WASHINGTON – Screening for chlamydia and gonorrhea infections using urine testing alone would have missed more than three-fourths of infections in a population of gay youth, a study has found.
"Urine screening alone is not a reliable proxy for all sites for gonorrhea and chlamydia infections in a youth men-who-have-sex-with-men population," reported Dr. Katie Plax at the annual meeting of the Pediatric Academic Societies (PAS).
Instead, it appears that triple screening – with pharyngeal and rectal testing done along with genital screening through urine tests – can enhance the detection of chlamydia and gonorrhea, especially in this high-risk population.
Dr. Plax and her coinvestigators screened 135 young men who have sex with men (MSM), aged 14-24 years, during 189 visits to a drop-in youth center in St. Louis that provides health and social services. Each of the youth had triple screening with nucleic acid simplification testing of urine, rectum, and pharyngeal specimens.
Of all the positive test results over the 12-month study, only 17% were from urine specimens, whereas 82% were in rectal or throat specimens. (There were 29 positive chlamydia tests in 26 of the 135 men, and 72 positive gonorrhea tests in 51 of the men. Twelve of the young men were positive for both infections.)
Urine screening alone would have missed 85% of chlamydia infections and 72% of gonorrhea infections, their analysis shows, while throat screening alone would have missed 88% of chlamydia infections and 43% of gonorrhea infections. Rectal screening had the highest yield, with the estimated rates of missed infections being 15% and 41%, respectively.
"More attention should be focused on the role that extragenital infections play," said Dr. Plax, director of the Adolescent Center at St. Louis Children’s Hospital and associate professor of pediatrics at Washington University in St. Louis. "For HIV-uninfected patients, this is a public health emergency, because we know that an STD [sexually transmitted disease] diagnosis is both a marker for potentially high-risk activity and also a potential cofactor for HIV acquisition."
Gonorrhea infections in particular "have been identified as one of the strongest and most consistent risk factors associated with HIV seroprevalence and HIV seroconversion," she said.
Almost half of the estimated 19 million new cases of sexually transmitted infections each year occur in youth aged 15-24 years, she noted. Moreover, the vast majority of gonorrhea and chlamydia infections – 85% – are asymptomatic.
The Centers for Disease Control and Prevention recommends routine laboratory screening for common STDs for all sexually active MSM, with screening tests selected based on types of reported intercourse. This is tricky to implement, Dr. Plax said, given that basic sexual history-taking still is challenging for many providers.
"We need to take better sexual histories. We can’t ask people, especially youth, are you gay, straight, or bisexual? They don’t identify that way," she noted. "You have to ask, do you have sex with men, women, or both?"
In another study reported at the PAS meeting, researchers found that physicians are documenting sexual histories and performing tests for sexually transmitted infections (STIs) infrequently in adolescent patients, including those who report sexual activity.
In this retrospective cross-sectional study of 1,000 randomly selected routine visits by patients aged 13-19 years, fewer than one-quarter of the patients had a documented sexual history. Of those who reported being sexually active, 38% underwent STI testing and 22% had ever undergone HIV testing specifically. Overall, only 2.6% of the patients had been tested for STIs in the year preceding their visit, and only 1.1% had been tested for HIV.
The patients were among 40,000 adolescents seeking care at 29 primary care practices affiliated with the Children’s Hospital of Philadelphia and the Children’s National Medical Center in Washington. The findings were reported by Rachel Witt, a medical student at the University of Pennsylvania, Philadelphia.
Dr. Plax reported that she and her coinvestigators had no disclosures. Ms. Witt had no disclosures.