Injection drug use, race, recent entry into care, and hepatitis C coinfection are the most significant predictors of syphilis infection among women living with HIV in the U.S., a study published in Clinical Infectious Diseases showed.
The study found that, between 2005 and 2016, the syphilis rate among 4,416 cisgender women in HIV care was 760 per 100,000 person-years. Researchers found that the syphilis rate did not change significantly during the study period.
In a multivariate analysis, four independent risk factors were associated with syphilis incidence: entry into care after 2010 (adjusted odds ratio: 2.3), injection drug use (aOR: 2.2), black race (aOR: 2.2), and hepatitis C coinfection (aOR: 1.9). Incidence was roughly twice as likely among young adults (ages 18 to 29) than women over 50. In addition, among women with HIV and syphilis, adults under the age of 50 were about 50% more likely to have a detectable HIV viral load than women over 50.
Of note, while annual testing is recommended for all sexually active people living with HIV (PLWH), 40% of study participants reported not having had sex during the past six months. Thus, the Centers for Disease Control and Prevention may be overestimating the number of sexually active adults in the U.S., study authors suggested.
"Sexual networks, regional syphilis rates, access to health care, and social marginalization form part of the complex causal web to explain why women with HIV remain vulnerable to syphilis," study authors observed. They recommended that HIV care providers ask women about drug use at each appointment and screen for syphilis, if needed.