Northwestern University researchers have put forth a coronavirus antibody test that they say can be completed using only a single drop of dried blood from a finger prick. The test, which is specifically designed to search for SARS-CoV-2 antibodies IgM and IgG, will help in “evaluating how effective policies such as social distancing or closing schools and restaurants are working to prevent viral transmission,” as well as eliminate the need for a clinical setting, according to the team’s lead author.
Thomas McDade, a biological anthropologist, said the test will also help in “ascertaining the true prevalence and mortality rate of infection.”
The researchers developed two dried blood spot-based protocols to test for SARS-CoV-2 IgG antibodies. Those who are tested will be sent a finger prick to elicit a small sample of blood, which is then stored on a special filter paper. The same is sent via regular postal service to the lab, where researchers then use enzyme-linked immunosorbent assay (ELISA) to detect IgG against the receptor-binding domain (RBD) of the spike protein, which is how the virus infiltrates human cells, according to the news release.
“The RBD is a section of the spike protein that is very ‘immunogenic’ – that is, it elicits a strong reaction from our immune system, including the product of antibodies specific to the RBD,” McDade said, in the news release. “We can, therefore, measure antibodies against RBD as an indicator of prior exposure with a high degree of sensitivity and specificity.”
McDade said the dried blood-spot sampling offers an inexpensive, painless way for people to collect their own blood in the convenience of their homes, possibly opening up the potential for widespread use in the public.
“By not requiring people to come into the clinic to have their blood drawn, we conserve clinical resources, keep people safe at home during shelter-in-place and greatly increase the potential reach of antibody testing,” he said, in the news release.
The next steps will require testing more samples to evaluate the sensitivity of the test, McDade said, as well as developing a web-based platform to help roll out antibody testing across Chicago.
Several studies involving antibody tests have so far yielded surprising results that suggest the number of COVID-19 infected individuals is far greater than the number of cases confirmed by local health departments. Several local officials have cited the need for widespread testing as regions begin to cautiously reopen the economy and local businesses.
The FDA recently updated its policy regarding COVID-19 antibody testing to crack down on companies offering unapproved “at-home” testing. As of Monday, the FDA had granted emergency use authorization to 12 tests, with over 200 others currently being reviewed.
“We will keep up our work to stop illicit tests from entering the U.S. and we encourage states, hospitals, and consumers to be on high alert and to make informed purchasing decisions regarding these tests,” the FDA said. “As important, those who use an antibody test need to understand its limitations and use test results as just one piece of data to inform decision making. All tests can provide at least some false results.”
The FDA advised that the antibody tests should only be used as part of a “well-conceived testing plan.”