A test for HPV detects pre-cancerous changes in the cervix earlier and more accurately than the Pap smear, according to a major clinical study published on Tuesday.
The randomized controlled trial – the "gold standard" of research – showed that the human papillomavirus test is more sensitive than the Pap smear, a widely used test that has been the standard in preventive health care for decades heard of women but has disadvantages.
Several experts predicted that the results would encourage efforts to completely replace the Pap test with the HPV test. "It's an important study," said Jason Wright, a gynecological oncologist at New York-Presbyterian / Columbia University Medical Center, who was not involved in the study. "It shows that HPV testing alone provides a high degree of accuracy" that puts you at risk for cervical cancer.
HPV infection is the most common sexually transmitted infection and is usually eliminated within a year or two of the immune system. But if an infection persists, it can lead to cell changes that develop into precancerous lesions and eventually malignancies. Almost all cases of cervical cancer are caused by HPV infections.
According to the American Cancer Society, about 13,240 new cases of invasive cervical cancer will be diagnosed in the US in 2018. About 4,200 women will die from the disease.
The study supports earlier research that showed HPV testing was superior to Pap testing. In recent years, as experts learned more about the role of HPV in cervical cancer, most medical groups have recommended that women in the US receive both the HPV test and the Pap smear – a practice called "co-testing ". Now, armed with the new study and earlier, some experts say that the Pap smear should be dropped. But others disagree, saying that the Pap smear can detect a small number of cases of abnormal cells that could be missed by the HPV test and that co-tests should continue.
Many of the medical groups have said that before switching to HPV testing, they will need to see clinical trial results – as provided by the new head-to-head study – to determine which test could be better recognized over time, the precancerous ones changes. These conditions can be treated before they progress to cervical cancer.
Kathleen Schmeler, a gynecological oncologist at the MD Anderson Cancer Center who was not involved in the study, was excited about the new results. "It's fantastic," she said. "It shows that you may only be able to do the HPV test and get rid of the Pap test."
But Mark Spitzer, a gynecologist at New Hyde Park in New York and former president of the American Society for Colposcopy and Cervical Pathology, objected. He said that although the study confirms earlier research showing that the HPV test is more sensitive than the Pap test, it did not answer a critical question: is the HPV test alone better than the HPV test and the Pap smear together, how is it currently exercising?
In the United States, the conventional Pap smear has been largely replaced with a liquid-based Pap cytology test. Cervical cells for the Pap and HPV tests can be taken simultaneously during a gynecological examination. Some women may not even know that they are being tested for HPV.
The decade-long study, which appeared in the Journal of the American Medical Association, included approximately 19,000 women divided into two groups: one with the HPV test for cervical cancer and the other with Pap cytology. In 2017, researchers in the study reported that among the women in the HPV-tested group, cases of precancerous lesions were significantly more common in the study compared to the Pap cytology group.
The Tuesday report detailed the study's "exit" results 48 months after the women were admitted and their first examination. For these final results, both groups were tested with both the HPV test and the Pap test.
The researchers reported that there were fewer cases of precancerous lesions in the HPV test group than in the Pap smear group. Because after the first examination of women cases of alarming cell changes were discovered and treated, said lead author Gina Ogilvie, a doctor and health scientist at the University of British Columbia. "The true benefit of co-testing is with the HPV test," she said.
The report, funded by the Canadian Institute for Health Research, found that adding HPV tests to the Pap test group yielded 25 lesions that would not have been found with the Pap test alone. By adding the Pap test to the HPV group, three more lesions were found.
Spitzer said that these three cases support the "small but significant benefits of co-testing."
Mark Schiffman of the National Cancer Institute, who has done extensive research on HPV, said the study confirms that it's important to switch from Pap smear alone to HPV testing. "This has built up for decades," he said, adding that the Pap smear was "crude and inaccurate," while the HPV test is much more precise, works at the molecular level, and provides information about the specific HPV type, which causes the problem. The Pap smear works, he said, just because women were often tested and because cervical cancer is slowly growing.
Most medical groups, including the American Cancer Society and the American College of Gynecologists, recommend that women at medium risk receive all HPV tests and Pap smears every five years between the ages of 30 and 65, even though they have a Pap test every three years say is an acceptable alternative. Women in their twenties are advised to get Pap smears, not HPV tests, because the virus is so common that most would look positively for infections that would most likely self-elucidate.
About 80 million people in the United States are infected with HPV, but most never develop any health problems, as most infections disappear by themselves, say the Centers for Disease Control and Prevention. But if infections last longer, they can cause not only cervical cancer, but also cancers of the anus and throat and cancers of the penis.
Therefore, doctors strongly recommend that children and young adults be vaccinated against HPV; a vaccine was approved by the Food and Drug Administration in 2006. The infection with HPV types targeted by the vaccine has been recommended by nearly two-thirds among teenage girls since HPV vaccination in the US, according to a study that also found there was a decrease in HPV infections in women from 20 to 24th
The US Preventive Services Task Force, an independent body that reviews the evidence of effectiveness for prevention services, is currently recommending "co-testing" for cervical cancer signs that other groups advocate. Last fall, however, a draft recommendation was issued suggesting that women receive either HPV tests every five years or Pap smears every three years, but a final recommendation has not been published.
The new study is likely to "help drive this forward," said Wright Newyork-Presbyterian / Columbia University Medical Center. He called the use of the HPV test only a "reasonable strategy", but found that the strength of the test – its sensitivity – could lead to more positive results and more testing. Not least for that reason he said: "We are far from replacing the Pap smear."