Urine Tests Miss Sexually Transmitted Infections

Pam Harrison

October 16, 2015

The majority of gonorrhea and chlamydia infections are missed when only urine is used to screen HIV-positive men, according to new research presented at IDWeek 2015 in San Diego.

"Many studies have shown that men who have sex with men have a higher risk for sexually transmitted infections than the general population, and a lot of these are extragenital infections that are asymptomatic," said Uriel Sandkovsky, MD, from the University of Nebraska Medical Center in Omaha.

"If you are trying to detect asymptomatic STIs, you should be testing other anatomical sites, not just the convenient one," he told Medscape Medical News.

Dr Sandkovsky and his colleagues evaluated urine, throat, and rectum samples from 149 HIV-positive men who have sex with men in Douglas County, Omaha, and found a rate of 12.1% for the combined incidence of gonorrhea and chlamydia.

Of the 18 participants who tested positive, 14 STIs were identified through pharynx or rectum samples, and only four were identified through the urine.

The incidence ratio of STI detection was better for the extragenital sites than for urine alone (11% vs 3%), Dr Sandkovsky reported. In fact, the chance of detecting either gonorrhea or chlamydia was 3.67 higher when extragenital sites were tested than when urine was tested.

Gonorrhea and Chlamydia

"Testing only urine would have missed all gonorrhea infections and 75% of chlamydia infections," he said. "The chances of finding either gonorrhea or chlamydia increase substantially when extragenital sites are tested."

The average number of sexual partners in the previous year was three for men who tested positive for an STI and for those who did not. And there was no difference in the reported use of condoms between the two groups.

However, men who tested positive for either gonorrhea or chlamydia were significantly more likely to have received anal sex in the previous year than men who tested negative for either STI (P = .02).

And men who reported cocaine use (P = .05) in the previous 6 months were significantly more likely to test positive for an STI than those who reported no cocaine use. The same was true for men who reported methamphetamine use (P = .004).

The rate of gonorrhea was 2.7% in the study cohort, which is 17 times higher than the rate for the county overall. And the rate of chlamydia was 10.7%, which is 18 times higher than the rate for the county overall.

Sarah Henn, MD, from George Washington University in Washington, DC, told Medscape Medical News that her institution routinely tests all three sites — the pharynx, the rectum, and the urogenital tract — when screening for STIs.

"For many years, we've also had our patients do self-testing. We give them a kit that has all three tests in it, they do the swabs themselves, based on their risk factors, and they give us a urine sample," she said.

Self-Testing for STIs

"We are not judging or stigmatizing a certain group of people," Dr Henn added. "We give these kits to men and women alike, and tell them, 'If you've had a penis in your mouth, do a throat swab, and if you've had a penis in your rectum, do a rectal swab," she explained. "They don't need to ask to be screened or admit to any behaviors face-to-face; they get the complete screening based on their own decision-making."

Dr Henn said that the rates of STIs seen in her clinics, where they treat mostly gay men, mirror those found by Dr Sandkovsky's team. And most of the STIs are found at extragenital sites.

"For example, we see rates of rectal chlamydia upward of 9% and 10%, and we see very little urogenital tract infections in our men," Dr Henn said, adding that any infection should be treated in accordance with STI guidelines.

"Asymptomatic STIs are a big deal in men who have sex with men, obviously, because of transmission to other partners," she said.

"We know that people who have STIs — gonorrhea or chlamydia — have a breakdown in the mucosal barrier in the form of irritation and inflammation. This increases the risk of getting other sexually transmitted infections, most importantly HIV," she explained.

Dr Sandkovsky and Dr Henn have disclosed no relevant financial relationships.

IDWeek 2015. Abstract 120. Presented October 8, 2015.

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