(P90) RETROSPECTIVE ANALYSIS OF HIV ANTIGEN/ANTIBODY FALSE POSITIVITY RATES IN A COMMERCIAL LABORATORY DURING THE COVID-19 PANDEMIC

Background:
The CDC-recommended HIV diagnostic algorithm is multistep, beginning with HIV p24 antigen/antibody (Ag/Ab) screening and reflexing as appropriate. Reports of a correlation between SARS-CoV-2 (SARS2) infection and false-positive (FP) HIV Ag/Ab results emerged during the COVID-19 pandemic. We investigated HIV Ag/Ab screening FP rates in patient cohorts with laboratory evidence of SARS2 infection/vaccination.

Methods:
Retrospective analysis identified individuals tested using the Labcorp HIV algorithm from 2016–2023. The algorithm started with the ADVIA Centaur® HIV Ag/Ab assay and reflexed to the Bio-Rad Geenius™ HIV 1/2 assay and the cobas® HIV-1/HIV-2 RNA test, as appropriate. Individuals with SARS2 PCR testing up to 2 weeks, 1 month, or 3 months before HIV testing from 2020 to 2023 were identified. A positive SARS2 PCR result was considered evidence of SARS2 infection.  Another cohort of individuals with SARS2 PCR and/or antibody test results up to 6 months before the HIV testing was identified. Positive SARS2 PCR and/or positive antibody test results were considered evidence of SARS2 infection and/or vaccination.

Results:
Between 2016 and 2023, 2 to 5 million samples were submitted annually for HIV testing, with an annual HIV FP rate of 0.13-0.18%. Over 23 million distinct individuals, mean age 35.9±13.5, had HIV testing performed. FP HIV Ag/Ab screens occurred in ~40,000 individuals, mean age 39.4±15.2. The SARS2 cohorts (2wk, 1m, 3m, and 6m) increased from ~370,000 to 1 million individuals with an average SARS2 positivity rate of 13.4%.  No significant relationship between FP HIV screens and SARS2 history was observed.

Conclusion:
No increase in FP HIV Ag/Ab screens was observed during the COVID-19 pandemic. Additionally, no correlation between SARS2 infection/vaccination and FP HIV Ag/Ab screens was observed. These data suggest that FP HIV Ag/Ab associated with SARS2 may vary by platform and highlights the importance of interpretation based on the HIV algorithm rather than individual tests.