The White House coronavirus outbreak has provided a high-profile example of the limitations of rapid diagnostic testing.

Why it matters: New kinds of tests are quickly coming onto the market and being used in places like schools and nursing homes, adding urgency to the debate over how such testing should be used.

Driving the news: The White House's main coronavirus mitigation strategy was testing, usually as an alternative to mask wearing and social distancing.

• The White House had been using rapid tests made by Abbott Laboratories, which had been authorized by the Food and Drug Administration only for detecting infections within the first 7 days of symptoms.
• But the Trump administration instead used the tests to screen for the virus among asymptomatic people, per the NYT.
• Rapid testing has also recently been problematic in Nevada, where more than 20 false positives were found in nursing homes, per Bloomberg. The state had ordered nursing facilities to suspend use of these tests, then lifted the ban at the federal government's urging.

The big picture: Rapid antigen tests are cheaper and get results much faster than polymerase chain reaction tests, which have been the standard in the U.S. for most of the pandemic so far.

• The downside is that they're less accurate. That means a certain proportion of people who receive these tests will be told they don't have the virus when they do, or vice versa. (One of the rapid Abbott tests isn't an antigen test, but it has similar tradeoffs to antigen tests, at least among asymptomatic people.)
• Antigen testing is becoming more widespread in the U.S., but there's no federal strategy for how it should be used. And more than 20 states either don't release or have incomplete data on the tests, leaving "officials and the public in the dark about the true scope of the pandemic as untold numbers of cases go uncounted," Kaiser Health News has reported.

Even before the high-profile testing failures of late, experts have been debating the best way to use cheap, rapid tests that don't catch every coronavirus case.

• “Antigen testing will not and cannot work for asymptomatic screening, and [it] will probably kill a lot of people,” Geoffrey Baird, the acting laboratory-medicine chair at the University of Washington, told The Atlantic.
• But other experts say the best way to catch an outbreak and stop it in its tracks is to test groups of people repetitively, making it less important when a testing regime misses a few cases.
• "Personally, I think they’re fine to be used as part of surveillance, and the key is to not misunderstand what a single negative test might tell you," said Ashish Jha, dean of the Brown University School of Public Health. “The key to the antigen tests is…you cannot use it as a one-time, one-off, you’re negative, you’re good to go, you don’t have to wear a mask and do social distancing.”

The bottom line: “I feel like the White House was an example of how not to use this test, and a harbinger of how these rapid tests are likely to start getting used more broadly," Jha said.

• For surveillance testing to be successful in places like schools and nursing homes, the same people have to be tested repeatedly, and then when a case is caught, that person's contacts must be traced and isolated.
• But in situations like getting on an airplane — which is more akin to being tested upon entering the White House, Jha said — the takeaways are relatively simple: "If you do this, it'll help…but you still have to do mask wearing."