AFTER HPV-FIRST testing was introduced in the CervicalCheck programme in March 2020, the intervals at which the majority of women were taking smear tests increased from three years to five years.
Many women who fall in the category of eligible for screening may wonder why – particularly after years of the cervical screening programme being under the microscope.
This seems to be borne out by Labour TD Alan Kelly who said that it is something he has been contacted about by members of the public.
“I do think that something that has got lost a bit is the move from 3 to 5 years… people need to explain why that is the case. It is something that has come to me.”
The advice for HPV-first cervical screening in Ireland is:
Before that, when cytology smear testing was in place, women aged 25-44 were invited by CervicalCheck for a smear test every three years, unless they had a history that would mean they needed to be screened more regularly.
Woman aged between 45-60 were invited every five years.
The thinking behind the increase in intervals
Professor of Cancer Prevention Peter Sasieni explained in a blog post that the three-year intervals for cytology-first screening and five-year intervals for HPV-first screening is based on the stage of progression of pre-cancerous cells.
Several studies have shown that the risk of pre-cancerous lesions within six years of a negative HPV test is similar to the risk of pre-cancer within three years of a negative cytology test, he notes, which is the reason for those intervals being chosen.
On the broader point of why we don’t screen more often to find more cancers, Professor Sasieni makes the point this way:
The UK’s National Screening Committee has recommended HPV testing every 5 years from age 25 to 64. They anticipated that 3-yearly rather than 5-yearly HPV testing from age 25-49 would result in 151 fewer cancers and 19 fewer deaths each year in the UK.
Three-yearly screening requires just over 1 million additional screens each year across the UK. Thus, it takes about 55,000 additional screens to prevent one additional cervical cancer death. Even if those women died on average 45 years prematurely, each additional screen would, on average, result in an additional 7 hours of life.
He added:
For comparison, if instead of doing an extra million tests a year in relatively well-screened women, we did an extra 120,000 tests a year in under-screened individuals to ensure that 90% of the eligible population are screened at least once every 10 years between 25 and 49, we could prevent an additional 705 cervical cancers each year.
There is also a cost-benefit argument here as well: if a health service is to make an argument for more investment in cancer services, would that money be best spent on cancer screening, instead of investing in cancer treatments, colposcopy services, or training more cytologists and gynaecologists, for example.
Dr Nóirín Russell said that the reason for the change to the intervals as part of the move from cytology testing to HPV testing is that not all women are at equal risk.
“If you are HPV negative, we know that that’s much better than having a negative smear, it’s a much better predictor that you are at low risk of developing cervical cancer. And that’s why the interval is 5 years and we know that the science backs that up.
“That doesn’t mean that you’ll never develop cervical cancer, but it means that you’re in that low-risk category. The role of screening is to divide you into a higher risk, or normal risk. And if you’re in the normal risk category, screen negative or HPV negative, then it doesn’t matter how often you do your test, you still stay in that ‘normal’ zone.
When you get a HPV-negative test, it should make you feel ‘that’s that bit sorted, I’m at low risk. I still need to know about symptoms, and if I get them, I may need a diagnostic test, but there isn’t a role for more screening in my life, because it won’t benefit me’.
“The underlining thing here is understanding what screening can and can’t do for you.”
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