Comparison of Three Commercially Available Peptide-Based Immunoglobulin G (IgG) and IgA Assays to Microimmunofluorescence Assay for Detection of Chlamydia trachomatis Antibodies

and 39%, respectively, for IgG and 7, 7, 3, and 7%, respectively, for IgA. The IgG seroprevalence rates for the PCR-positive women were two to three times higher than those for the PCR-negative women, i.e., 72 versus 29%, 72 versus 29%, 47 versus 26%, and 74 versus 25% for CT-EIA, SeroCT, CT pELISA, and the MIF assay, respectively. After discrepancy analysis, the sensitivity, specificity, positive predictive value, and negative predictive value were calculated for the IgG assays; for CT-EIA they were 84.7, 98.6, 98.4, and 86.7%, respectively; for CT pELISA they were 71.4, 97.3, 96.2, and 78.3%, respectively; for SeroCT they were 84.7, 98.6, 98.4, and 86.3%, respectively; and for the MIF assay they were 79.2, 83.1, 98.3, and 83.1%, respectively. In conclusion, these peptide-based ELISA systems for the serological detection of C. trachomatis infection performed as well as the MIF assay. Since these tests are less time-consuming, less expensive, and easier to perform than the MIF assay, they might be useful in the serodiagnosis of chlamydial infection. Chlamydia trachomatis infection is the most prevalent sexually transmitted disease in Europe and the United States. In women, this infection can lead to severe sequelae like ectopic pregnancy and tubal infertility. C. trachomatis serology has been used for both diagnostic purposes and large epidemiological studies. However, widespread introduction of C. trachomatis-specific serology has not gained wide acceptance. The microimmunofluorescence (MIF) assay (10) is still regarded as the “gold standard” in the serological diagnosis of C. trachomatis infections. However, the MIF assay is not suited for use by routine laboratories since reading of the specific fluorescence requires a high degree of expertise. Also, current serological tests employ either group-specific lipopolysaccharide (LPS) or reticulate bodies as antigen and thus show crossreactivity with C. pneumoniae (4). Serological cross-reactivity leads to high rates of false-positive results, especially in a population with a low prevalence of C. trachomatis infection, since the rates of C. pneumoniae seroprevalence are up to 60%. In addition, there have been reports on serological cross-reactivity due to proteins from other bacteria, e.g., Acinetobacter (2). Several user-friendly enzyme immunoassays with increased specificity have been developed by using LPS-stripped C. trachomatis particles (8). Recently, three commercially available assays have been developed by using specific synthetic peptides based on the major outer membrane of C. trachomatis. These assays have the potential to be both specific and sensitive. Proper comparison of these serological assays to the MIF assay is strongly needed since these new tests are well standardized, less expensive, and less laborious than MIF. Therefore, we analyzed these new commercially available, peptide-based enzyme-linked immunosorbent assay (ELISA) systems for the detection of specific serum immunoglobulin G (IgG) and IgA antibodies to C. trachomatis in relation to the detection of C. trachomatis infections in the corresponding cervical scrapings by PCR. The performances of these new assays were compared to that of the MIF assay.