ThinPrep Pap Test Allows Both Pap and HPV Testing From a Single Sample Collection Vial

PHILADELPHIA—The FDA has approved testing for HPV (human papillomavirus) directly from Cytyc’s ThinPrep Pap Test collection vial. HPV testing is performed using Digene Corporation’s Hybrid Capture HPV DNA Assay, the only HPV test currently approved for marketing by the FDA.

James Linder, MD, in an interview with Oncology News International at the annual fall meeting of the American Society of Clinical Pathologists (ASCP) and College of American Pathologists (CAP), called this an important advance “because studies underway seem to indicate that performing HPV typing on cervical cells can lead to better management of women with inconclusive or equivocal Pap smears, reducing the need for repeat office visits or unnecessary colposcopy or biopsy.”

With the ThinPrep Pap test, the physician collects the cervical cells in the traditional way, but rather than smearing a small portion of the cells onto a slide, the physician rinses the cells from the collection device into a vial filled with preservative solution. This vial is then sent to the lab where the ThinPrep 2000 Processor disperses and filters its contents to reduce mucus, blood, and inflammation, and applies a thin, even layer of cells to a microscope slide.

Pivotal clinical trials presented at the time of FDA approval of ThinPrep in 1996 showed 65% increased detection of low grade and more severe lesions with use of the ThinPrep system over conventional Pap smears in screening populations, said Dr. Linder, professor of pathology and associate dean, University of Nebraska Medical Center.

Dr. Linder was named president-elect of ASCP at the meeting. He is also medical director of Cytyc Corporation, Boxborough, Mass, manufacturer of ThinPrep.

Subsequent studies have shown 110% increased disease detection with the ThinPrep method, he said. “That translates into an immediate reduction in the false-negative rate.”

Dr. Linder stressed that abstracts and publications done independently of Cytyc confirm the value of the test and will be appearing in the near future.

The advantage of the ThinPrep approach, Dr. Linder said in the interview, “is that after the initial slide has been made for morphologic examination, additional tests can be done, because there are cells that remain in the sample vial. With ThinPrep, you actually have cells in the laboratory, and you can do HPV or other tests without having the women come back for a second visit.”

Another important aspect of the ThinPrep Pap Test, he said, “is the potential of ThinPrep to better detect high-grade lesions. The reports in the literature, again from independent investigators, are that with the ThinPrep approach, one typically detects between 33% and 50% more high-grade lesions. And these are the immediate precursors to cervical cancer.” These results, he said, are, for the most part, from investigators using the test in their daily practice.

“Pathologists and cytopathologists, once they have seen the ThinPrep morphology, find it much more acceptable than conventional smears,” he added.

He said that the cost of ThinPrep varies from market to market, but typically runs $20 to $30 more than conventional Pap screening. He does not believe this will be a difficulty for payers once they have been educated as to its value.

He said that many managed care payers have already taken public postures that they will cover use of the ThinPrep system, including United Health Care and Blue Cross, Blue Shield, in Massachusetts and several other states.

“For any new test,” he said, “but particularly for a new Pap test, one has to educate everyone involved as to its value—the clinician who orders the test, the laboratory that provides the test results, and the group that pays for the test.” He said that Cytyc has been communicating with all of these groups and finding “very good acceptance by all of them.”