Has the Pap test lost its value?
By John Biemer and Guliz A. Barkan source
The Pap test — a staple of women’s health checkups for generations — is one of medicine’s greatest success stories, saving the lives of countless women by detecting abnormal cells on the cervix that could turn into cancer. Yet the Pap test could be on the decline due to changing technology.
The Pap test is widely considered the most effective cancer screening test. As recently as 2000, an estimated 61 million Pap tests were performed in the United States, according to surveys conducted by the National Center for Health Statistics. But if recent proposals from the United States Preventive Services Task Force are approved, fewer Paps may be performed going forward, with a molecular test replacing them.
This month, the task force proposed that screening healthy women ages 30 to 65 for cervical cancer could be performed by either a Pap test or by a human papillomavirus DNA test instead — although a Pap would be performed every three years while the HPV test alone could be performed every five years.
The task force proposals, which are now in a public comment period, follow a study of 47,208 women undergoing routine cervical exams that demonstrated that a DNA test for HPV was more sensitive than the Pap at picking up lesions on the cervix that could progress into cancer.
However, critics of the HPV molecular test say it also is more likely to turn up with erroneously “positive” results (when there is no precancerous condition), which may lead to unnecessary treatment such as colposcopies and biopsies for patients who don’t need them. There also are concerns that setting the screening at five-year intervals may lead to women failing to follow up with gynecological checkups, which are also important for other health concerns besides cervical cancer screening. As a result, for the patient’s benefit, it may be better to have co-testing — both a Pap test and HPV testing at the same time — to ensure higher sensitivity in detecting cancer.
Cervical cancer was the most common cause of cancer deaths of women in the United States in the 1930s, but deaths dropped dramatically after the introduction of the low-cost, easily performed Pap test, which was developed by Dr. George Papanicolaou, a pathologist who emigrated from Greece.
In the Pap test, commonly referred to as a “Pap smear,” cells collected from the uterine cervix with a tiny brush are later placed on a glass slide.
Cytotechnologists and pathologists examine those slides under a microscope, scouring thousands of cells for any abnormality. From the perspective of patients, collecting cells for the HPV molecular tests also requires a speculum exam, so they won’t notice much difference.
Some strains of the human papillomavirus — the same virus that causes warts — have been linked to the development of cervical cancer. Infection by HPV, which is spread by sexual contact, still is common, especially in sexually active young men and women.
At least half of sexually active people will have HPV at some point in their lives, but the infection is usually transient and the body clears it on its own. That’s why the Pap test, rather than the HPV DNA test, is still preferable in women under 30 to see if precancerous changes in cervical cells already have taken place.
Some women, however, do develop persistent infections that can progress over time into invasive cancer. There are still nearly 13,000 new cases of cervical cancer in the United States each year and more than 4,000 deaths due to the disease, according to the American Cancer Society — though it now ranks as the 21st most common of cancers in women, according to the National Cancer Institute.
The biggest reason for its precipitous decline is vigilant surveillance. Although HPV vaccines and the HPV testing ultimately may lead to fewer Pap tests being performed, the goal remains the same: to stop a deadly disease in its tracks.
John Biemer, M.D., a former Tribune reporter, is a cytopathology fellow at Loyola University Medical Center in Maywood; Guliz A. Barkan, M.D., is the director of cytopathology at LUMC.