Study finds HPV test beats Pap smear

Procedure found more, earlier pre-cancers; health groups still back using both

A test for HPV detects precancerous changes of the cervix earlier and more accurately than the Pap smear, according to a large clinical trial published Tuesday.

The randomized, controlled study showed that the human papillomavirus test is more sensitive than the Pap smear, a widely used test that has been a standard part of women’s preventive health care for decades but which has several drawbacks.

HPV is the most common sexually transmitted infection and is usually eliminated by the immune system within a year or two. But when an infection persists, it can cause cellular changes that develop into precancerous lesions and, eventually, malignancies. Almost all cases of cervical cancer are caused by HPV infections.

About 13,240 new cases of invasive cervical cancer will be diagnosed in the United States in 2018, according to the American Cancer Society. About 4,200 women will die of the disease.

Over the past several years, as experts learned more about HPV’s role in cervical cancer, most medical groups have recommended that women in the United States get both the HPV test and the Pap smear — a practice called “co-testing.” Now, armed with the new and previous studies, some experts say the Pap smear should be dropped. But others disagree, saying that the Pap smear can catch a small number of cases of abnormal cells that might be missed by the HPV test and that co-testing should continue.

Many of the medical groups have said that before moving to HPV-testing only, they need to see clinical trial results to determine which test, over time, was better at detecting the precancerous changes. These conditions can be treated before they progress to cervical cancer.

Mark Spitzer, a gynecologist in New Hyde Park, N.Y., and past president of the American Society for Colposcopy and Cervical Pathology, said that while the study confirmed previous studies 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 decade-long study involved about 19,000 women who were placed in two groups: One using the HPV test to screen for cervical cancer and the other using a kind of Pap test called liquid-based cytology. In 2017, the researchers running the study reported that there were significantly more cases of precancerous lesions detected early in the trial among the women in the HPV-tested group compared to the Pap cytology group.

Tuesday’s report detailed the “exit” results of the study 48 months after the women were enrolled and first screened. For those final results, both groups were tested using both the HPV test and the Pap smear.

The researchers reported that there were fewer cases of pre-cancer in the HPV test group compared to the Pap smear group. That’s because cases of worrisome cellular changes already had been detected and dealt with after the women were first screened, said lead author Gina Ogilvie, a physician and public health researcher at the University of British Columbia. “The real benefit of co-testing is with the HPV test,” she said.