As the COVID-19 pandemic enters a new phase in the U.S., the way testing is being used is also changing and moving more towards a pooled and serial rapid test model with a view to reducing costs and minimizing community transmission.
During 2020, tests for SARS-CoV-2 had to develop as the pandemic continued. Initially focusing on accurate but time-consuming individual RT-PCR tests, there were problems with capacity, equipment availability, and the level of expertise required to carry out the tests.
These limitations prompted many diagnostic manufacturers and labs to develop fast tests that can be carried out by anyone, regardless of their background or knowledge level. These include a variety of different options, but largely fall under the definitions of lateral flow antigen tests or RT-LAMP tests.
Antigen tests, where antibodies bound to a test strip or device in turn bind to SARS-CoV-2 antigens if the virus is present in a sample, are quick and inexpensive, but generally a bit less accurate than other tests. RT-LAMP tests are more similar to PCR, but require less specialized machines and expertise—accuracy and costs of these tests falls somewhere between RT-PCR and antigen tests.
Since vaccination campaigns have really ramped up in countries like the U.S. and things are starting to get back to normal, national and state authorities are looking for ways to use COVID-19 testing to help this process in as accurate and economic a way as possible.
Although RT-PCR is definitely still the ‘gold standard’ test in terms of accuracy, its cost and specialist requirements are problematic from an economic and efficiency perspective.
This week the FDA announced it has issued an amendment to existing test regulations allowing specific RT-PCR tests for SARS-CoV-2 to be carried out on multiple samples at once. This will involve using pooled swab samples taken from asymptomatic individuals as part of serial testing programs. This should help with reducing costs as cases fall.
“We are in a new phase of the pandemic where the American people are being vaccinated and schools, workplaces and communities are beginning to re-open. Pooling specimens allows for more people to be tested, more quickly to identify any infections as part of a serial screening program. This provides faster identification of infections and can help prevent further spread of COVID-19,” Tim Stenzel, M.D., Ph.D., director of the Office of In Vitro Diagnostics and Radiological Health at the FDA, told Clinical OMICs.
The regulator has simplified the process for developers. If they already have an EUA for their RT-PCR test then the process to finalize the approval of pooled testing simply requires the submission of an email to the FDA containing requested information (outlined in section II of the amendment letter).
The FDA amendment currently applies just to RT-PCR tests, but it is also something that could work with RT-LAMP technology. This is something genomics company Color are exploring with a view to hopefully rolling out later in the year, according to Alicia Zhou, Ph.D., the company’s chief scientific officer.
“Pooled screening can be particularly useful in areas where prevalence is relatively low which should be expected as vaccination rates increase. As we’ve seen over the past year, the speed at which we are able to process test results for large populations is critical, and directly impacts not only a patient’s individual health, but clearance, surveillance and mitigation for the broader population,” she says.
Although she does acknowledge that pooled testing has its drawbacks, “for example, if there is a positive result in a pooled test, re-testing would be needed from all of the samples in that pool—but it represents another powerful resource to contain future outbreaks.”
Combining something like pooled asymptomatic testing with rapid tests could well be an option for the coming months. Where if a positive sample is detected, people then use rapid tests to narrow down who is infected.
There are now a number of (mostly antigen) fast tests approved for at home use that can be bought over the counter. Indeed, Australian manufacturer Ellume’s tests, the first to be approved for this use in the U.S., are now available in CVS pharmacies in some states and should be available in most places in the country by the end of May.
One of the problems with home tests is a potential lack of trust in the process and accuracy from authorities or other places wanting proof of an individual’s non-infective status.
According to an Ellume representative, the company has tried to overcome this potential problem by designing their test with digital connectivity. “Users are guided through the steps of the test and receive their result through a dedicated app, which is free to download via smartphone. This smartphone connectivity means that the user’s results can be found directly on the phone and have the potential to be shared with healthcare professionals, employers, or other event organizers at the user’s discretion.
“We do not currently partner with venues or specific employers to authorize a ‘testing passport,’ but it is possible in the future that rapid tests such as ours would allow for authorization to travel.”
The CDC and NIH also recognize the potential value of home tests and announced at the beginning of the month that they are running a trial program called ‘Say Yes! COVID Test’ to see if they make a real difference to community transmission.
The program started in Pitt County, North Carolina, and will soon be expanding to Chattanooga/Hamilton County in Tennessee. Up to 160,000 residents from the two areas will be able to test themselves at home up to three times a week for a month. The NIH is providing the tests—Quidel’s QuickVue At-Home COVID-19 Test—for free for the duration of the trial and will evaluate how effective the program is at reducing transmission.
“Scientific evidence is emerging that serial COVID-19 testing with rapid antigen tests can catch infected people early and empower them to take steps to protect themselves, their families and their entire community,” said Douglas Bryant, president and CEO of Quidel Corporation.
“Reliable and widely available testing is a critical part of our efforts to stop the spread of COVID-19. Regular screening with at-home COVID-19 tests can strengthen our prevention efforts,” said CDC Director Rochelle P. Walensky, M.D., in a press statement about the project.
“Combined with efforts to increase vaccinations, this important initiative will help us understand how best to utilize these new at-home tests to reduce viral transmission rates in communities.”