Becton Dickinson (NYSE:BDX) and Quidel are struggling to fulfill orders for rapid COVID-19 antigen tests as the virus continues to spread, according to a report in the Wall Street Journal.

The newspaper reported today that the two companies, which are the only ones that have FDA emergency use authorizations to sell the rapid diagnostics, cannot keep up with demand and that the Department of Defense is preparing another major order. The companies sell the analyzer equipment to perform the tests as well as the actual tests. Quidel told the Journal that it is having trouble meeting demand for analyzers, while BD is struggling to produce enough tests, the newspaper reported.

“It’s really a factor of incredibly high demand that is outpacing supply,” BD spokesperson Troy Kirkpatrick said in an email to Medical Design & Outsourcing.

BD won an EUA for an antigen test in July and plans to produce 10 million tests by the end of September, “an incredibly steep ramp up,” Kirkpatrick said. “As we hit October, we’ll be at a run rate of 8 million tests per month. And at the end of February 2021, we’ll have capacity for 12 million tests per month. So we are doing everything in our power, including standing up new manufacturing facilities, to ramp up manufacturing as quickly as possible to meet the incredibly high demand for rapid tests.”

Quidel, which won its antigen test EUA in May, told MDO it has distributed some 50,000 Sofia analyzers worldwide. The company is manufacturing over 1 million Sofia SARS antigen FIA rapid tests per week and aims to reach 1.8 million tests per week by September. Supply chain issues, including a shortage of nasal swabs, pose on-going challenges, according to a company spokesman. Quidel president & CEO Doug Bryant said in early August that demand “will far exceed what all of the manufacturers in the rapid antigen space can produce, for at least the next several quarters.”

Earlier this month, seven U.S. states formed a compact with the Rockefeller Foundation to expand the use of rapid point-of-care antigen tests to better manage the COVID-19 pandemic. The bipartisan group of governors leading the states — includes Louisiana, Ohio, Maryland, Massachusetts, Michigan, North Carolina and Virginia — are in discussions with BD and Quidel to purchase 500,000 tests per state, for a total of 3.5 million tests.

Antigen tests promise to produce results faster than their much more plentiful molecular counterparts used to diagnose the coronavirus. They are formulated to quickly detect fragments of proteins found on or within the virus by testing samples collected from the nasal cavity using swabs. Quidel landed the first COVID-19 EUA for an antigen test in May, saying it could produce results in 15 minutes. Quidel said its Sofia 2 SARS Antigen FIA test has 87.5% sensitivity (ability to exclude false negatives) and 100% specificity (ability to exclude false positives).

Antigen tests may produce results more quickly, but there are questions about their sensitivity. According to the World Health Organization (WHO), antigens detected are expressed only when the virus is actively replicating, meaning these tests work best to identify acute or early infection. How well the tests work depends on several factors, including the time from onset of illness, the concentration of virus in the specimen, the quality of the specimen collected from a person and how it is processed, and the precise formulation of the reagents in the test kits.

Based on experience with antigen-based rapid-diagnostic tests for other respiratory diseases such as influenza, in which affected patients have comparable concentrations of influenza virus in respiratory samples as seen in COVID-19, the sensitivity of these tests might be expected to vary from 34% to 80%, the WHO said in April. According to the Mayo Clinic, a positive antigen test result is considered very accurate, but there’s an increased chance of false negative results and a physician may recommend a molecular test to confirm a negative antigen result.

The federal government has priority over other customers for antigen tests and analyzers, the Journal reported. Most of the available tests and equipment are going to nursing homes, where the virus has taken a major toll.