- Category: HIV Prevention
- Published on Friday, 21 March 2014 00:00
- Written by Gus Cairns
One of the first studies of open-label pre-exposure prophylaxis (PrEP) for at-risk gay men in 3 U.S. cities shows that although the proportion of those initially offered or seeking PrEP who ended up taking it was similar in all cities, the amount of interest differed substantially. The demonstration project also found substantial differences in adherence between the cities, possibly due to a younger population in one, but lower adherence was not associated with lower motivation to take PrEP.
The Demonstration Project and Its Volunteers
From September 2012 to September 2013, a total of 1059 HIV negative gay/bisexual men and transgender women who attended sexual health clinics in San Francisco, Miami, and Washington, DC, were offered an opportunity to be screened for eligibility for open-label tenofovir/emtricitabine (Truvada) PrEP as part of a demonstration study run by the National Institute of Allergy and Infectious Diseases (NIAID).
A large minority of participants (37%) approached the clinic proactively asking for PrEP, and they were 50% more likely to eventually be prescribed it, with 56% of those starting PrEP being self-referrals. In contrast, two-thirds of those offered PrEP by their physician declined the offer. A somewhat lower proportion of self-referrals than physician referrals turned out to be ineligible for PrEP, showing that people who self-refer generally have a good idea of their eligibility; reasons for non-eligibility included not being at risk of HIV for the previous 3 months and testing HIV positive.
Self-referrals were more likely to be white, had a higher educational level, and were both more likely to have a high level of sexual risk and to regard themselves as being at risk.
53% of those initially referred or self-referred, and 60% of those deemed eligible, eventually started taking PrEP. Participants in San Francisco were more likely to meet eligibility criteria than others, but also more likely to decline an offer of PrEP, with 62% of those eligible turning it down. Conversely, participants in Miami were considerably more likely to turn out to be ineligible -- largely because they did not fall within risk criteria -- but were very much more likely to take up PrEP if it was offered, with only 22% of those eligible turning it down.
Participants in general averaged 32 years of age, with 20% of them under 25 and 18% over 45. Nearly half (48%) were white, and 35% Latino, with a surprisingly small 8% being black, though this may change as the Washington, DC, site recruits more participants. 42% had no health insurance.
Miami trial participants were younger than participants in San Francisco or Washington, more likely to be Latino or African-American, less likely to be insured, and less likely to report drug use or unprotected receptive anal sex in the prior 3 months. They were also much less likely to self-refer, but were 50% more likely to end up taking PrEP after initially being referred by physicians than San Franciscans.
The researchers commented on the low levels of uptake among black men and transgender women (there were only a handful of the latter in the study).
"Relatively few transgender women and MSM [men who have sex with men] of color were assessed for participation and enrolled in this study," the researchers comment. "Additional strategies to increase community awareness of PrEP and engage these populations in PrEP programs are urgently needed."
Drug Levels and Adherence
The most interesting results from this interim analysis, however, were probably the adherence figures, as determined by drug-level testing in a randomized selection of about one-third (196) of the volunteers.
There were very different adherence patterns between the 3 cities. In San Francisco, the majority of volunteers (52%) had tenofovir levels consistent with daily dosing. In Washington, DC, however, only just over one-third (35%) did, and in Miami only 13.5% did.
However, another 43% of participants in both Miami and Washington, and 40% in San Francisco, had levels consistent with taking 4 doses a week or thereabouts. This dose schedule -- while not recommended -- has been calculated by the iPrEx study researchers as being about 96% (minimum 90%) effective. 92% of San Franciscans, 78% of participants from Washington, and 57% of those from Miami appeared to be taking above this dose.
This left 27% of those from Miami, 18% from Washington, and 4% from San Francisco taking about 2 doses per week, which may offer something in the region of 70% protection. 11%, 2%, and 4%, respectively, were taking about 1 dose per week, which may offer very little protection. Finally, 4.5%, 2%, and none, respectively, had no detectable tenofovir in their blood at all.
Timing of doses clearly matters too: if someone is taking PrEP 2 days per week, it matters on which days and whether their exposures to HIV happen the day after or 4 days after they take PrEP.
Clearly, however, some participants are taking PrEP at times of their own choice and, if the Miami results are reproduced elsewhere, sub-optimal adherence is not always associated with lower motivation to take PrEP. It may have more to do with differences in knowledge, convenience, and lifestyle.
SE Cohen, E Vittinghoff, P Anderson, A Liu, et al. Implementation of PrEP in STD Clinics: High Uptake and Drug Detection Among MSM in the Demonstration Project. 21st Conference on Retroviruses and Opportunistic Infections (CROI 2014). Boston, March 3-6, 2014. Abstract 954.