Since its formation in August, our South San Francisco-based CLIA lab has processed over 90,000 COVID-19 test samples as part of our Healthy at Work program for organizations across the country. Our science and clinical teams closely monitor changing industry guidelines and are committed to iterating on our own practices to ensure best results for the people we serve.
We sat down with Deb Hanks, Verily’s head of Pathology, to talk about some of the common questions we’ve received about COVID-19 testing and our CLIA lab’s approach.
Q: There’s a lot of discussion about which method of sample collection is best. Why is Verily using nasal swabs?
Our goal with COVID-19 testing is to maximize the accuracy of the results we can deliver. Overall, nasal sampling has demonstrated the greatest consistency in results, which includes mid-turbinate and anterior nasal swabs. Such nasal swabbing is relatively comfortable and easy for healthcare providers (HCPs) and participants to collect. To date, thousands of individuals participating in Healthy at Work have been able to successfully take their samples while being supervised by HCPs and send them back to our labs for analysis.
Q: Verily just received Emergency Use Authorization (EUA) from the FDA to conduct self-collection testing. Can you explain a little more about what that means?
This week, we were granted Emergency Use Authorization by the FDA to perform self-collection testing. The testing that we and others across the industry have done to date has proven the high efficacy of nasal swabs. So, our User Experience team conducted extensive usability studies to develop easy-to-use nasal swab kits and clear instructions to help individuals take samples independently. By sending tests directly to individuals in our program, we aim to make it easier for them to participate and complete a test quickly at home. We’re planning to roll this out with at least one Healthy at Work customer before the end of the year.
Q: Saliva has been suggested as another type of sample for COVID-19 testing. Have you tried it with the RT-PCR assay?
We describe some of the different samples for RT-PCR testing in our recent white paper. Saliva is one of the simplest specimens for individuals to self-collect and has been used successfully for respiratory virus detection. It’s a logical specimen to consider for SARS-CoV-2 detection.
However, studies are still limited. We recently completed our first saliva test using the Thermo Fisher TaqPath RT-PCR assay. Based on the results, we’ve determined that saliva provides a less sensitive sample than nasal swabs. Approximately 70% of patients positive by nasal swab also came back as positive with saliva, while 30% came back as negative or inconclusive. We plan to continue using nasal swabbing for sample collection to ensure we are able to detect as many infections as possible.
Q: Can you explain a little more about viral load, and how that may impact what someone does after receiving a test result? Given recent publications on the long tail of virus RNA positivity after the infectious period, what do you think about samples with low viral load and the need to quarantine?
There’s been some discussion about the cycle threshold (Ct) values from RT-PCR, and whether or not there is any correlation with viral load. Industry data does show correlation with viral load; if you detect COVID-19 earlier in the cycling process, the sample is likely to have a higher viral load. However, we have not yet seen this data incorporated into the standard of care across the industry. The use of Ct values for any clinical interpretation would also require authorization from the FDA.
Q: How have the CLIA lab operations enhanced what you’re able to do through Healthy at Work?
Through Healthy at Work, we offer heterogeneous testing frequencies aligned to our customers’ needs. Our CLIA lab can process several thousand samples daily to support this breadth. At Verily’s South San Francisco office, for example, we have three testing cohorts: individuals who get tested twice per week, once per week and once every two weeks. This is primarily based on the frequency of coming onsite, but may also be tied to their role. For example, employees who must work in close proximity to others for extended durations are tested more frequently.
Our CLIA lab has also implemented a rapid and reliable turnaround time for results, providing the majority in less than 48 hours, to enable our customers and their teams to take any important action quickly. Fast, accurate results also enable our customers to quickly adapt their testing frequencies based on the latest data to ensure the safest environment possible.
Q: What’s coming next?
With the increase of testing over the holidays and the recent arrival of the vaccine, we’re working to expand operations for our CLIA lab and programs like Healthy at Work.
As an initial step, we previously switched to the pooled method for COVID-19 testing, based on the FDA’s Emergency Use Authorization (EUA) for the pooled assay for diagnostic testing. Pooling allows for more people to be tested at once, resulting in the conservation of reagents when the expected rate of positive detection is low. This method supports testing thousands of samples daily, quickly and efficiently. Pools that test positive are used to identify candidate individual positive samples, which are subsequently confirmed using individual tests. All positive samples identified by our pooling strategy are confirmed by individual re-testing to ensure a high level of confidence in the results. Using this pooling approach, positive samples can typically be identified with ¼ to ½ the number of tests compared to an unpooled RT-PCR test.
Speaking of the vaccine, we’re excited about its potential. In the meantime, we’re making testing available to as many people as possible through these difficult winter months. We’re exploring ways to further increase access to testing, as well as more flexible methods for sample collection.
For more information about Healthy at Work, please contact our team here.