Last week, Natick Public Schools asked enrolled families to respond to a survey gauging interest in Covid-19 pool testing. Pooled testing involves mixing samples from multiple people together in a "batch" or pooled sample, then testing the pooled sample with a diagnostic test. This approach increases the number of individuals that can be tested using the same amount of resources.
In a public presentation, NPS described pool testing as:
An efficient way to surveil a large population
Captures a moment in time
Effective method to detect asymptomatic infections
Provides an informed starting place for contact tracing
A portion of a Natick town-wide strategy to detect and contain COVID-19
NPS indicated 80-90% of students would need to participate for a pooled testing strategy to be successful, and asked if parents would be willing to pay for the service, which would cost between $200-$300, per student (for a total cost of approximately $1.5M for the District). It is unclear if these costs would also cover teachers and staff (approximately 850 employees) and if families would receive a refund in the event NPS returns to a fully remote model due to a rise in Covid-19 cases. (After this question was originally posted, former School Committee member Dave Mangan, clarified that an opt out of any contract would need to be negotiated if the schools went fully remote. See more below.)
Also uncertain is the impact a pooled testing program would have on NPS’s current and future budgets, which are currently in jeopardy due to the high reopening costs NPS incurred due to Covid-19 (approximately $5M). While the survey asked if families would be willing to donate money to cover the testing needs of other students, it is unclear if NPS might also seek funding from taxpayer dollars to help cover the full costs of the program.
How would NPS implement a pool testing strategy?
In the model proposed by NPS:
Pool testing would be conducted for a student just prior to their "in-person" week. This means they would be tested every other week.
Staff would also participate in pool testing.
A PCR test (saliva, not nasal swab) would be used to identify infections. PCR is the current "gold standard" for COVID-19 tests. The antigen test is not yet as accurate and would not be used.
The “pool” is the 10-12 students students in a classroom with during in-person learning. (The “pool” is larger at the high school.)
The test would be conducted on the Wed./Thurs. prior to a student returning to in-person learning.
If the pool was negative, the pool would be cleared to return to school. If there is a positive test in the pool, the class would learn remotely for the week.
Will the proposed model help NPS isolate infections and keep school open for in-person learning?
It is unclear if a once a week testing strategy will achieve the goals of a pooled testing program. The proposed PCR tests produce false negatives for 67% of patients four days after infection and produce false negatives for 20% of patients eight days after infection. This means they will likely produce false negatives even if a member of the pool is contagious, depending on where a pool member is in their infection and the corresponding effectiveness of the test.
There is also a question of if a once a week testing strategy is frequent enough to isolate infected pools and prevent spread to the larger NPS community.
Finally, it is currently unknown if enough NPS families are willing or able to participate in the pooled testing program. As of the morning of Friday, October 9, the School Committee Chair posted on Facebook that 700 NPS families (less than 80%) had responded to the survey. This is the second survey NPS sent to families about pool testing. According to remarks by the Superintendent of Schools, the first survey did not generate enough support for the program.
When will NPS decide if it will pursue a pool testing strategy?
Parents were surveyed a 2nd time last week, and NPS is receiving bids from companies that would perform the tests.
We expect an update will be provided at the next School Committee meeting on October 19. .
Note, if NPS is unable to pursue a pool strategy at this time, due to costs or concerns regarding efficacy, that does not preclude it from pursuing testing (potentially with different technology or at an increased frequency) in the future.
NPS presentation on pooled testing is available here: