Real-world HIV RNA and Antigen/Antibody Testing Among People Who Use Long-acting Injectable Preexposure Prophylaxis

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

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.

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 1 discordant pair with Ag/Ab negative (-) and RNA positive (+), and 1 with Ag/Ab(+) and RNA(-). Among 4 users with a positive Ag/Ab or RNA test, we identified 1 who acquired HIV before CAB-LA initiation with both Ag/Ab(+) and RNA(+), 1 likely false RNA(+), 1 likely false Ag/Ab(+), and 1 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.

The frequency of breakthrough HIV infection or LEVI syndrome in this real-world cohort was low during initial 3-7 months of injectable PrEP use. Ongoing assessment of the added value of HIV RNA testing for monitoring during CAB-LA PrEP use is warranted.