How Much Tubal Factor Infertility Is Caused by Chlamydia? Estimates Based on Serological Evidence Corrected for Sensitivity and Specificity

To estimate the proportion of tubal factor infertility (TFI) caused by Chlamydia trachomatis (CT), the etiologic fraction, from a retrospective study of CT antibody prevalence in TFI cases and controls, adjusted for sensitivity and specificity. Methods: We use published data on sensitivity and specificity to estimate the performance of assays in (a) women with a previous CT infection without sequelae and (b) women with TFI caused by CT. A model was developed and applied to antibody prevalence in TFI cases and controls from 1 published case-control study to estimate the proportion of TFI caused by CT. Results: The proportion of TFI episodes that were due to CT infection was estimated to be 45% (credible intervals: 28%, 62%). Models which assume that test sensitivity is higher in women with CT-related TFI than women with previous infection and no sequelae fit the data significantly better than models that assume the same sensitivity in all those previously infected. Conclusions: Greater attention needs to be paid to methods for characterizing the performance of CT antibody tests. Serological studies could be given a greater role both in CT etiology and in monitoring the effects of prevention and control programmes.