COVID-19 antibody testing could be possible with a microfluidic device invented at the University of Michigan (U-M) and developed by U-M startup Optofluidic Bioassay. The new system is believed to be the first microfluidic approach to a gold-standard testing protocol known as “enzyme-linked immunosorbent assay,” or ELISA.

A microfluidic device, or lab-on-a-chip, shrinks multiple lab functions onto a single chip millimeters to centimeters in size. The U-M researchers have previously published results showing that their device can work as well as the standard ELISA setup. They are currently validating it for use on COVID-19 antibodies.

The researchers' demonstrations have shown that they can detect synthetic COVID-19 antibodies, and now they’re working with researchers in New Jersey on experiments with human blood from COVID-19 patients.

“We are unique because we are a hardware company,” said Xudong Fan, U-M biomedical engineering professor and co-founder of Optofluidic Bioassay. “Anyone working on COVID-19 antibody tests can use their reagents in our device.”

The researchers believe rapid and accurate antibody tests could play an important role as governments, medical workers, scientists, and private citizens alike continue to navigate the pandemic. Antibody tests can reveal who has already been exposed to the virus and developed immunity, at least temporarily, and can safely go back to work. The researchers say their approach could give doctors critical, near-real-time insights into how a patient is responding to treatment, or a vaccine once one is developed.

Small-scale antibody testing has been done in some countries. Research projects are underway in the U.S., and while kits are beginning to materialize on the market here, they’re not yet widely available.

Antibody tests are one of two dominant types of COVID-19 tests, the other being polymerize chain reaction, or PCR. Antibody tests differ from PCR tests by detecting antibodies rather than the virus itself.

Rapid diagnostic antibody tests provide quick yes/no readings, but false positives can be a problem. And because they don’t give a lot of information, they aren’t useful in monitoring the immune system’s response during treatment.

“Our approach offers the best of both worlds,” Fan said. “We can achieve the quickness and simplicity of the rapid diagnostic test with the accuracy of the standard ELISA quantitative measure.”

Because their device generates sensitive and quantitative measurements, the researchers believe its use will go beyond identifying recovered patients, Fan said. “Antibodies begin to show up a few days after infection, so we could use this approach to monitor patients’ immune response to infection, treatment, and vaccination,” he said.

“The estimated cost of testing is a few dollars per test of two to three different antibodies, making this a very viable option for use in hospitals, doctors’ offices, field clinics, and potentially even pharmacies," said Xiaotian Tan, a doctoral student in biomedical engineering who is working on COVID-19 antibody testing with Fan.

The researchers say they plan to eventually apply for FDA Emergency Use Authorization.