Fewer than 1 in 1,000 women who undergo genital testing for chlamydia and gonorrhea also undergo rectal testing for those conditions, U.S. researchers report. More than one-third of women (age 18-44 yeras) report ever having had anal intercourse, which puts them at risk for rectal chlamydia and gonorrhea, HIV infection, human papillomavirus (HPV) infection, and anal cancer.

Centers for Disease Control and Prevention (CDC) guidelines do not currently recommend rectal chlamydia or gonorrhea screening of women who report anal sex, and it is unclear what proportion of women get such testing.

Dr. Guoyu Tao et al. from the CDC used data from a large U.S. commercial laboratory to estimate the frequency and positivity of genital, rectal, and pharyngeal chlamydia and gonorrhea testing in women. Findings were published online in Clinical Infectious Diseases.

Among 7.9 million women ages 15 to 60 who were tested for chlamydia or gonorrhea, fewer than 6,000 (<0.1%) had rectal tests and only about 0.5% had pharyngeal tests. Just over 10% of rectal tests were positive for chlamydia or gonorrhea: 8.0% tested positive only for chlamydia, 2.0% were positive only for gonorrhea, and 0.8% were positive for both.

About 80% of women who had a rectal chlamydia or gonorrhea test also had genital testing for chlamydia and gonorrhea and pharyngeal testing for gonorrhea. Only 40% had pharyngeal testing for chlamydia.

Genital tests were positive for chlamydia in 65.3% of women with a positive rectal chlamydia test – and were positive for gonorrhea in 41.6% of women with a positive rectal gonorrhea test.

If the 1,865 women testing at all three anatomical sites had undergone only genital testing, 47.5% of those with a positive chlamydia or gonorrhea test at the rectal or pharyngeal site would not have been identified as infected, and 46.5% of women with a positive rectal chlamydia or gonorrhea test would not have been identified.

Among women with a positive rectal chlamydia or gonorrhea test, only 20.0% had a follow-up test: 17.7% of these were positive on follow-up rectal testing, 5.2% were positive on follow-up pharyngeal testing, and 11.7% were positive on follow-up genital testing.

The researchers recommend “educating women and healthcare providers about risks of anal sex; implementing rectal screening for at-risk women by asking about anal sex when conducting a sexual history; and developing reminder systems to prompt clinicians to perform follow-up testing at all anatomic sites for women who had a positive rectal test.”

Dr. Philip A. Chan, from Rhode Island STD clinic reported, "The high rates of rectal gonorrhea and chlamydia were surprising, especially given this was a large sample across the United States. This suggests that rectal gonorrhea and chlamydia may be more common among women than previously thought. However, it should be noted that only a small percentage of all women had rectal testing performed, so the ‘true’ rate of these STDs among women who have anal sex is really unknown.”

“Physicians and other medical providers should be comfortable talking about sexual behaviors in order to comfortably screen people for STDs,” Dr. Chan said. “This includes evaluating for oral, vaginal, and anal sex, which may indicate the need for gonorrhea and chlamydia screening at these sites.”

Dr. Nicole Dukers-Muijrers and Dr. Genevieve van Liere from Maastricht University Medical Center reported, "Although CDC does not specifically recommend anorectal testing in women, recent guidelines from other countries advocate anorectal testing in women who report anal intercourse.”

“It should be acknowledged that even when women are tested based on the report of anal intercourse, still over half of the anorectal infections will likely be missed,” they said. “We consider it a good starting point to at least test women who report anal intercourse for anorectal infections, as is recommended by several international testing guidelines.”

“The proportion of single site anorectal chlamydia infections is substantial. Therefore, testing is important, as these single-site anorectal infections would be missed completely and remain untreated.”