Antibody tests can yield false positives, especially where infection rates are relatively low

Authors Brianna Abbott, Elbert Wang and Denise Roland discuss COVID-19 antibody testing. After a rocky rollout, higher-quality coronavirus antibody tests have emerged that, among other uses, are beginning to give a clearer picture of the pathogen’s spread. But for people who are simply curious about whether they’ve unknowingly been infected, some doctors and public-health authorities are still hesitant to recommend antibody tests.

The reliability of these tests for any one person, they say, comes down to a matter of probability: As with most other medical tests, that depends not only on a test’s quality but also on a disease’s prevalence within a community...“It’s a probability nightmare if the prevalence is low,” said Anthony Lemmo, chief executive of BioDot, a diagnostics manufacturing company. “That is really difficult for people to wrap their head around.”