A Double-Barreled Approach To Antibody Testing Could Improve Accuracy
MARY LOUISE KELLY, HOST:
Antibody tests that identify people who have previously been infected with the coronavirus do not always give correct answers, and false results can provide false reassurance. Guidelines from the White House suggest using two tests to get more accurate results. NPR science correspondent Richard Harris reports scientists are just now gathering data to see if that strategy will actually work.
RICHARD HARRIS, BYLINE: Entrepreneur Michael Wohl is trying to start up a business that will do quick and easy testing for the coronavirus. He realized early on a big challenge - making sure the results were accurate. Antibody tests on the market vary a lot, and even the best ones can falsely reassure people that they have already been infected and maybe don't need to worry so much.
MICHAEL WOHL: And I started doing the math of what can be done and figured out that we could do a second test.
HARRIS: Yes, it would cost more, but theoretically, at least, it could dramatically improve the outcome - provided, that is, that the second test is distinctly different from the first one so it's not making the same error. Wohl directs a program at the University of Rochester to teach entrepreneurship.
WOHL: When I came up with this idea, I put together a PowerPoint and sent it to the governor's office in New York and it - and the department of health. And it ended up propagating through the various government agencies.
HARRIS: The White House testing guidelines released at the end of April also embraced this concept, but with an important omission. The guidelines just say test twice, but they don't say use two different tests.
WOHL: One can infer, actually, if you look at the guidelines that the tests are the same tests given twice. But it's critical that the two tests are uncorrelated.
HARRIS: And there's another shortcoming. Nobody seems to have conducted real-world tests to see if the concept actually works for the coronavirus. So Wohl looked up a cousin at the University of North Carolina and asked him to see about getting evidence for this idea. The cousin, in turn, got a colleague interested in the question. John Schmitz, a pathology professor, says the idea is not new.
JOHN SCHMITZ: This is really modeling off what we do for a variety of other tests in our lab, like HIV testing.
HARRIS: A positive antibody test for HIV is confirmed with a different kind of test because a false diagnosis can have huge consequences. So while the concept is sound, Schmitz wants to see evidence. So he's starting to run his own tests. One hypothetical worry is that any single test might be detecting an antibody to a different virus.
SCHMITZ: Most cases, we don't really know what causes a false positive, to be honest with you.
HARRIS: Schmitz figures it will take a couple of months to get results from his study of the issue.
SCHMITZ: Given the pervasive talk in the field - you know, in the lay field, even - you hear about false positives, false positives. And see - you know, thought, we ought to look at this to try and - to get around that problem as best we can.
HARRIS: That thought has also occurred to a group at UC San Francisco and UC Berkeley. They have been running careful comparisons of antibody tests to measure the performance of those that are already on the market. Dr. Alex Marson at UCSF says they may be able to take the data they've already gathered and reanalyze it to see if different tests produce a different pattern of false positives, as would be needed for the two-test strategy.
ALEX MARSON: I think there's a lot of reason to believe that it's possible, but it would just take a little bit of work to actually compile that data.
HARRIS: He's also thinking about broader questions, such as when it would make sense to spend the money on two tests as opposed to running one slower but highly accurate test in a lab. Marson also points out that test accuracy is only one question. An equally important question is, what do these results actually mean?
MARSON: If you know that you have antibodies in your blood, are you safe from future infections? And that we do not know the answer to.
HARRIS: If antibodies don't signal immunity, these tests would still be useful for studying the spread of coronavirus through a population. But the results would not provide actionable information to individuals.
Richard Harris, NPR News. Transcript provided by NPR, Copyright NPR.