Two-part COVID-19 screening forms effective stop-gap at La Sierra

Widespread testing has long been touted by public health officials as one of the best ways to control the COVID-19 pandemic and save lives, but the process can be cost-prohibitive. Toward maintaining the safety of its campus members while reining in expenses, La Sierra University in February implemented a two-part testing process that replaces a contracted service and utilizes a less invasive method developed by one of its biologists and his research colleagues.

Following a five-month pilot with student-athletes, a weekly saliva-based screening for COVID-19 was initiated Feb. 16 during winter quarter for the limited number of students and employees who are allowed to study or work on campus during its closure due to the pandemic. Spring quarter began March 29, the first full quarter with the new method in place. The screening method is used in concert with a new, ‘gold standard’ rapid point-of-care PCR Cepheid GeneExpert Express molecular testing system purchased last fall to verify positive results from the saliva-based model. The rapid PCR test requires a nasal swab specimen collection method.

The two-part system stands to save the university tens of thousands of dollars per month while producing quick results and maintaining the safety of the campus community. The financial savings allowed the university to increase its campus testing frequency from two times per month to two testing clinics each week.

“For this protocol you don't have to wait in a long line, you just collect your saliva, turn it in, and you're free to go.” - Benae Anderson, health sciences and pre-medical major, resident assistant

Limited numbers of La Sierra students who attend in-person lab and studio classes under state guidelines, who live in dorms under health protocol, faculty and staff who are regularly on campus as teachers or essential employees, as well as vendors and others approved to enter the campus must also complete a weekly online COVID-19 symptom screening form which is emailed each day to campus members. Student-athletes during their playing season undergo testing for COVID three times a week, twice via the saliva-based system, and once with the PCR rapid test.

Since February, more than 2,500 saliva specimens have been collected during weekly COVID testing clinics in the Alumni Pavilion. Saliva samples are collected in small vials, replacing the nasal swab specimen-gathering method used at many public testing sites. The saliva samples are then processed in a lab in La Sierra’s Price Science Complex where a change in the solution from a bright pink to a clear yellow indicates a positive test. The few tests flagged by this process indicating possible positivity for COVID activated immediate isolation procedures while results were verified or nullified by the rapid PCR system. A website case tracker reports any active COVID cases weekly with one active case listed as of April 26.

Two-track system

A number of other universities and institutions also use saliva testing models for detecting SARS-CoV-2, the virus that causes the illness named COVID-19. The saliva test in use at La Sierra was developed by associate professor and virologist Arturo Diaz and his colleagues at the University of Wisconsin-Madison. Diaz then modified the protocol in his lab over a period of weeks for use on La Sierra’s campus. While the saliva test is not FDA approved, the Cepheid GeneExpert Express rapid PCR testing system does have the FDA’s green light. The saliva method produces results that are 90.5% concordant with qRT-PCR, or real-time quantitative reverse transcription polymerase chain reaction.

“Our current procedure is that individuals who test positive by the saliva test are immediately contacted and required to obtain a PCR test through La Sierra’s Student Wellness center and self-isolate until the results of that test are known,” Diaz said. “By using this strategy we’re able to screen a large number of people while saving money as the PCR test is only used on individuals who are likely positive. We can run about 20 saliva tests for the cost of what the university was being charged for one [contracted] PCR test.” The saliva-based tests, which take two to two-and-a-half hours, cost about $6 apiece with the university covering the expense for students and employees.

“This saliva test we use on campus differs from most others in that we don’t use polymerase chain reaction (PCR) to detect the presence of SARS-CoV-2,” Diaz continued. “One of the drawbacks of PCR is that it is expensive and requires sophisticated equipment and personnel with experience. Our test employs reverse-transcriptase loop-mediated isothermal amplification (RT-LAMP) to amplify specific parts of the SARS-CoV-2 genome present in saliva samples. The advantage of RT-LAMP is that it is easier to set up than PCR, and doesn’t require specialized equipment. Moreover, people with basic lab skills can be trained to run the test in a short period of time.” 

The RT-LAMP analysis produces easily observed results. “If there is SARS-CoV-2 genetic material present in the saliva sample, the reaction will copy so much DNA that the pH of the solution actually changes. This turns the solution from a bright pink to a clear yellow, signaling a positive test,” Diaz said.

The initial plan was to test individuals reporting symptoms of COVID-19 and also to implement universal routine testing at a rate of 25% of the campus per week toward increasing that number as the university had the capacity. The saliva-based testing allowed a more rapid move to universal testing of 100% of the campus each week.

Said Diaz, “As I read some of the primary literature it became clear that most individuals were infectious two to three days before the first sign of symptoms and that close to 40% of all infected did not exhibit symptoms. Thus, the only way to mitigate disease transmission was to establish systematic and ongoing testing in order to identify and isolate individuals who were infected.”

Diaz teaches virus research courses to undergraduates as part of the national SEA-PHAGES and SEA-GENES programs offered through the Howard Hughes Medical Institute. Following the pilot run in September, he established a COVID-19 testing center within a teaching laboratory at Price Science Complex.

Weekly tests of campus members for COVID-19 will continue at the discretion of the university’s Emergency Management Team which is responsible for the university’s COVID-19 response. The university is currently offering exemptions from weekly COVID-19 screenings for campus members who bring their official COVID-19 vaccination document to a campus screening clinic for verification. Twice-weekly screenings are planned for the upcoming fall quarter for campus members who are not vaccinated for protection against COVID-19.