King County officials explain ‘important limitations’ of COVID-19 antibody test
As antibody blood testing for coronavirus has ramped up, Seattle-King County Public Health broke down some “important limitations” to keep in mind.
While scientists at UW Virology have touted the method as “one of the best tests we can offer” from a diagnostic perspective, it also comes with some caveats.
“It is important to remember that these tests are not reliable for diagnosing if a person who is currently ill has COVID-19, and these tests should not be used for that purpose,” Seattle King County Public Health said in a recent blog post on its Public Health Insider page.
Rather, the test is designed to detect the presence of coronavirus antibodies only after a patient has fully recovered, sometimes months after the fact. That means the goal is less to determine who has the virus now, and more to get a sense of who might potentially be immune and ready to safely reenter the world.
It’s also what Fred Hutchinson scientist Trevor Bedford labels as the “gold standard” to “help dial in a lot of numbers.”
“By learning total number of infections we can better estimate population-level severity,” he described in early April.
There remains a question over immunity, though.
“Based on other coronavirus infections, most feel that infection will produce some protection,” said Public Health in its blog post. “However, we do not know how much, if any, protection against future COVID-19 infection may be provided by antibodies detected by different antibody tests.”
“It’s important to understand that there is no reliable way at this time to know if someone is protected based on results of an antibody test,” Seattle-King County Public Health’s Dr. Jeff Duchin added.
That being so, Public Health noted that it doesn’t currently know enough about immunity afforded by antibodies to make a recommendation, and that “no one should draw definite conclusions about their protection from COVID-19 based on currently available tests.”