What is an antibody test?
Unlike polymerase chain reaction (PCR) tests, which are intended to identify active cases of COVID-19 infection, antibody tests are designed to identify who has recovered from infection and developed an immune response.
The World Health Organization issued a warning this week there is no evidence yet that people who have had COVID-19 will not get a second infection. But the hope is that antibody testing will help determine whether people can safely begin returning to work without endangering themselves or others.
How reliable are antibody tests?
Antibody testing in the U.S. has gained momentum as governors and elected officials begin to discuss the route to reopening the economy. Last month the U.S. Food and Drug Administration (FDA) authorized the company Cellex to market the first antibody test for COVID-19. Since then, the agency has granted emergency authorizations for four more tests, expecting additional authorizations in the coming weeks.
But with limited data, the overall reliability of antibody testing kits is yet to be established. Insufficient testing has also muddled efforts to gauge overall prevalence of the virus. Some experts say the actual number of COVID-19 cases across the country may be much higher than reported, due to limited testing and a large number of asymptomatic cases.
How do tests get approved?
The FDA issued a policy allowing developers to begin marketing or using their testing products “once they have performed the appropriate evaluation to determine that their tests are accurate and reliable.”
In other words, manufacturers can bring their tests to the marketplace without an FDA review if certain conditions are met. Since the new policy was announced, the FDA has been inundated with requests, as more than 70 test developers have notified the agency that they have antibody tests ready for use.
While commercial manufacturers claim their tests have high sensitivity and specificity, the data is unclear. The FDA acknowledged that some developers are falsely claiming their tests have received FDA approval or authorization, as well as falsely claiming they can diagnose COVID-19. The agency says it will “take appropriate action against firms making false claims or marketing tests that are not accurate and reliable.”
- Coronavirus (COVID-19) Update: Serological Tests, FDA.
- The Promise and Peril of Antibody Testing for COVID-19, JAMA.
- The FDA authorizes 2 more coronavirus antibody tests, CNN Health.
- Antibody test study results suggest COVID-19 cases likely much higher than reported, ABC News.
- COVID-19 Antibody Seroprevalence in Santa Clara County, California, medRxiv.