New Zealand has had a national cervical screening programme for decades, which is credited with a 60% fall in cervical cancer rates since 1990.
The Ministry of Health intends to change from the current smear test-based screening programme — under which women are tested every three years — to a human papillomavirus (HPV) primary screening programme, under which women would be tested every five years.
However, a new study by University of Otago researchers Brian Cox and Mary Jane Sneyd suggests the five-yearly HPV screening programme was less effective than three-yearly testing.
The scientists, from Otago’s Hugh Adam Cancer Epidemiology Unit, evaluated Australia’s five-yearly HPV screening policy and found it reduced overall protection from cervical cancer.
Implementing HPV testing in routine screening programmes needed to be reconsidered, especially in countries with organised programmes and a high-quality infrastructure, Prof Cox and Dr Sneyd said.
New Zealand is yet to embark on a five-yearly HPV screening policy.
In July the Ministry of Health announced it would stagger the timeline to introduce the programme, with parts of it starting in 2019 and a full transition to HPV primary screening likely to start in 2021.
"They shouldn’t introduce it at the moment and they should certainly rethink it," Prof Cox said.
"There are ways of introducing a new screening programme safely, but if you just replace one with the other you will never know."
Prof Cox said his and Dr Sneyd’s study — published in the Journal of the American Society of Cytopathology — had found the effectiveness of the HPV test to detect high-grade cancer-causing abnormalities had been inflated in the Australian simulation study.
That study had counted the detection rate of all high-grade abnormalities, and not the lower detection rate of only those that would develop into cervical cancer.
New Zealand’s Ministry of Health had used the same simulation programme as Australia "and induced exactly the same error, unfortunately", Prof Cox said.
Prof Cox said he and Dr Sneyd’s evaluation of the Australian data showed there had actually been a reduction in protection from cervical cancer for Australian women.
He warned it was likely New Zealand women would see similar consequences if five-yearly testing was introduced.
"There are specific methods by which the introduction of a new screening policy can occur that allow the comparison of the ability of two screening tests to reduce cervical cancer and these are vital for the safe introduction of any new screening policy," he said.
"The medical principle of ‘first do no harm’ should be foremost, so that no increased risk to women occurs from replacing three-yearly cervical smears with five-yearly HPV testing ."
HPV testing and smear testing could be run simultaneously and a proper assessment made of protection levels at three years and five years, Prof Cox said.
"Changing the test and expanding the timeframe all at the same time is very risky," he said.
"If it is a better test, you would expect over a three-year period you would get better results than the current smear test."
In June national screening unit director Jane O’Hallahan said a new fit-for-purpose IT system was needed before five-yearly HPV testing was introduced.
"Continuing to have regular screening every three years offers women the best protection by detecting changes that could indicate an increased risk of developing cervical cancer," she said.
"New Zealand has one of the most successful cervical screening programmes in the world, so we need to make sure improvements to the programme are carefully rolled out to protect the integrity of the programme."
