Editorial: Changing the definition of a Covid death

Director general of health Dr Ashley Bloomfield and the Public Health Agency's deputy director-general Dr Andrew Old arriving to announce the changes. Photo / Mark Mitchell

Editorial

EDITORIAL

Drums had been beating for the past few weeks over New Zealand deaths with Covid, compared with other territories around the world.

As New Zealand continues to trudge through a wintry second wave of Omicron, 360 per million reported deaths were just behind India (374 per million) and Australia (414).

Now the definition of a Covid-19 death in New Zealand will change from tomorrow.

In announcing the change, the Ministry of Health states our Covid-19 statistics will be more accurate as deaths will be linked to Covid only where it is believed the virus is the underlying or contributing cause.

The ministry previously recorded all deaths within 28 days of a positive test, plus any death that was attributed to Covid-19 after medical review.

It's estimated this shift in definition will pinpoint the virus as an underlying or contributing factor to somewhere between two-thirds and three-quarters of deaths previously recorded.

For some time, it has been known that Covid-19 infection can cause death from heart attacks and strokes and other causes that may not be attributed to the virus. Deaths from other infections, such as influenza, have always been underestimated. Only about 5 per cent of deaths linked to influenza have the infection recorded as the cause of death.

With the change, New Zealand will be more in step with the international reporting standard specified by the World Health Organisation (WHO), which defines a death from Covid-19 as "a death resulting from a clinically compatible illness in a probable or confirmed Covid-19 case, unless there is a clear alternative cause of death that cannot be related to Covid-19 disease, e.g., trauma".

It's to be hoped this will also allow for more meaningful comparisons across different countries and time periods.

Public Health Professor Michael Baker with the University of Otago in Wellington, says all health agencies and researchers want "valid" health statistics or measure what they intend to measure. He believes this change will increase the confidence we have that deaths attributed to Covid-19 are, in fact, valid.

As part of the change, all New Zealand's Covid-19 mortality data will be revised, including current and previously reported numbers.

The difficulty remains that cause of death can be a vague area. Dr William Schaffner, professor of infectious diseases at the Vanderbilt University Medical Centre in Nashville told Medical News Today: "Deaths are, to a degree, imprecise. A physician must make a judgment of cause of death." Ultimately, someone has to make the call whether the person would have lived if they did not have the virus.

Added to this is political pressure. One study found the probability of underreporting of Covid-related deaths for countries with the most stringent policies was 58.6 per cent, compared with- a 28.2 per cent for countries with the least stringent policies.

This adjustment is unlikely to improve public confidence or silence critics of New Zealand's pandemic response. Changing methodology and retrospectively altering statistics - while reasonable when fully understood - are more likely to heighten suspicion among the ill-informed.