An online risk calculator developed by researchers at the UCLA Fielding School of Public Health and the Los Angeles LGBT Center may allow more men who have sex with men to make a better decision before determining whether pre-exposure prophylaxis (PrEP) is right for them.
- PrEP consists of the anti-HIV drugs emtricitabine and tenofovir disoproxil fumarate (Truvada), which is the only medication currently approved for HIV PrEP.
- Studies have shown that PrEP reduces HIV incidence by 92% in HIV-negative patients who are at high risk for HIV, including men who have sex with men.
An online risk calculator created by researchers at the UCLA Fielding School of Public Health and the Los Angeles LGBT Center may allow more men who have sex with men (MSM) to make a better decision about whether pre-exposure prophylaxis (PrEP) is right for them.1
PrEP is a mix of the anti-HIV drugs emtricitabine and tenofovir disoproxil fumarate (better known as Truvada). Currently, this combination drug is the only medication approved for HIV PrEP. Studies have shown that PrEP reduces HIV incidence by 92% in HIV-negative people who are at high risk for HIV, including MSM.2,3 Patients who use PrEP must take the drug daily and visit their healthcare providers every three months for follow-up. Although PrEP can reduce the risk of HIV infection significantly if taken daily, patients who use it should take even further precautions, such as using condoms, to reduce risk.
The CDC recommends PrEP for gay or bisexual men who have engaged in condomless anal sex or have been diagnosed with a sexually transmitted infection in the past six months. The CDC also recommends PrEP for HIV-negative MSM and who are in a relationship with an HIV-positive partner. (Refer to CDC guidelines on this matter, issued in 2014, at: .)
New research suggests that the CDC guidelines may not be stringent enough because the guidelines omit important characteristics that could put a patient at greater risk for contracting the virus that causes AIDS. However, according to researchers, the new online risk calculator may fill the 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, MD, PhD, co-author of the study and a professor of biostatistics at the Fielding School in a statement accompanying the research publication. “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.”
Check the Data
The Los Angeles LGBT Center is one of the largest HIV testing providers in Los Angeles County for gay, bisexual, and MSM. The center serves approximately 13,000 individual clients annually, according to lead author Matthew Beymer, PhD, MPH, a post-doctoral scholar in the department of medicine, division of infectious diseases, at the David Geffen School of Medicine at UCLA.
Researchers scrutinized data on various behavioral risk factors for HIV at each visit among center clients between January 2009-June 2014. Scientists examined behavioral data and HIV test results to determine characteristics of MSM who were HIV-negative when the study began and then tested positive for HIV during a follow-up visit, compared to subjects who continued to test negative for HIV through their follow-ups. About 9,480 men were included in the study.
Researchers developed an HIV-risk algorithm for recommending PrEP to clients of the Los Angeles LGBT Center. Unlike the CDC guidelines, these researchers asked about several factors that could put a subject at higher risk for infection, such as substance use, number of sex partners, age, race or ethnicity, and other partner-level factors.
Results suggest that if all individuals who scored 5 or higher on the test’s risk scale had been administered PrEP, then 75% of HIV infections would be avoided during follow-up. These findings indicate the model performed better than the CDC guidelines since the researchers who created the model studied behaviors not considered in the current CDC recommendations.1
Researchers admitted that one limitation of the calculator may be its inapplicability to heterosexual and transsexual patients, those who use drugs by injection, or people who live outside Los Angeles. Also, the researchers noted the calculator does not take into account situations in which HIV-negative men are in long-term relationships with HIV-positive men.
What’s the next step? Scientists say it is to evaluate whether MSM respond positively to the calculator as they assess their need to take PrEP. Even after receiving education about PrEP, 25% of center clients still remain unsure about their PrEP candidacy, researchers said.
- Beymer MR, Weiss RE, Sugar CA, et al. Are Centers for Disease Control and Prevention guidelines for pre-exposure prophylaxis specific enough? Formulation of a personalized HIV risk score for pre-exposure prophylaxis initiation. Sex Transm Dis 2017;44:48-56.
- Grant RM, Lama JR, Anderson PL, et al; iPrEx Study Team. Preexposure chemoprophylaxis for HIV prevention in men who have sex with men. N Engl J Med 2010;363:2587-2599.
- Thigpen MC, Kebaabetswe PM, Paxton LA, et al; TDF2 Study Group. Antiretroviral preexposure prophylaxis for heterosexual HIV transmission in Botswana. N Engl J Med 2012;367:423-434.