New Trier Saliva Test: Is it Enough to Open the School?

As COVID-19 cases exceed record levels, New Trier opened up Tuesday for in-person classes in conjunction with an unapproved saliva-based test.

New Trier High School students are returning to in-person instruction, contrary to thresholds the Reopening Advisory Board set that, if followed, would demand fully remote instruction. As of November 9, the numbers of new COVID-19 cases are over three times higher than the minimum the board established for all teachers and students to stay at home, and the positivity rates also exceed the specified levels. “It’s concerning to me that these red metrics are just seemingly being ignored,” said Katie Wright, a New Trier parent.

On October 22, New Trier’s district signed a contract with SafeGuard Screening, LLC to perform COVID-19 testing used to screen students and staff who wish to participate by providing a saliva sample they collect themselves at home. This test is not the widely publicized saliva test developed at the University of Illinois. SafeGuard’s CEO Ed Campbell, an Associate Professor at Loyola University’s Department of Microbiology and Immunology, developed the test for Lagrange School District 102, where he is the current vice president of the school board. He said that Loyola University is not officially connected to the test, though he did say that they operationalized the test at his lab at the university. 

Campbell said this test would give the district an understanding of how much infection is going on in the school system and allow the district to use the information to assess risk and respond appropriately. However, the utility of this new test and the significance of a negative result does not seem to have been established.

An October 27 Brookings Institute analysis said that individuals subjected to screening, such as what is happening at New Trier, will commonly engage in risky behavior because they assume they are not infectious. They cited the White House outbreak, which has resulted in at least 48 confirmed cases, where precautions were not consistently maintained. The paper said that similar behaviors were reported among college students. They pointed out the paradox that a testing regimen can embolden behaviors that increase transmission. And this occurs even when the tests being used have demonstrated an appropriate level of clinical accuracy.

In late August, the Trump Administration eliminated the requirement for FDA approval of certain laboratory tests including some for COVID-19. In response to this deregulation, Dr. Michael Carome, director of Public Citizen’s Health Research Group said in the New York Times, “Suppose you get a Covid test and you actually have the infection and it comes back negative. You may believe you’re OK and that may leave you in your home, exposing family and friends to the virus when you should quarantine.”

In an alert about fraudulent coronavirus tests where samples are collected at home, the FDA warns, “You will risk unknowingly spreading COVID-19 or not getting treated appropriately if you use an unauthorized test.” The FDA is supportive of COVID-19 testing with at-home collection when the tests have FDA emergency use authorization, which requires that tests be validated.

Campbell indicated that his company did not seek FDA authorization and the lab did not obtain a government certification that its test results are accurate and reliable. If specific results are reported to patients, certification is required. However, CMS (Centers for Medicare and Medicaid Services,) the federal agency that regulates testing labs, has stated that they will not enforce this regulation and will not cite uncertified facilities if they only refer people who indicate a positive result to a certified testing facility, as New Trier reports doing.

Dr. Richard Novak is head of infectious diseases at the University of Illinois at Chicago and has been leading a clinical trial on the Moderna COVID-19 vaccine. He discussed the importance of properly validated tests. “[A test without validation] may be no better than a coin flip,” he said, and that it would be hard to have faith in such a test. He explained that in the development of a clinical COVID-19 test, researchers normally compare the new test’s results to the most accurate test presently available, known as the “gold standard.”

Dr. Campbell was unable to provide specific data that would validate results from SafeGuard’s lab tests against a gold standard or other reference, other than approximate numbers based on what he’s seen from his own school district’s use, which he said are protected under contract. 

Dr. Campbell could not cite any negative results that were confirmed by gold-standard tests, but he mentioned an anecdotal negative result from his company’s test that was contradicted by a PCR test, which he called a “presumed false negative.” No other comparisons or test validations were performed to conclude what a “negative” result on this new test actually means. 

A false negative result occurs when a test such as this one fails to correctly identify an infectious individual. The person may be misled into believing that they are free of the disease and may unknowingly spread a contagious disease such as COVID-19. The more frequently this happens with a test, one that is intended to make a school safer by keeping possibly infectious people out of the school, the less useful and potentially more dangerous the test becomes.

