In a small study in San Francisco, Abbott’s BinaxNOW identified infectious people nearly as accurately as a P.C.R. test.
Two tests made by Quidel and BD repeatedly delivered false-positive results, prompting the state to stop using them.
Federal officials relied too heavily on the tests, then took the results for granted, experts say.
Six months into the pandemic and with no coherent national testing strategy, the Trump administration is encouraging private development of an array of faster and cheaper techniques.
The usual diagnostic tests may simply be too sensitive and too slow to contain the spread of the virus.
Declining antibody levels do not mean less immunity, experts say. Besides, two widely used tests may detect the wrong antibodies.
A study found that the Abbott ID Now machine was less accurate when it processed short, dry swabs.
In a Fox News Channel interview, Mr. Trump also angrily revived grievances about special counsel Robert S. Mueller III and promised a swift economic rebound.
President Trump said he and Vice President Mike Pence, as well as the White House staff, would now be tested on a daily basis.
In both red and blue states, governors, health departments and hospitals are finding innovative ways to cope, but still lack what experts say they need to track and contain outbreaks.