September 4, 2003
Less-frequent testing could mean fewer unnecessary follow-up exams and savings in both money and anxiety, according to Debbie Saslow, PhD, director for Breast and Gynecologic Cancer at the American Cancer Society. "If you use the liquid Pap, don't do it every year because you are going to get a lot of false-positives," she said.
For more than 15 years, the cancer society has recommended against annual Pap tests, Saslow said. But evidence of the sensitivity of the new tests might persuade doctors and patients to lengthen the amount of time between tests, she speculated.
However, the American College of Obstetricians and Gynecologists issued a practice bulletin July 31 that recommends that most women, including all under age 30, have an annual Pap test regardless of the testing method used. The US Preventive Services Task Force and CDC both endorse screening every three years for many sexually active women.
A federally funded trial, the ASCUS/LSIS Triage Study, resolved the question of what to do about the mild abnormalities that often show up on Pap tests. Although most abnormalities were known to go away, physicians remained confused about which irregularities were more dangerous and needed more monitoring. The study found that testing for HPV identified virtually all the common abnormalities - known as atypical squamous cells of undetermined significance - that needed treatment. Findings of the multicenter, 5,000-woman trial showed that HPV tests "do a beautiful job of clarifying ASCUS," according to Mark Schiffman, MD, co-director of the National Cancer Institute trial. "In medicine, it's rare to have an answer that is so clear."
FDA recently approved the HPV test as a screening tool that could be used in combination with the Pap test in women over 30. A recent study reported that the ThinPrep Pap test, a liquid based instrument, produced an unacceptably high rate of false positives among women taking oral contraceptives, a contention the manufacturer, Cytyc Corp., denies.
For the study, "Oral Contraceptive Pills Are Associated with Artifacts in ThinPrep Pap Smears that Mimic Low-Grade Squamous Intraepithelial Lesions" in Cancer Ctytopathology (2003;99;(2):75-82), Ohio State University pathologists rechecked the Pap tests of 84 women on birth control pills whose initial results with ThinPrep were diagnosed as abnormal. On reexamination, two-thirds of the women had no abnormalities, the study said.
"So we are telling these poor ladies that they have a venereal disease when they don't," said Gerard J. Nuovo, MD, professor of pathology and the study's lead author.
A spokesperson for Cytec Corp. maintained the fault was not with the test but with the laboratory that conducted the test. The effect of birth control pills on the appearance of cells is well known, and is an important part of the company's four-day training course on using the system, said the spokesperson.
Nuovo said physicians should be alert to the possibility that Pap results with ThinPrep that show low-grade abnormalities could actually be perfectly normal changes.