A cervical screening test (smear test) is a method of preventing cervical cancer by detecting abnormal cells in the cervix (lower part of the womb).
Cervical screening is not a test for cancer, but it is a test to check the health of the cervix. Most women's test results show that everything is normal. But for one in 20 women, the test will show some changes in the cells of the cervix.
Most of these changes will not lead to cervical cancer and the cells will go back to normal on their own. In some cases, the abnormal cells need to be treated to prevent them becoming a problem later.
The screening programme
In the UK, cervical cancer is the second most common cancer in women under 35 (after breast cancer). About 2,800 women a year are diagnosed with cervical cancer.
The NHS Cervical Screening Programme aims to reduce the number of women who develop cervical cancer and the number of women who die from the disease.
All women aged between 25 and 64 are invited for cervical screening. Being screened regularly means that any abnormal changes in the cervix can be identified early on and, if necessary, treated to stop cancer developing.
It is estimated that early detection and treatment can prevent up to 75% of cervical cancers from developing.
- The uterus (or womb) is a hollow, pear-shaped organ in a woman where a baby grows during pregnancy.
Why a cervical screening test should be done
Changes in the cells of the cervix can be caused by certain types of human papilloma virus (HPV).
HPV is the name of a family of common viruses that affect the skin and the mucus membranes (moist tissue that lines parts of the body), such as those in your cervix, anus, mouth and throat.
It is estimated that eight out of 10 people in the UK are infected with HPV at some point in their lifetime. For most people, the virus goes away without treatment and does not cause any harm. But infection with some types of HPV can cause abnormal tissue growth and other changes to cells, which can lead to cervical cancer. Other forms of HPV can cause genital warts.
HPV infection is passed on through skin-to-skin contact. The types of HPV that can cause abnormalities in the cells of your cervix are transmitted through sexual contact.
There are high-risk and low-risk types of HPV. Types HPV-16 and HPV-18 are considered high risk for cervical cancer. If you have repeated infections with these high-risk types of HPV, you are more at risk of developing cancerous cells in your cervix.
Regular cervical screening detects abnormal cell changes in the cervix early on, before cancer has had a chance to develop.
If any changes are found, your GP will discuss with you whether to wait and see if the changes go away on their own, or whether you need treatment.
How common are abnormal results?
Nine out of 10 screening results are normal. Around one in 20 show mild cell changes. For most women with abnormal results, the cells will go back to normal without treatment. If your results show abnormal cells, you will be sent for screening every six months to monitor the cells. You will only be given treatment if the cells do not go back to normal.
One in 100 test results show moderate cell changes and one in 200 show severe changes. If you show more serious cell changes, you will be sent for a colposcopy to investigate further.
It is extremely rare for cancer to be diagnosed from a cervical screening test. Less than one in 1,000 test results show invasive cancer.
As with all screening tests, cervical screening is not 100% accurate. Regular screening can stop up to 75% of cancers from developing, but it does not prevent every case.
It is not yet known which early changes in cervical cells will later develop into cancer and which will not. So some women will be treated for abnormalities that may have cleared up on their own if they had not been treated.
The most important thing is to do all you can to prevent cervical cancer from developing. Attend a cervical screening when you're invited and make sure you get your results.
When a cervical screening test should be done
The NHS Cervical Screening Programme in England offers free tests to all women between the ages of 25 and 64.
Women who are registered with a GP are invited for screening tests. Since 2003, women have been offered screening at different intervals depending on their age:
- Women should receive their first invitation for screening at 25.
- Women aged 25-49 are invited for screening every three years.
- Women aged 50-64 are invited for screening every five years.
- Women aged 65 or over are only screened if they have not been screened since they were 50 or have had recent abnormal test results.
If you have not had a cervical screening test within the appropriate time, you may be offered one when you next visit your GP or family planning clinic.
Make sure your GP has your correct name and address and inform them of any changes so they can contact you when you are due to have a screening test.
If you are not registered with a GP surgery, you can arrange to have cervical screening tests at a well woman or family planning clinic, or at the genito-urinary medicine (GUM) department of a local hospital. You will find details of all these in your telephone directory.
