Thursday, 2 September 2021

Test test test

This week's Newsroom column made the case for freeing up rapid antigen testing for use at essential workplaces during outbreaks and Level 3/4 restrictions. 

There's something like half a million essential workers and perhaps a hundred thousand in Auckland. The government maintains no register of them, and it would be impossible to run daily testing of a hundred thousand essential workers during Level 4 through current testing systems anyway. The PCR swab regime has been buckling under demand and is providing very slow results. Saliva-based PCR testing is far better and far more scalable, but may not be able to get to a hundred thousand tests a day - and may not be cost-effective for broad surveillance testing in lower-risk essential workplaces.

Rapid antigen tests give results in about fifteen minutes. They are not likely to catch cases with low viral loads but are decent at high viral loads - the people who would wind up being infectious. Having workers run a self-test before starting shifts would add an additional layer of protection. But no rapid antigen test has been authorised for use in New Zealand. It is unclear whether MedSafe has even considered any - I have a request in with them for more information. 

The Newsroom column is also available on our website, where all my links to sources are preserved. 

A snippet:

Antigen tests are not as sensitive as PCR tests overall but are reliable when a person is infectious. For high viral loads, the Abbott BinaxNOW test proved as accurate as PCR tests in one assessment but missed one person whose low viral load was only caught by PCR. The test costs about $5 (more in the United States) and gives results in about fifteen minutes. Other antigen tests are broadly available in Europe, at less than a dollar per test. The Canadian government has been distributing packs of tests to small businesses for employee testing, for free.

These kinds of tests make more sense for broad population screening. If there is no reason to suspect someone has the virus, but you want to prevent infectious people from boarding an airplane, a rapid and low-cost test that can be administered in the departure lounge before boarding makes a lot of sense.

The New Zealand government’s testing regime is almost exclusively swab-based PCR tests. The system very obviously cannot keep up with the amount of testing required in major outbreaks. It takes too long to collect samples; samples must be collected by a limited number of trained professionals; it takes too long to process tests; it takes too long to return results to those who have been tested; and, it is rather expensive.

The University of Illinois’s saliva-based PCR test has been available in New Zealand on a private basis since January, thanks to the University’s New Zealand partner, Rako Science. Rako has advertised that it can test up to ten thousand people per day. Its collection method does not require scarce nurses for sample collection and can be scaled up much more readily. Depending how long it takes to get samples to the lab, it can provide results in about four hours. The Ministry of Health, for months, inexplicably refused to consider adding this option to the government’s testing regime.

But the real testing job is an order of magnitude larger still, if we want to turn Delta into Iota.

The Ministry of Health has reported transmission among essential workers in Auckland. This type of transmission has made it difficult for New South Wales to control its outbreak.

The government could, today, order a couple million rapid antigen tests. They are broadly available. It could distribute those test kits to every essential workplace in Auckland and require that every essential worker be tested every day before starting work.

It could be a condition of a Level 4 modified to suit Delta.

Within about fifteen minutes, each worker’s result would be available. Infectious workers could be sent to government testing stations for confirmation. And workplace transmission would be sharply reduced.

Why are employers not doing this on their own as part of normal health and safety prudence? The tests are currently prohibited in New Zealand. In April 2020, the government banned all point-of-care tests unless they are approved by MedSafe, and MedSafe has not seen fit to approve any tests. Pedants might argue that this does not constitute a ban, but banning anything that has not been approved while deciding not to approve any options sounds an awful lot like a ban. It is unclear whether MedSafe has even evaluated any options.

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