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Use This Easy Calculator to Determine if PrEP is Right for You

This PrEP Calculator Determines Whether You're at Risk for Contracting HIV

CDC guidelines for who should use PrEP aren't inclusive enough. Here's how to expand it. 

For nearly four years, the Centers for Disease Control and Prevention has recommended PrEP, the one-a-day HIV prevention pill, for those at "substantial risk" for becoming HIV-positive. That includes gay or bisexual men who have had a sexually transmitted infection in the past six months, and those in serodiscordant relationships (where one person is HIV-positive and the other is not). But advocates have been arguing that these guidelines do not go far enough; and now there's a study to prove it. 

The study from the University of California Los Angeles Fielding School of Public Health suggests that CDC is missing a vast number of people who at high risk.

Working with the Los Angeles LGBT Center, which serves around 13,000 people every year, the researchers reviewed data collected between January 2009 and June 2014 about a variety of HIV risk factors reported by the Center's clients. They also used behavioral data and HIV test results to determine which characteristics distinguished men who have sex with men who were HIV-negative when the study began and subsequently tested positive for HIV during a follow-up visits. The data included everything from use of substances, number of sex partners and the ages, race, and other details about those partners.

Then, using what they'd learned, UCLA researchers built an HIV-risk algorithm, and ran the data from the Center to determine if using that algorithm instead of CDC guidelines would make a difference.

The results, published in the January issue of Sexual Transmitted Diseases, showed that if all the Center clients who the algorithm indicated had a risk score greater than or equal to five on the test’s scale (51 percent) had been given PrEP, then 75 percent of the eventual HIV diagnoses would have been averted.

The researchers went further, developing a PrEP calculator, available at (part of a new HIV-prevention program aimed at L.A.'s gay and bi men of color), which asks 13 questions to get at the details most important in determining risk factors.  

“To the best of our knowledge, this PrEP Calculator is the first of its kind to be based on real-world data,” Robert Weiss, co-author of the study and a professor of biostatistics at the Fielding School, said in a statement. “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.”

After you complete the questionnaire, you are given a score to determine if you are at high or low risk for contracting HIV. 

“Ultimately," lead author Matthew Beymer added, "this HIV risk score can be used by the client to determine if PrEP is right for them.”

But keep in mind that the calculator is mainly for gay and bisexual men. Beymer suggested the calculator might not be adequate in determining the risk for straight or trans people, injection drug users, those outside Los Angeles, nor those in serodiscordant relationships. 

Of course, those in serodiscordant relationships and injection drug users were already included in those the CDC recommends consider PrEP. Trans women who had sex with men were lumped with gay and bi men in the CDC's PrEP study and aren't specifically mentioned in the federal recommendations; but they are in the World Health Organization's.

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