Many Rectal STIs in Women Missed by Genital Testing Only

Pam Harrison

August 28, 2018

Testing women for the presence of sexually transmitted infections (STIs) only at the urogenital site will miss approximately 20% of STIs in women who report having receptive anal intercourse, a STD (sexually transmitted disease) surveillance network study indicates.

"As an obstetrician-gynecologist, I thought it would be interesting to analyze data from women who report having receptive anal intercourse and see what the rates of chlamydia and gonorrhea might be," Eloisa Llata, MD, MPH, Centers for Disease Control and Prevention, Atlanta, Georgia, said in podcast prepared by the journal, Obstetrics & Gynecology.

"[W]e found that about one in five women who reported having receptive anal intercourse will only be infected at the rectal site, so if we only screen women with a urine-based approach, we are going to miss these women and the opportunity to stop transmission," she added.

"So this study underscores the need to ascertain a comprehensive sexual history for all patients, male and female, in order to identify risky behaviors and to test accordingly," Llata emphasized.

Llata and colleagues published the study online August 6 in Obstetrics & Gynecology.

The researchers collected and analyzed data from the STD Surveillance Network involving 10 state and local health jurisdictions for all visits between January 2015 and December 2016.

The researchers included 94,094 visits made to STD clinics in five jurisdictions in the analysis.

A total of 7.4% of women presenting for care during a 2-year interlude reported having receptive anal intercourse.

Some 94.1% of women were tested for Chlamydia trachomatis at the urogenital site, whereas 94.5% were tested for Neisseria gonorrhea at the same site.

Fewer women, at 76.9%, were tested for the same two STIs at the rectal site.

C trachomatis positivity was 9.1%, and N gonorrhea positivity was 5.4% among women tested only at the genital site.

Results differed among women who were tested only at the rectal site. In this subgroup of women, C trachomatis was detected in 26.7% of samples and N gonorrhea in 6.1% of them.

Investigators then identified infection rates for each of the two STIs separately in women who were tested at both the genital and rectal sites.

Analysis of this subgroup of women found that 10.4% of women tested positive for C trachomatis; of these, 20.9% of women were positive for the infection at the genital site only, whereas 58.6% of women tested positive at both the genital and rectal sites.

Another 20.5% of women were positive for C trachomatis only at the rectal site.

For women who were tested at both the genital and rectal site for N gonorrhea, 4.5% of women had been infected with the STI.

Of these, 24.2% of women had genital infections only; 57.8% were positive for N gonorrhea at both genital and rectal sites, and 18.0% had evidence of N gonorrhea only at the rectal site.

Treatment of STIs

Documentation of treatment for rectal C trachomatis was not available in all women, but among those in whom treatment was documented, more than two thirds of patients were treated with a single dose of azithromycin (1 g). A small proportion of patients were treated with doxycycline, 100 mg twice daily for 14 days.

Among women with rectal N gonorrhea infections, almost three quarters received ceftriaxone, 250 mg, and azithromycin, 1 g.

The majority of women with either infection received treatment within a week of diagnosis.

Llata noted during the journal's podcast that complications of untreated STI genital infections include infertility and ectopic pregnancy.

"The sequelae of rectal infection [are] still a bit unknown," she noted, "but one of them could be continued transmission to other sexual partners," she suggested.

Women with rectal STI infections could also "auto-inoculate" the vagina, where they risk transferring the rectal infection to the vaginal site and cause the same complications of infertility and ectopic pregnancy, Llata said.

Further, STIs in the rectum might increase the risk for HIV acquisition, as has been well documented in men who have sex with men.

"The STD clinics [included in this analysis] generally see an underserved population, so patients who are at higher risk for STDs do attend these clinics," Llata noted.

"But this is not just an STD clinic problem, and given how common anal sex is, I think it is equally important to think about STD risk even in the general pool of women who are considered lower risk," she added.

"You can't just assume a chlamydia or gonorrhea infection will be isolated if you just test the urogenital site," Llata reiterated.

The authors have declared no relevant financial relationships.

Obstet Gynecol. Published online August 6, 2018. Abstract

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