Chlamydia antibody testing in screening for tubal factor subfertility: the significance of IgG antibody decline over time

BACKGROUND: Chlamydia (C.) trachomatis antibody testing in screening for tubal factor subfertility is limited by false negative results, i.e. negative Chlamydia antibody tests in patients with tubal pathology at laparoscopy. The present study was performed to determine whether decline in C. trachomatis IgG antibodies over time is responsible for those false negative results. METHODS: A total of 39 women with an initial titre of greater than or equal to64 were re-studied after 4-7 years. A new serum sample was collected from each patient. The initial and the second serum sample were tested for C. trachomatis IgG antibodies using a micro-immunofluorescence assay (MIF). A species-specific enzyme-linked immunosorbent assay (ELISA) was used to validate the MIF test results. All patients filled out a questionnaire to determine risk factors for renewed C. trachomatis infection between the initial and second serum sample. RESULTS: Seven of the 39 patients (18.0%) showed a decline (>2 titre steps) in IgG antibodies by MIF over a period of 4-7 years, but IgG antibodies never became undetectable. In the 7/39 patients who showed a decline by MIF, signal/cut-off values by ELISA did not change. CONCLUSION: A decline in IgG antibody titre is not a significant cause of false negative Chlamydia antibody test results.