Study of COVID-19 POC Tests Finds Antibody Tests Can Complement PCR Diagnostics

The project aims to provide the test performance data needed by doctors and public health officials to decide which tests to employ and provide an understanding of how reliable the results are.

In head-to-head comparisons of a dozen tests, the researchers have already found that many of the tests performed reasonably well, especially two weeks or more after infection, when levels of antibodies in the blood begin to peak. However, many of the test kits have false positive rates that may exceed the proportion of people who have been infected in some communities. This means that a large proportion of those testing positive on an antibody test may not actually have had COVID-19.

The UCSF/UC Berkeley team has so far evaluated 10 point-of-care tests – tests much like home pregnancy or HIV tests, which are called, in general, lateral flow assays – and two different set of tests based on a common laboratory antibody detection method called ELISA (enzyme-linked immunosorbent assay). Each test was assessed for sensitivity – how likely it is to detect antibodies in the blood of coronavirus-positive patients – and for specificity – how good they are at distinguishing people who are infected from those who are not. A high specificity means a low false positive rate.

Out of the 10 point-of-care tests, “there are multiple tests that have specificities greater than 95%. So there is some reason for guarded optimism,” said Alex Marson, MD, PhD, an associate professor of microbiology and immunology at UCSF and scientific director for biomedicine at the IGI. “Although it is important to point out that if these infections are rare in a population, a false positive rate of 5% could cloud the picture of the information coming in.”

“Several of our tests had specificities over 98 percent, which is critical for reopening society,” added Patrick Hsu, PhD, an assistant professor of bioengineering at UC Berkeley and investigator at the Innovative Genomics Institute, a joint research collaboration between the two campuses focused on CRISPR.

Some government officials have suggested providing those who test positive with a get-out-of-jail-free card – an “immunity passport” to a normal life. However, the researchers have cautioned that additional critical information is still required before assuming that antibody tests can safely predict protection from future infections. The extent to which positive results by serology may reflect a protective immune response will require further study, Hsu emphasized. “More research is needed to understand if antibody assays can be used as predictors of protection against reinfection and to prioritize return to work.”


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