A cervical smear is a screening test aiming to identify women with pre-cancerous changes in order to initiate therapy before cancer develops.
Women aged 25 - 64 are routinely invited to have a smear test; once every 3 years until the age of 49, then once every 5 years until the age of 64. Around 80% of the women invited attend. Routine screening can prevent up to 75% of cervical cancer but unfortunately there are still around 2500 cases of cervical cancer per annum in the UK. Half of those cases occur in women who have never had a smear test, making non-attendance at routine screening the biggest risk factor in developing cervical cancer. Other risk factors include:
In the UK, the first invitation for screening is now at the age of 25, although many think this age should be lowered to 20, as demonstrated by the case of Jade Goody. This has raised discussion regarding the Cost Vs Benefit ratio, as the chance of developing cervical cancer under the age of 25 is small - approximately 2.3% of cervical cancers. Cervical cancer is also rare over the age of 65 and as such women will only have further smears beyond the age of 65 if they receive an abnormal smear result during routine screening: she will then be offered further smears and treatment if appropriate.
The cells sampled are from the Transformation zone. The cervix is the lower part of the uterus, and the area of the cervical canal where the epithelium changes from squamous to columnar is the transformation zone. This is where cell mutations arise that can lead to Cervical Intraepithelial Neoplasia (CIN); the precursor to cervical cancer.
Liquid based cytology is now the method of choice used to analyse the cells. The sample is obtained by using a speculum to visualise the cervix. A cervical brush is gently rotated 5 x clockwise around the centre of the cervix, to obtain a sample. The end of the brush is then broken off into a container of preservative fluid and sent to the laboratory to be analysed.
The cells are analysed to look for abnormalities in the appearance of the nucleus and other aspects of morphology (dyskaryosis).
This is a more detailed examination of the cervix. In this test a speculum is inserted into the vagina so that the cervix can be seen. A colposcope is a magnifier, which is used to visualise the cervix in more detail. A liquid (acetic acid and iodine) is painted onto the cervix to show up any abnormal cells. During colposcopy it is usual to take a biopsy to examine the cells in further detail. Treatment for any abnormal cells can sometimes be given at the same time.
The treatment offered will depend upon the extent of abnormality present. Options include:
A local anaesthetic is used before any treatment.
Risks of colposcopy and treatment include:
A cone biopsy is used when all the abnormal cells cannot be seen during colposcopy because the cells extend into the cervical canal. This a minor operation when a cone shaped piece of tissue is removed from the cervix so that it can be examined under the microscope.
For more information on cervical cancer, and other gynaecological malignancies, see here.
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