What cervical screening can and cannot do

Deciding to go for cervical screening is your choice.

To give your informed consent you'll need to understand what:

cervical screening can do
cervical screening cannot do
the risks are

What we mean by giving your informed consent

What cervical screening can do

Human papillomavirus (HPV) is the main cause of cervical cancer. Finding HPV and abnormal cells early is the best way to prevent cervical cancer developing.

Regular cervical screening can save lives.

This is because it can find:

HPV before it causes abnormal cells in the cervix
pre-cancerous abnormal cell changes before they get the time to turn into cancer
cancer at an early stage before symptoms develop and when it is often easier to treat

What cervical screening cannot do

The main limitations of cervical screening are:

it will not prevent all cases of cervical cancer
some people will still develop cervical cancer even if they go for regular cervical screening appointments or test negative for HPV
it will not find every abnormal cell change and some are missed
false positive and false negative results
it tests for HPV, the cause of 9 in 10 cervical cancers, so it will not find cervical cancers not caused by HPV

Developing cancer after cervical screening

You can still develop cervical cancer even if your cervical screening result does not find HPV or abnormal cells changes.

If cervical cancer is found in between your cervical screening appointments, we call this interval cancer. This is because it is found in the interval between your previous and your next cervical screening appointment.

Interval cancers are not common. But they happen in every screening programme across the world.

Cancers develop after cervical screening and colposcopy because:

screening is not designed to find all abnormalities
you had a false negative cervical screening test or colposcopy result

This is why it is important to:

book and attend your cervical screening test when it's due
check for symptoms of cervical cancer
always talk to your GP about symptoms

Urgent advice: Contact your GP immediately if:

you have concerns or symptoms of cervical cancer

Even if you have had a recent normal screening result, never ignore symptoms.

Requesting a review

If you developed cervical cancer after screening you can ask for a personal cervical screening review.

A review may help you or your family if you:

are looking for answers or ways to understand how and when your cancer developed
want to ask questions about your screening journey

How to request a personal cervical screening review

False positive and false negative results

False positive and false negative results happen in every screening programme.

They happen in both:

These types of results may cause unnecessary worry or be harmful for some people. But the benefits of cervical screening outweigh these limitations for most people.

False positive results

Your result may be positive even though there is no HPV infection or changes to cells of the cervix. This is called a false positive.

A false positive may mean you will have further tests you do not need and find there was no risk of cancer at that time. This can cause you to worry.

False negative results

Your result may be negative even though there is a HPV infection or abnormal cells in the cervix. This is called a false negative.

A false negative may mean that you are told that you do not need further tests or treatment when there is actually a risk of cancer at the time. This could be a missed chance to stop cancer developing.

Because we check for HPV first this means there are fewer false negatives than before 2020.

False negative colposcopy results

A false negative colposcopy result is when:

your cervical screening test finds HPV
your colposcopy does not find any abnormality and your result is normal
you later get a diagnosis of cancer or your biopsy result shows a high chance cells will turn into cancer

How abnormal cells can be missed

We check your screening sample for HPV first.

If we do not find HPV, we do not need to check for abnormal (pre-cancerous) cells. This is because your risk of developing cervical cancer is very low if you do not have HPV.

If we find HPV in your sample, we will check the sample for any abnormal cells. But sometimes abnormal cells can be missed.

This can happen because:

sometimes abnormal cells do not look much different to normal cells
there may be very few abnormal cells in the sample
the person reading your sample may miss the abnormality (this happens occasionally, no matter how experienced the reader is)

Risks

The main risks of cervical screening are anxiety, overdiagnosis and overtreatment.

Anxiety

Anxiety is a risk of cervical screening.

You may have anxiety:

while waiting for results
when a result is abnormal

Overdiagnosis and overtreatment

Overdiagnosis in cervical screening is when you have a positive result for HPV but do not have high-grade abnormal changes to cells in the cervix.

Overdiagnosis can lead to a referral to colposcopy even though you do not have high grade abnormal changes. Overtreatment can happen at colposcopy.

Sometimes during colposcopy the cervix looks abnormal and a treatment is done. After the colposcopy and treatment, the tissue is tested in a lab. If the lab test does not find high-grade abnormal changes it means you had treatment you did not need. This is known as overtreatment.