Antibodies for COVID-19 test incorrectly half the time


News: The Center for Disease Control and Prevention in the United States said that antibody tests to determine whether a person has been infected by the COVID-19 virus may be wrong up to 50% of the time.

Here are five components of the story:

  • In a new set of guidelines released on May 23, the CDC said health officials or health care providers who are using antibody tests need to use the most accurate test they can find and might need to test people twice.
  • Antibody tests, often called serologic tests, look for evidence of an immune response to infection. “Antibodies in some persons can be detected within the first week of illness onset,” the CDC says. They are not accurate enough to use to make important policy decisions, the CDC said.
  • A false positive will lead someone to believe they have been infected when in fact they have not been. There’s little evidence now about whether having been infected gives people immunity to later infection, but doctors worry that people will behave as if they are immune if they get a positive antibody test.
  • “It cannot be assumed that individuals with truly positive antibody test results are protected from future infection,” the CDC says in the updated guidelines. “Serologic testing should not be used to determine immune status in individuals until the presence, durability, and duration of immunity is established.”
  • Several researchers and public health experts have in the past cautioned against relying on the results and use of antibody tests.

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