How accurate are the coronavirus tests used in the U.S.? Months into the outbreak, no one really knows. When the new virus began spreading, the Food and Drug Administration used its emergency powers to OK scores of quickly devised tests, based mainly on a small number of lab studies showing they could successfully detect the virus. That's very different from the large patient studies that can take weeks or months, which experts say are needed to provide a true sense of testing accuracy. There have been more than 2 million confirmed coronavirus cases in the U.S. and more than 115,000 deaths. Cases in nearly half of U.S. states are rising. Most COVID-19 tests in the U.S. don't give data on real-world performance, including how often the tests falsely clear patients of infection or falsely detect the virus. That information is lacking for all but a few of the roughly 80 commercial screening tests available. Last month, the FDA warned doctors of a potential accuracy problem with Abbott Laboratories' rapid ID Now test, which delivers results in roughly 15 minutes. The test has been lauded by President Donald Trump and used to screen the president, his staff and visitors to the White House. The FDA alert followed a preliminary report by New York University that found Abbott's test missed between a third to one-half of infections caught by a rival test in patients screened for the virus. Dr. Colin West of the Mayo Clinic worries doctors and patients have put too much confidence in the current crop of tests.