Optimal methods for collecting and storing vaginal specimens for prostate-specific antigen testing in research studies

Validity of Partner Reports of Recent Condomless Sex

BACKGROUND

Prostate-specific antigen (PSA), a biomarker of vaginal semen exposure, is less susceptible to bias than self-reported condom use behaviors. We examined the agreement of self-reported recent condomless sex (RCS) within couples and how these reports related to PSA detection.

METHODS

We analyzed data from a study conducted in Vietnam, 2017 to 2020, of 500 different-sex couples using condoms and no other contraceptive method to prevent pregnancy for 6 months. We assessed enrollment and 6-month data from vaginal swabs and questionnaires from both partners. We calculated Prevalence-Adjusted Bias-Adjusted Kappa (PABAK) to evaluate agreement of men's and women's reports. Among couples with detected PSA, we assessed partner concordance of RCS reporting.

RESULTS

At enrollment (n = 499), 79.8% of couples reported no RCS, 16.4% reported RCS, and 3.8% had partner-discordant reports (PABAK, 0.93; 95% confidence interval, 0.91-0.97). At 6 months (n = 472), 91.7% reported no RCS, 5.7% reported RCS, and 2.5% had partner-discordant reports (PABAK, 0.98; 95% confidence interval, 0.96-1.0). Among couples with detected PSA at baseline (11%, n = 55), 36% reported no RCS, 55% reported RCS, and 6% had discordant reports; at 6 months (6.6%, n = 31), 58% reported no RCS, 35% reported RCS, and 3% had discordant reports.

CONCLUSIONS

We observed high agreement regarding condomless sex within couples in a population using condoms as contraception in Vietnam; however, a high proportion of couples with detected PSA had both partners reporting no RCS, indicating that concordant reporting of no RCS does not indicate lack of semen exposure.

Effectiveness of erectogenic condom against semen exposure among women in Vietnam: Randomized controlled trial

A key barrier to the consistent use of condoms is their negative effect on sexual pleasure. Although sexual pleasure is a primary motivation for engaging in sex and is an integral part of overall sexual health, most programs to improve sexual health operate within a pregnancy and disease-prevention paradigm. A new condom, CSD500 (Futura Medical Developments; Surrey, UK), containing an erectogenic drug was developed for use among healthy couples to improve sexual pleasure by increasing penile firmness, size and erection duration. We conducted a randomized controlled trial to test whether promoting the novel condom CSD500 for improved sexual pleasure is effective in reducing condomless sex compared to the provision of standard condoms with counseling for pregnancy and disease prevention. We randomized 500 adult, heterosexual, monogamous couples in Thanh Hoa province, Vietnam to receive either CSD500 (n = 248) or standard condoms (n = 252). At enrollment and after 2, 4, and 6 months, we interviewed women and sampled vaginal fluid to test for the presence of prostate-specific antigen (PSA), an objective, biological marker of recent semen exposure. We registered the protocol before trial initiation at ClinicalTrials.gov (identifier: NCT02934620). Overall, 11.0% of women were PSA positive at enrollment. The proportion of follow-up visits with PSA-positivity did not differ between the intervention (6.8%) and control arms (6.7%; relative risk, 1.01; 95% confidence interval, 0.66–1.54). Thus, we found no evidence that promoting an erectogenic condom to women in a monogamous, heterosexual relationship in Vietnam reduced their exposure to their partner’s semen. These findings might not hold for other populations, especially those with a higher frequency of condomless sex.

Prostate-specific antigen concentration in vaginal fluid after exposure to semen

OBJECTIVE

Prostate-specific antigen (PSA) is the best established biomarker of semen exposure. PSA in vaginal fluid returns to pre-exposure concentrations within 24-48 h, but the speed of decay during the first 10 h is unknown. We sought to determine how fast PSA concentrations decline during the first 10 h after exposure to semen.

STUDY DESIGN

Women in the 50 enrolled couples were intravaginally inoculated with 10, 20, 100 and 200 μl of their partner's semen and then collected vaginal swabs immediately after, 30 min, 4 h and 10 h after exposure. Forty-seven sets of samples were tested for PSA. Mixed linear models for repeated measures examined the association between log-transformed PSA values and sampling time and semen exposure volume. Sensitivity analyses excluded data from nonabstainers. Fixed-effect estimates from the statistical models were graphed.

RESULTS

PSA values were highest at 200 μl inoculation volumes and at earlier post-exposure time points, then decline steadily. The lowest inoculation volume (10 μl) corresponded to the smallest concentration of PSA throughout the post-inoculation time points. Average PSA levels return to clinically non-detectable levels within 10 h only at the lowest semen exposures. The PSA decay curve assumes a very similar profile across all time points and semen amounts.

