Study: COVID-19 Antibody Tests, Rapid Finger Pricks Effective

New findings from a Michigan Medicine study indicate that antibody testing is predictive of prior COVID-19 infection and rapid screening methods, even from finger pricks, are effective testing tools.

The research team analyzed antibody tests conducted on more than 500 subjects in patient care settings, finding that people who had COVID-19, including those with mild symptoms, produced antibodies, according to the study.

“For a long time, people were very worried that people with mild COVID did not make immune responses,” said Charles Schuler, MD, a clinical assistant professor of allergy and immunology at Michigan Medicine, in a press release. “This should give people confidence that the tests that are available to them aren’t just random number generators. They’re actually giving them something useful.”

Further, the findings indicate that rapid screens can predict infection with nearly the same precision as antibody tests conducted in a lab, which could be useful for providers, according to Schuler.

“I was actually surprised at how well some of these tests did because it’s a very different experiment,” Schuler said in the press release. “[If you have] a patient at a clinic that does not have a lab on site, we can find out if you had COVID before and we can do it now and we can do it at low cost.”

The researchers also examined lateral flow assays, which Schuler describes as modern litmus tests, also known as a drop of blood or serum placed on filter paper that changes color to indicate whether antibodies are present.

The researchers compared 3 rapid screens taken by finger pricks or blood draws in point-of-care settings to serology tests assessed in a lab. They examined samples from 512 patients, of whom 104 had a history of COVID-19 and a positive PCR test, according to the study.

Despite some false positives, 2 rapid tests agreed with positive lab results between 93% and 97% of the time. Both tests outperformed the third brand, which lost its FDA emergency use authorization during the trial.

“I think the FDA has done a nice job regulating bad tests out of the market,” Schuler said in a press release. “These are still accurate in a point-of-care setting…[so], you’ve got a test that can be taken to different parts of the world and can be done without the need for a higher-complexity lab setting.”

Schuler added that these point-of-care antibody tests could help determine who is prioritized in places where immunization lags.

“It’s important to vaccinate everyone,” he said. “But, if you can direct vaccines to people, in particular, who may be totally unprotected, something like this would be useful. I do think more data is [sic] needed to say that from a policy perspective.”

There were some limitations to the study, including the study population being 90% health care workers. However, the research team will continue evaluating with a new focus and to get more concrete answers.

“This is a down payment on, hopefully, a lot of great future data” Schuler said in a press release. “While antibodies may or may not tell you how immunity happens, they might tell you about reinfection risk. That is the functional clinical significance that we need to know as soon as possible.”

REFERENCE

COVID-19 antibody tests, even rapid finger pricks, are effective, new study finds. Michigan Health Lab. Published March 31, 2021. Accessed April 2, 2021. https://labblog.uofmhealth.org/lab-report/covid-19-antibody-tests-even-rapid-finger-pricks-are-effective-new-study-finds