'Hope over smear test alternative' is the headline from BBC News today. It reports that testing for the common sexually transmitted infection human papillomavirus (HPV) may be a better screening tool for cervical cancer than smear tests. In addition, 'testing for HPV was so sensitive it only needed to be done every six years - compared to three years for smears', the BBC adds.
The story is based on UK research which has looked at the proportion of people who are initially reassured by a negative smear test or by the new HPV test and who later go on to show early signs of cervical cancer and how long it takes these women to develop this abnormality. This second report of a large, local study provides reliable information that supports extending the use of the test; however, more research into how the test might be used, either separate from the smear test or in addition to it, will be required. Larger studies will also need to look at the number of cases of cancer itself that could potentially be prevented by different screening strategies.
It is worth pointing out to women who may be confused by the headline 'hope over alternative' that the HPV test is carried out on a sample from the cervix obtained in the same way as a conventional smear test; the alternative is not, for example, a blood test that removes the need for a cervical examination.
Where did the story come from?
Dr Jack Cuzick and colleagues from Queen Mary s School of Medicine and Hammersmith Hospital carried out this research which was funded by a Cancer Research UK programme grant. Dr Cuzick had received funding from the makers of the test. The study was published in the peer-reviewed International Journal of Cancer.
What kind of scientific study was this?
This was a retrospective cohort study that reported the long-term findings from the Hammersmith Study in women aged 35 or over. This study, of almost 3,000 women, reported on how accurate the usual cervical smear test (cytology) was compared with the newer DNA-based tests for the HPV virus. The researchers found that the newer test was more sensitive: it picked up more women with an abnormal result in the initial test who were subsequently shown to have abnormal cervical cells when examined more closely by colposcopy and biopsy. Colposcopy is a procedure where the cervix is closely examined in the clinic and often a piece of tissue, a biopsy, is taken to confirm the degree of abnormality found on the cervical smear.
Signs of early cervical cancer are pre-cancerous cells called cervical intraepithelial neoplasia (CIN), and these are divided into 'grades' of severity, graded CIN1+, CIN 2+ and CIN3+. The researchers wanted to know if these new tests were specific; that is, how good they were at correctly excluding women who did not go on to show abnormal cells (graded more severe than CIN2+ or 3+) when a biopsy was carried out. Women went on to have colposcopy and biopsy if they had an abnormal initial result either on a conventional cervical smear test or on the newer HPV test. The biopsies were the standard by which the accuracy of both tests were judged.
