Sexually transmitted infections (STIs) are common among men who have sex with men (MSM) who have been diagnosed with primary HIV infection, but they can easily go undiagnosed if a clinician relies on observing symptoms before conducting STI screening, according to a Swiss cohort analysis published in Clinical Infectious Diseases. The study also found that condomless sex was more likely to occur among people with primary HIV infection than those with chronic HIV infection.
STI rates have been rising in MSM and people living with HIV in the U.S. and elsewhere. People with primary HIV infection tend to be regarded, on the whole, as a sexually active population that may be at risk for acquiring other STIs.
The Centers for Disease Control and Prevention (CDC) recommends annual syphilis, gonorrhea, and chlamydia screening for sexually active people and screening every three to six months for MSM with multiple or anonymous sex partners. But these screening goals may not be met because of the challenges of three-site screening (rectal, pharyngeal, urethral), which is essential to detect asymptomatic STIs.
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Swiss investigators studied the Zurich Primary HIV Infection (ZPHI) cohort to gauge STI rates in a contemporary population of people who were recently infected with HIV and to identify predictors of STIs. The ZPHI is an open-label observational single-center study of people with documented primary HIV infection.
From June 2015 through January 2017, researchers offered regular STI screening to all ZPHI participants who had a clinical visit. Tested participants also completed a behavioral questionnaire. The investigators diagnosed chlamydia and gonorrhea from urethral, rectal, and pharyngeal swabs; they used blood samples to detect syphilis and hepatitis C virus. Researchers used generalized linear mixed-model logistic regression to identify STI predictors. In a prospective subsample of participants who tested negative for STIs at a baseline visit, they used a Cox proportional hazards model.
Among 214 cohort members with a clinical visit during the study period, 174 (81%) agreed to at least one STI screening, and 58 of those 174 (33%) were found to have a total of 79 diagnosed STIs. Numbers broke down as follows:
- Twenty-nine people tested positive on their first STI screen; of them, nine (31%) had an STI on a later screen.
- Seventy-three people tested negative on their first screen; of them, 21 (29%) tested positive on a later screen.
- Seventy-two people had a single STI screen; of them, eight (11%) tested positive.
The most frequently detected STIs were chlamydia (51%), gonorrhea (25%), and syphilis (19%). More than half of chlamydial (62.5%) and gonorrheal (53.3%) infections involved the rectum. Screening detected three incident hepatitis C infections.
Overall STI incidence among people with an initial negative screen was 56 per 100 person-years. When the analysis was limited to MSM, STI incidence reached 61.6 per 100 person-years. (The researchers detected only one STI among people who reported heterosexual HIV risk.)
A multivariable Cox proportional hazard analysis restricted to MSM identified two independent predictors of incident STI: having STI symptoms (adjusted hazard ratio [aHR] 3.03, 95% CI 1.17 to 7.84) and any recent drug use (aHR 2.63, 95% CI 1 to 6.9). Bivariate analysis confirmed associations between incident STI and recent use of noninjectable cocaine, cannabis, and all other noninjectable drugs (combined).
A multivariable model limited to MSM identified four independent predictors of a positive STI test: insertive anal sex in the past three months (adjusted odds ratio [aOR] 6.48, 95% CI 1.14 to 36.76), both insertive and receptive anal sex in the past three months (aOR 4.61, 95% CI 1.01 to 20.96), reporting STI symptoms (aOR 3.4, 95% CI 1.68 to 6.89), and reporting condomless sex (aOR 2.06, 95% CI 1.14 to 3.74). In the same analysis, two variables predicted lower odds of a positive STI screen: more time since HIV diagnosis and higher CD4 count.
Comparing 169 MSM in the ZPHI with 5,105 MSM in the Swiss HIV Cohort Study who did not have documented primary HIV infection, regression analysis determined that men diagnosed with primary HIV infection had more than five-fold higher odds of subsequently having condomless sex with an occasional partner (adjusted odds ratio [aOR] 5.58, 95% confidence interval 3.68 to 8.8) compared with the chronically infected participants in the Swiss HIV Cohort Study.
The investigators stress that most of the detected STIs (66%) in their cohort had no symptoms, and most chlamydial and gonorrheal infections were rectal. Because most STIs were asymptomatic, they added, "a symptom-based testing approach would fail to both accurately detect STIs and interrupt the transmission chain by prompt treatment." They suggest rectal, pharyngeal, and urethral STI screening every three months for MSM with recent condomless sex or drug use, regardless of symptoms.