Read about screening for cervical cancer.
What screening is
Screening means testing people for early stages of an illness before they have any symptoms. For screening to be useful the tests:
- must be reliable at picking up the illness
- must be simple and quick
- overall must do more good than harm to people taking part
What is cervical cancer screening
Cancer screening involves testing apparently healthy people for signs that could show that a cancer is starting to develop.
Cervical screening is a way of preventing cancer by finding and treating early changes in the neck of the womb (cervix). These changes could lead to cancer if left untreated.
The screening uses a test called cytology, which many people know as the smear test. A nurse or doctor takes a sample of cells from the cervix with a small brush. They send the sample to a laboratory to be checked for abnormalities. In some cases, samples are also tested for a virus called human papilloma virus (HPV) that increases the risk of cervical cancer.
Who has cervical screening
The NHS cervical screening programme invites women from ages 25 to 64 for cervical screening. Women aged 25 to 49 are invited every 3 years. After that, women are invited every 5 years until the age of 64.
You need to be registered with a GP to get your screening invitations.
Why younger women don't have screening
We know from research that cervical cancer is very rare in women younger than 25. But changes in the cervix are quite common in younger women. So, screening them leads to unnecessary treatment and worry. Scientists have worked out that screening younger women leads to more harms than benefits.
The cervical screening test
The screening test involves taking a sample of cells from the surface of the cervix. The test is called liquid based cytology (LBC).
To have the test you take off your underwear and lie on your back on a couch. You need to lie with your knees drawn up and spread apart. If this position is difficult for you, you can ask your nurse to take the cell sample when you are lying on your side with your knees drawn up.
To take the sample of cells, the doctor or nurse gently slides an instrument called a speculum into your vagina so that they can see the cervix clearly. Having the speculum put in may be a little uncomfortable, but it shouldn't hurt. It can be more uncomfortable if you are very tense. Try to relax. Taking a few deep breaths can help.
The doctor or nurse gently scrapes the surface of your cervix with a small soft brush. This collects a sample of cells from the outer layer of the cervix. They put the sample into a pot of liquid and send it to the laboratory. Then they take out the speculum and the test is over. You can get down from the couch.
In the laboratory, a pathologist puts the sample under a microscope. They examine the cells and report any abnormal ones. They may also test to see whether the HPV virus is present in the sample.
In the future, primary HPV testing will be rolled out across England. This means that they will test the sample of cells for HPV first. If HPV is found, they will then test for cell changes.
After the cervical screening test
The laboratory sends the results of your test back to your GP surgery. They will write to you with the result, usually within 2 weeks of having the test.
What the results mean
There are several different results you can have after a screening test. Most women have a normal result. In this case you will be invited for screening again in 3 to 5 years depending on your age.
Problems with the result
Some results are due to problems with the test rather than because there are any abnormal cells. You may be told that you need a repeat test because yours could not be read properly. This is sometimes called having an inadequate sample. This could be because:
- there were not enough cells in the sample
- you have an infection and it wasn't possible to see the cells clearly enough
- you were having a period and there was too much blood to see the cells clearly
- the cervix was inflamed and it wasn't possible to see the cells clearly enough
In all these cases, the letter you get will ask you to go back and have another test. This is usually about 3 months later.
If you have an abnormal result
Around 1 in 20 women (5%) have an abnormal result after a cervical screening test. It means that there are some changes to the cells on the cervix. These changes are not cancer. The cells often go back to normal by themselves. But in some women, if not treated, these changes could develop into cancer in the future.
Abnormal results can be reported in 2 different ways. You are most likely to be told you have:
- borderline or mild cell changes (also called low grade dyskaryosis)
- moderate or severe cell changes (also called high grade dyskaryosis)
It is very rare for an abnormal result to show that a cancer has already developed, especially if you have been having regular screening. But this is possible.
If you have a cervical erosion
This has nothing to do with cervical cancer. Cervical erosion is a condition often picked up by cervical screening tests. You may hear it called an ectropion. It means that there are glandular cells on the surface of the cervix. Glandular cells are normally only seen inside the cervical canal. The cervix often looks a little inflamed in areas of erosion.
