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Self-collection of Vaginal Swabs for the Detection of Chlamydia, Gonorrhea, and Trichomoniasis: Opportunity to Encourage Sexually Transmitted Disease Testing Among Adolescents

WIESENFELD, HAROLD C. MD, CM; LOWRY, DONNA L. B. MD; HEINE, R. PHILLIPS MD; KROHN, MARIJANE A. PhD; BITTNER, HEATHER MD; KELLINGER, KATHLEEN CRNP; SHULTZ, MARYANN CRNP, AND; SWEET, RICHARD L. MD

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Abstract

SEXUALLY TRANSMITTED DISEASES (STDs) continue to represent a major public health concern despite aggressive STD control efforts during the last several decades. 1 In 1996, chlamydia and gonorrhea accounted for more than two thirds of all notifiable diseases in the United States. 2 Pelvic inflammatory disease, often a complication of chlamydial or gonococcal infections, is a major cause of reproductive morbidity, including infertility, ectopic pregnancy, and chronic pelvic pain. Trichomonas vaginalis is the most prevalent nonviral sexually transmitted pathogen, with an estimated 5 million cases each year. 3 In addition to lower genital tract symptoms, T vaginalis is associated with adverse pregnancy outcome, such as premature rupture of fetal membranes. 4 The recent evidence implicating STDs in facilitating HIV transmission has made the control of STDs an even higher priority. 5

The burden of STDs falls on adolescents. The highest reported rates of chlamydia and gonorrhea are among those between the ages of 15 and 24 years. 6 Although screening programs for many STDs are cost effective, compliance to undergo testing remains a major barrier, particularly among adolescents. 7 Compliance with standard STD testing by pelvic examination is hampered by a fear of an uncomfortable examination, mistrust of healthcare providers, loss of privacy and, particularly among adolescents, a sense of invulnerability and denial of being at risk for STDs. 8

Despite the recent availability of highly sensitive diagnostic tests and single-dose therapy, most STDs are undetected and untreated. 1 Noninvasive strategies for specimen collection using DNA-amplification testing provide the opportunity to overcome many barriers to STD screening. We and others have previously demonstrated that polymerase chain reaction (PCR) and ligase chain reaction amplification of noninvasive specimens, such as self-collected distal vaginal swabs or urine, is an effective strategy for the detection of chlamydia, gonorrhea, and trichomoniasis. 9–12 Although urine samples are easy to obtain, drawbacks of using this method include the requirement of a large sample volume, maintenance of refrigeration during transport, and the risk of spillage. We undertook this study to evaluate the feasibility of self-collection of distal vaginal swabs to detect the three most common and treatable sexually transmitted infections (i.e., chlamydia, gonorrhea, and trichomoniasis) among female high-school students attending school-based health clinics.

Methods

This Institutional Review Board-approved study took place in the student health centers of two public high schools in Pittsburgh, PA, from 1997 to 1998. The student health centers are staffed by nurse practitioners and provide a wide variety of medical services, such as sick visits, sports physicals, routine examinations, STD testing, and psychological counseling. All students between 13 and 19 years attending the student health centers were eligible for participation, regardless of their reason for seeking care and recent sexual activity. Upon arrival to the clinic, students were approached to enroll by the health center staff and informed consent was obtained. Each participant completed a brief medical questionnaire in private to facilitate honest responses. Multiple-choice questions were presented concerning demographic information, reason for visit, history of STDs, STD risk factors (e.g., number of partners, new sexual partners, frequency of intercourse, barrier contraception use), and current gynecologic symptoms. Participants were then given a PCR collection kit (Amplicor C trachomatis Test, Roche Diagnostics, Branchburg, NJ). A simple diagram showing the collection technique was provided, and instructed participants to insert a single swab 1 inch into the vagina, rotate the swab for 20 seconds, and then place it into PCR transport fluid. Specimens were then refrigerated at 4 °C and shipped to the research laboratory twice weekly, where they were immediately frozen and later run in batch. After specimen collection, participants were given a second multiple-choice questionnaire about their attitudes concerning the self-collection technique. In particular, we asked whether the self-collected swab was easy to perform, if they prefer this approach to a pelvic examination, and if they would test themselves more often if self-collected sampling was widely available. To ensure confidentiality of participant identification, subjects were assigned a unique identification number for use on the questionnaire and laboratory specimens.

