The University of Wyoming (UW) has prioritized testing for its community during the COVID-19 pandemic. Its testing program started at the beginning of the school year and has been an important tool as UW monitored the presence of the virus.
It started with randomized testing. Then it evolved into weekly tests for all employees and graduate students on campus and twice-weekly tests for all undergraduate students on campus. Through a partnership with Vault Health, all of these tests were free to the UW community. But they were costly to the university. So the school started developing its own test that saves time, money, and resources.
The samples are run just across town at the Wyoming State Vet Lab (WSVL) and they're done in batches or pools.
"We have scarce resources. I mean, everybody is testing. So resources are really hard to come by," said WSVL Director Will Laegried. "So by pooling samples, we use one-quarter of the number of resources. That comes also with a reduced cost. If you're using a quarter as much, the cost goes down significantly."
This allows them to test more people. They take the saliva of four people, combine it, and do a test. Laegried said combining the samples dilutes them very little and it doesn't cause a higher rate of false positives. The machine that combines them tracks whose saliva it is by using a QR code etched on the bottom of their tubes. The QR code is linked to a person's campus ID when they check-in for testing.
"It keeps track of every sample and every movement of every sample," said Laegried.
Another big advantage to using robotic machines like this is that someone doesn't have to do tedious tasks like putting hundreds of samples together. Laegried said this will be even more important when students return and the number of tests increases significantly.
If a pool tests positive, then all four people in that pool have to take an individual confirmatory test to find which is carrying the virus.
"That's kind of a standard procedure that is used. And we do that all the time with animal diseases," said Dr. Donal O'Toole at the WSVL. "Like for some of the common viral diseases, like if a herd is tested, we will do pooling. Sometimes the pooling is small, like five samples in a pool or 20 samples in a pool. And it's just to try and bring the cost down."
But it's only an efficient system if the rate of positive cases is low.
"If you've got a high number of positives, there's a lot of retests being done to identify who in that pool was positive. Was it one person or two people?" said O'Toole. "And so instead of it just being a one-stage test, it's a lot of positives and you're doing a lot of retesting to identify which individual, rather than groups of four."
Laegried agreed and said UW has actually been doing fairly well.
"Even at the worst this fall in the university, from a testing standpoint, the number of cases was relatively low, certainly less than 10 percent," he said. "So from an efficiency standpoint, we're still ahead of the game by having people undergo pooled testing, [or] surveillance type testing."
He does admit it's an inconvenience for people to be retested, but the number of confirmatory tests really isn't that high. One problem with this approach is how results are communicated.
If your result is part of a negative pool, the email simply thanks you for your participation. If your result is part of a positive pool, it tells you to come back for an individual retest. This has confused many UW community members. But Laigrid said this might not be such a bad thing.
"So what we don't want to have people do is get a negative result and think, 'I'm good to go. I can go about my business as normal because I'm not infected.' That's just not what a negative test tells you," he said.
A negative test result only tells you that the test didn't detect the virus on the day you gave your sample. There's a chance you could have been exposed before giving your sample and were carrying the virus, but it hadn't replicated enough yet to be detectable. There's also a chance that you were exposed after giving your sample and started carrying the virus.
The university is currently testing between two and three thousand people a week. That number will increase when students return to campus. UW believes this vigorous testing approach is the best way they can keep COVID-19 numbers under control.