Abstract: Objective To evaluate the specificity of antibodies（anti-TP） to Treponema pallidum detected by chemiluminescent microparticle immunoassay （CMIA）,and to analyze TP infection in the patients before blood transfusion. Methods CMIA was used to detect the anti-TP in 92 169 cases of pre-transfusion patients. The sera with initially positive anti-TP was then confirmed by T.Pallidum particle agglutination（TPPA）. Results 2 825 serum samples were anti-TP positive by CMIA. Among them,2 680 were confirmed to be positive by TPPA assay. Compared with the TPPA assay,the false positive rate of the CMIA was 0.16%,and the positive predictive value was 94.87%. In the samples with S/CO value between 1 and 2,the seroprevalence of anti-TP was 72.8%,while in the samples with S/CO value more than 5,the seroprevalence of anti-TP was 100% when tested with TPPA,showing a significant difference among all S/CO value groups（χ²=138.26,P<0.001）. The positive rate of anti-TP antibodies increased with age （χ²=353.69,P<0.001）,and was significantly higher in elderly people over 60 years（χ²=206.97,P<0.001） . The TP infection rate in females is much higher than that in males（χ²=4.86,P=0.027）. Conclusions A part of blood recipients before transfusion have TP infection. CMIA shows high sensitivity and useful for mass screening in detection of anti-TP,but low S/CO value indicates relatively high false positive TP infection . Finding anti-TP positive samples with TPPA is necessary,especially in low S/CO value. The positive rate of anti-TP increased with age,and the false positive rate was higher in the elderly,indicating that the positive results of syphilis test in this population should be cautiously treated.

Key words: Treponema pallidum antibody, Chemiluminescent microparticle immunoassay, Treponema pallidum particle assay