CEO SUMMARY: Pooled testing helps the clinical lab staff at the hospital in Saratoga Springs, N.Y., do more COVID-19 tests when supplies might otherwise run short. Lab managers estimate this method has saved 5,000 test cartridges since May. Pooled testing also helps the physician staff in the emergency department identify patients who may be positive for COVID-19, so the hospital can cohort patients to different care units as needed. Doing so also helps conserve personal protective equipment for staff.
“TO POOL OR NOT TO POOL?” That is the question many clinical laboratory directors are asking to support efforts to perform greater numbers of COVID-19 tests as the pandemic gathers momentum.
At Saratoga Hospital, a 171-bed community hospital in Saratoga Springs, N.Y., the lab team answered that question with a “yes.” In fact, it is now in its eighth month of using pooled testing.
As a method of testing, pooling has been successful in conserving supplies. It is useful for identifying patients who are positive for COVID-19 and those who are not. This allows treating physicians to segregate patients into COVID and non-COVID units.
In the spring, when supplies became the main obstacle to testing more patients for COVID-19, Saratoga Hospital conducted an assessment of the concept of pooled testing. Validation studies were performed and, once the laboratory found that pooled testing would be feasible, the administrators decided to use pooled testing whenever possible since then.
As of the end of the first week of November, almost 7,000 patients in pools of three to five specimens each were performed at the Saratoga Hospital laboratory. Only 26 of those patients were positive for COVID-19, or less than 1% of all patients tested.
“We have used pooled testing since the spring and continue to do it today because it’s been a very successful program for us,” Josenia Tan, MD, Chair and Medical Director of the hospital’s Department of Pathology, said in an interview with The Dark Report. “Our hospital has been able to test all patients admitted to triage for isolation and use of appropriate PPE.”
Enable High Levels of Testing
For Richard Vandell, MS, MT (ASCP) SC, SH, Administrative Director of Laboratory Services, a critical benefit of the pooled approach is that it enables Saratoga Hospital to continue COVID-19 testing at a high level.
“To do all of that testing, we have used a little more than 1,400 test cartridges, meaning we have saved over 5,000 cartridges to date,” he commented. “That level of conservation means we were able to sustain testing at the same level during this entire time. Pooled testing for COVID-19 has allowed us to continue to test because we are maintaining a self-fulfilling ability to do so.”
Three Lessons Learned
For Tan, there were three significant lessons learned that other labs would find useful as they start pooled testing for SARS-CoV-2:
Know the infection rate in your service area,
Understand the capability of your lab to do pooled testing, and
Get regulatory approvals to do this form of testing.
“Knowing the infection rate in your community is essential for doing pooled testing successfully,” said Tan. “If the rate is too high, your lab will use too many supplies because of the need to do repeat individualized testing. An infection rate of 5% or less is best.
“If the COVID-19 infection rate is higher than 5%, then too many pools of specimens will be positive,” she noted. “When that happens, your lab will need to test each specimen in the positive pools again. The need to run those additional tests reduces or eliminates the benefits of pooling.”
Since the pandemic began, New York State has had infection rates reach as high as 44% on April 4 and as low as about 1% from the beginning of June through late October. In the first week of November, the positivity rate rose to about 2.4%, according to data from the New York State Department of Health (NYSDOH).
Know Lab’s Capacity
“The second lesson is that it’s necessary to know the capacity of your lab and your staff,” she added. “What is the productivity of your lab’s testing platform, and what are the capabilities of your lab staff?”
The lab at Saratoga Hospital runs three shifts and about 1.2 million billable tests per year, Vandell noted. Since the pandemic began, the lab has processed 64,000 coronavirus tests. The primary platform for these tests (and the pooled tests) is the Cepheid GeneXpert RT-PCR test. In addition, the lab also performs a rapid antigen test. The Abbott ID NOW and Rheonix platforms are in development, Vandell reported.
The third lesson is to get the regulatory approvals needed for pooled testing. Saratoga Hospital’s lab team sought that approval from the NYSDOH public health laboratory at the Wadsworth Center in Albany, Tan said. “To help us assess the feasibility of pooled testing, we engaged the staff at the Wadsworth lab almost as a consultant,” she added.
