New cervical smear test could improve screening accuracy

BMJ 1998; 317 doi: (Published 12 December 1998) Cite this as: BMJ 1998;317:1611
  1. Richard Woodman
  1. London

    A new cervical cancer smear test, which promises to save thousands of lives by reducing the potential for human error in identifying abnormal cervical cells, has successfully completed early stage trials and could be launched within three years, researchers in the United Kingdom announced this week.

    The test, developed by Cancer Research Campaign (CRC) scientists at Cambridge University, uses antibodies that home in on Cdc6 and Mcm5, two recently discovered protein molecules that regulate DNA replication and are only present in cells which have the potential to replicate. A green fluorescent or brown dye is used to highlight these antibodies so that any abnormal cells stand out much more clearly than those identified using the conventional smear test, which gives a false negative result in 10-30% of cases.

    Gareth Williams and fellow researchers Nick Coleman and Ron Laskey said that the results of a small blinded trial of the new test in East Anglia on 58 cervical smears taken from women recalled for examination showed that the test was 100% efficient at detecting abnormalities. Out of 58 smears, roughly half of which were abnormal, the test correctly identified all smears with abnormalities, whereas the standard test missed three of them. The three problem cases were then re-examined conventionally and shown to have low grade abnormalities. However, further investigation of the patients by biopsy found high grade abnormalities in all three. The results were published this week in the Proceedings of the National Academy of Sciences (1998;95:14932-7).

    The researchers emphasised that the existing cervical smear programme in the United Kingdom was the most successful public health cancer screening measure and that their test would add to this.

    Gordon McVie, CRC director general, said: “This discovery is amazing because it effectively makes any suspect cell stand out from the crowd. I believe it could be an ideal solution to the mistaken cervical smear diagnoses which we have, sadly, all heard so much about. In the short term, we hope it could be used in addition to normal screening procedures to improve human assessment of cervical smears. In the future, the test could be automated so that only suspect cervical smears would be scrutinised by the human eye. This could also save the cervical screening programme millions of pounds in reduced manpower costs.”

    The CRC's commercial arm has signed a deal with the California company diaDexus to carry out the necessary trials and development work before the test is launched, which is expected to be by 2002. Health secretary Frank Dobson welcomed the improved accuracy of the new test and pledged that the government would find the money to introduce it in the United Kingdom if benefits were confirmed.

    The political sensitivities of cervical cancer screening in the United Kingdom were underlined in a report published by the Public Accounts Committee last week--The Performance of the NHS Cervical Screening Programme in England--which warned that lives remain at risk because there are still “worrying failures at every stage of the cervical screening process.” The report said that health authorities could prevent 84% of cervical cancers by screening women every five years, yet 13 health authorities had not yet achieved the target of screening 80% of women aged 25 to 64 within the previous five years.

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    Frank Dobson discusses the new test with researcher Dr Nick Coleman

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