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Medicine | HEALTH MATTERS

Casting a skeptical eye on visual Pap test

It has a high rate of cancer detection -- and perhaps of false positives too.

June 16, 2003|Trudy Lieberman | Special to The Times

During my last doctor's visit I noticed a sign in the exam room urging patients to ask about a new Pap test called PapSure. Curious, I asked my doctor for more information.

My doctor said she was unfamiliar with the scientific evidence for the test's benefit, but added that she'd heard that the test -- which costs $75 and is not covered by health insurance -- was effective. The test, she said, has "good results and picks up every little infection." Still skeptical, I decided to look further into the test.

PapSure, a visual screening exam performed in the doctor's office, is another in a string of new cervical screening technologies that aim to increase the accuracy of the traditional Pap smear, which misses about 50% of all cancers and pre-cancers. With PapSure, physicians apply a solution to the cervix and use a special light to spot abnormal tissue, in effect combining a traditional Pap smear with a visual examination.

The new techniques, which are being marketed to doctors nationwide, involve different technologies. They include ThinPrep, in which the Pap smear sample is put into a liquid fixative instead of smeared on a slide, and HPV testing, which looks for viruses that cause cervical cancer.

As with many promising new technologies, PapSure and other screening tests are being heavily promoted and adopted by doctors who may not have a lot of time to evaluate the scientific pros and cons of a particular test. And the science isn't always definitive.

No studies have been done, for instance, that show PapSure actually reduces cervical cancer deaths. Research has shown that PapSure, like most new cervical screening technologies, is more sensitive than the traditional smear. That means it picks up more abnormalities.

According to Watson Diagnostics, which is marketing PapSure, the exam, when combined with a Pap smear, roughly doubles the detection rate of suspicious areas. This means that women who have negative results on both tests are very unlikely to have undetected cervical cancer, said Ellen McCune, Watson's vice president of sales and marketing for women's health.

Proponents of PapSure and similar tests say that improved detection techniques may save lives down the road. About 5,000 women die of cervical cancer each year in the U.S.

Although no one would argue with the value of saving lives, PapSure has some drawbacks. Some researchers say it is not very specific: Not every abnormality or infection it finds will be cancerous or pre-cancerous. In other words, it produces a lot of false positives.

"Between 20% and 30% of all women screened with PapSure will have positive test results, but most of these women will not have cancer or pre-cancer," said Dr. Thomas Wright, director of gynecological pathology at Columbia University's College of Physicians and Surgeons.

Traditional Pap smears are less sensitive and will identify fewer women who are at risk of developing cancer or already have it. About 5% to 10% of women who are given the Pap smear alone will be told they have abnormal results, said Wright. But clinicians point out that even if a single Pap smear misses an abnormality, it would likely be caught the next time, if the woman has regular exams, because invasive cervical cancer takes time to develop.

About 50 million U.S. women will have a Pap smear in a given year. If PapSure were used on every woman screened, it could result in 20% of those women being told they have an abnormality when they may not. That's 10 million women who may undergo further testing to make sure they don't have a disease. So the question becomes: Should 10 million women undergo further testing to find the 6,000 women who may be missed by traditional Pap smears? If you are the woman whose cancer was missed, the answer is probably yes. But the answer is not as clear when you consider the impact on the broader population.

No major medical societies, including the American College of Obstetricians and Gynecologists, have issued guidelines recommending these new cervical cancer screening tests. And most insurance companies have yet to pay for PapSure. "There are no adequate studies in the medical literature for its use as a replacement for Pap smears or in conjunction with them," says Dr. Vinny Jaeger, senior medical director for Health Net Inc., a large, managed-care organization.

McCune says Watson hopes to persuade health insurers to pay for PapSure. Watson, she says, hopes to emulate the success of Cytyc, the company that heavily promoted its ThinPrep technology a few years ago. Today, about 60% of all Pap smears in the U.S. are done using ThinPrep and other similar technologies, doubling the cost of cervical screening.

What my doctor didn't tell me drives home the point. I have made my choice. I will spend the $75 on a dinner out as a reward for having regular Pap smears -- still the best way to prevent cervical cancer.

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