Polymerase chain reaction testing for C trachomatis was performed according to manufacturer’s recommendations using 50 μl processed sample (Roche Molecular Systems). Specimens with equivocal results were reamplified and considered positive if the second amplification result was positive. Five specimens were initially equivocal, and all five results were resolved as negative. N gonorrhoeae PCR (Roche Molecular Systems) was performed using up to 100 μl processed sample. A modified Cobas Amplicor N gonorrhoeae test amplifying the cytosine methyltransferase gene was carried out following a previously published protocol. 13 All positive results were confirmed as positive by performing a second amplification assay using the 16S rRNA gene as target. The presence of T vaginalis was determined by PCR amplification targeting a 102-bp fragment within the ferredoxin gene. Twenty-five microliters of each vaginal sample were added to an equivalent volume of master mix containing oligonucleotides (200 μM each of dATP, dCTP, dGTP, and dUTP), 0.25 μM each of TVA5 and TVA6 trichomonas-specific primers targeting the ferodoxin gene, Taq polymerase, uracil N-glycosylase, and 4.5 nm fluorogenic TaqMan-labeled probe with a sequence that was internal to the primer pair. 14 The specimens were then amplified in a thermocycler for 40 cycles, and were subsequently placed in a spectrometer to measure fluorescence. Equivocal specimens were rerun in duplicate, and if still equivocal would be analyzed by Southern blot for the presence of the amplified 102-bp fragment. Three specimens were rerun after initially testing equivocal for T vaginalis, and were ultimately deemed negative. This PCR assay for T vaginalis is highly sensitive and specific when compared with culture (Jeanne Jordan PhD, personal communication, 2000). In a previous study, we demonstrated a 91.8% sensitivity of PCR for T vaginalis on distal vaginal samples. 10

Categoric variables were analyzed using chi-square analysis or Fisher exact test, where appropriate. Variables that were significant by chi-square analysis were modeled by multivariable, binary, unmatched logistic regression. Odds ratios and 95% confidence limits are presented to assess the strength of the association, present estimates of association controlled for confounding variables, and determine statistical significance. Odds ratios are presented as pointed estimates of relative risks because of the high frequency of some of the outcomes studied.

Results

We enrolled 228 adolescent females with a median age of 16 years and nearly equal numbers from grades 9 to 12. The ethnic background of our population was evenly divided between blacks (46%) and whites (47%). Most participants were being seen in the health clinic for concerns other that were not gynecologic or STD related, such as sports injury, headache, and viral illnesses. Approximately 75% of students who were advised of the study by a health center worker agreed to participate. Only 41% of students presented to the centers requesting to be tested for STDs, mostly responding to study advertisements placed in school bathrooms indicating the importance of STD screening and offering participation in this study. One hundred and sixteen participants (51%) reported a gynecologic symptom (e.g., lower abdominal pain, vaginal discharge, dysuria) but only 3% believed that they may have been infected with an STD.

Forty-three percent of the females reported that they had never had a gynecologic examination, and one half of students (51%) had never previously been tested for STDs. A prior history of an STD was present in 14% of participants, with chlamydia, gonorrhea and trichomoniasis reported by 22 (10%), seven (3%), and 11 (5%) participants, respectively. One subject reported being infected with HIV.

Sexual activity was common among participants, with 206 (90%) reporting a history of sexual intercourse. The mean age of onset of sexual activity was 14.4 years, and the median lifetime number of sexual partners was two. Having multiple sexual partners was common among the sexually active youth; 25% and 46% reported at least two sexual partners in the preceding 3 months and 1 year, respectively, and 67% reported at least two lifetime sexual partners. A majority of students (169/209, 81%) responded that they had ever used condoms, but only 57% reported that they used a condom the last time they participated in sexual intercourse. Inconsistent condom use, which was defined as failing to use condoms during all episodes of intercourse, was reported by 66% of students.

Forty (18%) participants tested positive for C trachomatis, N gonorrhoeae, or T vaginalis. Chlamydia was diagnosed in 18 women (8%), trichomoniasis in 23 (10%), and four women (2%) were positive for gonorrhea. By univariate analysis, testing positive for an STD was associated with a prior history of chlamydia, recent sexual activity (within the last month), age at first intercourse ≤ 13 years and was more common among blacks (Table 1). Following multivariable analysis, prior history of chlamydia, and sexual activity within the last month remained significantly associated with testing positive for an STD (Table 2). Testing positive for an STD was not associated with the presence of symptoms, inconsistent condom use, or age. Similarly, participants seeking care for STDs (symptomatic and asymptomatic) had a similar rate of STDs as those who presented to the clinics for other reasons (15.6% versus 18.8%, P = NS).

