Public health experts urge caution in use of coronavirus antibody tests

Public health experts urge caution in use of coronavirus antibody tests

Antibody tests which tell people if they have been infected with coronavirus are not very reliable and should only be used with caution, the Association of Public Health Laboratories and the Council of State and Territorial Epidemiologists said Thursday.

The association issued new guidelines to help state public health labs and others decide how and when to use the tests, often called serologic tests.

The tests, which look for antibodies in the blood, can show someone was infected. But it’s still not clear if having antibodies to Covid-19 means a person is immune to further infection, the strength of the immunity or for how long, the groups said in a joint statement.

“Until more evidence about protective immunity is available, serologic test results should not be used to make staffing decisions (return to work), decisions regarding the need for personal protective equipment or need to discontinue social distancing measures,” the statement said.

The guidelines include information on the different types of serologic tests, current testing availability, how to choose the right test for population studies, how to interpret the test results and continuing research needs for evaluating the tests.

The tests can be used for determining how widespread the coronavirus may be in a community or population, whether a person can serve as a convalescent plasma donor and to detect whether a person has had an immune response.

Some context: The US Food and Drug Administration at first allowed manufacturers to begin selling antibody tests in mid-March without any federal review and without knowing whether the tests even worked.

The FDA has since changed that policy and now requires validation of the tests.