Guidelines from the Centers for Disease Control and Prevention (CDC) and other sources that identify individuals likely to benefit from Truvada (tenofovir disoproxil fumarate/emtricitabine) as pre-exposure prophylaxis (PrEP) are not sensitive or specific enough to identify many young Black men who have sex with men (MSM) at high risk for HIV, Reuters Health reports. A high proportion of individuals in a long-term cohort whom guidelines would not have indicated were at high risk for the virus contracted HIV over the course of a recent study. 

Publishing their findings in the journal AIDS, researchers analyzed data on 300 HIV-negative 16- to 29-year-old African-American MSM participating in uConnect, a longitudinal study that ran between 2013 and 2016. The average age of the participants was 22.3.

Forty-nine percent of the cohort were good PrEP candidates, meaning they were at significant risk of contracting HIV, according to the CDC guidelines, as were 72 percent according to the HIV Incidence Risk Index for MSM (HIRI-MSM) and 86 percent according to Gilead Sciences’ package insert for PrEP (Gilead manufactures Truvada).

During a cumulative 390 years of follow-up, the participants contracted HIV at a rate of 8.5 percent per year (meaning that if 1,000 such individuals lived for one year, an estimated 85 of them would contract the virus).

A test that yields a positive or negative result has two measures: specificity, which is the rate at which the test correctly identifies a negative outcome; and sensitivity, which is the rate at which the test correctly identifies a positive outcome.

The CDC guidelines had an overall accuracy rate in predicting who would become HIV positive, including a specificity of 52 percent and a sensitivity of 52 percent. The respective overall accuracy, specificity and sensitivity rates of an HIRI-MSM score of 10 or higher were 54 percent, 85 percent and 30 percent; the corresponding rates for the Gilead guidelines were 57 percent, 94 percent and 15 percent.

During the study, the proportion of participants who were aware of PrEP increased from 32 percent in 2013 to 64 percent in 2015.

The investigators found that factors associated with contracting HIV included being unemployed as opposed to having full-time employment, being uninsured, testing positive for a rectal sexually transmitted infection during the previous two years, using poppers and having partners who were at least 10 years older.

Factors that predicted having a lower awareness of PrEP included identifying as bisexual rather than gay and more closely identifying with the African-American community. Factors that predicted a higher level of awareness of Truvada as prevention included having participated in an HIV prevention program and having more social contacts who are living with HIV.

Many of the factors associated with HIV risk among this population are not included in the PrEP-use guidelines. The addition of sex with older partners as a risk factor would theoretically increase the CDC’s accuracy rate to 61 percent, by raising its sensitivity to 69 percent (while maintaining its specificity at 52 percent).

To read the Reuters Health article, click here (free registration with Medscape is required).

To read the study abstract, click here.