The FDA warned Tuesday that those relying on a rapid test to see if they’ve contracted COVID-19 should double down on them. Initial results from National Institutes of Health studies show that antigen tests may be less reliable in detecting the highly transmissible Omicron variant, and most antigen tests should be done twice, on two separate days. “Early data suggests that antigen tests do detect the Omicron variant but may have reduced sensitivity,” the FDA said in a statement. It recommended those seeking the most reliable results get a PCR test, as that detects the virus on a molecular level. “Although the data is preliminary, the FDA believes it is important to share with the public,” a spokesperson told Politico. “We will continue to keep the public informed if additional information comes to light.”