NEW YORK – As the SARS-CoV-2 pandemic continues throughout the world, more diagnostic firms are adding rapid antigen testing to their COVID-19 testing portfolios.
Roche is no different, announcing earlier this month that it planned to launch a SARS-CoV-2 antigen test in Europe by the end of September, pending regulatory approval.
The company has since received CE marking for the test and said it began selling it this week. It has also filed for Emergency Use Authorization with the US Food and Drug Administration, which is still pending.
The point-of-care test, developed by Korean diagnostic firm SD Biosensor, doesn't require an instrument and returns results in 15 minutes with a sensitivity of 96.5 percent and a specificity of 99.7 percent, according to Roche.
Roche decided to distribute the test after screening a number of available antigen tests, said Christian Paulus, Roche Diagnostics' head of R&D for point of care, adding that the test "stood out from a performance perspective." Roche entered a non-exclusive distribution agreement with SD Biosensor and is distributing its version of the test under Roche's name. Under the agreement, SD Biosensor can work with its existing distribution network to sell its product, Roche said.
SD Biosensor has multiple SARS-CoV-2 tests available, including a molecular detection test, a rapid chromatographic immunoassay for antigen detection that Roche will launch, an IgM and IgG antibody test, and a fluorescent immunoassay to detect SARS-CoV-2 viral nucleoprotein antigens.
Roche's chromatographic test will join Abbott's BinaxNow point-of-care test as one of the only instrument-free SARS-CoV-2 antigen tests available, but Roche said its test will be indicated for use with nasopharyngeal samples from both symptomatic and asymptomatic individuals – which no other antigen test has been cleared for so far. But Emily Volk, president-elect of the College of American Pathologists, noted that just because antigen tests haven't been indicated for use with asymptomatic people doesn't mean they aren't being used that way.
"Laboratories around the country have been testing both symptomatic and asymptomatic patients, whether or not the EUA permitted it, quite frankly," Volk said.
One of the main concerns when using lateral flow antigen tests, especially in comparison to gold-standard molecular PCR tests, is a decrease in sensitivity. "You can't amplify a viral protein, whereas you can amplify viral genetic material," Volk said. This decrease in sensitivity could lead to false negative results.
Roche tested 426 symptomatic and asymptomatic samples to determine sensitivity and specificity of its test and the studies "showed no differentiation in sensitivity and specificity between those two groups," Paulus said.
Volk mentioned, too, that the sensitivity and specificity in real-world scenarios often depend on the end user, since they control how much reagent is used, how well the sample is collected, whether the kit was stored at the right temperature, and other variables. "If their sensitivity and specificity claims pan out in the field, that's great, but a lot of that will depend on how user-friendly the kit is," she said.
Nathan Ledeboer, an associate professor of pathology and laboratory medicine at the Medical College of Wisconsin, said the throughput antigen tests can achieve depends on the application but noted they have allowed for the expansion of the overall pool of people being tested and helped alleviate some supply chain issues by offloading some of the burden on PCR testing. Antigen testing has "allowed [us] to be a little bit smarter about who we use PCR testing for," he said. "It really allows us to be targeted on where we need high-sensitivity tests," like for patients coming in for surgery.
The faster turnaround time for rapid antigen tests – they typically take under 30 minutes compared to multiple hours for a typical PCR-based test – would likely help with discharging people from emergency departments and triaging COVID-19 patients into appropriate units, Volk said, but she emphasized that lateral flow testing isn't a replacement for PCR. However, she added that the COVID-19 response needs many different tools and that antigen testing could offload a bit of the PCR demand, especially in high-prevalence communities.
Ledeboer said antigen testing becoming more widely available could also help change the role of PCR testing, using it for confirmatory testing while antigen testing is used for rapid screening. "In the symptomatic or the diagnostic indication, so far we haven't seen a huge impact [from antigen testing]," he said. "But where we've seen the huge impact is really being able to expand into those asymptomatic populations where we just haven't had the capacity to date to be able to screen them."
Not having an instrument also removes a barrier to fast testing, although Ledeboer noted the lack of instrument likely has an impact on sensitivity. But without an instrument, deployment of antigen testing can be more creative, allowing for the reduction of transmission in community settings, screening before getting on airplanes or other forms of shared transportation, and to target missed populations, such as those in poor or rural areas.
Getting rid of instrumentation is also vital to making testing cheaper, said Eric Topol, a professor of molecular medicine at Scripps Research. "If a test can be done for a dollar or less a day, then people would do that before they go out each day," he said.
Rebecca Lee Smith, an associate professor of epidemiology at the University of Illinois, also emphasized the importance of regular testing. "Daily testing in quarantine could enable faster identification of cases and shut down transmission chains faster," she said. "Screening at workplaces and public areas would allow more safety in essential industries."
One concern Ledeboer mentioned, however, is the likelihood of Roche's test actually making it to the commercial market. When Abbott's BinaxNow test was announced, Ledeboer said, there was a lot of excitement in the laboratory community to deploy the test commercially. However, the US Department of Health and Human Services purchased 150 million Abbott tests, monopolizing its supply and stopping it from making it to the commercial market, likely until the end of 2020. Ledeboer said there is high demand for an instrument-less rapid antigen test in the commercial market and he hoped Roche's test would be available for sale.
Topol said the testing of asymptomatic individuals was key, since they are most responsible for spreading the disease. "The asymptomatic is the dominant category, when you add presymptomatics and those who never develop symptoms to asymptomatics, you've got most of the source of infections right there," he noted. "It's essential that they be tested." The goal, he added, is a practical test that picks up people who don't know they're infected.
As for testing capacity, Roche expects to have 40 million tests available per month upon launch, with plans to double capacity by the end of the year.
"We need more than 5 million [tests] a day to start to get our arms around the virus," Topol said. But part of the problem with the tests is that they're for use in doctors' offices, schools, clinics, and not for home, he said. "It's great that they can do 40 million a month, but getting them out there in all these places isn't as ideal as getting them in every household," Topol said.