Table 1
Table 1:
Factors Associated With Testing Positive for an STD*
Table 2
Table 2:
Predictors of Testing Positive for an STD by Multivariable Logistic Regression*

Nearly 13% of adolescents who had never previously had a gynecologic examination tested positive for an STD. Among those infected, 87% did not think that they currently had an STD, and half (51%) would not have sought STD testing if this study was not offered. Thirty-two percent of infected women had never previously had a pelvic examination. Self-collection of distal vaginal swabs was reported as easy to perform by almost all participants (99%), and 83% of the 113 subjects who previously had a gynecologic examination preferred the method to a standard gynecologic evaluation. Nearly all participants (97%) stated that they would test themselves more often if self-testing were widely and easily available.

Discussion

Current STD-control efforts are hampered by barriers to the delivery of quality health care to those at risk for STDs. Obstacles exist at the individual, provider, and community levels regarding the access and delivery of health care. 15 Once the individual has recognized the need to seek care, the decision whether and where to do so is often influenced by fear of undergoing a painful examination, concerns of confidentiality, and the stigma associated with STDs. 8,16,17 Moreover, the delivery of quality STD care to women currently requires a knowledgeable provider skilled in the performance of a gynecologic examination. Noninvasive STD testing has provided a means to overcome some of the aforementioned barriers to STD care by eliminating the need for a skilled provider and a potentially painful and embarrassing pelvic examination. In a clinic setting, noninvasive testing would still require that healthcare practitioners recognize the need for STD screening. Both urine and distal vaginal swab samples assayed using new DNA-amplification technologies, such as PCR and ligase chain reaction, have been shown to be highly sensitive and specific for detecting C trachomatis and N gonorrhoeae, and are ideal for self-collected STD testing. 9–11

We have shown that in a high-school population, noninvasive testing using self-collection of a single vaginal swab enhances the detection of the three most common treatable STDs. The availability of noninvasive testing more than doubled the number of students who underwent STD testing. One half of the participants had not previously been tested for STDs, and more than 40% had yet to undergo a gynecologic examination. Importantly, 12.6% of those students who never had a gynecologic examination were infected with either chlamydia, gonorrhea, or trichomoniasis. Denial of being infected with an STD is a large component in the reluctance to undergo testing among at-risk youth. In our population, nearly all (97%) participants did not think that they were infected with an STD, and while most adolescents in this study would not have undergone testing outside of this study, 18% tested positive for an STD. The results of this study show that providing a simple painless test that is performed in privacy may further encourage STD screening among adolescents.

Our results confirm those other studies showing that STDs are common and often asymptomatic in women. 18 The detection of these silent infections is the key to reducing their reproductive sequelae and limiting their spread. Comprehensive screening for chlamydia within a health-maintenance organization has been linked to a reduction in subsequent cases of pelvic inflammatory disease. 19 Although efforts to improve STD screening among women receiving preventive health care are important, only a fraction of STDs will be detected by this strategy because less than half of at-risk youth seek routine preventive health services. 20 As such, other approaches that bypass the standard outpatient visit are needed to detect STDs among noncompliant populations. Bringing novel nonconventional screening strategies to the communities at-risk for STDs, and thereby eliminating many barriers associated with seeking health care, are needed to enhance STD control efforts.

This study illustrates the acceptance of self-collected swabs from the distal vagina for STD testing among adolescents. Urine sampling is also noninvasive, and although simple to collect, this method involves a large sample volume, risk of spillage during transport, and the requirement to maintain refrigeration from the time of collection to laboratory processing. Swab samples are more stable at room temperature and are more suitable for community-based screening. Moreover, use of vaginal swabs eliminates the fear of drug testing that may preclude widespread use of urine samples among substance abusers, a group at high risk for STDs. 21

Many screening programs use risk factors to restrict costly testing to those with the greatest likelihood of being infected with an STD. In our cohort, factors associated with being infected with an STD included a prior history of chlamydial infection and sexual activity within the last month. Despite these associated risk factors, 13.7% of our cohort without a history of chlamydia and 6.7% of those not participating in sexual intercourse within the preceding month were infected with an STD. Our study supports the recommendations of the US Preventive Services Task Force to routinely screen all at-risk adolescents. 22

The use of self-collected swabs from the distal vagina for STD testing can be easily implemented in a high-school setting where it is widely accepted by students. This strategy enabled screening of adolescents who may not have otherwise undergone testing. With one swab we were able to test students for chlamydia, gonorrhea, and trichomoniasis—the three most prevalent treatable STDs in the United States. Using novel strategies for STD testing, particularly among historically noncompliant yet at-risk adolescent populations, may ultimately have an important impact on the control of STDs.

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