The smear test (cervical smear, pap smear) is a screening test which allows doctors to predict those women who are likely to develop cancer of the neck of the womb (carcinoma of the cervix) in time to prevent it developing.

Cancer of the neck of the womb (carcinoma of the cervix) is one of the commonest cancers affecting women. It causes a significant number of deaths each year.

It has been found that looking at a tiny number of the cells from the neck of the womb (cervix) allows us to predict those people who are likely to develop cancer later on. Looking at the cells in this way is called cervical cytology.

The women most at risk of cancer of the cervix are those who are or have been sexually active, and in the UK, women between the ages of 25 and 65 are offered the opportunity of a cervical smear at regular intervals - three yearly between 25 and 49, and five yearly between 50 and 64.

The sample for the test is taken by a doctor or nurse, who examines you internally. Sometimes this will involve you lying on your back, with your legs bent up and apart, and sometimes lying on your side with your legs bent up.

The doctor or nurse may examine you internally, with a hand, but the smear test involves inserting a plastic or metal instrument (speculum) into the vagina, which holds the walls of the vagina open, so that they can see the neck of the womb (cervix). A wooden or plastic device (spatula), which is usually little more than a specially shaped lolly/popsicle stick, and/or a specially shaped brush is then stroked round the opening in the neck of the womb.

You do not usually feel this, although the speculum may cause some discomfort, occasionally. The spatula or brush is left with some cells from the surface of the cervix attached to it. These are smeared on to a glass slide or deposited in a container of liquid. This is sent off to a special cytology laboratory to be examined under a microscope.

Examination of the slide is fairly quick, but involves great expertise. Most laboratories will have some backlog, and your doctor or nurse should be able to tell you how soon the results will be back.

Make sure you know how you will find out the results, and if you do not hear, it is worth checking back on the result with your doctor.

The majority of smears come back normal. Some are normal, but show evidence of other things such as a thrush infection, which are chance findings, not what the smear is designed to detect. You should discuss with your doctor whether and how to act on such chance findings.

On some occasions there are not enough of the right sort of cells on the slide (a "scanty" smear) for the laboratory to reliably comment. On these occasions they ask for a repeat smear. As a woman gets older the cells of the cervix come away less easily, and sometimes, after a few scanty results, we have to give up on trying to get a smear.

Blood obscures the view of the cells, and the test is not usually performed if you are bleeding. If it has inadvertently been done at the beginning or end of a period, this may be another reason that the laboratory asks for a repeat.

If the cells look inflamed, or unusual, suspicious, or actually cancerous, the lab will suggest a repeat smear after a few months, or possibly referral to a specialist (gynecologist) for a closer look at the cervix using a sort of microscope (colposcopy).

If the smear is normal, the doctor will suggest you have a routine repeat after a length of time, between three and five years. This seems reasonable, as the average length of time a typical cancer of the cervix takes to develop is 10 to 12 years.

If the result is abnormal, follow up will be sooner and your doctor will advise.

Do not get too anxious over inflamed or slightly abnormal smear results. The majority of these settle back to normal with little or no action. If we did not act on all of these, however, we would not be able to prevent cancer and save lives, which the screening systems have been shown to do.