screening reactive samples were tested by TPPA for confirmation and by quantitative TRUST for the reactivity of syphilis.Results 666 out of a total of 21 049 serum samples were reactive under the screening program.Among the 666 reactive samples,169 were reactive to TRUST.One in the 169 samples was confirmed negative on TPPA,and the faulse positive rate on ELISA was 0.6％ (1/169).In those 666 reactive samples,497 were nonreactive to TRUST.74 in the 497 samples were confirmed negative to TPPA,with faulse positive rate of ELISA as 14.9％ (74/497).In the group of 591 TPPA confirmed positive samples,the TRUST negative rate was found 71.6％ (423/591),significantly higher than the TRUST positive rate (chi-square test,x2=110.025,P=0.000).Conclusion Among the results fiom reverse sequence syphilis screening program,majority of the samples which showed positive treponemal antibody,would have negative nontreponemal antibody.We therefore recommended a more reasonable reverse sequence syphilis algorithm to be used.Faulse positivity could be eliminated if TPPA was performed on all screening reactive samples by ELISA a first and then followed by quantitative TRUST on samples that were TPPA confirmed as positive.
ABSTRACT
S1-M1-80 cells, derived from human colon carcinoma S1 cells, are mitoxantrone-selected ABCG2-overexpressing cells and are widely used in in vitro studies of multidrug resistance(MDR). In this study, S1-M1-80 cell xenografts were established to investigate whether the MDR phenotype and cell biological properties were maintained in vivo. Our results showed that the proliferation, cell cycle, and ABCG2 expression level in S1-M1-80 cells were similar to those in cells isolated from S1-M1-80 cell xenografts (named xS1-M1-80 cells). Consistently, xS1-M1-80 cells exhibited high levels of resistance to ABCG2 substrates such as mitoxantrone and topotecan, but remained sensitive to the non-ABCG2 substrate cisplatin. Furthermore, the specific ABCG2 inhibitor Ko143 potently sensitized xS1-M1-80 cells to mitoxantrone and topotecan. These results suggest that S1-M1-80 cell xenografts in nude mice retain their original cytological characteristics at 9 weeks. Thus, this model could serve as a good system for further investigation of ABCG2-mediated MDR.