Which men stand to benefit most from access to PrEP?

New data from the PROUD pre-exposure prophylaxis (PrEP) study have identified the characteristics of the gay and other men who have sex men (MSM) who are most likely to benefit from PrEP. Study participants were randomised to receive immediate or deferred PrEP. Analysis of the baseline sexual characteristics of men in the deferred arm who became infected with HIV showed that a rectal sexually transmitted infection (STI) and reporting recent unprotected anal sex with two or more partners were associated with especially high HIV incidence rates. Findings were reported to the recent conference of the British HIV Association (BHIVA) in Manchester.

The PROUD trial recruited 544 MSM in the UK. They were randomised to receive either immediate PrEP or deferred treatment. There were no infections in the PrEP arm.

In the present analysis, investigators focused their attention on men in the deferred arm who became infected with HIV. Their aim was to identify the characteristics of men at highest risk of HIV who would most benefit from PrEP. They considered baseline characteristics including diagnosis with a rectal STI, number of recent unprotected receptive anal sex partners, use of drugs during sex (chemsex), use of post-exposure prophylaxis (PEP) and relationship status.

A total of 253 of the 269 men assigned to the deferred arm were included in the analysis; 13 men randomised to the deferred arm were excluded due to lack of follow-up HIV test results, two due to co-enrollment at multiple sites and one due to HIV positivity at baseline visit. These individuals contributed 220 person-years of follow-up. There were 20 HIV infections, an incidence rate of 9.1 per 100 person-years.

Baseline characteristics significantly associated with diagnosis with HIV were a rectal STI (p = 0.01) and unprotected receptive anal sex with two or more partners (p = 0.02).

Twelve men who seroconverted had a baseline rectal STI. They contributed 69 person-years of follow-up, and had an HIV incidence rate of 17.4 per 100 person-years.

A total of 18 men who became infected with HIV reported recent unprotected receptive anal intercourse, and six of these individuals had unprotected receptive sex with two or more partners. They contributed 132 person-years of follow-up and had an incidence rate of 13.6 per 100 person-years.

Incidence was also higher among men reporting use of PEP (12.5 per 100 person-years) and chemsex (11.6 per 100 person-years), but the higher incidence associated with each of these characteristics was not statistically significant. Nevertheless, the researchers said that all the risk factors examined placed men at above the level of `substantial risk` identified by the World Health Organization as indicating the need for PrEP.

The investigators conclude by noting guidance from the General Medical Council that states that it is a doctor’s duty to explain the risk of HIV to patients and to provide them with information on all options to reduce their risk. “This has to include PrEP,” state the researchers.