Abstract:

Objective To investigate the performance and signal-to-cutoff（S/CO）ratio setting scheme for the detection of anti-Treponema pallidum（TP） antibody by chemiluminescence microparticle immunoassay （CMIA）. Methods Anti-TP antibody was detected in 116 patients by CMIA,which was confirmed by fluorescent treponemal antibody absorption test（FTA-ABS）. The results of FTA-ABS were used as gold standard. The performance of CMIA was evaluated by receiver operating characteristic（ROC） curve. Results There were 116 patients detected by CMIA,including 98 patients with S/CO>1.1 and 18 patients with S/CO≤1.1,of which 70 cases were positive,16 cases were weakly positive,and 30 cases were negative by FTA-ABS. The clinical diagnosis results were positive in 58 cases and negative in 58 cases. According to the FTA-ABS results,the area under curve of anti-TP antibody detected by CMIA was 0.885,and the Youden index was 0.757. The optimal cut-off value of anti-TP antibody S/CO ratio of CMIA was 3.66,the sensitivity was 95.7%,and the specificity was 80.0%. When the positive predictive value of anti-TP antibody detected by CMIA was ≥95%,the S/CO ratio was 4.25. According to the clinical diagnosis results,the area under curve of anti-TP antibody detected by CMIA was 0.944,and the Youden index was 0.764. The optimal cut-off value of anti-TP antibody S/CO ratio of CMIA was 4.25,the sensitivity was 87.9%,and the specificity was 88.5%. Conclusions CMIA has high sensitivity,no missed diagnosis and certain case misdiagnosis rate,so it is suitable for preliminary screening.

Key words: Anti-Treponema pallidum antibody, Chemiluminescence microparticle immunoassay, Treponema pallidum particle agglutination assay, Fluorescent treponemal antibody absorption test, Syphilis