Testing of introital samples for chlamydia and trichomonas - adapted from the American Journal of Ob

Author: Barbara Apgar
Date: Nov 15, 1996

Chlamydia trachomatis and Trichomonas vaginalis are common sexually transmitted infections associated with adverse pregnancy outcome. Since patients are frequently asymptomatic, diagnosis on the basis of symptoms or physical findings is unreliable. If methods of sampling were available for patients to perform self-collection, more women might be screened and adequately treated. Witkin and associates compared the usefulness of introital and endocervical specimens in the detection of chlamydial and trichomonal infections.

Three hundred women were included in the study. In addition to the introital and endocervical specimens, specimens were obtained from the posterior vaginal vault in 219 patients. Introital specimens were obtained by briefly inserting a sterile Dacron swab just inside the introitus. Samples were tested by polymerase chain reaction (PCR).

Endocervical Chlamydia was detected in 36 of the women tested. All but one of these patients also had positive introital samples. None of the women with negative endocervical samples had positive introital samples. Specificity and sensitivity of the introital samples were 100 percent and 97.2 percent, respectively.

Vaginal trichomoniasis was present in 22 women. All but one of these women and none of the women with negative results on vaginal PCR testing yielded positive results. Compared with vaginal PCR, specificity and sensitivity of the introital specimens were 100 percent and 95.5 percent, respectively.

Results indicated that Chlamydia was present in 12 percent of the pregnant women and Trichomonas was present in 10 percent, underscoring the need for accurate screening of pregnant women during the prenatal course. The ability to detect these organisms at the introitus was probably related to the presence of sloughed Chlamydia-containing endocervical cells and viable or nonviable Trichomonas. Because PCR is highly sensitive, few organisms were necessary for detection. Results of this study demonstrate that testing from the introitus is nearly as sensitive as endocervical or posterior vaginal sampling and would prevent the need for speculum placement in high-risk conditions such as placenta previa and preterm rupture of the membranes.

Use of minimally invasive introital samples to detect Chlamydia and Trichomonas could facilitate more widespread testing. Patients could be instructed on proper collection technique. This would allow for community-based screening in populations with limited access to health care because of geographic, social or financial impediments. High-risk women or children reluctant to undergo speculum examination could also be adequately screened.

The authors conclude that PCR testing of introital specimens is highly sensitive and specific for the detection of Chlamydia and Trichomonas in pregnant women and thus provides an alternative for speculum examination in selected women in whom such-examination is risky or impossible to perform.

Witkin SS, et al. Detection of Chlamydia trachomatis and Trichomonas vaginalis by polymerase chain reaction in introital specimens from pregnant women. Am J Obstet Gynecol 1996;175:165-7.

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