Studies on the Detection of Serum Specific IgA and IgG Antibodies to C. trachomatis in the Diagnosis and Epidemiological Survey of Chlamydial Infection

We evaluated the clinical usefulness of serological procedures in the diagnosis of chlamydial infection by measuring serum specific IgA and IgG antibodies to C. trachomatis with indirect immunoperoxidase assay and ELISA, respectively.1. The positive rates of serum IgA and IgG antibodies were found to be 40.0% and 72.2% in the non-gonococcal urethritis patients (NGU) having C. trachomatis antigen, respectively. Of those without C. trachomatis antigen, the positive rates of IgA and IgG antibodies were 10.0% and 68.0%, respectively. The positive rate of IgA antibody was significantly higher (p < 0.01) in NGU with C. trachomatis antigen than in those without it. This result suggested that IgA antibody might be a good marker of active chlamydial infection in NGU.2. In pregnant women of the third trimester, the positive rates of IgA and IgG antibodies were 44.4% and 72.7% in those having C. trachomatis antigen, respectively, while 8.9% and 24.1%, were found in those without it. The positive rates of IgA and IgG antibodies were significantly higher (p < 0.01) in the former than the latter, which suggested that the detection of both IgA and IgG antibodies would be useful for the screening of chlamydial infection in pregnant women.3. The positive rate of IgA antibody was 30% in non-gonococcal cervicitis patients and prostitutes, weather there was the presence or absence of C. trachomatis antigen. In these cases, the usefulness of serological diagnosis seemed to be lessened, and therefore, the detection of C. trachomatis antigen must be repeated.4. In four pregnant women having C. trachomatis antigen at the first trimester of pregnancy and not receiving treatment during follow-up for the entire pregnant period, three showed the persistence of the antigen and positive antibodies. This result demonstrated that IgA antibody persisted with the antigen for a long period.