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Prevalence of viral and bacterial STIs in patients with PrEP testing

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BACKGROUND: The DHHS HIV treatment guidelines recommend evaluation of HIV-1, HCV, HBV, and bacterial sexually transmitted infections (STIs) prior to prescription of HIV pre-exposure prophylaxis (PrEP). Diagnostic panels were developed to facilitate guideline-recommended baseline evaluations and monitoring on PrEP. We investigated the prevalence of STIs among patients for whom PrEP panels were ordered in the United States.
METHODS: This was a retrospective database analysis of results reported for PrEP panels ordered from Aug 2019 through Dec 2021. PrEP Baseline panels tested for HIV-1, syphilis, chlamydia, gonorrhea, HBV, and HCV infections, while PrEP Monitoring panels tested for HIV-1, syphilis, chlamydia, and gonorrhea. Tests with valid results were interpreted per CDC and treatment guidelines. Prevalence of infection was determined using combined data from Baseline and Monitoring panels.
RESULTS: PrEP panels were ordered for 2,316 patients and were ordered more than once for 332 patients; average patient age was 43 years, and most (71%) were male. Laboratory evidence consistent with HIV-1 infection was seen in 2.7% of patients. Syphilis infection was seen in 9.7% and evidence of previously treated or early syphilis in 7.1% of patients. Chlamydia and gonorrhea were seen in 4.1% and 2.2% of patients, respectively. Active HCV infection was seen in 1.3% and past HCV infection in 7.2% of patients. Most patients (47%) had no evidence of HBV exposure or immunity; 38% had evidence consistent with HBV vaccination, and 13% with recovery from HBV infection; 1% had biomarkers consistent with active HBV infection.
Among patients with more than one test, acquisition of HIV-1 infection was seen in one patient; syphilis was acquired by 1.8%, chlamydia by 2.2%, and gonorrhea by 0.6% of patients; no patients acquired HCV or HBV. The most frequent coinfection with HIV-1 was syphilis (1.2% of patients), followed by chlamydia and gonorrhea (0.3% of patients, each), active HCV (0.2% of patients) and HBV (0.06% of patients).
CONCLUSIONS: The prevalence of STIs in patients with PrEP testing was high compared to the general population. These findings may reflect a bias toward testing symptomatic individuals and/or high-risk behavior in this patient group. Continued vigilance for STIs, even among asymptomatic PrEP users, is warranted.