Real-world HIV RNA and antigen/antibody testing among people who use long-acting injectable PrEP.

Abstract

Background: People who use long-acting injectable cabotegravir (CAB-LA) for preexposure prophylaxis (PrEP) can have ambiguous HIV test results if HIV is acquired during its use. The 2021 CDC PrEP guidelines recommend both HIV antigen/antibody (Ag/Ab) and RNA testing at CAB-LA initiation and follow-up.

Methods: We conducted a cohort study using the HealthVerity database to evaluate the utilization of HIV testing among people who use CAB-LA PrEP. We identified and adjudicated HIV Ag/Ab and RNA tests with a positive result, and estimated the incidence of breakthrough HIV infection or long-acting early viral inhibition (LEVI) syndrome. Testing agreement, false positive test rates, and positive predictive value were explored.

Results: Among 384 people who use CAB-LA PrEP with both HIV Ag/Ab and RNA testing with a median follow-up time of 4.2 months, we found one discordant pair with Ag/Ab(-) and RNA(+), and one with Ag/Ab(+) and RNA(-). Among four users with a positive Ag/Ab or RNA test, we identified one who acquired HIV before CAB-LA initiation with both Ag/Ab(+) and RNA(+), one likely false RNA(+), one likely false Ag/Ab(+), and one inconclusive Ag/Ab(+) due to insufficient follow-up. We identified no persons with confirmed breakthrough HIV infection or LEVI syndrome, or with RNA testing resulting in an earlier HIV diagnosis compared with Ag/Ab testing alone.

Interpretation: The frequency of breakthrough HIV infection or LEVI syndrome in this real-world cohort was low during initial three to seven months of injectable PrEP use. Ongoing assessment of the added value of HIV RNA testing for monitoring during CAB-LA PrEP use is warranted.