How do home tests for coronavirus work? Where can I get one?

But to truly make a difference, experts say, the tests first must become much cheaper and more widely available.

For months, consumers have been able to buy home collection kits. But these are quite different from the new rapid home tests. The older home collection kits usually sell for $110 to $150 at retailers such as Costco, Walmart or at testing companies, including LabCorp and Quest Diagnostics. With collection kits, people swab their nostrils or spit saliva into a vial and send the sample for processing at a lab. The companies say it takes 24 to 48 hours to get results.

What makes the three newly authorized home tests different? Users swab their nostrils and can get results in roughly 15 minutes from the single-use tests.

The first home test that received emergency use authorization from the FDA, on Nov. 17, was Lucira Health’s “All-In-One” test kit. The single-use molecular-based test kit, developed by a California biotechnology company, is expected to sell for less than $50. But the Lucira test won’t be available to consumers nationally until early spring because the company is just beginning to prepare for large-scale manufacturing. Another hurdle: The kit requires a prescription, in part so that clinicians can report test results to local, state and federal agencies tracking coronavirus cases.

After swirling a nasal specimen into a solution, Lucira users plug a vial into a portable, battery-operated device that uses a light to indicate the test result within 30 minutes.

The second rapid home test that received FDA authorization — a kit made by Australian company Ellume — does not require a prescription. The Ellume test was authorized Tuesday and will cost $30, with the initial batches being shipped in the first week of January. Supply will be limited at first, with 100,000 test a day produced in January but the company plans to increase manufacturing to 1 million a day by mid-2021.

The Ellume test uses a nasal swab to collect a sample. Users are required to download a smartphone app to learn their result.

The third rapid home test — authorized by the FDA on Wednesday — has perhaps the best chance of having a swift impact. Abbott Laboratories says it expects to deliver 30 million BinaxNOW tests in the first quarter of 2021 and 90 million more in the second quarter.

For months, the federal government has been sending millions of the $5 Abbott BinaxNOW tests to nursing homes and schools throughout the country. The test has been administered under the supervision of health-care workers or others trained to use it.

The home version of BinaxNOW is essentially identical but will cost $25 because it requires patients to order the test through a smartphone app called Navica, after answering health questions. A partnering telehealth company called eMed will have certified guides supervising administration of the test by video to make sure consumers use it correctly.

Under the authorization, a user needs a prescription from a doctor who suspects the patient has been infected and is within the first seven days of symptom onset.

Most coronavirus tests fall into two types: Polymerase chain reaction (PCR) tests — a molecular process that is more precise but more expensive and takes longer because the sample is usually processed by a lab; and antigen tests, which detect proteins on the surface of the virus and are usually faster and cheaper but slightly less accurate.

Most rapid home tests being developed are of the antigen type, and they are said to be more than 90 percent accurate at detecting the virus and avoiding false test results. As new versions are refined, accuracy is improving.

Experts worry that members of the public may use the results from such tests as tacit permission to disregard precautions such as wearing masks or maintaining distance from others — even though the tests are not foolproof. They may miss cases in people who were recently infected and do not have enough virus to detect. People also may test negative and acquire the virus within hours of the test, unknowingly becoming contagious.

The Lucira test is expected to be available to patients of Northern California’s Sutter Health and South Florida’s Cleveland Clinic “in the near future” but not reach the national market until early spring, the company says.

Ellume said it will be announcing a major partnership soon with a major retailer — such as Walgreens, CVS or Walmart — to sell the test and is in talks to supply the test directly to companies and universities.

Abbott’s BinaxNOW home test will be available through smartphone app. Users must first fill out a screening questionnaire developed by its partner eMed. Test kits will then be shipped by eMed to qualifying customers.

Insurance companies and the federal government, through Medicare and Medicaid, have been reimbursing the cost of tests for people with covid-19 symptoms, or those who have had close contact with an infected person or with someone showing symptoms.

For months, experts have urged the federal government and insurance companies to cover testing for asymptomatic people because transmission by those people is such a huge part of the outbreak. Federal officials have indicated they want many of the newly authorized tests to be used for asymptomatic people, but it is not clear whether federal officials will issue policies that would require asymptomatic testing to be covered by insurance.

Two of the new home tests — the $50 Lucira and $25 Abbott BinaxNOW — are available only by prescription, which makes reimbursement for their use more likely.

The cost of the $110 to $150 home collections kits sold at major retailers is not reimbursed. With those tests, customers are paying for the collection kit and convenience of testing at home and avoiding a wait in line at a testing site. In most cases, the cost of processing the sample in the lab is reimbursed by insurance or government.

Experts expect the FDA in the coming weeks to authorize many more tests that could be cheaper and more accurate.