Normal squamous epithelial cells from the cervix under the microscope
In January, we wrote about the changes to the cervical screening programme in Wales. This change extended the standard interval between screens for most people to 5 years.
The change made headlines, with many people worried the longer interval would result in cervical cancers being missed. But the changes were based on years of research into making cervical screening more effective.
The study, published in The BMJ, analysed real-world data to confirm findings from years of research, confirming that using HPV testing as the first-line test on cervical samples is more accurate at predicting who is at risk of developing cervical cancer, compared with cytology – the previous method of testing.
Alongside previous research, this shows that the time interval between cervical screens can be safely extended for those who test negative for HPV.
What is HPV primary testing?
HPV is a common infection that most people will get at some point in their lives without it causing any harm. But some types, or strains, of HPV are linked to cancer. Even for these higher-risk strains, most HPV infections are cleared by our immune systems on their own.
However, if they are not, HPV can cause changes to the cells. If left untreated over a long period of time, these cell changes can lead to cancer.
HPV primary testing is now the process used across most of the UK to test the samples taken during cervical screening.
The process is for women, trans men and some non-binary people and involves a health professional, usually a practice nurse, taking a sample from the cervix that’s then sent off to the lab. The laboratory will check for high-risk HPV. If high-risk HPV is found, the laboratory will test the sample for abnormal cell changes.
The previous cervical screening test used cytology, which looks at cervical cells in the sample and aims to detect any unusual changes.
As having an HPV infection comes before abnormal cells developing, HPV primary testing detects people at risk of developing cervical cancer at an earlier stage.
This means the new test is more accurate at detecting who is at higher risk of developing cervical cancer than the previous test.
What did the study do?
This study, carried out by researchers from King’s College London and funded by us, included 1,341,584 people participating in the NHS England HPV primary testing pilot between 2013 and 2019.
In the pilot, several sites across England partially converted their cervical screening offering from cytology testing to HPV primary testing. This allowed researchers to compare HPV primary testing to the standard cytology test used at the time.
People aged between 24 and 64 years old were included in the study, each undergoing cervical screening with either HPV primary testing or the standard cytology test.
Whichever test was used, people aged 24-49 were invited for a second screening test in 3 years if they had a negative result. People aged 50-64 were invited back in 5 years if they had a negative result. These 3- and 5-year gaps reflect what is currently offered in the English cervical screening programme, and were the standard screening intervals used at the time.
In those who had cytology testing, if abnormal cells were found, they would be referred for further testing.
In those who had HPV primary testing, samples that tested positive for HPV were then analysed to look for cell changes. If abnormal cells were found, people were referred for further testing. If no abnormal cells were detected, people were asked to return in 12 months for another test.
What were the results and what do they mean?
The study found that HPV primary testing was significantly better at picking up abnormal cell changes than cytology testing in all age groups.
They also found that in people aged 24-49, those who tested negative with HPV testing were significantly less likely to develop abnormal cells or cervical cancer by their second screen than those who tested negative with cytology testing.
However, for people aged 50-59, this difference wasn’t observed. Similarly, people aged 60-64 had their final cervical screening test, and no difference was observed in cervical cancer cases in the follow-up period after receiving a negative HPV or cytology test.
Although the reasons for this aren’t exactly clear, it may be because people over 50 are less likely to develop cervical cancer.
Significantly, these results add to existing research that supports extending screening intervals from 3 to 5 years for all people who test negative using HPV testing.
This is because they not only show that HPV testing is more sensitive at detecting people with abnormal cells, but that the risk of developing abnormal cells is significantly lower in people who had a negative HPV test compared with a negative cytology test, making it safe to extend the intervals between screens for people who test negative for HPV.
There are risks associated with cervical screening as well as potential benefits, so it’s important that people don’t have additional screening that they don’t need. Extending the interval with HPV primary testing helps to maximise the balance of potential benefits and risks.
If somebody’s result indicates the presence of HPV, they will be invited back for screening sooner or referred for other tests, depending on whether there are also signs of abnormal cells in the cervical sample.
Overall, cervical screening every 5 years with HPV primary testing will save more lives from cervical cancer than screening with the previous test every 3 years.
What’s happening in the UK?
In 2015, the UK National Screening Committee recommended that all UK nations implement HPV primary testing.
England, Wales and Scotland have all fully implemented HPV primary testing. Northern Ireland has not moved to HPV primary testing, but we hope this change will be implemented soon.
In 2019, they then recommended that 5 yearly intervals for people who test negative for HPV should be implemented.
As mentioned, Wales implemented the new intervals in January, and Scotland actually implemented them back in 2020. England has not yet announced any changes to intervals.
Michelle Mitchell, our chief executive, said: “This large study shows that offering cervical screening using HPV testing effectively prevents cervical cancer, without having to be screened as often.
“This builds on findings from years of research showing HPV testing is more accurate at predicting who is at risk of developing cervical cancer compared to the previous way of testing. As with any change to a screening programme, this will be monitored to ensure that cervical screening is as effective as possible for all who take part.
“It’s important to remember, screening is for people without symptoms. So, if you notice any unusual changes for you, do not wait for a screening invitation – speak to your doctor.”