Caution urged if symptomatic get rapid virus tests

Such tests may miss some infections or give wrong positive results.

Bloomberg

One of the first states to receive rapid, low-cost coronavirus tests from the U.S. government is cautioning against their use in asymptomatic people, a group it was hoped would benefit most from the technology.

Antigen tests like one from Abbott Laboratories that look for telltale viral proteins may miss some infections that can be picked up by costlier gold-standard assays and can incorrectly return positive results. The rapid tests aren’t recommended for people without symptoms who haven’t been exposed to a COVID-19 patient, and those who undergo one should be informed of the limitations, the Louisiana Department of Health said in guidance issued last week.

The recommendations highlight issues with tests like Abbott’s $5 BinaxNOW, which the U.S. Department of Health and Human Services is spending $750 million on and were used in the White House.

State health officials are increasingly concerned that people without symptoms should be screened with more costly but more reliable polymerase chain reaction assays because of worries about the rapid tests’ performance, according to Jeff Engel, a senior adviser at the Council of State and Territorial Epidemiologists.

HHS “made this purchase without any studies on the novel use in which they’re deploying these tests,” Engel said. “I think that’s careless.”

HHS is providing antigen tests for use in symptomatic and asymptomatic people, said Mia Heck, an agency spokeswoman, in an email. Abbott didn’t respond to a request for comment.

The U.S. Food and Drug Administration also issued an alert on antigen tests, warning on Tuesday that they can produce incorrect positive results.

Problems are more likely in populations with low virus prevalence, or when the test is improperly performed, the FDA said in a statement.

Nursing homes and other care settings have reported false positives from antigen tests, the FDA said. Any type of test is subject to some inaccuracies, and it’s important to follow instructions for antigen testing, confirm results when needed and consider the likelihood of a false positive when looking at results, the agency said.