After your screening test, if you have treatment for abnormal cervical cells, you will be asked to attend screening annually (once a year) for some years afterwards, depending on how serious the cell changes were.
If you are not sure when your next screening test should be or if you have any questions about the NHS Cervical Screening Programme, ask your GP or practice nurse or visit the NHS Cancer Screening website.
Who should have a screening test?
All women between the ages of 25 and 64 can have free cervical screening tests through the NHS.
Screening used to start at the age of 20 (and still does in Wales, Scotland and Ireland), but the age was changed to 25 in England because cervical cancer is rare in women under 25.
Because young women's bodies are still developing and changing, they may have an abnormal test result when there is nothing wrong. This could lead to unnecessary worry and treatment. So screening women younger than 25 may do more harm than good.
If you are under 25 and worried about your risk of developing cervical cancer or about sexual health generally, see your GP or go to your local GUM clinic for advice.
The HPV vaccination
Since September 2008, there has been a national programme to vaccinate girls aged 12 to 13 against human papilloma virus (HPV). There is also a three-year catch-up campaign, which will offer the HPV vaccine to girls between the ages of 13 and 18.
The vaccine used in the programme (Cervarix) protects against the two types of HPV that are responsible for about 70% of cervical cancer cases (HPV-16 and HPV-18). However, the vaccine does not protect against all types of HPV, so is not guaranteed to prevent cervical cancer.
Following the introduction of the national HPV vaccination programme, regular cervical screening will continue to play an important role in detecting potentially cancerous cell changes in the cervix in women between the ages of 25 and 64.
Who may not need a screening test?
Cervical cancer is rare in the following people:
Women who are not sexually active
The risk of cervical cancer is very low in women who have never been sexually active. As the risk is so low, women in this category may choose not to have a cervical screening test when invited.
However, if you are not currently in a sexual relationship but have been in the past, it is recommended that you have regular cervical screening.
Women over 65
Women aged 65 and over who have had three normal test results in a row are not called back for further cervical screening tests. It is very unlikely that women in this category will go on to develop cervical cancer.
If you are over 64 and have had abnormal results, you will continue to be invited for screening until the cells return to normal. Women aged 65 and over who have never had screening are entitled to a test.
If you have never had a screening test and have been sexually active, you should have a test, regardless of your age.
Women who have had a hysterectomy
Women who have had a total hysterectomy (removal of the womb and cervix) will no longer be invited to attend cervical screening.
Women who have had a hysterectomy which has left all or part of the cervix in place will be invited to screening once their post-operative care has finished.
Women who have had a total hysterectomy for the treatment of cancer, or who had CIN (a type of cervical cell change that can lead to cancer) at the time of total hysterectomy, may need another test called a vault smear. A sample of cells is taken from the vagina, close to where the cervix used to be. Vault sampling is part of the follow-up treatment for hysterectomy but not part of the cervical screening programme.
How it is performed
Making an appointment
You will receive a letter from your local primary care trust (PCT) or GP asking you to make an appointment for a cervical screening test.
You can have the test at your GP surgery or a family planning clinic. Most women choose to have their test taken by their GP or practice nurse. You can ask to have your test taken by a female doctor or nurse if you prefer.
It is best to have the screening test in the middle of the menstrual cycle (between periods), so book your appointment to coincide with this.
The cervical screening test usually takes around five minutes. You will be asked to undress from the waist down and lie on a couch. The doctor or nurse will gently put an instrument, called a speculum, into your vagina. This holds the walls of the vagina open so that the cervix can be seen. A small brush-like instrument is then used to gently wipe some cells off the surface of the cervix.
It may be a bit uncomfortable or embarrassing, but for most women it is not painful. If you find the test painful, tell the doctor or nurse because they may be able to reduce your discomfort. Try to relax as much as possible as being tense makes the test harder to carry out. Taking slow, deep breaths will help.
In the laboratory
The process of taking cell samples has been improved in recent years to make it more accurate. The cell sample is now taken using liquid-based cytology (LBC), rather than the Pap (Papanicolaou) smear test that was used previously.