CONCLUSIONS

The PSA decay curve is similar for varying semen exposure volumes, with average PSA concentrations remaining above clinical thresholds 10 h after exposure at all except the very smallest semen exposure levels. PSA is an objective marker of recent exposure to semen, permitting such detection with high accuracy.

IMPLICATIONS

This study clarifies how PSA values vary at different semen exposure levels and time points during the first 10 h post-exposure. Future contraceptive studies that use PSA as a semen biomarker will be better informed about PSA concentrations at different sampling times and exposure amounts.

Vaginal Prostate Specific Antigen (PSA) Is a Useful Biomarker of Semen Exposure Among HIV-Infected Ugandan Women

The practical feasibility of using prostate specific antigen (PSA) as a biomarker of semen exposure was examined among HIV-infected Ugandan women. Vaginal fluids were obtained with self-collected swabs and a qualitative rapid test (ABAcard^®p30) was used to detect PSA. Trained laboratory technicians processed samples on-site and positive PSA tests were compared to self-reported unprotected vaginal sex (UVS) in the last 48 h. A total of 77 women submitted 126 samples for PSA testing at up to three study visits. Of these samples, 31 % (n = 39/126) were PSA positive, and 64 % (n = 25/39) of the positive PSA samples were accompanied by self-report of no UVS at the study visit the PSA was collected. There were no reported difficulties with specimen collection, storage, or processing. These findings provide preliminary data on high levels of misreported UVS among HIV-infected Ugandan women using practically feasible methods for PSA collection and processing.

Recent Biomarker-Confirmed Unprotected Vaginal Sex, But Not Self-reported Unprotected Sex, Is Associated With Recurrent Bacterial Vaginosis

BACKGROUND

Self-reported unprotected vaginal sex seems to increase risk of bacterial vaginosis (BV). However, the validity of self-reports is questionable, given their inconsistency with more objective measures of recent semen exposure such as detection of prostate-specific antigen (PSA). We examined whether recent unprotected sex, as measured both by PSA detection on vaginal swabs and by self-report, was associated with increased BV recurrence.

METHODS

We analyzed randomized trial data from nonpregnant, BV-positive adult women recruited from a sexually transmitted disease clinic. Participants received BV therapy at enrollment and were scheduled to return after 4, 12, and 24 weeks. Bacterial vaginosis (by Nugent score) and PSA were measured at each visit. We used Cox proportional hazards models to examine the association between PSA positivity and recurrent BV. We also evaluated associations between self-reported unprotected sex (ever/never since the last visit and in the last 48 hours, analyzed separately) and recurrent BV.

RESULTS

Prostate-specific antigen and BV results were available for 96 women who contributed 226 follow-up visits. Prostate-specific antigen positivity was associated with increased BV recurrence (adjusted hazard ratio [aHR], 2.32; 95% confidence interval [CI], 1.28-4.21). In contrast, we observed no significant increase in BV recurrence among women self-reporting unprotected sex since the last visit (aHR, 1.63; 95% CI, 0.77-3.43) or in the last 48 hours (aHR, 1.28; 95% CI, 0.70-2.36).

CONCLUSIONS

Estimates from earlier studies linking self-reported unprotected sex and BV may be biased by misclassification. Biomarkers can improve measurement of unprotected sex, a critical exposure variable in sexual health research.

The Stability of Prostate-Specific Antigen in Semen Under Various Temperatures

Prostate-specific antigen (PSA) is most commonly used for identifying semen, especially in the absence of sperm. However, PSA concentration varies according to storage temperature and duration, and little is known about its stability in semen. This study was therefore aimed to determine the stability under five different temperatures: -80, -20, 4, 25, and 37°C; and nine different durations: 1, 2, 3, 5, 7, 14, 30, 90, and 180 days. All samples were stored at -80°C after being secreted from the volunteers' body until analyzed. Results showed that the PSA concentration declined significantly over time under all temperatures studied except -80°C. At -20 and 4°C, PSA was still detectable on Day 180 with 50% and 70% decrease from its original concentration, respectively. At 25 and 37°C, PSA was detected up to Day 7 and 3, respectively. This information might assist forensic scientists understand more about PSA nature and integrate it into their works.

Effects of initiating a contraceptive implant on subsequent condom use: A randomized controlled trial

OBJECTIVE

To evaluate whether initiation of a contraceptive implant, a method of long-acting reversible contraception, reduces condom use, as measured by a biomarker of recent semen exposure [prostate-specific antigen (PSA)].

STUDY DESIGN

We conducted a randomized controlled clinical trial in which 414 Jamaican women at high risk for sexually transmitted infections (STIs) attending family planning clinics received the contraceptive implant at baseline ("immediate" insertion arm, N=208) or at the end ("delayed" insertion arm, N=206) of a 3-month study period. Participants were tested for PSA at baseline and two follow-up study visits and were asked about their sexual activity and condom use.

