Objective:To investigate the correlation between the level of treponema pallidum specific antibodies(TPAb)and immunoglobulin A/E/M/G(IgA/E/M/G)and IgG subtypes in active syphilis patients,so as to provide a basis for the comprehensive di-agnosis and treatment and prognosis evaluation of clinical syphilis.Methods:Active syphilis patients admitted to the First Affiliated Hospital of Soochow University in 2023 were divided into 1∶4+and 1∶16+groups according to the syphilis toluidine red unheated se-rum test(TRUST),and healthy control group were selected for the detection of TPAb by chemiluminescence microparticle immunoas-say(CMIA).The contents of IgA/E/M/G and IgG1/2/3/4 were determined by immunoturbidimetry.Results:A total of 206 patients with active syphilis(125 males and 81 females)aged(46.05±19.58)years were included in this study.Compared with the healthy control group,IgG2 was decreased and TPAb,IgA/E/M/G and IgG1/3/4 levels were increased in the active syphilis group,with statistically significant differences in TPAb,IgE and IgG1/2/3 levels(P<0.05).Compared with the healthy control group,TRUST 1∶4+group had statistical differences in TPAb,IgE and IgG2,and TPAb was significantly correlated with IgE and IgG2/4.The levels of TPAb,IgA/E/M/G and IgG1/2/3 in TRUST 1∶16+group were statistically significant,and TPAb was significantly correlated with IgE and IgG4(P<0.05).In addition,there were significant differences in TPAb,IgG and IgG1/3 between the two positive groups(P<0.05).Conclu-sion:The levels of TPAb and Ig in active syphilis patients with different TRUST titers are significantly different.TPAb combined with Ig can be used to monitor the strength of syphilis activity,IgA/M/G and IgG1/3 may be candidate biomarkers.