Cervical cancer

In some cases, a cervical smear test may report that abnormal cells are present in a sample when, in fact, the cells in question are normal. This type of abnormal report is known as a 'false positive'.

False negative results

When a cervical smear test fails to detect an existing abnormality, the result is referred to as a 'false negative'. Even under the best conditions, a few smears are reported as normal when they are not. Several factors can contribute to a smear test reporting a false negative:

• When irregular cells are located high in the cervical canal they are difficult to reach under normal cervical smear test procedures.
• During your period menstrual blood can mask abnormal cells which would then not be visible to the screener.
• An inadequate sample - when not enough cells are collected during the smear test.
• Human error, in which the person reviewing the slide misinterpreted abnormal cells as normal.

However, despite this, the risk of a woman developing cervical cancer is greatly reduced if a regular screening programme is followed.

Reporting of Abnormal Cervical Smear Test Results

Two methods are used to report on the status of cells in your cervix, the class and the CIN (cervical intraepithelial neoplasia):

• Class I: All cells appear normal. No follow-up is needed.
• Class II (or CIN I): Although most doctors consider Class II or CIN I normal, some cells may show minimal changes, probably due to vaginal or cervical infection. Your doctor will probably repeat the cervical smear before doing other tests.
• Class III (or CIN I-II): Cells are definitely abnormal, with more obvious changes. This abnormal development of cells is called dysplasia. If the dysplasia is mild, it is classified as CIN I; moderate dysplasia is reported as CIN II.
• Class IV (or CIN III): The cells are more abnormal in appearance; the cells have much darker nuclei (centres). These findings may indicate severe dysplasia or carcinoma in situ, a precancerous condition. Cancer is still not conclusive at this stage.
• Class V: This finding indicates that cervical cancer is present and requires further diagnostic tests and treatments.