US federal health guidelines on pre-exposure prophylaxis (PrEP) to prevent HIV transmission should be modified because current standards could miss some who should be on it, suggests a study from the University of California – Los Angeles (UCLA) Fielding School of Public Health.
Pre-exposure prophylaxis, or PrEP, is a measure that has proven to be highly effective in preventing HIV transmission during unprotected sex. While not entirely foolproof, studies have shown taking daily doses of tenofovir disoproxil-emtricitabine, or Truvada, is 92% effective in preventing HIV infection when taken correctly and consistently.
Since 2012, the US Centres for Disease Control and Prevention has recommended PrEP for gay or bisexual men who have had condomless anal sex or been diagnosed with a sexually transmitted infection in the past six months. The CDC also has recommended PrEP for HIV-negative men who have sex with men (MSM) and who are in a relationship with an HIV-positive partner.
The UCLA study suggests that those guidelines do not go far enough, because they omit important characteristics that could put someone at high risk for becoming infected with the virus that causes Aids. Working with the Los Angeles LGBT Centre, the researchers have developed an online risk assessment calculator, which could fill that gap.
"To the best of our knowledge, this PrEP Calculator is the first of its kind to be based on real-world data," said Robert Weiss, co-author of the study and a professor of biostatistics at the Fielding School. "We hope that our PrEP calculator will allow more MSM to make a more-informed decision before deciding whether or not PrEP is right for them."
The Los Angeles LGBT Centre is one of the largest HIV testing providers in Los Angeles County for gay, bisexual and MSM, with approximately 13,000 individual clients served annually, said lead author Matthew Beymer, a post-doctoral scholar in the department of medicine, division of infectious diseases, at the David Geffen School of Medicine at UCLA.
Between January 2009 and June 2014 the centre collected data on various behavioral risk factors for HIV among clients at each visit. Centre personnel used behavioral data and HIV test results to determine what characteristics distinguished MSM who were HIV-negative when the study began and subsequently tested positive for HIV during a follow-up visit from those who remained HIV-negative through the follow-up visits.
Using these data the researchers built an HIV-risk algorithm, which they use as a standardised mechanism for recommending PrEP to clients of the Los Angeles LGBT Centre. Unlike the CDC guidelines, they asked important questions about a number of factors that could put one at higher risk for becoming infected, including substance use, number of sex partners, age and race or ethnicity, and other partner-level factors.
The researchers found that if all individuals who had a risk score greater than or equal to five on the test's scale – 51% of those who used the calculator – had been given PrEP, then 75% of HIV infections would be averted during follow-up, assuming adequate regimen adherence and near complete effectiveness.
This made the researchers' model better than the CDC guidelines because it took into account behaviors that aren't considered in the current guidelines.
Based on these findings, they developed the risk calculator. The researchers will then assess whether men who have sex with men find it useful in determining if they should start taking PrEP. Even as late as September 2016, 20% of the Los Angeles LGBT Centre's clients were unsure if PrEP was right for them, Beymer said.
"The findings from this study will allow MSM to determine their overall risk for HIV based on their own data and previous data collected at the Los Angeles LGBT Centre," Beymer said. "Ultimately, this HIV risk score can be used by the client to determine if PrEP is right for them."
Beymer said that a limitation of this calculator is that it may not be appropriate for heterosexual and trans individuals, injection drug users, or people living outside of Los Angeles. In addition, it does not consider situations in which HIV-negative men are in long-term relationships with HIV-positive men.
Abstract
Background: Preexposure prophylaxis (PrEP) has emerged as a human immunodeficiency virus (HIV) prevention tool for populations at highest risk for HIV infection. Current US Centers for Disease Control and Prevention (CDC) guidelines for identifying PrEP candidates may not be specific enough to identify gay, bisexual, and other men who have sex with men (MSM) at the highest risk for HIV infection. We created an HIV risk score for HIV-negative MSM based on Syndemics Theory to develop a more targeted criterion for assessing PrEP candidacy.
Methods: Behavioral risk assessment and HIV testing data were analyzed for HIV-negative MSM attending the Los Angeles LGBT Center between January 2009 and June 2014 (n = 9481). Syndemics Theory informed the selection of variables for a multivariable Cox proportional hazards model. Estimated coefficients were summed to create an HIV risk score, and model fit was compared between our model and CDC guidelines using the Akaike Information Criterion and Bayesian Information Criterion.
Results: Approximately 51% of MSM were above a cutpoint that we chose as an illustrative risk score to qualify for PrEP, identifying 75% of all seroconverting MSM. Our model demonstrated a better overall fit when compared with the CDC guidelines (Akaike Information Criterion Difference = 68) in addition to identifying a greater proportion of HIV infections.
Conclusions: Current CDC PrEP guidelines should be expanded to incorporate substance use, partner-level, and other Syndemic variables that have been shown to contribute to HIV acquisition. Deployment of such personalized algorithms may better hone PrEP criteria and allow providers and their patients to make a more informed decision prior to PrEP use.
Authors
Matthew R Beymer, Robert E Weiss, Catherine A Sugar, Linda B Bourque, Gilbert C Gee, Donald E Morisky, Suzanne B Shu, Marjan Javanbakht, Robert K Bolan
[link url="http://newsroom.ucla.edu/releases/cdcs-guidelines-for-pre-exposure-prophylaxis-may-not-go-far-enough-ucla-school-of-public-health-study-suggests"]University of California – Los Angeles material[/link]
[link url="http://journals.lww.com/stdjournal/pages/articleviewer.aspx?year=2017&issue=01000&article=00011&type=abstract"]Sexually Transmitted Diseases abstract[/link]