For women between the ages of 30 and 65 who are at risk of contracting human papillomavirus, a promising test might be an alternative to the dreaded Pap smear. Harper notes that using both Pap smears and HPV testing can mean up to 30 percent of women could have a false positive. He said that physicians will have to make the choice between HPV testing and co-testing based on cost-effectiveness studies and their own discretion, while continuing to improve outreach for underserved and inadequately screened women to combat such high rates of cervical cancer.
Numerous medical groups have said that before moving to HPV testing only, they needed to see clinical trial results - such as the kind provided by the new head-to-head study - to determine which test, over time, was better at detecting the precancerous changes.
Of the women who tested negative on the HPV test, just 22 women showed grade 3 or worse cells, while the Pap smear group, found 52 women ended up with abnormal cells.
Cervical cancers are one of the leading causes of cancer deaths among women.
Because the HPV vaccine that is recommended for adolescents is still limited in its use, testing for the presence of the HPV virus, in general, will continue to be a crucial part of cervical cancer prevention. "Since it's a better test at about the same cost and can be done less often, it should replace Pap testing", he says. They detect only around 55 percent of true cases, according to a study by the Canadian Cervical Cancer Screening Trial Study Group, and requires a special process using a liquid medium that takes several days. The Pap smear worked, he said, only because women were tested often and because cervical cancer grows slowly. The HPV test may only be needed every five years, Durand said, "because it's such an accurate test".
Cervical cancer screening is essential because almost 13,000 women in the US are diagnosed with cervical cancer annually. They also found that the HPV test was a better predictor of women who would be cancer free in future compared to Pap test.
In most provinces, Pap tests are recommended every three years.
The cytology-based Pap smear involves looking for cancer or precancer cells by testing cells taken from a woman's cervix. They can't rely on HPV testing, Schmeler says, because nearly everyone in that age group will contract HPV and in many cases it goes away on its own. "This has been building for decades", he said, adding that the Pap smear is "crude and inaccurate" while the HPV test is much more precise, operates on the molecular level and can provide information on the specific type of HPV causing the problem.
After four years, the women who got HPV tests were less likely to have serious changes that can lead to cervical cancer, a diagnosis of cervical intraepithelial neoplasia 2 or 3 (CIN2 and CIN3), Ogilvie's team found. From the participants, 9,552 women were screened using HPV test and those who were negative for the test came back after four years for a check if they had a pre-cancerous or cancerous lesion.
But Mark Spitzer, a gynecologist in New Hyde Park, New York, and past president of the American Society for Colposcopy and Cervical Pathology, disagreed. Now, armed with the new study and previous ones, some experts say the Pap smear should be dropped. These conditions can be treated before they progress to cervical cancer. This new study could prove important in deciding on practice guidelines.
Human papillomavirus (HPV) is a DNA virus from the papillomavirus family.
For women under 25, the Pap test is still the standard because many young women are infected with HPV, Ogilvie said. Both group were tested again using both methods after four years. Partly because of that, he said, "we're a long way away from replacing the Pap smear".
In addition to finding more precancers in the initial screening, women who had the HPV test had a "significantly lower likelihood" of having precancer in the cervix when they exited the study four years later.