Retrospective study describes false-positive HIV test results in Argentinians who had COVID-19

A previous bout with COVID-19 could increase the odds that an HIV ELISA test will yield a false positive result, a retrospective Argentinian study conducted in 2020-2021 showed.

About This Study

“Increased risk of false positive HIV ELISA results after COVID-19” was published online on Feb. 8, 2023, in AIDS. The lead author is Laura G. Alfie of Universidad de Buenos Aires.

Key Research Findings

The goal of this retrospective study was to evaluate the rate of false positive HIV serology results in individuals with a previously confirmed COVID-19 diagnosis, with and without detectable SARS-CoV-2 antibodies. In addition, the researchers analyzed samples from vaccinated subjects who had two doses of Sputnik V vaccine but no evidence of previous infection with SARS CoV-2.

The SARS-CoV-2 and HIV viruses have similar surface glycoproteins and epitope motifs, raising the question whether the commonly used ELISA (enzyme-linked immunoassay) test might confuse antibodies to these viruses. The study showed that this may indeed be the case.

Blood stored at the Infectious Disease Biobank of Argentina from donors who were not living with HIV was tested for HIV. Six hundred seventy-four participants had been diagnosed with COVID-19 between April 2020 and August 2021; 200 participants had a COVID-19 diagnosis but no detectable SARS-CoV-2 antibodies, and 47 participants had been vaccinated against the respiratory virus.

Overall, 15 of the 921 samples tested positive for HIV. In three cases, the HIV result was confirmed by a second test, HIV viral load was detectable, and the donors were contacted. The other 12 samples were negative on a second ELISA test and confirmatory assays – i.e., they were false positives.

Normally, about 0.4% of positive HIV tests are not confirmed by a second test, the study authors stated. In the current study, 1.3% of samples falsely tested positive for HIV. That rate rose to 1.4% when the analysis was limited to blood from donors who had been diagnosed with COVID-19, and to 1.8% for donors who had had COVID-19 and had detectable antibodies to SARS-CoV-2. No HIV false positives were found among the vaccinated group, although all samples in that group had detectable IgG antibodies against SARS-CoV-2.

Discussion Highlights and Implications for Practice

Testing centers and healthcare providers should be made aware of the possibility of false positive HIV test results in people who have had COVID-19, the study authors urged. However, they cautioned that the results need to be confirmed in other countries using different versions of the ELISA test.

By Barbara Jungwirth