Because syphilis screening guidelines for women are limited (all pregnant women should be screened early), US researchers sought to inform future advice by pinpointing factors linked to newly diagnosed syphilis in US women with HIV. This retrospective analysis involved women in the CNICS cohort, which includes HIV-positive people in 8 US cities. The researchers focused on women who made HIV clinic visits at a CNICS site from January 2005 through December 2016. Participants self-reported details of drug use, alcohol use, and sex behavior. The researchers defined incident syphilis as a newly positive test after a negative test or a 4-fold jump in RPR titer--both with a confirmatory treponemal test.
Among 4795 women in care for HIV, 4416 (92%) got tested for syphilis at least once. Of those 4416 women, 417 (9.4%) tested positive, and 119 of those women had incident syphilis during follow-up. Syphilis incidence came to 760 cases per 100,000 person-years for these women in HIV care at an urban center in 2005-2016.
Among the 4416 women tested for syphilis, median age stood at 47 (interquartile range 38 to 54), 64% were black, 28% white, and 8% of another or unknown racial/ethnic group. Three quarters of women reported sex as their HIV acquisition risk factor, and 18% reported drug injecting. Almost one quarter of these women (23%) had HCV coinfection.
Reported sex risk factors in the past 6 months were less than 100% condom use in 48% of women, having an HIV-positive sex partner in 15%, having sex after drugs or alcohol in 14%, and having more than 2 sex partners in 7%. While 13% of women reported problem alcohol use, 19% used marijuana, 8% cocaine or crack, 3% methamphetamine, and 3% opioids. The proportion of women reporting injecting drugs rose from almost 10% in 2008 to about 20% in 2015 and 2016.
A multivariable model adjusted for age, race, drug injection, HCV coinfection, HIV load above 500, and CNICS site identified five independent predictors of incident syphilis at the following adjusted odds ratios (aOR) and 95% confidence intervals (CI):
-- Drug injection as HIV risk factor: aOR 2.2, 95% CI 1.3 to 3.9, P < 0.01
-- Black vs white race: aOR 2.2, 95% CI 1.3 to 3.7, P < 0.01
-- HCV coinfection: aOR 1.9, 95% CI 1.1 to 3.4, P = 0.02
-- Initial CNICS visit 2005-2010 vs 1994-2004: aOR 1.9, 95% CI 1.2 to 2.9, P < 0.01
-- Initial CNICS visit 2011-2016 vs 1994-2004: aOR 2.3, 95% CI 1.4 to 4.0, P < 0.01
Younger age tended to boost odds of newly diagnosed syphilis (18-29 vs 50+ years, aOR 1.9, 95% CI 0.9 to 3.6, P = 0.08).
An analysis limited to women 18 to 49 years old confirmed these same risk factors, except the odds for first CNICS visit in 2005-2010 or 2011-2016 versus 1994-2004 rose to 3.0 and 3.4. And another risk factor joined the list: An HIV load above 500 copies boosted incident syphilis odds 60% (aOR 1.60, 95% CI 1.0 to 2.5, P = 0.04).
CNICS investigators believe their findings "support an intersection between the syphilis epidemic and the drug use epidemic among women in the US." They noted that the link between incident syphilis and drug use may be mediated by transactional sex or sex networks. The researchers stressed that pregnant women run a particularly high risk of adverse outcomes from syphilis and suggested that "current syphilis screening recommendations may be inadequate."
1. Dionne-Odom J, Westfall A, Mugavero MJ, et al. Incident syphilis rates and predictors in US women with HIV, 2005-2016. Conference on Retroviruses and Opportunistic Infections (CROI). March 4-7, 2019. Seattle. Abstract 47.
2. Kidd SE, Grey JA, Torrone EA, Weinstock HS. Increased methamphetamine, injection drug, and heroin use among women and heterosexual men with primary and secondary syphilis - United States, 2013-2017. MMWR Morb Mortal Wkly Rep. 2019;68:144-148.