Pap (cervical) smear test

Reviewed by Dr Philip Owen, consultant obstetrician and gynaecologist

Why take a smear test?

The cervical smear test is designed to detect pre-cancerous changes in the cervix (neck of the womb). Pre-cancerous changes (properly called cervical intra-epithelial neoplasia, or CIN for short) are common in all age groups and cause no symptoms. This means that women will not be aware of CIN unless they have a smear test.

Are pre-cancerous changes (CIN) important?

There is always the potential that pre-cancerous changes might go on to become actual cancer of the cervix. It is also possible for pre-cancerous changes to go away by themselves. However, it is not possible for your doctor to predict which woman's pre-cancerous changes will go away untreated and which woman's pre-cancerous changes will go on to actual cancer.

It is not certain how long it takes for the abnormal cells to develop into cancer. If preventive measures are not taken cancer does develop in up to 50 per cent of cases, although this might take several years to happen.

How is a smear test carried out?

The smear test is taken in conjunction with a pelvic examination. A sample of surface cells is taken from the cervix with a small flat wooden spatula or a small brush. The specimen is placed on a small glass slide, fixed, stained and sent away to a laboratory to be examined under a microscope. The laboratory technician will then classify the smear test into either normal, borderline abnormal, mild, moderate or severely abnormal.

What happens if the smear is normal?

The woman is informed and it is recommended that the smear test is repeated in three years' time.

What happens if the smear is borderline or mildly abnormal?

The woman is informed and it is recommended that the smear test is repeated in 6 or 12 months time.

What happens if there is a moderate or severe abnormality?

The woman will be informed and invited to attend a colposcopy clinic for further investigation and treatment.

What is a colposcopy?

This is a procedure in which the gynaecologist examines the surface of the cervix using a magnifying instrument known as a colposcope. Although cell changes cannot be seen directly, the fine blood vessels under the cervix develop in a characteristic way during cell changes.

The gynaecologist will look out for such signs and in cases where cell changes have occurred, estimate how far they have grown and exactly how much they have changed.

Biopsies will be taken from the site on the cervix where the colposcopy has identified that cell changes have taken place.

How are cell changes in the cervix treated?

If tissue cell changes have occurred, the woman will normally be advised to have this tissue removed. There are several ways of doing this including a diathermy loop or using a laser. Most procedures can be performed with local anaesthetic while the woman remains awake. Following these procedures there may be some slight bleeding but the cervix heals quickly. The pre-cancerous tissue has now been removed and will be replaced by new, healthier tissue.

What happens after this treatment?

Depending on the severity of the pre-cancerous changes that have been removed, the woman will be advised how often she should attend for follow-up smear tests. This form of treatment is highly effective but pre-cancerous changes can return, so continued follow-up is essential.

How often should smear tests be carried out?

Women should not wait until they notice gynaecological symptoms before having an examination. In Britain, a screening programme is in place for examination of women over the age of 20 every three years. It is recommended that women ensure they are registered on this programme via their GP. Three-yearly examinations are sufficient - more frequent examinations do not produce better results in the prevention of cervical cancer.