P072 A Case of Persistent Non-Specific HIV Reactivity in a Patient on PrEP

Introduction Uncertain HIV diagnosis can be further complicated by PrEP and SARS-CoV-2.

Case Report A 32-year-old man tested negative with a combined antibody-antigen test for HIV in January 2021. A routine postal Ab-Ag test result was then indeterminate in April 2021. He was re-tested in the clinic with the same result. He had taken daily PrEP since 2012 but stopped during the pandemic, restarting event-based PrEP around January 2021. There had been one episode of potential risk with a known male partner, who subsequently tested HIV negative. The patient had Oxford Covid vaccine in January 2021, and SARS-CoV-2 infection in February 2021.

Dolutegravir was added to Emtricitabine/Tenofovir in April 2021. HIV diagnosis was coded onto the patient‘s GP record and he informed close friends and his employer. UKHSA and local laboratory bloods over following months showed no evolution in serology. In October 2021, antiretrovirals were stopped. Weekly testing for ~1 month took place in November 2021 with no change in serology and undetectable HIV-1 RNA and DNA. PrEP was restarted in January 2022.

He was referred to an indeterminate retrovirus clinic (IDRIS), stopping PrEP one week beforehand. Non-specific reactivity to HIV was confirmed by repeat testing on fresh samples and review of prior test results. Stable reactivity was noted in 1 of 2 Ab-Ag tests only, with persistently unreactive western blot and repeatedly undetectable DNA/RNA using three perimeter sets. An HIV-negative diagnosis was given.

Discussion It is known that PrEP can affect interpretation of HIV test results. Another possible cause is cross-reactivity between HIV and SARS-CoV-2 proteins. More research into interactions between PrEP, Covid and HIV serology is needed. Early MDT review involving sexual health physicians and virologists is needed in complex cases.