Jan 4, 2000
A self-collected test for human papilloma virus (HPV) is as sensitive as Pap smears in screening for cancerous and pre-cancerous lesions of the cervix, according to researchers at Columbia University College of Physicians & Surgeons. Because it is simpler than a Pap smear, self-administered HPV testing could help increase the number of women screened for cervical cancer in both the developed and developing worlds.
"The woman herself can collect this sample," says Dr. Thomas Wright, associate professor of pathology and lead author of the study appearing in the Jan. 5 issue of the Journal of the American Medical Association. "We hope that this will become a routine lab test that can be collected during a woman's routine visit to her health care provider."
Although existing screening programs have been associated with a five-fold reduction in the incidence of cervical cancer worldwide, approximately 360,000 cases of cervical cancer were detected in 1990, with 190,000 women dying of the disease. Many women around the world do not receive regular cervical screening. More than half the 12,800 women diagnosed with cervical cancer in the United States each year have not had a Pap smear in the past three years.
The Papanicolaou test, or Pap smear, is the most widely used screening test for cervical cancer. For a Pap smear, a health professional must insert a speculum in a woman's vagina to expose the cervix and scrape cells off of it. The cells are then examined under a microscope by a highly trained technician, who can examine a maximum of about 80 Pap smears per day.
Obtaining a self-collected sample for HPV testing requires that a woman collect a sample of vaginal secretions with a small swab resembling a Q-Tip. The swab is then analyzed for DNA from 13 species of human papilloma virus considered to be of "high carcinogenic risk." Infections by one of these 13 species are found in more than 96 percent of women with cervical cancer.
Dr. Wright and his colleagues in both the United States and South Africa recruited 1,415 previously unscreened African women ages 35 to 65 from an area outside of Cape Town, South Africa for the study. The women collected a vaginal swab for human papilloma virus testing. Health professionals then administered four screening tests for cervical cancer, including a Pap smear, direct visual inspection of the cervix, a photograph of the cervix, and clinician-collected swab for HPV. Women with abnormalities on any of the screening tests were referred for further evaluation to determine if a cancer or precancer were present.
Of 1,365 women screened and adequately followed up, 500 had a positive result on one or more of the screening tests. Of those, 47 were found to have high-grade cervical disease, a likely precursor to cancer. Nine others had cervical cancer. The self-collected vaginal swab identified 37 of the 56 women with high-grade cervical disease or cancer, for a sensitivity of 66.1 percent. The Pap smear identified 38 of the 56 women, for a sensitivity of 67.9 percent. The false-positive rate for the self-collected HPV test was 17.1 percent, and 12.1 percent for the Pap smear.
"I think Pap smear will still be used for cervical cancer screening, especially in young women," says Dr. Wright. "But the HPV self-test could extend effective screening for cervical cancer to thousands of women who would otherwise not get any form of screening."
In developed countries, co-author and assistant professor of public health Dr. Leslie Kuhn believes that HPV testing could be especially useful for screening women in their 40s and 50s. Although cervical cancer most commonly strikes women of that age, many fail to get Pap smears because they have stopped seeing a gynecologist, the physician who most commonly administers the test. Also, HPV is more strongly associated with cervical cancer in older women than it is in younger ones. An HPV test could easily be collected during a visit to the general practitioner, since it involves a much less invasive, uncomfortable, and specialized procedure than the Pap smear.
HPV might bring cervical cancer screening to many thousands of women in developing countries who do not now receive the tests for a variety of reasons ranging from lack of access to qualified health professionals to social taboos on performing Pap smears.
The other researchers who contributed to the study were Dr. Attila Lorincz of the Digene Corporation Dr. Lynette Denny of the University of Cape Town, South Africa and Amy Pollack of AVSC International. The study was supported by funding from the Bill and Melinda Gates Foundation, AVSC International, the Cancer Association of South Africa, and the South African Department of National Health.