The science behind the screening test changes

Earlier this month the Cervical Screening Programme in Wales announced it was changing. As we enter Cervical Cancer Prevention Week, Alice Davies, Cancer Research UK’s health information manager, looks at the reasoning behind the controversial decision

EVERYONE with a cervix aged between 25 and 64 will now be invited for a cervical screening every five years – bringing Wales in line with the recommendations of the UK National Screening Committee.

This is different to what has been happening, where women aged 25-49 have been invited to cervical screening every three years and women aged 50-64 have been invited every five years.

It’s a decision that’s made headlines, with many people worried that the longer interval between screening tests will result in cervical cancers being missed.

So much so, a petition asking for the decision to be reversed will be debated in the Senedd this week (January 19).

But there’s more to this change than meets the eye.

The extension of s creening intervals has been recommended because the test used in cervical screening has changed.

The new test detects who is at higher risk of developing cervical cancer more accurately than the previous test used. This means that the current intervals between screening tests can be safely extended for people who are not at high risk.

To understand why the new cervical screening test is better at spotting women at higher risk of cervical cancer, it’s helpful to know how cervical cancer develops.

Virtually all cases of cervical cancer are caused by human papillomavirus (HPV) infection. HPV is a common virus that infects the skin and cells lining the inside of the body. There are over 100 different types and around 13 “highrisk” types are linked to cancer.

Eight in 10 people will be infected with HPV at some point in their lives, but in most cases the infection will be cleared on its own and they will never know they had it.

However, sometimes these infections aren’t cleared. This is when damage to DNA can happen, which causes changes to the cells in our body. These cell changes can be resolved on their own, but they can also lead to cancer if left untreated over a long period of time.

The previous cervical screening test aimed to detect unusual changes in the cervix.

The new test involves the same procedure of taking a sample from the cervix but tests for HPV first – known as “HPV primary testing”. Wales was the first UK nation to bring in this type of testing in 2018.

As having HPV infection comes before abnormal cells developing, HPV primary testing detects women at risk of developing cervical cancer at an earlier point.

Screening every five years with HPV testing offers at least as good protection as the old test being offered every three years. Cervical cancer usually takes many years to develop and if someone tests negative for HPV, then their risk of developing cervical cancer in the next five years is very small.

The UK National Screening Committee has recommended all UK nations implement the new cervical screening test and intervals.

Scotland has already brought in this change, with England to follow suit soon. Northern Ireland has not moved to HPV primary testing, but we hope this change will be implemented soon.

If a person’s sample tests negative for HPV, they will be invited back for routine cervical screening in five years. This is because their risk of developing cervical cancer is very low.

But if their 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.

So the new test allows women to be invited back for screening based on their risk of developing cervical cancer, rather than just their age.

It’s important to remember that no cancer screening test is 100% accurate and a negative result doesn’t guarantee a clean bill of health. If you spot any changes that aren’t normal for you, speak to your doctor.

Cancer screening is for healthy people who do not have any symptoms, so if you notice anything that doesn’t feel right between screens, then don’t wait for your next appointment, speak to your doctor straight away.