By Dr. Linda Jacobson DVM
I recently learned a new term: epistemic trespassing. “Epistemic trespassers are experts who pass judgment on questions in fields where they lack expertise.” (I don’t know the term for non-experts who pass judgment on questions in fields where they lack expertise!) We are all super-familiar with this behaviour during COVID-19. I’ve been guilty of it on many occasions, especially the part where you try to predict the future of the pandemic. I have definitely stopped trespassing on the field of fortune-telling!
Although we’d prefer not to figure out own own strategies, the reality is that Omicron cases have soared, public health messaging has become more and more confusing, contact tracing is not occurring, PCR tests are largely unavailable and our organizations have to come up with some COVID-related decision-making. The challenge is how to keep people safe, while ensuring that we can continue to function as effectively as possible.
I’ve found Twitter an invaluable resource. It suffers from an excess of vitriol and sensationalism, for sure, but it also contains a host of real experts who share abundantly of their time and expertise, as well as posting links to and interpretations of cutting-edge research. I consider my Twitter “echo chamber” to be part of what is termed “medical Twitter”, and I’ve learned so much from it. Clearly, these groups need to be carefully curated, and information needs to be checked. And I do, of course, follow Dr. Scott Weese very closely, both on Twitter, the OVMA COVID-19 guidelines, the wormsandgerms blog and the CVMA Townhalls.
So, what to do? We do what we do best as animal welfare organizations: do as much as we can with limited resources, think strategically, focus on human and animal safety and well-being.
Toronto Humane Society recently joined the Ontario government’s provincial rapid testing program, through Creative Destruction Laboratories. This program is free for businesses and provides rapid tests exclusively for asymptomatic testing. The only problem is that tests have not been available since we joined and we are still waiting for our first batch. In the meanwhile, we have managed to scrape together our own limited supply of rapid tests, supplemented by kits that staff and volunteers managed to acquire on their own.
What do rapid antigen tests actually mean?
It’s been weird to learn how much rapid antigen tests are like parvo SNAP tests. Our recent study showed that “a positive is a positive” when using the SNAP test for kittens with suspected panleukopenia. While false positives can occur with COVID rapid tests, in general that’s also the thinking for these rapid tests.
Rapid antigen tests detect higher viral loads and results agree very closely with virus isolation, which detects live, viable virus. The COVID PCR test is much more sensitive, and picks up lower viral burdens that may be below the infective threshold and/or may be non-viable. Exactly the same for panleukopenia, other than that we don’t have the virus isolation research.
How to use rapid tests with very limited supplies?
The amazing Dr. Weese summed it up beautifully in this week’s CVMA Town Hall: Target testing to situations where the pre-test likelihood of a positive test is highest.
For the tests we’ve purchased (that are not subject to CDL/government program restrictions), we therefore decided to prioritize as follows:
- “Test to Return” – strategically-timed rapid tests for people who are symptomatic (i.e. presumed positive) or have tested positive by any test and are asymptomatic. Once negative, staff and volunteers may return to the facility. This exceeds current Ontario government guidance. (This approach provides the highest pre-test likelihood of a positive test.)
- Now that we have some more tests, we have added “Test to Stay” for asymptomatic close contacts. Again, timing is strategic, based on limited supplies of tests. And once again it exceeds official requirements. (In our view, this is the second-highest pre-test likelihood of a positive test.)
Our flow charts are here:
Where to swab?
We’ve also suggested to our staff that it seems to make sense to swab the throat first, and then the nose (with the same swab), based on recent research findings that Omicron may be more likely to be present in saliva. This is not how the tests are labelled, and not yet officially recommended in Canada (although it is recommended in the UK), but it could take months for that to change. In the meanwhile, we want the highest possible likelihood of a positive test if the person truly is positive. It’s a fine balance. Testing is all voluntary at our organization right now, and nobody is obliged to follow our suggestions.
What I’ve outlined above may not be the best way to do this testing, and it’s most definitely epistemic trespassing, but like everyone else, we are doing the best we can with the resources and information we have.