“To be able to introduce pooling, we modified the collection method,” Vandell explained. “We changed the number of nasopharyngeal swabs placed in each tube of viral transport media from one to up to five, as needed. This gave us the flexibility to meet the emergency department’s needs. The testing method for SARS-CoV-2 remained the same.”
The lab was testing emergency department patients for SARS-CoV-2 to determine which ones needed to be admitted to the hospital. When assessing these patients, the lab team worked closely with physicians in the emergency department who were assessing patients’ symptoms, Tan and Vandell explained.
Ideally, the lab wanted to test five specimens in each pool, but it was not always feasible for the emergency department to collect that number without making some patients wait an inordinately long time. Rather than keep patients waiting in the ER, the lab would run as few as three specimens if needed, Vandell said.
To prove that pooled testing produced an accurate result, the lab compared quantitative data from positive pools against the individual positive patients in the pool. “We saw very little difference in the measured data, and this proved that pooling results were accurate,” Vandell said.
“We work very closely with our emergency department to assess patients by their symptoms to determine which specimens to include in the pool,” he added.
Pooled testing not only helps conserve supplies, but also allows the ER staff to know which patients are positive so that treating physicians and nurses can segregate positive COVID patients from non-COVID patients. “We want to cohort our patients because doing that allows us to conserve the personal protective equipment for our staff and reduce the level of anxiety among healthcare workers in the hospital,” Vandell said. “That has been an institutional goal for us, and the pooling strategy has been a huge part of achieving that goal.
“Of course, with the continuing supply-chain shortages, a significant reason to continue doing pooled testing is to conserve supplies,” he explained. “Even now, in November, we do a count every day of our testing supplies because we are continually making decisions about how to conserve supplies.
“Our lab team has done this since the beginning of the pandemic,” added Vandell. “Without pooling, we might not be able to continue to do the level of COVID-19 testing we’ve been doing.”
For the lab team, the recent rise in the positivity rate is a new concern. “In the last week in October, we were at 2.4% for symptomatic patients,” Vandell commented.
“That’s an important distinction because in our pooling technique, we try to screen out symptomatic patients to keep our incidence rate low,” he commented. “A few weeks ago, we had a positivity rate of 2.4% in the community. One day during the first week of November, we had seven positives out of a total of 64 symptomatic patients at one of our testing facilities. That’s a concern because that’s about an 11% positivity rate for COVID-19 in our community.”
Lab Team Publishes Study of Pooled Testing Results
SARATOGA HOSPITAL’S IDEA WAS TO USE POOLED TESTING AS A STRATEGY for patients at low risk for SARS-CoV-2 who would be admitted to the hospital, according to, “Pooled Testing for SARS-CoV-2 in Hospitalized Patients,” a study published in the Journal of Hospital Medicine in September.
In the article, Josenia Tan, MD, Chair and Medical Director of the hospital’s Department of Pathology, and colleagues, described how viral testing for SARS-CoV-2 early in the pandemic was limited due to supply shortages—especially reagents.
For the lab’s assessment of pooled testing, the team collected nasopharyngeal samples from emergency room patients who were at low risk of SARS-CoV-2 infection in groups of three for the pooled testing. Over three weeks, the lab tested 530 patients in 179 cartridges and had four positive test groups requiring the use of 11 additional cartridges. This level of infection showed an overall positivity rate of 0.8% among those tested.
“This strategy resulted in the use of 340 fewer cartridges than if each test were performed on one patient sample,” the authors wrote.
In conclusion, they added, “Pooled testing of low-risk populations allows for continued testing even when supplies are relatively scarce.” Once the lab team had validated the process for pooled testing, Tan and other senior lab administrators decided that pooled testing would be useful throughout the pandemic. Since then, the lab has used pooled testing before any patients are admitted.
Contact Josenia Tan, MD, at 518-583-8442 or JTan@saratogahospital.org; Richard Vandell at 518-583-8443 or firstname.lastname@example.org.