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

Price, Malcolm J. PhD*; Ades, AE PhD*; Welton, Nicky J. PhD*; Macleod, John PhD*; Turner, Katy PhD*; Simms, Ian PhD; Horner, Paddy J. MD*,‡

doi: 10.1097/OLQ.0b013e3182572475
Original Study

Objectives: 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.


From the *School of Social and Community Medicine, University of Bristol, Bristol, United Kingdom; Health Protection Agency, Colindale, London, United Kingdom; and Bristol Sexual Health Centre, University Hospital Bristol NHS Foundation Trust, Bristol, United Kingdom

The authors thank Dr. Kate Soldan for providing expert advice during the project and commenting on the manuscript.

Conflicts of interest and sources of funding: Supported by a UK Medical Research Council Grant (G0801947).

Correspondence: Malcolm Price, PhD, Canynge Hall, 39 Whatley rd, Bristol, BS8 2PS, United Kingdom. E-mail:

Received for publication October 10, 2011, and accepted January 21, 2012.

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© Copyright 2012 American Sexually Transmitted Diseases Association