University of Michigan
Department of Pediatrics
Evidence-Based Pediatrics Web Site

Question

• Does PCR on a swab of the vaginal introitus have better diagnostic yield than standard cervical specimens obtained by pelvic exam?

Clinical Bottom Lines

1. PCR on vaginal introitus swabs has better sensitivity for detecting genital chlamydia infections in women than PCR or culture on standard cervical swabs, and far outperforms PCR or cultures obtained from urine or urethral swabs.
2. Self-collected specimens from the vaginal intoitus showed lower sensitivity than health care worker collected specimens (81% vs. 92%).
3. PCR on first 5cc of clean catch urine specimen yielded only 73% sensitivity.
4. This represents a highly effective non-invasive collection site, potentially eliminating the need for speculum exam; but there may be significant ramifications in terms of missed opportunities for performing comprehensive exams.

Summary of Key Evidence

1. Study consisting of n=300 women presenting to County Health Department STD clinic in Pittsburgh, PA.²
2. All women underwent swab sampling of vaginal introitus, urethra, and cervix for PCR, EIA and culture. First 5cc of clean catch specimen used for urine PCR.
3. n=200 women instructed on self-collection of urine and vaginal introitus specimens.
4. Study used an expanded gold standard – any positive culture or PCR. If culture was negative but PCR positive from any site, an alternate PCR probe was used to confirm positivity.
5. Prevalence of chlamydia in this population was 37/300 patients (12.3%).
6. PCR on cervical specimens showed sensitivity of 86% vs. 84% by culture and 68% by EIA.  PCR on urethral specimens showed 75% sensitivity vs. 54% by culture. PCR on vaginal introitus specimen showed sensitivity of 92%.
7. In the n=200 sub-population performing self-collection techniques, PCR on introitus specimens yielded sensitivity of only 81%, and on clean-catch urine – 73%.

Additional Comments

• Lower yield of self-collected specimens is likely technique related as women were unmonitored during collection.
• Authors comment on the potential for anonymous mail-in testing but this has significant implications in terms of missed opportunities for obtaining comprehensive exam with pap smear and inspection for other genital infections/abnormalities in a population which is at high risk.

Citation

1. The vaginal introitus: A novel site for chlamydia trachomatis testing in women.  American Journal of Obstetric Gynecololgy 1996; 174: 1542-1546.

CAT Author: Michael Gill, MD, PhD

CAT Appraisers: John G. Frohna, MD

Date appraised: April 17, 2000