The FDA considers nasopharyngeal swabs to be most accurate, but authorized use of nasal tests because they have relatively comparable performance, an agency spokesman said. The FDA has seen a variable performance with tests using saliva, and has issued specific recommendations for labs looking to validate tests with that sample type, he said.
To address the collection concerns, some test makers are sending trained nurses and other health workers to people’s homes to take throat or nasopharyngeal swabs. Such measures, however, are one limitation on the number of at-home tests available.
Microdrop LLC sends nurses to the homes of Houston residents who are elderly, disabled, or don’t have access to mass transit, said Jani Tuomi, co-founder of the at-home testing company. The nurses wear masks, gloves, and other protective gear.
The Houston city government is paying for the tests, which list for $135, said Mr. Tuomi. The test maker, which can process more than 10,000 swab tests a week, plans to give the tests in Texas and select other areas later, he said.
“I think our focus should be in our own backyard,” Mr. Tuomi said.
Also limiting at-home testing is the capacity of labs to analyze results. Rutgers University’s RUCDR Infinite Biologics can process 30,000 tests a day. Given the constraints and FDA concerns about detecting infections in asymptomatic people, the lab’s marketing partners are restricting sales to those with symptoms, Dr. Brooks said.
One partner, Hims Inc., asks potential customers to fill out an online assessment asking questions including whether they have come into contact with any confirmed cases and if they are experiencing any symptoms associated with Covid-19 like a dry cough or shortness of breath.
“The FDA is trying to prioritize those that are symptomatic, so, if you do not have any symptoms at all, physicians won’t be able to prescribe the test at this time,” Hims Chief Executive Andrew Dudum said.