The NZ government needs to immediately abandon its scepticism about non-symptomatic testing for COVID-19

June 17, 2020

Aotearoa New Zealand has been consumed today by discussion of the varied fiascos around the government’s COVID-19 border quarantine and self-isolation policies and practices. Obviously there have been a wide range of failures here, which cannot be reduced to a single source. But I want to draw attention to a specific, very consistent element of the Ministry of Health’s attitude to COVID-19 policy that has, in my view, caused problems for the government’s COVID-19 response from the beginning, and which now risks wrecking the enormous progress the country has made in the goal of eliminating COVID-19.

Put bluntly, the Ministry of Health is absolutely convinced that there is very little point in testing non-symptomatic people. This has been clear in their testing guidelines from the beginning, and the great difficulty people had getting tested. It is now confirmed in testimony from people who have recently arrived in the country, and who were unable to persuade MoH staff to test them even as part of the government-overseen isolation process. Per this 1 News report:

She and her family members also didn’t get tested before leaving yesterday, because she was told it was optional. “She then said to us that it was pointless us having the test done unless we were showing any symptoms.” Another woman who stayed at the same hotel as the two new positive cases says she was told the same thing. She got a test anyway, but now, home, still hasn’t received her result.

Why is the MoH so determined not to test non-symptomatic people? Obviously the following is somewhat conjectural, but in my view some core elements of the NZ government’s view on COVID-19 are as follows:

First, the government is convinced that asymptomatic transmission of the virus is extremely rare. Asymptomatic here means not just “non-symptomatic”, but “will never become symptomatic.”

Second, the government is convinced that symptomatic cases can be identified when symptoms emerge, and contact tracing can then take care of any transmission that took place in the few days before symptoms emerged.

Third, these opinions are supplemented by the recognised statistical fact that interpreting the likelihood of a false positive in a test result is highly dependent on the underlying probability that the individual being tested has the condition.

Fourth, the government is convinced that for these reasons, those calling for widespread testing of non-symptomatic people are being irrational. To the extent that the government are willing to test non-symptomatic people they will do so reluctantly and tardily, in order to (in their eyes) placate a hysterical public and media, or at best out of a hyper-abundance of caution, rather than for good public health policy reasons.

Fifth, and particularly irrationally, these attitudes have been extended even to the testing of individuals in mandatory isolation to attempt to prevent new COVID-19 cases from circulating within the country.

All of these positions are problematic. It is plausible but not established that asymptomatic transmission is very rare; it is easy to miss the symptoms even of symptomatic cases – as in fact happened with the two new cases of COVID-19, one of whose symptoms was apparently (mis)attributed to a pre-existing condition; the risk of statistical artefacts can be greatly reduced by repeated testing; it is in fact extremely rational to adopt a policy of broader testing, as I argued in an earlier post; and none of this makes any sense when you’re talking about a process that has specifically been designed to prevent new COVID-19 cases from entering an as-far-as-we-know currently otherwise virus-free country.

And yet the Ministry of Health and the government more broadly, in my view, remain in the grip of a baseless conviction that calls for testing of non-symptomatic cases are fundamentally silly, a demand to be placated rather than acted upon. Until the MoH abandons this idée fixe, the country will not be able to adopt a fully rational COVID-19 pandemic policy.

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