The head of the brush on which your cells have been collected is broken off into a small pot of preservative liquid, or rinsed directly into the preservative liquid.
The sample is then sent to a laboratory, where it is treated to remove any other material that may have been picked up, such as mucus or blood. A sample of the remaining cells is put on a slide and laboratory staff look at the cells under a microscope to see if there are any abnormal cells.
Research has shown that this new method of collecting and testing a sample of cells is more accurate than the Pap smear test and decreases the number of inadequate screening results. This means that you are less likely to be called back for a repeat screening because your test was unclear.
Results of a cervical screening test
The results of your screening test will be sent straight to your GP or family planning clinic. Your surgery or clinic may not contact you if your results are normal.
Before you leave your screening, ask when your results are expected, then contact your GP or clinic to get your results. The Cancer Screening Programme aims to notify people within 14 days with the results of their test.
They should also contact you if there is an abnormal result or if the test could not be read properly.
Different types of results:
This means that there are no cell changes. No action is needed and you do not need your next cervical screening until it is routinely due.
You may be told you need to have a repeat test because the first one could not be read properly. This may be because not enough cells were collected or they could not be seen clearly enough on the slide. You will be asked to go back and have another screening test to take another sample of cells.
You may be told your result is borderline. This means that, although there are some cell changes, they are very close to being normal and will go away on their own.
You will be asked to return for another screening test in six months to check that the cells have returned to normal.
If you have abnormal results, you may be told you have:
- mild or slight changes (mild dyskaryosis),
- moderate cell changes (moderate dyskaryosis), or
- severe cell changes (severe dyskaryosis).
Dyskaryosis is a term used to describe the changes to the cells.
Your results may also refer to CIN. This stands for cervical intra-epithelial neoplasia and is the medical name for cervical changes.
- CIN 1 refers to mild changes,
- CIN 2 refers to moderate changes, and
- CIN 3 refers to severe changes.
All these results show that you have pre-cancerous cells. This does not mean that you have or will get cancer. It just means that some of your cells are abnormal and, if they are not treated, they may develop into cervical cancer.
Further investigation and treatment
Not all abnormal changes need to be referred for further investigation or treatment. Your GP may recommend waiting to see if the changes disappear on their own and ask you to return for another screening in six months' time.
If further investigation is needed, your GP will refer you for another screening test or to a specialist (gynaecologist) for an examination called a colposcopy.
A colposcopy is a simple examination that shows the extent of cell abnormality and helps your GP to decide if you need treatment.
An instrument called a colposcope, which is like a large microscope, is used to look at the cervix in more detail. A small sample of tissue (biopsy) may also be taken from your cervix.
For more information, go to the section on colposcopy.
If screening shows that you have abnormal cells in your cervix, your GP may recommend that you have them treated. The aim of treatment is to remove or destroy the abnormal cells in your cervix.
It may be possible for you to have treatment at the same time as your colposcopy. Other more invasive types of treatment will require a separate appointment.
Types of treatment:
The treatment you will be offered depends on how many abnormal cells you have in your cervix and how advanced the changes are.
Large loop excision of the transformation zone (LLETZ)
Also known as LEEP or diathermy, this procedure uses a small tool and an electrical current to cut away the affected area of tissue and seal the wound at the same time. The advantage of this treatment is that the cells are removed rather than destroyed, so the tissue can be sent for further tests to confirm the extent of the cell changes and make sure the area of your cervix that contains the cells has been removed.
This is a small operation that, in most cases, requires an overnight stay in hospital. A cone of tissue is cut away from your cervix to remove all the abnormal cells.
A cold probe is used to freeze away the abnormal cells in the cervix.
This is sometimes called laser ablation. Lasers pinpoint and destroy abnormal cells in the cervix. If necessary, a laser can also be used to remove a small piece of the cervix itself.
A hot probe is applied to the cervix to burn away and remove the abnormal cells.
A local anaesthetic (where the area is numbed but you are still awake) is given before any of the treatments described above. A cone biopsy may require a general anaesthetic (where you are asleep).