CDC Study Reinforces the Importance of Annual STI Testing Among MSM

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A new Centers for Disease Control and Prevention (CDC)-led study of sexually transmitted infection (STI) rates among men who have sex with men (MSM) found that one out of eight had an STI in the rectum or throat, and one-third of men hadn't been screened at all in the past year.

"These data suggest that gay and bisexual men are at elevated risk for extragenital STDs, which could increase risk and contribute to the threat of drug resistance," said Kyle Bernstein, Ph.D., Sc.M., a co-author of the paper and the branch chief for epidemiology in CDC's Division of STD Prevention.

The research was published April 12 in the CDC's Morbidity and Mortality Weekly Report (MMWR). In 2017, researchers handed out self-swabbing kits to more than 2,000 men. Ultimately, 2,075 swab kids including both rectal and throat samples were tested for chlamydia and gonorrhea and included in the analysis.

Of the men who tested positive for gonorrhea, 4.5% of cases were found in the rectum and 4.6% in the throat. Among those who tested positive for chlamydia, 7.3% were found in the rectum and 1.4% in the throat.

These results don't necessarily track with prior estimates, which were based on a systematic review of studies published from 2000 to 2016. For example, prior estimates pegged the prevalence of rectal gonorrhea at 6.1% (compared to 4.5% in the recent study) and prevalence of rectal chlamydia at 9% (compared to 7.3% in the recent study).

According to Bernstein, the findings are significant because they hint at a more realistic STI prevalence rate in the total population of MSM in the United States.

Unlike prior studies of MSM -- which have primarily recruited participants from medical centers and sexual health clinics -- the men in this study were recruited from bars, clubs, fitness centers, and other locations frequently patronized by MSM.

This recruitment strategy paints a more accurate picture of STI rates in the community, instead of among a subset of MSM who seek medical care, Bernstein said. The study's main limitation, he cautioned, is that it recruited from five major urban centers (Houston, Miami, New York City, San Francisco, and Washington, D.C.), so it's not necessarily representative of MSM who live outside urban settings.

Still, Bernstein said, "I think it's a much better representation than men who show up to an STD clinic."

Within the MSM who were evaluated as part of the study, certain groups had higher risk than others. For example, men who had HIV were more likely to have rectal gonorrhea compared to men where were HIV negative (an 8.2% prevalence rate for men with HIV compared to a 3.3% rate for HIV-negative men).

However, prevalence of both throat infections was about the same in men who were HIV negative and those who were HIV positive.

The results, said Bernstein, "suggest that both groups have a high prevalence" of STIs, and MSM should be screened regularly for STIs regardless of their HIV status.

Meanwhile, young men ages 18 to 29 were more likely to be diagnosed with gonorrhea in the rectum and throat, as well as rectal chlamydia. Black and Hispanic MSM had higher rates of throat gonorrhea than white MSM, but the researchers didn't find any differences in the rate of other types of infections between ethnic groups.

Among the cities, MSM living in San Francisco had the lowest rate of infections overall.

One of the most glaring stats to emerge from the study was the fact that 33.6% of participants had not been screened in the prior year. And yet, current testing guidelines state that MSM who have oral and anal sex should be tested for STIs in these anatomic sites at least once per year.

Although disappointing, this figure tracks roughly with prior estimates of the number of MSM who are screened less frequently than guidance recommends, Bernstein said. The problem isn't the guidance itself, he said, but rather that "there's a suboptimal uptake of these recommendations."

Notably, the STI prevalence among men who hadn't been tested in the past year was about the same as those who had -- again reinforcing the idea that frequent STI testing is especially important in sexually active MSM.

Ultimately, said Bernstein, providers need to be recommending these tests, and patients should feel empowered to ask their providers about them. The Food and Drug Administration also recently cleared the first tests to diagnose rectal and oral gonorrhea and chlamydia.