Low correlation of serology with detection of Chlamydia trachomatis by ligase chain reaction and antigen E1A

The aim of the present study was to evaluate the diagnostic accuracy of serology by using new assays for the detection of gen us a nd species-specific IgG, IgM, IgA and secretory IgA antibody in female sex workers, Cervical swabs and first void urine (FVU) from 314 female sex workers were submitted to nucleic acid amplification by ligase chain reaction (LCx, Abbott). Concomittantly, blood samples were tested for the presence of IgG, IgM and IgA antibodies using a genus-specific assay (rELISA, Medac) and species-specific test (SeroCT, Orgenics). Chlamydia trachomatis infection was detected in a total of 30 (9.6%) female sex workers by LCR. With rELISA, seroprevalences for IgG, IgM, and IgA antibody to Chlamydia were 88.9%, 19.1% and 62.7%, respectively. IgG and IgA antibody prevalences against C. trachomatis (SeroCT) were 65.0% and 23.9%, respectively. In comparison to the positive LCR results obtained from cervical swab and/or FVU, the sensitivity of rELISA for Chlamydia IgG, IgA and IgM detection was 93.3%, 83.3% and 16.7%, respectively. With SeroCT, the sensitivity for C. trachomatis-specific IgG and IgA detection was 86.7% and 33.3%, respectively. The specificities of both serologic tests in comparison to LCR were very low. In conclusion, the correlation of serology with active C. trachomatis infection of the lower genital tract is very low. According to our results, serologic testing for Chlamydia can exclude active infection of the lower genital tract with a high reliability (greater than or equal to 95%). However, detection of C, trachomatis can only be reliably achieved by nucleic acid amplification assays.