U.S. regulators have approved a new type of coronavirus test that administration officials have touted as a key to opening up the country. The Food and Drug Administration on Saturday announced emergency authorization for antigen tests developed by Quidel Corp. of San Diego. The test can rapidly detect fragments of virus proteins in samples collected from swabs inside the nasal cavity, the FDA said in a statement. Currently, the only way to diagnose active COVID-19 is to test a patient’s nasal swab for the genetic virus material. While considered highly accurate, the tests can take hours and require expensive, specialized equipment. Quidel says its tests can produce results in 15 minutes.