Tests that look for the human papillomavirus, or HPV, are more accurate than traditional Pap tests at detecting the precancerous lesions that lead to cervical cancer, according to a Canadian study of more than 19,000 women. 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.
"In the USA, co-testing is now the recommended gold standard, and neither doctors nor their patients should be willing to give up the added benefit you get from screening with a Pap test and HPV test together", he says. They also found that women with negative HPV test were more likely to not have cancer for the next four years, compared to the ones that had a negative Pap test. At the end of the four-year study, the women were tested with both tests.
There's a vaccine that prevents most cancer-causing strains of HPV, but once a person has become sexually active, it's too late to get it.
Leslie Massad, MD, a professor of obstetrics and gynecology at Washington University in St. Louis, wrote an editorial to accompany the study and agrees with its conclusion that HPV tests perform better than Pap tests.
Pap smears rely on the human eye to get results, says Dr. Diane Harper, a professor of medicine who researches HPV at the University of MI, "and it's far preferable to detect problems on a molecular level". Women with negative Pap smear results received a second Pap smear after 24 months. He called use of the HPV test only a "reasonable strategy" but noted that the test's strength - its sensitivity - could result in more positive results and more testing.
Yet almost a third of women aged 24 to 64 - 1.2 million - missed their cervical smear test in 2016/17, with just 72 per cent of those who qualify being tested, down from 75.7 per cent in 2011. Out of the subjects who examined negative in the HPV test, just twenty-two had abnormal cells, whereas out of those who tested negative in the Pap smear, fifty-two women had abnormal cells.
Schmeler often works in Latin America where, in countries like El Salvador, cervical cancer is one of the most common cancers in women primarily due to poor screening programs. These conditions can be treated before they progress to cervical cancer. Some are still skeptical of relying on HPV testing alone, and co-testing, or using both the HPV test and a Pap smear, is still the standard. He said that although the study confirmed previous research showing that the HPV test is more sensitive than the Pap test, it didn't answer a critical question: Is the HPV test alone better than the HPV test and the Pap smear together, as is current practice?
The Task force states that for women aged between 29 and 65 HPV tests alone every five years can be the only screening test.
Almost all cases of cervical cancer are caused by persistent infections of high-risk HPV, which causes changes to cervical cells.
In the first round of screening at the start of the study, more cases of CIN3+ were found in women who had HPV tests (7 per 1,000 women) than women who had smear tests (4.4 per 1,000 women). Harper notes that using both Pap smears and HPV testing can mean up to 30 percent of women could have a false positive. "Most women and doctors are not willing to give up this additional impact", he added. They could also get a Pap test every three years. Women also filled out questionnaires about lifestyle and sexual health history to ensure differences in results were not down to imbalances between the test groups.
Even the most ideal tests can also be limited by the fact that not all women are receiving regular and timely screening. Partly because of that, he said, "we're a long way away from replacing the Pap smear".