MSM in London diagnosed with early syphilis are a priority group for PrEP, suggests UK study

Gay and other men who have sex with men (MSM) recently diagnosed with early syphilis are a priority group for HIV pre-exposure prophylaxis (PrEP), results of a study published in Sexually Transmitted Infections suggest. Over two years of follow-up, 11% of men diagnosed with early syphilis subsequently became infected with HIV. Incidence of rectal sexually transmitted infections and syphilis re-infection was also high.

“Our study highlights early syphilis as a risk factor for HIV acquisition in MSM,” write the investigators. “Intensive risk reduction and PrEP would be beneficial for HIV-negative MSM with early syphilis by reducing their risk of HIV acquisition.”

Results of clinical trials and real-world experience have shown that PrEP is a highly effective way of preventing HIV infections in MSM. However, in the UK access to the therapy via the NHS is limited, meaning that it is important to identify which patients should be prioritised for PrEP.

Investigators at 56 Dean Street, London, therefore designed a study examining the characteristics of MSM diagnosed with early syphilis (primary, secondary or latent) and their subsequent incidence of sexually transmitted infections and HIV.

The clinic is located in Soho, central London, and a large number of its patients are MSM.

The study population consisted of 206 men diagnosed with early syphilis between January and June 2014. Their median age was 35 years. Just under half (42%) reported recent drug use during sexual activity (‘chemsex’). At the time of syphilis diagnosis, 47% of men were HIV-positive and 53% were HIV-negative. For the majority of men (93%), syphilis treatment consisted of intramuscular benzathine penicillin.

The HIV-positive men were slightly older (37 vs 32 years) than the HIV-negative men. Otherwise, there were no significant baseline differences according to HIV status.

Men who were HIV-positive compared to HIV-negative at baseline had much higher rates of subsequent infection with several sexually transmitted infections, including rectal chlamydia (50 vs 27 cases per 100 person-years, p = 0.004), rectal gonorrhoea (66 vs 33 cases per 100 person-years, p = 0.0044) and syphilis re-infection (26 vs 10 cases per 100 person-years, p = 0.004).

HIV incidence was also monitored among the men who were HIV-negative at baseline. Up to February 2016, these 110 individuals contributed 144 person-years of follow-up. A total of 12 men (11%) were newly diagnosed with HIV, an incidence of 8.3 per 100 person-years.

“Identifying key risk factors for HIV acquisition allows us to better target prevention strategies, particularly in the context of limited economic resources,” conclude the authors. “In our population, high levels of subsequent bacterial rectal STIs [sexually transmitted infections], along with a rising problem of ‘chemsex’ use, suggest that the approach must be on multiple levels, supporting the inclusion of regular STI screening in PrEP management guidelines and chemsex support.”