The Trump administration official in charge of the United States's COVID-19 testing strategy said Thursday backlogs are improving and most lab results are coming back within three days or less. 

COVID-19 outbreaks in the south and west have strained laboratory testing capacity, leading to turnaround times of several days or even weeks, hampering efforts to contain the spread of the virus.

Over the past seven days, 56 percent of COVID-19 tests had a turnaround time of three days or less, which Assistant Secretary for Health Adm. Brett Giroir characterized as an improvement.

Over the past month, 45 percent of test results came back from commercial labs within three days, he said. 

“We’re seeing an improvement week over week,” Giroir said in a call with reporters, adding that turnaround times of 10-14 days are “outliers.” 

“I expect that to get markedly better in the next couple of weeks,” he added. 

Giroir said the administration is working with commercial labs to prioritize faster results for people in nursing homes, hospitals and people who are presumed to have COVID-19. 

Turnaround times need to be as fast as possible to contain the outbreak, experts say. While public health officials say people should be self-isolating while they wait for their test results, there’s little data to indicate how often that’s happening. Longer turnaround times run the risk of making it less likely someone will self-isolate, especially if they’re not experiencing any symptoms.

Long turnaround times also make it much harder to quickly test, trace and isolate the contacts of people who have tested positive for COVID-19, running the risk that those individuals are spreading the virus in their communities. 

Commercial labs like Quest and LabCorp perform about half of COVID-19 testing in the U.S. 

Turnaround times at Quest, one of the largest commercial labs in the U.S., is over two days for priority 1 patients — hospital patients and asymptomatic health care workers —  and seven days for everyone else, the company stated in an update posted Wednesday. 

“Persistent high demand has strained our testing capacity and extended delays for test results,” the update reads. 

“We expect that as our capacity continues to grow, we will be able to return to average turnaround times in the range of 1 day for priority 1 patients and 3 days for most other patients.” 

Turnaround times at LabCorp are between two and three days from specimen pickup, but “faster” for hospitalized patients, according to an update posted this week. 

“We continue to be focused on reducing the time it takes for a patient to receive their result, and as additional equipment and supplies become available, we expect the average time to improve,” the update reads.

Point of care tests, which return results in about 15 minutes, are becoming more available but are mostly being sent to nursing homes, where residents are at higher risk for serious illness and death.

“Right now, everything coming off the line in terms of new instruments are getting shipped to nursing homes,” Giroir said. 

Giroir has said he hopes the wider availability of those tests will ease the strain on commercial labs.

Some experts argue the Food and Drug Administration (FDA) should approve tests that are less sensitive than tests that need to be sent to a lab.

Currently, the FDA requires COVID-19 tests have a minimum of 80 percent sensitivity, meaning it could return false negatives 20 percent of the time. 

Tests with lower sensitivity return results faster and can be done at home and still catch many infections, experts argue. 

“By putting a premium on the accuracy of tests, we fail to test a majority of people with COVID-19 and these built-in delays actually undermine our ability to timely identify cases which is the key purpose for widespread testing,” Dr. Ashish Jha, professor of global health at the Harvard T.H. Chan School of Public Health, wrote in a TIME op-ed published Wednesday. 

“If everyone took an antigen test today—even identifying only 50 percent of the positives—we would still identify 50 percent of all current infections in the country – five times more than the 10 percent of cases we are likely currently identifying because we are testing so few people."

Giroir said Thursday some of the less sensitive tests might be useful in some situations but provide a false sense of security in others. For example, he said some tests have a sensitivity of 20 to 30 percent, meaning they miss infections 70 to 80 percent of the time. 

“I’m sure as more things come closer to market that are not in the 20 - 30 percent sensitivity range but is in the 70 - 80 percent range then we have to understand where it fits into the overall ecosystem, where it might be helpful and where it might not be,” he said. 

"I don’t think that would do a service to the American public by having something that’s wrong 7 out of 10 times and potentially could give somebody a false sense of security that they’re negative," Giroir said.