Aug. 25, 2021 -- Earlier this summer, the CDC announced the first update since 2015 to treatment guidelines for sexually transmitted infections (STIs). While the CDC added several new screening recommendations, including one-time screening for hepatitis C for all adults over 18, there remained little guidance for screening for STIs such as chlamydia and gonorrhea in heterosexual men.
“It’s a pretty obvious discrepancy,” says Jodie Dionne-Odom, MD, who studies infectious disease in women at the University of Alabama at Birmingham Hospital.
The CDC says all sexually active women under 25 should get tested every year for chlamydia and gonorrhea, and women over 25 should also be tested if they have risk factors including new or multiple sex partners or a sex partner with an STI. Men who have sex with men (MSM) should be screened at least once a year, the CDC recommends, and those at higher risk should get tested every 3 to 6 months.
But for heterosexual men at low risk for infection, there is little evidence to support routinely screening for chlamydia and gonorrhea, the recommendations state.
A simplified explanation for this disparity comes down to cost and benefit.
“With limited health care dollars, you focus your resources on where the biggest bang for the buck is,” Dionne-Odom says, which means focusing testing on higher-risk groups.
Young adults under 25 as well as MSM consistently have the highest rates of STIs. Communities of MSM are smaller than the general population, which makes STIs easier to spread, explains Ina Park, MD, a community medicine doctor at the University of California, San Francisco, and co-author of the 2021 CDC treatment guidelines.
Sex without condoms and multiple sexual partners can also make this group more vulnerable, the CDC says. People under 25 also are more likely to have more than one sex partner at a time and change partners more quickly than older adults. But if both young men and women are at higher risk, why isn’t testing more balanced between both sexes?
“Obviously, women who have sex with men are getting these STIs from somewhere,” Park says.
Unfortunately, women’s anatomy makes them more vulnerable to STIs than men.
“The lining of the vagina is thinner and more delicate than skin on the penis, so it’s easier to for bacteria and viruses to penetrate,” the CDC says. Women are also more likely to not have symptoms when they have an STI, which is why screening is so important, Park notes.
Not only are women more vulnerable to infection, they also are more likely to have complications from STIs, compared to men. Chlamydia and gonorrhea can cause pelvic inflammatory disease in women, where the infection spreads to the uterus, fallopian tubes, and ovaries. This can lead to complications such as infertility or ectopic pregnancy, where the fertilized egg grows outside the uterus. Untreated STIs during pregnancy have also been tied to miscarriage, preterm labor and birth, and low birth weight. Congenital syphilis -- when a woman with syphilis passes the infection to the baby during pregnancy -- can lead to infant death before or shortly after birth and can cause permanent bone, liver, and brain problems.
But when you look at the health impacts of these same STIs in men, they are often benign, Dionne-Odom says. STIs can cause epididymitis, the inflammation of a small tube at the back of the testicle that carries sperm, which can rarely lead to fertility problems. But this condition is also uncommon, says Park.
“In my career -- which is now going on 15 years -- I have seen less than five cases, and I work in an STI clinic,” she says.
STIs can also increase the risk of getting HIV, the virus that causes AIDS. While both men and women, regardless of their sexual orientation, can get HIV, MSM have the highest prevalence of HIV, compared to any other group in the U.S. Chlamydia and gonorrhea can cause inflammation of the genital tract or the rectum, which can make someone more vulnerable to contracting HIV if they come in contact with the virus. It’s for this reason that clinicians also encourage MSM with STIs to start pre-exposure prophylaxis (PrEP), a medication that helps protect against HIV, Dionne-Odom says.
While screening younger women and men who have sex with men for STIs could help prevent more serious health problems down the line, the potential health benefits for heterosexual men are not as clear.
“Data are insufficient to draw definitive conclusions about the effectiveness of screening heterosexual men at low risk for gonorrhea and chlamydia,” Laura Bachmann, MD, chief medical officer for the CDC’s Division of STD Prevention, writes in an email. “More research is needed.”
And with the low risk of long-term complications in heterosexual men, there is little momentum to get that research funded, says Jeffrey Klausner, MD, an STI specialist with the Keck School of Medicine at the University of Southern California in Los Angeles.
“No one has said, ‘Well, this is a 20 million-dollar question,’” he notes.
And while it makes sense that by screening heterosexual men and detecting and treating more STIs, you could lower STI rates in the general population and in women, he says, studies have not found that to be the case.
Given the direct health benefits of screening in women and lack of evidence for screening heterosexual men, universal testing efforts are just not cost-effective, Dionne-Odom says.
“At $70 a test, if you test everyone in your community, that's a lot of dollars that could be going towards HIV prevention. It could be going towards making sure pregnant women have access to penicillin for syphilis,” she says. “You can imagine all the other places you could argue where those dollars could be spent.”
While these STI screening recommendations focus more on MSM and women, they are not “prescriptive standards,” Bachmann says. “The guidelines advise health care providers to always consider the clinical circumstances of each person in the context of local disease prevalence.”
Park would ultimately support expanding testing guidelines to include heterosexual men, but that would also need to accompany expanded access to STI tests, she says. Men -- especially younger men -- do not always have a primary care provider or regularly see a doctor. And with the closing of STI clinics, it has become harder for people to easily get tested, Dionne-Odom says. At-home STI testing kits could be one solution, but these kits can also be expensive.
“It would be wonderful in terms of reducing stigma if we normalize STI testing and said everybody has to do it,” Park says. “We’re just not there yet.”