As more diagnostic tests for Covid-19 enter the market to meet continued demand, providers and suppliers are starting to tackle the next challenge of Covid-19 testing: processing capacity.
Labs do not have sufficient processing capacity to scale Covid-19 testing
Early in the outbreak, the primary factor limiting Covid-19 testing in the United States was access to the tests themselves. While the number of tests available on the market has significantly expanded, the majority of those tests require the same RT-PCR technology for analysis. Now, the challenge is processing capacity.
As a nation, we've been heavily reliant on commercial labs and a select number of hospital molecular labs that have the necessary RT-PCR systems to scale up testing. But the test volumes are overwhelming lab capacity:
- The two largest commercial lab companies, LabCorp and Quest, estimate processing 20,000 and 30,000 tests per day, respectively
- Smaller national players, like Mayo Medical Labs, can churn out 3,000-5,000 a day
- More local and regional hospitals are coming on line with molecular testing, like MedStar in Washington, D.C., generally with lower daily capacity.
These limits to processing capacity are now driving backlogs. For example, at a testing rate of only 2 tests per 1,000 residents conducted daily, California alone had over 57,000 tests pending results on March 28.
All in all, last week the U.S. processed an average of 95,000 tests per day. If that rate holds, to test all persons 65 and older in the U.S. alone—which excludes the millions of people in other high-risk populations like health care providers, first responders, and those with underlying health issues—would take 552 days. Status quo is not good enough.
Emerging solutions to expand testing capacity center on diversification.
To improve processing capacity, test developers are focused on diversifying testing options. Introducing flexibility into testing, they hope, will mitigate backlogs. This is manifesting a few different ways:
1. Expanding processing options for existing tests
While more companies' tests continue to enter the market, those that have already secured EUAs for Covid-19 are expanding their testing and processing capabilities by adapting the tests to accommodate different specimens and sample collection devices and be run on additional processing systems. John Osiecki, director of medical and scientific affairs at Roche Diagnostics explained, "At the outset, you're looking for the optimal system to develop a test, that can meet the demands and potential surge capacity a pandemic may bring...now we're looking at how to expand sample types and what alternative collection devices we can use." Expanding the processing options for individual tests means that samples can be run processed by whichever system is available first, rather relying on availability of a single instrument.
Last week, Quidel Corporation and Thermo Fisher Scientific each received expanded EUAs allowing their tests to be run on additional instruments. Quidel’s Lyra assay received authorization to run on three additional instruments (the Applied Biosystems 7500 Standard from Thermo Fisher Scientific, Roche's LightCycler 480, and Qiagen's Rotor-Gene Q) and to accommodate specimens from more accessible parts of the nose, in addition to the more invasive oro- and nasopharyngeal specimens. Likewise, the amendment to Thermo Fisher Scientific’s EUA authorizes use of additional interpretive systems and sample extraction methods. Roche was granted expanded EUA claims on March 31, authorizing additional specimens for their cobas test, the first commercial Covid-19 test to receive EUA from FDA.
2. Introducing point-of-care testing that doesn’t require offsite lab processing
As of Wednesday, April 1, three companies received EUAs for rapid, point-of-care Covid-19 diagnostic tests. Tests developed by Mesa Biotech and Abbott in particular are designed to be deployed at sites that are shouldering much of the outpatient testing burden, such as physician's offices, temporary screening facilities, urgent care, long-term nursing facilities, and EDs. These "point-of-care" tests do not need to be batched and sent to offsite labs for processing, meaning they do not cannibalize any current processing capacity or exacerbate processing bottlenecks. Instead, they add to the overall denominator of testing potential. For example, Abbott plans to provide 50,000 tests per day.
3. Developing new types of tests
While the majority of tests that have secured FDA authorization are PCR tests, the next wave poised to enter the market includes a number of serological tests. Serological tests may be designed to detect the presence of antibodies that fight the virus, rather than the virus itself, so they are not ideal for diagnosing active viral infection.
If a patient is tested before their body has a chance to build up antibodies, the test may generate a false negative result, even though they may be sick. At the same time, a positive test indicates only that a person has been exposed to the virus, and generated an immune response, but does not indicate when. "Virus is detected by proxy, but that doesn't mean that the patient is still transmitting the virus—that introduces a bunch of unknowns," Osiecki points out. The presence of antibodies could mean that the patient is actively sick, or that they've already gotten over the virus and are safe to be around others. While this type of test could be useful down the line for measuring community spread, it is less effective for the current goal of "flattening the curve."
Each of these developments aims to expand the United States' capacity to process Covid-19 diagnostic tests. For providers, this means less time spent waiting on pending tests and quicker time to diagnosis and next steps for patient management. More broadly, it means getting patients into quarantine faster to minimize the number of people they may inadvertently put at risk – ultimately, flattening the curve.