Women with bacterial vaginosis (BV) should be encouraged to use condoms with all acts of sex, according to results of a recent multicenter study published in Sexually Transmitted Diseases, which found an association between detection of prostate specific antigen (PSA), a marker of recent semen exposure, in vaginal swabs and recurrence of BV. The research was a joint effort of investigators from The Ohio State University, George Washington University, the Centers for Disease Control and Prevention, and Columbus Public Health.
Ninety-six women who had been enrolled in a 24-week, randomized, double-blind, placebo-controlled trial of vitamin D supplementation for BV recurrence were analyzed. PSA results were available for all 96 of these subjects, who were recruited for the original study from an urban, public, sexually transmitted disease (STD) clinic. All of the women were positive for BV at the time of enrollment, and all received treatment with metronidazole 500 mg orally twice daily for 7 days. The researchers assumed all of the women were at risk for recurrent BV during the follow-up period.
The median age of the women in the secondary analysis of study data was 26.5 years and most were African-American. Sixty percent were using no contraception, and 7% said they had used condoms with every sex act over the past 3 months. Median number of male partners was 10, and 31% of the women said they had had sex with women at some point in their lives.
In addition to being positive for BV, 9% of the women tested positive for Chlamydia trachomatis, 8% were positive for Neisseria gonorrhoeae, 17% were positive for Trichomonas vaginalis, and 2% were HIV-positive. None of the women had syphilis.
The women were interviewed about their sexual behavior at four study visits. The questions included whether they had had unprotected sex since their last visit, as well as how many times they had had sex without using a condom. This self-reported data were compared to the PSA data.
PSA marker associated with BV recurrence
PSA was detected from vaginal swabs taken at 22% of 187 follow-up visits, and recent unprotected sex as indicated by PSA positivity was significantly associated with BV recurrence. The unadjusted hazard ratio (HR) for the effect of PSA on BV recurrence was 2.15 (95% CI: 1.23-3.77). The HR was 2.32 (95% CI:1.28-4.21) when adjusted for documented BV risk factors such as sexual frequency since the last visit, age, non-white race, and current use of hormonal contraception.
There was no significant association, however, between self-reported, recent unprotected sex, either since the last visit or in the last 48 hours, and BV recurrence. Some previous research had suggested that consistent condom use was associated with a lower risk of BV, while other studies had found no or a modest protective benefit. The researchers stated that self-reported condom usage is a “flawed measure,” and that studies using biological markers of semen exposure such as PSA have routinely shown that female research subjects under-report in response to inquiries about unprotected sex or condom use. “This finding sheds light on the prior inconsistent literature linking unprotected sex and BV risk,” they wrote, “and suggests that the variation in earlier studies may relate to misclassification from self-reported condom use.”
The current results were similar to those of two previous studies using biomarkers to confirm recent unprotected sex to investigate the risk of BV recurrence, and demonstrated the value of such biomarkers to improve measurements of unprotected sex, which is a “critical exposure variable in sexual health research,” according to the research team.
Although BV is not currently considered to be a sexually transmitted infection, this study offers “strong support for the idea that BV is related to sexual exposure,” concluded the researchers. As such, they recommended that women at risk of BV recurrence be “strongly counseled to use condoms with every sexual act.”