(CNN) Scammers continue to capitalize on coronavirus misinformation by offering fake antibody tests, the FBI warned, which could be used to steal personal information.
The FBI said this month that fraudsters are touting fake or unproven antibody tests and marketing them to people to steal Social Security numbers or health insurance information.
Antibody tests are used to determine whether someone was infected with Covid-19 in the past and has since developed antibodies, which protect the body from becoming infected with Covid-19 again.
The US Food and Drug Administration has approved some antibody tests, and they've all been previously tested by the National Institutes of Health's National Cancer Institute or another government agency. But it's not easy to make that distinction when you're being offered an antibody test over the phone.
The FBI said being offered a test at all is one sign you're being scammed. Labs test patients who request them, and if marketers offer free tests or dangle incentives for getting one, that's a red flag.
Other warnings include targeted ads on social media, email or unsolicited phone calls -- if you're being offered a test without expressing interest through your doctor, say no, the FBI said.
And if you've received individual calls, texts or emails from unknown people telling you that the government requires you to take an antibody test, that's not true either. Antibody tests are voluntary.
Before you agree to any antibody tests, the FBI recommends you talk with your doctor -- they should know the tests that are FDA-approved and considered accurate. The FBI also suggests using well-known labs approved by your health insurance and never sharing personal information with anyone besides your health care provider.
This is just the latest in a months-long string of coronavirus scams. Since the pandemic began in March, fraudsters have called and texted people saying they've been infected with coronavirus and lead them to a link to submit personal information. Scammers also call people and tell them they must provide a hospital with personal and financial information over the phone because someone they know is sick with coronavirus.
The coronavirus antibody tests aren't always reliable as it is, because it's not clear when coronavirus antibodies develop in the body or whether every coronavirus patient will develop antibodies at all. But tests could become an important indicator of the virus's spread when scientists answer some lingering questions.
Even FDA-approved coronavirus antibody tests may be inaccurate up to 50% of the time. In May, the CDC warned healthcare providers that coronavirus antibodies are expected to be low in most of the country, so testing could create more false-positive results (meaning that the test results indicate they've been infected when they haven't), and they shouldn't be used by policymakers to decide when to reopen spaces like offices and dorms.