Sexual Risk Behavior, Partnership Type Are Predictors for PrEP Adherence

Adherence to HIV pre-exposure prophylaxis (PrEP) was higher among individuals with riskier behavior and sexual partnership, according to a recent study of men who have sex with men (MSM) and transgender women (TGW).

The study, conducted by investigators with the University of California San Diego Medical Center Antiviral Research Center and published in the journal AIDS Patient Care and STDs, involved more than 300 MSM and TGW who participated in the California Collaborative Treatment Group and the TAPIR study (Daily Text Messages to Support Adherence to PrEP in At-Risk for HIV Individuals) between 2013 and 2016.

“Individuals with higher HIV risk behaviors and in riskier partnerships (those with either a single HIV+ or multiple partners) had higher PrEP drug levels at the end of the study suggesting a maintained strong motivation for PrEP adherence,” study author Jill Blumenthal, MD, assistant professor of medicine at the University of California San Diego Medical Center, Antiviral Research Center, told Contagion^®. “Our findings suggest that recent sexual risk behavior and partnership type may be important predictors of PrEP adherence in MSM.”

The study used a modified Calculated Risk Score to determine HIV risk based on reported condomless anal sex acts in the last month and current sexually transmitted infections but did not adjust for viral load. Partnerships types were categorized by number of partners and HIV status. Risk behaviors remained consistent over 48 weeks, but partnership type changed, with more individuals reporting no or a single HIV-negative partner by the end of the study, increasing from 0.5% to 9%. PrEP adherence was measured by levels of tenofovir-diphosphate (TFV-DP).

Median TFV-DP levels were 1247 fmol/punch among participants at moderate risk of HIV, 1186 among those at high/very high risk, and 1026 among those at low risk. Among partnership types, TFV-DP levels were 835 for those with no or a single HIV-negative partner, 1099 for those with a single HIV+ partner, and 1210 among those with multiple partners.

“What is unique about this project is that we looked at those risk behaviors in men who have sex with men over a shorter period of time based on number of sex acts as opposed to partners,” Blumenthal said. “In addition, we examined if partnership type itself was associated with PrEP adherence, which has never been evaluated in MSM.”

Noting that risk and partnership status can change, the study could help clinicians know what to expect when patients are put on PrEP, specifically when to have certain conversations and how to initiate treatment when risk is highest.

The study cohort included individuals enrolled in a PrEP demonstration study with the majority classified as having at least moderate risk of HIV infection and most participants (86%) reporting multiple partners at baseline. More research is needed to explore whether these findings are consistent in different population groups, as well as outside of the research setting, Blumenthal said.

Other studies have demonstrated that those at higher risk for HIV infection are more likely to adhere to PrEP regimens. A recent study of young black and Hispanic MSM found that targeting PrEP to those at highest risk of HIV could be the most effective at reducing transmission.

To help reduce sexual risk among MSM, investigators at the University of Pennsylvania School of Nursing recently developed an interactive tool called My Desires & Expectations.