RESULTS

At baseline, 24.9% of women tested positive for PSA. At both follow-up visits, the prevalence of PSA detection did not significantly differ between the immediate versus delayed insertion arm [1-month: 26.1% vs. 20.2%, prevalence ratio (PR)=1.3, 95% confidence interval (CI)=0.9-1.9; 3-month: 25.6% vs. 23.1%, PR= 1.1, 95% CI=0.8-1.6]. The change in PSA positivity over the three study visits was not significantly larger in the immediate arm compared to the delayed arm (1-sided p-value of .15).

CONCLUSIONS

Contraceptive implants can be successfully introduced into a population at high risk of unintended pregnancy and STIs without a biologically detectable difference in unprotected sex in the short term. This information strengthens the evidence to support promotion of implants in such populations and can help refine counseling for promoting and maintaining use of condoms among women who choose to use implants.

IMPLICATIONS

Sex unprotected by a condom was not higher over 3 months in women receiving a contraceptive implant, compared with those not receiving the implant.

The use of biomarkers of semen exposure in sexual and reproductive health studies

Biomarkers of semen exposure have been used in studies investigating the safety and efficacy of barrier methods of contraception. They have been used as objective indicators of semen exposure when studying sexual behaviors and in human immunodeficiency virus/sexually transmitted infection research interventions where participants are advised to avoid unprotected sex. Semen biomarkers have also been used to assess or validate self-reported sexual behaviors or condom use in reproductive health settings. Prostate-specific antigen (PSA) and Y chromosome DNA (Yc-DNA) have each been evaluated in the past as semen biomarkers and are the most widely used in the field. While both are considered reliable for evaluating exposure to semen, each has unique characteristics. In this report, we summarize the literature and provide some considerations for reproductive health researchers who are interested in using PSA or Yc-DNA as semen biomarkers. We also synthesize our previous published work on the optimal conditions of collecting and storing specimens and assay performance in the presence of other vaginal products that may influence various assays. Semen biomarkers are innovative and promising tools to further study and better understand women's reproductive and sexual health and behavior. More research is needed to better understand the strengths, limitations, and optimal performance conditions of specific assays in vivo.

Biological markers of sexual activity: tools for improving measurement in HIV/sexually transmitted infection prevention research

Research on interventions to prevent HIV and other sexually transmitted infections (STIs) is heavily influenced by participant reporting of sexual behavior, despite uncertainty about its validity. Exclusive reliance on participant self-report often is based, overtly or by implication, on 4 assumptions: (1) no feasible alternatives exist; (2) misreporting can be minimized to levels that can be disregarded; (3) misreporting tends to underreport sensitive behaviors; and (4) misreporting tends to be nondifferential with respect to the groups being compared. The objective of this review are to evaluate these assumptions, including a review of studies using semen biomarkers to evaluate the validity of self-reported data, and to make recommendations for applying biological markers of semen exposure detectable in women to further strengthen research on HIV/STI prevention. Increasing evidence shows that semen biomarkers provide an important means of assessing and augmenting the validity of studies on HIV/STI prevention. Additional biomarkers are needed to assess male exposure to vaginal sex and both male and female exposure to anal sex. Methods and study designs that incorporate biomarkers into studies collecting self-reported behavioral data should be considered where possible.

Detection of two biological markers of intercourse: prostate-specific antigen and Y-chromosomal DNA

BACKGROUND

Although biological markers of women's exposure to semen from vaginal intercourse have been developed as surrogates for risk of infection or probability of pregnancy, data on their persistence time and clearance are limited.

STUDY DESIGN

During 2006-2008, 52 couples were enrolled for three 14-day cycles of abstinence from vaginal sex during which women were exposed in the clinic to a specific quantity (10, 100 or 1000 μL) of their partner's semen. Vaginal swabs were collected before and at 1, 6, 12, 24, 48, 72 and 144 h after exposure for testing for prostate-specific antigen (PSA) and Y-chromosome DNA (Yc DNA).

RESULTS

Immediately after exposure to 1000 μL of semen, the predicted sensitivity of being PSA positive was 0.96; this decreased to 0.65, 0.44, 0.21 and 0.07 at 6, 12, 24 and 48 h, respectively. Corresponding predicted sensitivity of being Yc DNA positive was 0.72 immediately postexposure; this increased to 0.76 at 1 h postexposure and then decreased to 0.60 (at 6 h), 0.63 (at 12 h), 0.49 (at 24 h), 0.21 (at 48 h), 0.17 (at 72 h) and 0.12 (at 144 h).

CONCLUSIONS

Overall findings suggest that PSA may be more consistent as a marker of very recent exposure and that Yc DNA is more likely to be detected in the vagina after 12 h postexposure compared to PSA.