The key questions
What is the chance of a false negative test result?
On average, for every 1,000 tests carried out, 959 tests will be negative, but 4 of these will be a false negative.
What is the chance of a false positive result?
On average, for every 1,000 tests carried out, 41 of these will be positive, requiring a repeat test or referral for colposcopy. Of the 41 tests, 12 will be confirmed as CIN requiring treatment (true positives). The remaining 29 will be confirmed as false positives.
If I have a normal smear test result, what is my chance of developing cervical cancer in the next three to five years?
Assuming 250,000 women attend for screening each year in CervicalCheck, in women with a negative screening test, 39 will go on to develop invasive cervical cancer within 3.5 years and 90 will go on to develop invasive cervical cancer within 5.5 years. This includes true negatives and false negatives.
What was the controversy with CervicalCheck and the Scally report?
The controversy surrounding the CervicalCheck programme relates to the identification of false negative results by the screening programme. An audit was undertaken to check the quality of the programme. This audit involved reviewing previous cervical screening tests in women who had subsequently developed cervical cancer. The focus was on false negative results, ie, women who had a normal screening test but went on to develop cervical cancer.
The Scally report reviewed this process and highlighted the difficulty in conducting these audits due to a concept called ‘recall bias’, ie, those reviewing the slides as part of the audit may be aware the woman went on to develop cervical cancer.
The report was critical of the process, particularly that the women involved were not informed of this audit and that the HSE policy on Open Disclosure was not generally followed. The report also highlighted the significant delays experienced by women and many examples of poor communication with the women affected and their families.
We do not yet know if Ireland has a different rate of false negative results for cervical cancer screening compared with other countries.