New Test Identifies More Cervical Cancers

But one expert wonders if it would be cost-effective

THURSDAY, June 28, 2007 (HealthDay News) -- A new computerized test called the ThinPrep Imager detects more high-grade cervical cancers than a conventional Pap smear, Australian researchers report.

The advantage of this new test is that it could lead to fewer women being retested based on inconclusive Pap smear findings, and allow for a longer time between screenings, the researchers said.

"In the samples read by the ThinPrep Imager, there was a significant 17 percent increased detection of high-grade lesions," said researcher Dr. Annabelle Farnsworth, medical director of the Cytology Department at Douglass Hanly Moir Pathology, in North Ryde. "There was also a 50 percent decrease in unsatisfactory slides," she added.

"The ThinPrep Imager is significantly better technology than conventional Pap smears," Farnsworth said. The study was funded by the Australian National Health and Medical Research Council.

In the study, Farnsworth's team used the computerized ThinPrep Imager reading system to evaluate liquid-based cytology slides. The imager is designed to highlight any slides that need further examination. These slides were then examined by a cytologist.

The researchers found that in samples from 55,164 Australian women, the ThinPrep Imager found 1.3 more cases of high-grade cervical abnormalities per 1,000 women screened than the conventional Pap test.

In addition, with the ThinPrep Imager there were fewer unsatisfactory slides than with the conventional test -- 1.78 percent vs. 3.09 percent. This means that fewer women might need repeated smears, Farnsworth said.

However, the ThinPrep Imager also found more low-grade cell lesions, which could result in higher rates of further testing, Farnsworth noted. But improved detection of moderate and severe changes does allow for the possibility of longer intervals between screenings, she added.

The study findings are published in the June 30 issue of the British Medical Journal.

Manual screening of conventional Pap smears has been around for decades, but liquid-based cytology is now replacing it in many countries, the researchers noted. Conventional smears are made by transferring material, taken from the cervix by a collection instrument, directly onto a glass slide. Liquid-based cytology slides are made by rinsing the collection instrument in liquid to make a "suspension," which is processed in a laboratory to produce a single layer of cells.

Another advantage of the new technology is that a health-care provider can also perform human papillomavirus (HPV) testing, Farnsworth said. HPV is the cause of 70 percent of all cervical cancers.

"Liquid-based cytology slides were always meant to be read by computerized technology," Farnsworth said. "It's taken a long time for this to happen."

Farnsworth also said that in an unpublished paper, her team showed that not only is the ThinPrep Imager more accurate, but it's faster than conventional methods. "This is a much more streamlined method for reading the smears," she said. "This takes cytology into the new millennium."

Debbie Saslow, director of breast and gynecological cancers at the American Cancer Society, said the additional costs associated with this technology may not be worth the potential benefit of introducing it into the United States.

"You have a cost-benefit analysis here that hasn't been done," Saslow said. "On one side, if you use this imager you pick up some lesions that might not have been picked up by conventional reading. In addition, you are going to save some time.

"On the downside, there is a cost to buying this imager. There is a cost to increased number of biopsies that will turn out to be negative," she said.

Saslow said this study might be used to help evaluate whether or not this technology should become common practice in the United States.

"Liquid-based testing is being used extensively in this country," she said. "But we don't know whether the imager is cost-effective and we don't know whether it is going to be cost-effective when you add HPV testing."

More information

The American Cancer Society can tell you more about cervical cancer.

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