An informal social media poll showed that 89% of respondents, who either signed up for the program or read New Trier’s materials about the program, believed that the person tested is definitely or probably not infected with the coronavirus if they are allowed into the classroom after their test has been processed. 

Dr. Campbell said that the aforementioned individual, who the company’s test incorrectly returned negative, had a very low viral load per the PCR test, and stated that it would “likely not have led to them being infectious.” However, his statement is not supported by current scientific consensus. An Oct 27 Brookings Institute analysis stated, “Overinterpreting the biomedical literature on the relationship between low concentrations of SARS-CoV-2 and infectiousness is dangerous and not supported by current evidence … As it currently stands, the scientific literature supports the proposition that cases missed due to reduced test sensitivity may well be infectious.” 

When asked about the fact that his company hasn’t been able to demonstrate a false negative rate, Dr. Campbell said, “To understand what our false negative rate is, you'd actually have to do a diagnostic test on all the samples that we've run, and that would have a tremendous cost associated with it and reduce the value of the test.” 

However, it is not necessary to verify each person’s test result in order to establish test reliability. For example, one company that recently applied for FDA authorization for their test, Agena Bioscience, evaluated specimens with known status, 63 positive and 60 negative. They ran each sample through their test as well as an FDA-approved reference test, and were able to provide specific data about their test’s accuracy, including both false negative and false positive test results. 

Dr. Kamaljit Singh, an pathologist and infectious disease physician and the director of Microbiology and Infectious Diseases Research at NorthShore University HealthSystem, has advised nursing homes seeking weekly screening tests to ensure the veracity of their tests. He recommends that they meet minimum standards and that the results are reliable, and encourages organizations to rely on labs with clear and certified test performance. Dr. Singh said that even small variations in testing need to be verified by the FDA and in some cases, labs are periodically sent samples with a known status from an independent agency and asked to provide results for them as part of continual monitoring. Campbell said that his company’s test involved the fusion of two tests, and that there has been no published study of his test’s efficacy. 

New Trier’s fact sheet states that the results of this test have been validated, citing two University studies of the different tests Campbell based his test on. Dr. Campbell himself verified that no paper has been published or submitted to a regulatory agency validating it. New Trier also states that “experience in LaGrange District 102 has also validated these results.” In a paper published in The BMJ, a leading medical journal, questions are presented for assessing the validation of a diagnostic or screening test. It would be difficult to interpret the unpublished, informal, and anecdotal reports coming back from the deployment of this test in a school district as meeting the standards described.

Even if one were to assume that this test had a low false negative rate without supporting data, the Brookings Institute paper warns:

The case for high-frequency testing relies crucially on two assumptions: false-negatives will be detected on repeat testing 2-3 days later, and “false negatives” represent non-infectious people. Unfortunately, each of these assumptions is fatally flawed.

What happens if a college student is exposed on a Sunday, tests negative on a Friday, attends parties Friday and Saturday nights, and then develops symptoms on the next Sunday when they also test positive? Very similar outbreaks have already been documented. This scenario ... poses a prime opportunity for rapid spread since the virus has been transmissible for at least 1-2 days by the time symptoms set in. Even short testing windows may fail to mitigate transmission due to risky behaviors during the infectious, pre-symptomatic period. Considering how recent behavioral models that failed to account for preventive misconception among college students, this scenario goes from plausible to likely.

Again, the much publicized outbreaks among frequently tested White House staff remain a sad example of this. 

New Trier has reopened for classes in the midst of the highest COVID-19 numbers our state has yet seen. It has done so partly by soothing the public with assurances of frequent student screening. However, the test has not been validated or appropriately understood. While it appears a “positive” result is likely a true positive, it is unclear exactly how reassuring a “negative” result will be - and how many infectious students it will miss. The possibility of the test’s mere presence encouraging behavior at high risk for viral spread looms large.

District Superintendent Paul Sally refused to respond to multiple requests for comment.