New Johns Hopkins COVID-19 antibody test proves highly accurate

In an initial study published in the Journal of Clinical Microbiology, a saliva-based SARS-CoV-2 antibody test from Johns Hopkins Bloomberg School of Public Health was deemed highly accurate in its capabilities and capable of turning out results within mere hours.

“If our saliva-based assay’s accuracy is borne out in larger studies, this noninvasive approach could make it easier to identify, at a population level, who has already had a SARS-CoV-2 infection and where gaps in seropositivity remain heading into the winter and beyond,” said Dr. Christopher Heaney, study senior author and an associate professor at the Bloomberg School. “This could inform targeted vaccination efforts and, after vaccines start to roll out, help figure out how long vaccine-induced antibodies last–all without repeated, invasive blood draws.”

The test, which offers potential gains in the world of large-scale screening and epidemiological surveys, is based on antigens from the SARS-CoV-2 virus. In the initial study of 24 participants, that test successfully detected antibodies from all involved. These participants had confirmed COVID-19 exposure and displayed symptoms for more than two weeks before the test. Negative results were produced from people before the COVID-19 pandemic.

Johns Hopkins researchers developed the test using a panel of 12 known viral antigens already used for blood-based antibody tests. By contrast, saliva samples can be collected merely by rubbing a sponge between people’s teeth and gums. The test was shown to be highly specific, providing a low rate of false positives. For one viral antigen, the scientists found negative results for it in all 134 of the pre-COVID-19 samples.

The scientists are hopeful that an optimal algorithm could enable the test to reliably detect SARS-CoV-2 antibodies starting around the 10-day mark, though not before.