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Why is CervicalCheck using HPV tests instead of testing for all smear abnormalities?

TheJournal.ie spoke to Noirin Russell about some of the common questions about the change to the cancer screening programme.

Image: Shutterstock/Komsan Loonprom

IN MARCH OF last year, the CervicalCheck screening programme began using HPV-first testing instead of cytology smear tests.

The free cancer screening programme received a number of queries about why this change happened. To mark Cervical Cancer Prevention Week this week, we’ll aim to answer some of them with answers from the clinical director of CervicalCheck, Dr Nóirín Russell.

You can register for the free CervicalCheck programme here.

During Level 5 Covid-19 restrictions, you may be waiting longer than usual for a smear test appointment, but it’s advised to book one now for a later date. Some colposcopy clinics are prioritising high-grade abnormalities during current restrictions. 

First: some general points about the CervicalCheck programme

CervicalCheck is a free programme that screens women aged 25-65 in Ireland for cancer through a test (formerly a smear test, now a HPV test), and divides them into low-risk and high-risk groups.

The women who receive a negative result are in the low-risk group, and come back for a test in 3-5 years, while the high-risk group are referred on to colposcopy clinic for further examination, where around 80% of women don’t require treatment, but may require another examination in six months’ or a year’s time.

If you experience symptoms of cervical cancer, such as a pain in your pelvis; bleeding between periods; vaginal spotting or discharge; or pain/ bleeding during sex, the professional medical advice is to contact your GP for a consultation and do not wait until your regular CervicalCheck appointment is due.

Between 30 March and 6 July, the CervicalCheck programme was paused as Ireland grappled with the Covid-19 pandemic. In November and December, 6,000 samples were received a week when around 4,000 were expected.

117,000 women in 2020 were screened; around 50% the number they had expected to screen at the beginning of this year.

Why is CervicalCheck no longer testing for abnormal cells?

CervicalCheck still screens for abnormal cells that can cause cervical cancer, but the way that they do it has changed.

Previously, a cytology smear test was carried out to look for any cervical cell abnormalities, and then if that test found an abnormality, women were referred to a colposcopy clinic to test whether those abnormalities were low-grade or high-grade. 

But studies have shown that the results are better if you test for HPV in cervical cells first, and if it is found, then refer the woman on for further examination.

If you want to see the science, in countries which have been using HPV testing first for a longer period shows that if 1,000 people are screened, about 20 people will have abnormal (pre-cancerous) cervical cells. The studies go on to show:

  • In screening with a cytology smear test, 15 of these 20 people will have these cells found – five people will not, and may go on to develop cervical cancer. This makes the old cervical smear test 75% accurate.
  • In screening with a HPV-first test, 18 of these 20 people will have these cells found – two people will not, and may go on to develop cervical cancer. This makes the new cervical smear test between 85-90% accurate.

“Primary HPV testing is a much better test,” Dr Russell said. ”With cytology, or smear tests, there’s a one in 200 false negative rate. So one in 200 women are given the normal results, and actually the abnormality is there but not detected. Whereas with HPV testing, that goes down to one in 500. So it’s a much better test.”

“So you’re very likely to be in the 980 women who get the negative result. And you’re very unlikely to be one of the two women in that 20 who get a negative result [when there is an abnormality].”

Remind me what HPV is again?

HPV, or human papillomavirus, is very common virus, and the most common sexually transmitted infection worldwide.

Most HPV infections have no noticeable symptoms and over 90% are cleared by the body’s immune system after two years. But in some cases, HPV can develop into cancer in both men and women.

There are over 200 types of HPV: 40 of which can infect the genital tract. Of these 40, 13 are considered to be high-risk or capable of causing cancer.

Not all cervical cancers are caused by HPV – is it not better to test for abnormal cells because then you can catch all types of cervical cancer?

“It’s a better predictor of who’s going to go on and develop cervical cancer,” Dr Russell says, adding that smear tests are still a very good test – but limited.

