The NHS cervical screening programme in England and Wales is switching to liquid based cytology to minimise the number of smear tests that are unsuitable for testing. It is also going to change the frequency of screening to intervals based on age, it was announced this week.
The change followed pilot studies of liquid based cytology showing that it was associated with fewer "inadequate" cervical smear tests, so reducing the number of women recalled for repeat testing. Use of liquid based cytology was also associated with quicker reporting time.
The current screening programme, which uses the Pap smear test, requires a sample of cells to be collected—usually by a GP or nurse working in a community clinic—from the cervix with a disposable spatula. The sample is spread on to a glass slide and sprayed with, or dipped in, a liquid to fix it before being sent to a hospital laboratory for examination.
In contrast, the spatula device used to collect cervical cell samples in liquid based cytology techniques is simply rinsed or broken off into a vial of preservative fluid, with minimal risk of sample loss. The sample is then sent to the hospital laboratory, where the slide is prepared by the cytology team and examined.
The National Institute for Clinical Excellence (NICE) requested pilot studies after a systematic literature review carried out as part of its health technology assessment programme indicated that liquid based cytology could provide substantial benefits but provided insufficient evidence to justify nationwide introduction of the technology.
The pilot studies, carried out at three sites in England (Bristol, Newcastle, and Norwich), showed that the technique reduced the number of false negative test results. Results from the Bristol pilot study showed that the rate of inadequate smears fell from 9-10% to 1.5% and reduced the average waiting time for test results from eight to two weeks.
The NHS cancer screening programme also announced that the frequency of cervical screening is being changed from the current interval of every three to five years for women aged 20-64 years. Women will be invited for a first test at the age of 25 years and will be offered screening every three years until the age of 50. Cervical screening will then be offered every five years for women aged 50-64 years.
The decision was based on recommendations by scientists working for Cancer Research UK who found that a more effective screening programme could be provided by changing the frequency of screening according to the risk of cervical screening at different ages.
Julietta Patnick, director of the NHS cancer screening programmes, said: "The introduction of liquid based cytology offers a major improvement to the cervical cancer screening programme." She added: "I am also pleased that we are standardising the interval for screening based on good evidence from our own programme. These changes, in our view, mean that English women will have access to the best cervical screening programme in the world."
The NHS programme has been associated with a 42% drop in the incidence of cervical cancer in England and Wales between 1988 and 1997. Up to 300 000 women a year, however, are estimated to need repeat testing because their smears cannot be read properly.
Liquid based cytology will be introduced over the next five years as health professionals taking cervical cell samples and laboratory staff who assess them are retrained. The evaluation report of the pilot estimated that it would cost £10m ($17m; €14m) to convert from conventional screening to the new method.
The government has agreed to provide £7.2m over two years to start the programme, and additional funding will come from primary care trusts. It is hoped, however, that the changes will prove cost effective in the longer term, reducing the number of inadequate smears that laboratory staff have to examine and the frequency of retesting.