Application of automatic chemiluminescent microparticle immunoassay in detection of Treponema pallidum specific antibodies

Shi Xiaolin; Wu Meihui

doi:10.3969/j.issn.1674-7151.2024.01.013

Abstract：Objective To investigate the clinical application of chemiluminescent microparticle immunoassay(CMIA)in the screening of Treponema pallidum specific antibodies,and to analyze the false positive rate and influencing factors.Methods A total of 11015 serum samples from physical examiners,outpatient visiters and inpatients in Weihai Second Hospital Affiliated to Qingdao University from January to July,2023 were collected.CMIA method was used for preliminary screening,and the positive samples with S/CO≥1 were re-examined using Treponema pallidum particle agglutination test(TPPA).TPPA was used as the confirmation method to compare the coincidence rate of CMIA with TPPA of different S/CO values.The receiver operater characteristic(ROC)curve was drawn and the area under ROC curve(AUC)was calculated to evaluate the predictive value of CMIA for syphilis using Graphpad Prism 9 software.The patients were divided into three groups according to age such as＜40 years old group(60 cases),40-65 years old group(55 cases)and＞65 years old group(26 cases),and the false positive rates of CMIA in each group were calculated.Results The positive rate of CMIA was 1.28%and that of TPPA was 1.07%.When S/CO value was 1-2,the false positive rate was 93.75%,and when S/CO value was＞10,the false positive rate was 1.00%.The AUC of CMIA was 0.973,95%confidence interval(95%CI)was 0.948-0.998,and the cut off value for detection of syphilis antibody by CMIA was 4.62.The sensitivity and specificity for diagnosis of syphilis were 93.2%and 91.3%.The false positive rates of CMIA in＜40 years old group,40-65 years old group and＞65 years old group were 18.33%(11/60),7.27%(4/55)and 44.44%(8/26),respectively.Conclusions CMIA has high sensitivity,high automation and high throughput,which could be used as a mass screening test for syphilis.However,CMIA has high false positive rate for pregnant women and elderly population,and it needs to be combined with TPPA to improve the accuracy of syphilis results.