An erosion will not harm you. It is common in teenagers, in pregnancy, and in women on the pill. It can cause slight bleeding, especially after sex. Usually it goes away by itself without any treatment.
If you have mild cell changes
Currently, what happens if you have borderline or mild cell changes (low grade dyskaryosis) varies depending on where you live.
In England, Northern Ireland and Wales
If you have borderline or mild cell changes, the laboratory will test your sample for the human papilloma virus (HPV). HPV is a very common virus. Most women have it at some point in their lives, and in most cases your body will get rid of the virus without you ever knowing you had it.
It can be passed from person to person during intimate sexual contact. Certain types of HPV increase the risk of cervical cancer.
If no HPV is found in the sample, it is called HPV negative. In this situation the cell changes are very likely to go back to normal or stay the same. So it is safe for you to go back to the routine screening programme and have tests every 3 to 5 years, as normal.
If your sample shows a type of HPV that increases cervical cancer risk, you will get an invitation for a test called a colposcopy. Colposcopy means looking very closely at the cervix using a specialised magnifying instrument called a colposcope. This test can show whether you need treatment for the abnormal cells.
In Scotland, your doctor or nurse will either suggest a colposcopy or ask you to go back for another screening test (a repeat smear) in 6 months time. If your next test is normal you may have 2 further tests, 6 months apart, before going back to regular screening every 3 to 5 years.
If your repeat test shows abnormal cells, you will then have a colposcopy to check them more closely. You may then need some treatment.
If you have moderate or severe cell changes
If you have moderate or severe cell changes (high grade dyskaryosis), you will be referred for a colposcopy. The doctor or specialist nurse will take a sample of cells (a biopsy) from the abnormal area. They may ask you to go back for treatment depending on the result of the biopsy. Or in some clinics, they may offer you treatment at the same time as the colposcopy.
You usually only need treatment once. Then you have follow up tests to check that the treatment has worked.
If you have an abnormal test and have successful treatment you are very unlikely to get cervical cancer if you continue to have screening. If you don't have treatment, you are at risk of getting cervical cancer in the future.
Benefits of cervical screening
Scientists and experts estimate that cervical screening saves around 4,500 lives each year in the UK.
Women screened between the ages of 35 to 64 are thought to have a 60 to 80% lower risk of being diagnosed with cervical cancer in the 5 years following the test compared to women who haven't been screened. The benefit of screening increases with age.
Since cervical screening started in the 1980s in Great Britain, rates of cervical cancer have almost halved.
Possible harms of cervical screening
Cervical screening works very well but, like any screening test, it isn’t perfect. In a few cases, tests will seem to find abnormal changes that aren’t really there. This is called a false positive result. It leads to unnecessary worry for the woman and also the need for more tests.
There is also a risk that cell changes may be missed. This is called a false negative result. So it is important to go for screening every time you are invited.
Sometimes it is difficult to tell whether changes in the cervix will go back to normal or will develop into cancer after some years. So, some women will have treatment for changes to cervical cells that would not have caused any harm if they had been left alone. This is called overdiagnosis or overtreatment. For a few women, the treatments may cause problems such as bleeding afterwards or a small increase in future pregnancies of having the baby early.
It is hard to know exactly how often women are overdiagnosed or overtreated in this way. But in women from their early 20s to mid 60s, the benefits of preventing cervical cancers are very great.
Since 2008, girls aged 12 and 13 have been offered a vaccination against the human papillomavirus (HPV). The vaccine can prevent over 70% of cervical cancers.
It is important for girls to have the vaccination when it is offered at school. But there are many types of HPV linked to cervical cancer. Although the vaccine protects against the 2 types that cause most cases of cervical cancer, it doesn't protect against all of them. This means that screening is still important for girls who have been vaccinated.
As well as attending for screening when you are invited, you still need to look out for any unusual changes to your body. Check for any abnormal bleeding, unpleasant discharge or pain after sex. If you notice anything unusual, make an appointment to see your doctor and get it checked out.
Smoking can increase the risk of cervical cancer. Cancer causing chemicals in cigarette smoke can go into the blood and travel around the body. These chemicals can damage the cells of the cervix.
Talk to your GP if you think you are at higher than average risk of cervical cancer.