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Opinion: Cheap antigen tests may be the answer to Arizona reopening its schools — even if they are less sensitive at detecting positive COVID-19 cases with low viral loads.

Kyle Freese opinion contributor

Published by AZCentral.

Coronavirus

Returning our children, teachers and administrators to school is one of the more difficult challenges we have faced during the SARS-CoV-2 pandemic.

However, false dichotomies promoted by nonexperts only act to divide public opinion.

The question is not “can we return to school or not?” but rather “When and how can we return?” While there is no silver bullet, the challenge is solvable.  

On Thursday, Gov. Doug Ducey and the Arizona Department of Health Services unveiled the county-level benchmarks for returning to (hybrid) in-person instruction for schools, which include two consecutive weeks of 1) fewer than 100 cases per 100,000 individuals, 2) percent test positivity below 7%, and 3) hospital visits for COVID-like illness below 10%.

Benchmarks are just a starting point

Taken together, these are important metrics to consider when making return-to-school decisions, but we must understand that infectious disease outbreaks are dynamic and that our responses must be a function of the situation; ideal solutions will likely differ across populations and schools and should be tailored to the characteristics of each.

More foundational to the benchmarks above is the need to rethink our testing strategies so that schools can open and continue to function.

The media is replete with stories of schools reopening only to close within a matter of days because of positive test results. Without a fundamental shift in our approach to testing and isolation, this story will likely replay itself throughout the country for the foreseeable future.

Why daily testing matters for schools

It is not news that widespread testing and targeted isolation are cornerstones of slowing the spread of SARS-CoV-2. Unfortunately, testing is often characterized by prohibitive costs, long wait times and prolonged laboratory processing. For school-age children, the challenge is compounded because this group typically has fewer COVID-19 symptoms when infected, which means they would not be prioritized for testing in the current environment.  

A growing number of public health professionals are advocating for a change in the current testing paradigm to focus less on the accuracy of individual viral tests and more on the rapidity and frequency of testing.

Though the “gold standard” PCR has high sensitivity — i.e. it can detect low concentrations of virus — these tests can be expensive and often have slow turnaround times. Conversely, tests with lower sensitivity are typically cheap and quick.

Cheaper antigen tests are the way to go

Importantly, as our understanding of SARS-CoV-2 improves, these highly sensitive PCR tests might not be necessary at this stage of the pandemic when our goal is to drive down the R-effective (the number of people in a population susceptible to infection by an individual).

Using cheap antigen tests (those that would likely cost just a few dollars and can be done at home by collecting saliva), results could be available in near real-time. Even though these types of tests are more likely to miss positive cases with low viral loads, the individuals we care most about identifying are those with high viral loads — i.e. the most likely to be infectious.

Furthermore, if these tests are done daily, even if a positive individual is missed one day, they are likely to be identified on the next if they are at the beginning of their infection and their viral load is increasing.

Speed matters more than accuracy now

The concept has been discussed at length by Dr. Michael Mina of the Harvard T.H. Chan School of Public Health and amplified by other experts such as Dr. Ashish K. Jha, who said it well in a recent TIME article: “Speed matters much more than test sensitivity in controlling a pandemic.”

Of course, the volume of tests needed would be associated with significant costs and logistical challenges, but if we are serious about returning to school and work safely and sustainably, we must support the exploration of these solutions.

Overall, successful return-to-school protocols must be tailored, easily modified and data driven. We should focus on the data, admit that there is no easy solution, and push for practical approaches.

Kyle Freese, MPH, PhD, is an epidemiologist with STChealth, a public health intelligence company in downtown Phoenix. Reach him at kyle_freese@stchome.com; on Twitter, @Epi_DrFreese.