Available funds and disease prevalence affect whether pooled testing is feasible and desirable, notes University of Kansas Health System microbiology laboratory director
Pooled testing for the SARS-CoV-2 coronavirus has its supporters and its critics. There is no one-size-fits-all when it comes to pooling multiple patients’ biological samples into a single COVID-19 test in the hopes that the result will be all negative. Several factors must be in place for COVID-19 pooled testing to be viable at individual clinical laboratories. The experience of medical labs that considered doing pooled testing are informative.
For example, when Rachael Liesman, PhD, Director of Microbiology in Pathology and Laboratory Medicine at the University of Kansas Health System in Kansas City, researched developing a plan for pooled testing of COVID-19 patients for her health system, she found the strategy less than ideal for two reasons:
- First was the rate of infection in the population being tested. If the rate was too high, pooled testing produced too many positive results, making the process impractical.
- Second was the need for expensive automated equipment in the microbiology laboratory, the funding to buy that equipment, and the room to accommodate it.
Last summer, as Liesman and her microbiology lab staff were evaluating pooled testing, she spoke with Dark Daily’s sister publication The Dark Report. “We were trying to decide whether pooled testing really would save us anything,” she said in the exclusive interview. “We were looking at the barriers and trying to understand what we’d gain and what we’d lose.”
Deciding Against Pooled Testing at University of Kansas Health System
After careful consideration, the lab staff stopped considering pooled testing due to increased prevalence in the community, Liesman said in December. “Our positivity rate is double what we were seeing in the summer,” she noted.
“Of course, the biggest challenge with pooling specimens is you have to have a patient population that has a low enough virus prevalence to make it worth your time,” she noted. “For us, there may be some patient populations that have a low enough level of prevalence, but not enough to make pooling feasible.”
University of Kansas Health System’s microbiology laboratory has been running 800 to 1,000 COVID-19 molecular tests 24 hours a day, seven days a week, although the lab runs fewer tests on the weekends. On Jan. 8, the number of new coronavirus cases in Kansas was at 1,780 per million, according to the COVID Tracking Project (CTP). That was about the highest rate since the pandemic began early in the year.
“One of the challenges in any lab is when you get specimens arriving in volume of say 100 or 200 specimens every few hours,” Liesman explained. “When that happens, you have to determine rapidly which of those specimens you would want to pool and which of them you wouldn’t pool. Or, if you had the right circumstances, you could pool all of them.
“You might have asymptomatic patients in one group and symptomatic patients in another group. So, then you could put all samples from one group into a pool. But if you’re not set up that way, just figuring that part out could be really time consuming,” she noted.
“Another challenge,” Liesman added, “is if your laboratory doesn’t have liquid handlers, which are the instruments that do the pooling for you.”
Manual versus Automated Pooling
In a clinical laboratory without liquid handlers, the task of pooling is not automated and instead requires staff to do the work manually—one specimen and one pool at a time.
Without the right equipment, Liesman noted, somebody in the lab must physically take five tubes and combine them in into one tube. And that one person has to ensure the test tube of pooled specimens is appropriately stickered. Then, once that is completed, the information must be input into the laboratory information system (LIS).
“We have a liquid handler because we purchased one from Hamilton specifically for COVID testing. But getting all that information into the computer system can take a lot of time,” she said. “A lot of labs don’t have access to this type of instrumentation, which means the process becomes very hands-on.
“We already see repetitive-use injuries, and if many of your staff are spending their eight-hour shifts doing pipetting motions, then they’re at greater risk for repetitive-use injury,” she added.
In addition, having humans doing repetitive motions in a clinical laboratory increases the risk of specimen-handling errors such as tubes being mislabeled or misplaced. “Those mistakes are very hard to find,” Liesman noted. “For us, we’ve been asking if we have the resources to do pooling successfully. And, if we put all these resources into it, what do we gain? That’s the big question for us.”
As Dark Daily reported in “University of Vermont Microbiology Laboratory Identifies Inefficiencies When Performing Pooled Testing for COVID-19,” the microbiology laboratory at the University of Kansas is not the only lab to have considered pooled testing and found it not desirable.
For a clinical laboratory to successfully initiate and maintain an effective program for pooled testing of the SARS-CoV-2 coronavirus, it must have specific equipment available to reduce manual touches of the specimens and automate as many work processes as possible. The lab’s manager must also consider the staffing required to handle pooled testing. Even then, if disease prevalence climbs above a certain level, pooled testing will not be a viable solution.
These are the reasons why many medical laboratories have considered a pooled testing arrangement but decided it would not be appropriate for their organization. Meanwhile, at other clinical labs pooled SARS-CoV-2 testing has been a major success, partly because it enables the labs to test many more patients using the same quantity of test kits and related supplies.