With its recent transition to in-house saliva testing, Cal Poly is screening between 600 and 3,500 students per day for COVID-19.
With the program still in its infancy, the team of professors who created the test said they are hopeful that this number will increase to 4,000 tests per day.
As the university begins to release information regarding a fall quarter that is “as close to normal as possible,” it appears that frequent testing will play a large part in these plans.
“We’re doing a lot of this to support the volume that would allow us to feel safe to come back in person,” biological sciences professor Jean Davidson said.
What’s the difference between a saliva test and nasal swab?
The saliva test is more accurate, according to biological sciences professor Nathaniel Martinez.
The nasal swab test requires a person to stick a swab up their nose to collect a sample that may contain COVID-19. Sometimes people swab incorrectly and don’t collect a proper sample, Martinez said. With the saliva test, though, people just need to spit in a tube to collect a sample.
“With saliva, there’s really no way around it. You either spit in the tube, or you don’t,” Martinez said.
The saliva test is designed to be less invasive and prevent long lines, Davidson said.
Creating a quick test
In early March, Davidson started testing out machines.
“We spent a couple days trying to see if we could even play in the big leagues,” Martinez said.
Cal Poly asked Davidson if she could develop an in-house COVID-19 test in September, and it turned out her team could.
The primary challenge the group faced was adapting their test to process thousands of tests a day. The answer: more robots.
The lab contains nine pipetting robots that move drops of saliva from one place to another as well as three qPCR machines that test the samples for COVID-19. Most of this infrastructure already existed in various faculty labs across the university.
These machines are able to free students in the lab from “mind-numbing work,” Davidson said, and they now monitor the machines and work on making the process more efficient.
“The undergrads can watch and be in charge of those robots, but not do the tedious, moving things,” Davidson said.
But, more machines were not the only answer. Davidson said they tried to move away from a “cumbersome protocol” and refine the process down to six steps.
First, students deliver small, plastic tubes containing 2 milliliters of saliva to the lab. A custom barcode is printed on the tube to match it to the person whose sample it belongs to.
Once the tube gets to the lab, it is heated at 115 degrees Celsius for 15 minutes to deactivate the virus so it’s no longer contagious, Davidson said.
When the virus enters the body, it steals a piece of the host’s cell membrane and slips inside like a letter into an envelope, which protects the virus and allows it to infect the body. The heat breaks the so-called envelope and damages the RNA of the virus, preventing it from infecting any more people. The heating step makes the saliva samples safe to handle.
“It’s like taking the motor out of a car,” Martinez said. “It’s still there, you can see it, but it can’t really do anything.”
Saliva is thick, so the heating cycle liquifies the sample and makes it easier to work with. Next, students in the lab remove the caps, and the tubes wait in a rack for testing.
A pipetting robot plucks saliva out of five tubes and combines them into one plate. The robot records which samples are in the group, so if the group tests positive, the lab can test the original samples individually.
Combining five samples into one test allowed the lab to process more tests a day. Because creating the reaction to test these samples can be costly, pooling them together also allows for a more cost-effective operation.
A robot then moves the plate into a qPCR machine, which tests the samples for COVID-19. If the group tests positive, the lab traces back to the original samples and tests those individually.
Because the lab tests asymptomatic students, very few samples contain COVID-19. For those samples that do contain the virus, the saliva results will include the amount of virus present in the sample at the time that it was collected. This number can help to place where a person is in their infectious journey and better allows the university to understand how the virus is spreading within the community.
Planning for the future
Once the lab reaches the ability to run 4,000 tests per day, or roughly 20,000 per week, the university will have the capacity for all students and faculty to be tested twice every week. According to Davidson, this volume of testing is consistent with CDC guidelines and allows for robust surveillance.
In the midst of a successful launch for saliva testing, Davidson said she is already looking forward to the future applications of the testing infrastructure.
“I’m really curious to see what we could do with this beyond the COVID-19 world,” she said. “I’m exceedingly proud of what we put together and just thrilled that we could help serve our community at this time.”