Women's health

An alternative to beat PAP's high false-negatives

A switch to HPV testing for cervical cancer screening may be in the offing. Bringing sexual partners out of the shadows

By Amanda Alvarez

The frequent use of PAP smears has been highly effective in preventing cervical cancer by catching it early. It does, however, have its limitations, the most important of which is the high false-negative rate. To increase the overall sensitivity of the test, current guidelines call for it to be repeated every one to three years.

A new study from the December issue of The Lancet took as its premise that certain high-risk types of human papillomavirus (HPV) are the cause of almost all cervical cancers. The researchers also noted that HPV testing of cervical smears is more sensitive - albeit less specific - in detecting cervical cancer than the PAP test. They then compared the results of the predictive values of HPV with those of cytology to come up with the best management strategy for women who were HPV-positive.

The study, headed by Cancer Research UK and several medical centres around the country, looked at 11,085 women between the ages of 30 and 60. Those who were positive for high-risk HPV but had negative PAP smears and those with borderline PAP test results were randomly assigned to two groups either to have an immediate colposcopy or a second HPV test, cytology and colposcopy 12 months later. The researchers selected 825 women randomly out of the sample. Among them, HPV testing turned out to be as effective for establishing women at risk at 12 months as immediate colposcopy. Of the 164 women who were positive for HPV initially, 73 (45%) had negative PAP smear results. Another 23 had borderline cytology, of which eight were HPV negative at six and 12 months. Further more, no cervical cancer was found in any of the women who initially had negative HPVs.

LONGER INTERVALS
Based on the results, the authors suggested that HPV testing could be used for primary screening of women over age 30. For those who were HPV-positive, PAP smear results would then be used to triage the women according to risk for cervical cancer. All of those who were HVP positive would be tested again in 12 months. The majority who were both HPV negative and had negative PAP smear results would not be tested again for, say, three to five years. The suggestion was that the approach could improve detection rates without increasing the colposcopy referral rates.

The Lancet's Eduardo L Franco, in an accompanying editorial, endorsed the idea of lengthening the screening interval for those women with negative results for both cytology and HPV. He was cautious, though, about the idea that women be screened initially with HPV, because those at high-risk would be separated out and only then have a PAP smear. He pointed out that should testing go in this direction, it would be a paradigm change in which the search for sexually transmitted viruses would become the focus of cervical cancer detection. This method would have one significant advantage in the editorialist's view: it would put responsibility for prevention not just on the woman but on her sexual partners as well.

See also My speculum nightmare