Professor Henry Kitchener:

It is important for us to distinguish between the 30% level of false negatives that was referred to and the limits of cervical screening in terms of preventing cervical cancer. The 30% figure is derived from a paper we cited in the British Medical Journalwhich compared women who had been screened with women who had not been screened. It is clear that screening affords a very high level of protection, and that level of protection happens to be a little higher in older women than in younger women. All in all, there is a figure of around 30% for where screening fails to prevent cancer.

The reference Deputy Kelly makes to the proportion of false negative smears that might be expected is a different question and a very difficult one to address, because to evaluate the proportion of false negative smears, one would have to undertake a thorough examination of a large number of women with varying smear results, colposcope them to establish the actual state of the cervix, and determine in what proportion the smears had been false negative. That would be perhaps an important figure to know but an extremely difficult figure to arrive at reliably.

It is important that the public does not conflate a 30% inability of cervical screening to prevent cervical cancer in a population and any suggestion of 30% false negatives in routine cervical screening.