Serological tests for Chlamydia trachomatis infections.

In her review of the current methods of laboratory diagnosis of Chlamydia trachomatis infections, Black (1) reported that serologic tests were generally not useful in the diagnosis of genital tract infection caused by C. trachomatis and that the presence of immunoglobulin M (IgM) antibodies was an unreliable marker of acute infection in adolescents and adults. Chlamydial infections during pregnancy cause a variety of perinatal complications. Inclusion conjunctivitis, pneumonia, and other complications develop in neonates born to mothers infected with C. trachomatis. Delivery of low-birth-weight infants and premature rupture of membranes occurred more frequently in women infected with C. trachomatis. It also has been suggested that C. trachomatis infection in pregnant women may be related to premature labor and to perinatal death. Contrary to Black’s assertion, Gencay et al. (2) reported that the rates of IgM seropositivity for C. trachomatis during pregnancy were significantly higher in mothers who had given birth to infants with complications than in matched controls. The frequency of chorioamnionitis and meconium-stained amniotic fluid was also higher in the anti-C. trachomatis IgM antibodypositive pregnant women. However, in serological studies of C. trachomatis infections, the possibility of cross-reactivity with C. pneumoniae should be considered. We also reported that some babies born to IgG and IgA antibody-positive pregnant women had fetal and neonatal distress (3). Although Black (1) reported that the enzyme immunoassay (EIA) should be used only for serosurveys of high-risk populations or for the detection of IgM in infants with chlamydial pneumonitis, a commercially available EIA kit used in our study detected serum IgG, IgA, and IgM antibodies against C. trachomatis (3). Several investigators have reported that 2 to 20% of pregnant women harbor C. trachomatis in the endocervix. Pregnant women who carry C. trachomatis in their genital tracts may suffer from a general disturbance of immunoregulation. Although transmission of the organism from mothers to their infants generally occurs at the time of delivery with passage of the infant through the infected cervix, the possibility of intrauterine infection has been reported (5). Chorioamnionitis is a frequent finding in cases of prematurity and respiratory insufficiency in premature babies and may be attributable to intrauterine infection. Detection of C. trachomatis antigen from endocervical specimens has been used widely for the purpose of screening for chlamydial infections during pregnancy. These tests are easily performed and less costly than culture but have lower sensitivities and low positive predictive values in low-prevalence populations such as in Japan. However, we reported four infants who developed neonatal C. trachomatis infections and whose mothers had no detectable chlamydial antigens during pregnancy (4). The fact that neonates having the symptoms of chronic lung disease also manifest elevated serum IgM levels to C. trachomatis suggests that these respiratory tract disorders arise from infections during pregnancy (5). Early diagnosis and appropriate treatment of chlamydial infections may reduce these complications. Detection of serum antibodies to C. trachomatis during pregnancy also permits more laboratories to diagnose perinatal chlamydial infections and is also useful for screening for infection.