“We know that there’s a lot of transient abnormality and transient cell changes on the cervix. The majority of low-grade changes, the majority of changes on a woman’s cervix, she’ll deal with those herself, nature will sort it out, they will resolve, and everything will be fine. That’s what happens with the majority of cell changes.

“But what the problem is, is if you have a persistent HPV infection, it just keeps on niggling and niggling at the cells, keeps on making them abnormal, or makes them persistently abnormal – that combination of abnormal cells and persistent HPV infection – that’s what the risk factor is for going on to develop cancer. 
“So if you have that combination of persistent HPV infection that keeps on making your cells abnormal and refuses to let them go back to normal – that’s where the risk factor for cancer is.”

She says that this is why smoking is a risk factor for cervical cancer.

“What smoking does it predisposes you to to retaining your HPV – it makes it more difficult for your immune system to clear out the HPV,” Dr Russell says.

For women who had procedures for pre-cancerous cells/ high-grade precancerous cells before and tested negative for the HPV virus, why would this be a better test?

Dr Russell says that for women who had tested negative for HPV but have had procedures for precancerous cells, it’s likely that they had HPV that developed, but their bodies cleared the HPV out before the test was carried out. 

“In the old programme, when you had a cytology test that had [a high-grade abnormality], we didn’t routinely look for HPV. You were referred on to colposcopy, had a treatment, and you were only tested for HPV as part of your follow up.
“So the vast majority women who had treatments for abnormal cells actually had HPV prior to that, but just didn’t know about it.”

Dr Russell said that the evidence from the UK and Australia on women who have had a treatment for abnormal cells before shows that the new way of testing is “as good and as safe and, in fact, better”.

Nearly all cervical cancers – over 92% – are caused by HPV. Because there are some types of cervical cancer that are not detected by either the old smear test or the new HPV test, women are being reminded to be aware of the symptoms of cervical cancer, which include bleeding between periods; unusual vaginal discharge; or pain during sex.

If you experience these symptoms, you need to get checked outside of CervicalCheck.

Is this a cost-cutting measure from the HSE?

“No it’s not a cost cutting measure,” Dr Russell said.

“Part of the Hiqa report [into switching to primary HPV testing] was they had to work up a cost-effectiveness – as you have to do with anything in healthcare. But this is absolutely not a cost-cutting measure.”

“If a better test comes online, then I’ll be the first person in the queue advocating for that better test for Irish women. This is about getting the best test, not the cheapest test.”

As time went on and more research was published, the case got stronger and stronger in favour of HPV-first cervical cancer screening, Dr Russell said.

A 2017 report by Ireland’s health watchdog Hiqa recommended HPV cervical screening, coupled with a HPV vaccination programme, to reduce the incidence of cervical cancer and the prevalence of abnormal cells.

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This type of cervical screening has been introduced, to date, in Australia, England, the Netherlands and Wales.

In Australia, the high uptake rates of both HPV-led cervical screening and the HPV vaccine (this has a 98% uptake rate) combined means they are on target to be the first country in the world to eliminate cervical cancer.

A better test for the whole cervix

“The problem with cytology,” Dr Russell adds, is “you’re just brushing a woman’s cervix, you’re just brushing off a few cells at the part of the cervix that’s visible in the vagina.”

“The average cervix length is three, three and a half centimetres, and yet you’re only sampling the cells on the lower, maybe half a centimetre.

“So we know that if there is an abnormality further up in the cervical canal, we won’t pick it up in a smear test [the old way of testing].”

There are two types of cervical cancer: squamous and glandular carcinomas.

“We know that screening is much better at detecting squamous carcinomas because they tend to be the ones on the surface, whereas the glandular ones, they’re up further, and screening with with cytology [the old way of screening] is not as good as detecting those.”

 You can check if you’re on the CervicalCheck register here; read more about the CervicalCheck screening programme here.

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