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Cervical Screening Test

December 21, 2010
Women are routinely invited to have regular cervical screening tests. The tests are done to prevent cervical cancer (and not to diagnose cancer as some people wrongly think). During each test some cells are scraped from the cervix. The cells are looked at under a microscope. In most cases the cells look normal. Abnormal ‘pre-cancerous’ cells are found in some cases. If necessary, these cells can be treated before they turn into cancer.

What is a cervical screening test and how is it done?

Diagram detailing the uterus and cervix
The cervix is the lower part of the uterus (womb). It is often called ‘the neck of the womb’. A doctor or nurse will put an instrument called a speculum into your vagina. This gently opens the vagina and the cervix can be seen at the top of the vagina. A thin plastic or wooden stick with a small brush at the end is then used to gently scrape off some cells from the surface of the cervix. The cells on the brush are then sent to the lab. This is done by one of two ways:

The traditional smear method

In this method, the cells scraped onto the brush are ‘smeared’ onto a glass slide. The slide is sent to the lab. The cells on the glass slide are looked at under a microscope to see if there are any abnormal cells present. This method was the one used for many years, and so the cervical screening test was known as the ‘cervical smear test’.

Liquid based cytology

This is a newer method that is gradually replacing the smear method. In this method, the head of the brush that contains the cells is broken off into a pot that contains special preservative liquid. (Or, the brush is rinsed to wash the cells into the pot.) The liquid is sent to the lab where it is spun to separate out the cells. The cells are then placed on a slide and looked at under a microscope to see if there are any abnormal cells present.

In both methods, the procedure to obtain the cells is very similar. It is just how the cells on the brush are dealt with that is different between the two methods. Liquid based cytology is now being phased in as the preferred method. This is because it is more likely to produce a good set of cells that can be looked at under the microscope. With the smear method, about 1 in 10 tests had to be repeated because the cells were not seen. This was because of mucus, blood, etc, that was also smeared onto the slide. A result could not be given. However, a repeat test is much less likely to be needed with the liquid based cytology method. In short, it is a more reliable way of testing.

Most women find that the procedure to obtain the cells is painless, or only slightly uncomfortable. (The speculum may feel a bit cold though.) It only takes a few minutes to do. The ideal time to have the test is about mid-way between periods.

Why are cervical screening tests advised?

The test checks the cells from your cervix. In most women the cells are normal. Abnormal cells are found in some women. An abnormal result does not mean cancer in the vast majority of cases. Abnormal cells indicate that cancer may develop sometime in the future. Treatment can be given to prevent cancer from developing in women with abnormal cells. So, the test aims to prevent cancer, and not to detect cancer.

Who should have a cervical screening test?

All women should have regular tests. The test is free on the NHS. Depending on where you live, there are some differences in the routine invitations that are issued:

  • First invitation for screening in England is at age 25. It is age 20 in Scotland and Wales and Northern Ireland.
  • Routine recall (repeat screening test):
    • England: Routine three yearly recall for test between ages 25-49, then five yearly until aged 65.
    • Scotland: Routine three yearly recall for test from age 20 until aged 60.
    • Wales: Routine three yearly recall from age 20 until aged 65.
    • Northern Ireland: five year recall recall from age 20 until aged 65. (However, many GPs run their own recall at an interval of three years.)
  • From the age of 65, most women do not need any more tests. However, women aged 65 or over who have not had a test since age 50, or have had recent abnormal tests, will still be advised to be screened. So, a test may be advised for some women aged 65 or more.

Note: the ages and timings described above can be confusing as they differ between parts of the UK. They may also change as health officials review the screening programmes. See the resources at the end under ‘Further sources of information’ for up-to-date information and policy for each part of the UK.

Why is the cervical screening test important?

Cervical cancer (cancer of the cervix) is not uncommon. In recent years the number of cases has fallen due to cervical screening tests. However, there are still over 2000 new cases of cervical cancer diagnosed each year in the UK. Most of these occur in women who have never had a screening test, or who have not had one for many years. Cervical cancer can be prevented if you have regular screening tests.

Where do I go for a cervical screening test?

Most women have the test at their GP practice. It is usually done by the practice nurse. You can have it done at a family planning clinic if you prefer. A copy of the result is usually sent to you and your GP. This can take up to 6-8 weeks after the test. Ask at your GP practice for the result of the test if you have not had it by this time.

A computer system is used. Your record on the computer is updated when you have a test so it knows when your next one is due. You should get a letter asking you to make an appointment to have a test when it is due. Computerised recall systems are good – but not foolproof. Contact your GP if you have not been invited for a test in the last 3-5 years (as appropriate, depending on your age).

What do the results of the cervical screening test mean?

Normal result

About 9 in 10 routine cervical screening tests are normal. You will be sent a letter inviting you for another one in 3-5 years. (Note: a normal result means you have a very low chance of developing cancer of the cervix – not a 100% guarantee that it will not occur.)

Inadequate test

This sometimes occurs. This simply means no result can be given. For example, if the smear method was used, an inadequate test may occur because there was some blood or too much mucus on the slide and the cells could not be seen properly. Sometimes it is because a smear of cells was too thick or too thin to assess properly. You will be asked to attend for a repeat test. However, with the newer liquid based cytology method (described above), the number of tests that are ‘inadequate’ and need repeating is much less than with the traditional smear method.

Abnormal result

Some changes in the cells are found in about 1 in 10 tests. There is a range of changes that may occur. In nearly all cases, these changes do not mean cancer.

Minor or borderline abnormal changes are quite common. These often clear away on their own and most mild changes do not progress to anything serious. However, any change needs to be monitored as some may progress to become more serious in the future. A repeat test after 3-12 months is commonly advised, depending on the type and degree of change. Often the changes will have gone when the test is repeated. If the changes do not go, or the changes are more marked, then a referral to colposcopy is advised. Rarely, a cancer of the cervix is diagnosed by a cervical screening test.

What is colposcopy?

Colposcopy is a more detailed examination of the cervix. In this test a speculum is gently put into the vagina so the cervix can be seen. The doctor uses a magnifier (colposcope) to look at the cervix in more detail. A liquid is used to ‘paint’ the cervix which shows up the abnormal cells. It takes longer than a normal screening test (about 15 minutes). It is done by a specialist at hospital. During colposcopy it is usual to take a small piece of tissue from the cervix (biopsy) to make a more detailed assessment of the cells.

Can abnormal cells be treated?

Yes. A minor abnormal change often goes away by itself. This is why a repeat test after 3-12 months may be all that is needed. If the cells remain abnormal, or the changes are more marked, then treatment is offered. This will stop cancer from developing in the future. The types of treatments that are used include:

  • Cryotherapy – freezing the affected area of the cervix to destroy the abnormal cells.
  • Laser treatment – this destroys or cuts away abnormal cells.
  • Loop Diathermy – a thin wire cuts through and removes the abnormal area of cells.

These treatments are done as an out-patient and do not take long. They are usually successful and are usually needed only once. Follow up and regular screening tests are needed for the next few years to check that the treatment has been successful. It takes a few weeks for the cervix to heal after treatment. Once it has healed, a normal sex life can be resumed. Treatments do not affect fertility.

Some common questions about the cervical screening test

How effective is the cervical screening test?

The test is about 80% effective. This means that for every 10 women who would have developed cancer of the cervix, about 8 cases can be prevented. So, although it does not detect an abnormality every single time one occurs, overall it is a reliable test.

I have never had sex. Do I need a cervical screening test?

The test is recommended for all women – even if you have never had sex. However, the risk of getting cervical cancer is very low if you have never had sex. This is because the main cause of cervical cancer is a past infection with the HPV virus. This is a common virus that is normally passed on by having sex. (See leaflet called ‘Cancer of the Cervix’ for details.) You may decide that you do not want to have a test if you have never had sex.

I have had a hysterectomy – do I need to have a cervical screening tests?

This depends on the type of hysterectomy, and why it was done. Your doctor will advise. In general, if you have a total hysterectomy (removal of the uterus and cervix) for a reason not due to cancer, then you no longer need cervical screening tests. Some types of hysterectomy leave the cervix, and some are done to remove a cancer. In these situations, a test of the cells of the remaining cervix, or of the top of the vagina, may still be advised.

Does the cervical screening test really save lives?

Yes. By studying the statistics of cancer cases since the tests began it is estimated that between 1,100 and 3,900 cases of cervical cancer are prevented each year in the UK.

In summary

The ‘take-home message’ is: you are very unlikely to develop cervical cancer IF…. you have regular cervical screening tests at the times advised by your doctor AND…. you have treatment when advised if abnormal cells are detected.

LEARN MORE Cervical Screening Programmes:
England NHS cervical screening website for England
Wales Cervical Screening Wales
Northern Ireland HSC Public Health Agency
Scotland Scottish Cervical Screening
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