Pap Test, Part 3

by National Cancer Institute

(Page 3 of 3)

13. Who is at risk for HPV infection?

HPV infection is more common in younger age groups, particularly among women in their late teens and twenties. Because HPVs are spread mainly through sexual contact, risk increases with number of sexual partners. Women who become sexually active at a young age, who have multiple sexual partners, and whose sexual partners have other partners are at increased risk. Women who are infected with the human immunodeficiency virus (HIV) are also at higher risk for being infected with HPVs and for developing cervical abnormalities. Nonsexual transmission of HPVs is rare. The virus often disappears but sometimes remains detectable for years after infection.

14. Does infection with a cancer-associated type of HPV always lead to a precancerous condition or cancer?

No. Most HPV infections appear to go away on their own without causing any kind of abnormality. However, persistent infection with cancer-associated HPV types increases the risk that mild abnormalities will progress to more severe abnormalities or cervical cancer. With regular followup care by trained clinicians, women with precancerous cervical abnormalities can be treated before cancer develops.

15. Have any studies been done to examine HPV testing and treatment options for mild Pap test abnormalities?

Findings of the ASCUS/LSIL Triage Study (ALTS), a major clinical trial (research study with people) funded and organized by the National Cancer Institute (NCI), suggest that HPV testing in women with ASC-US may help identify underlying abnormalities that need a doctor's attention. The study results suggest that testing cervical samples for HPVs can identify which ASC-US abnormalities need treatment. A negative HPV test can provide reassurance that cancer or a precancerous condition is not present.

16. What are false positive and false negative results?

The Pap test is a screening test and, like any such test, it is not 100-percent accurate. Although false positive and false negative results do not occur very often, they can cause anxiety and can affect a woman's health.

A false positive Pap test means that a patient is told she has abnormal cells, but the cells are actually normal. A false negative Pap test occurs when a specimen is called normal, but the woman has a significant abnormality that was missed. A false negative Pap test may delay the diagnosis and treatment of a precancerous condition. However, regular screening helps to compensate for the false negative result. If abnormal cells are missed at one time, chances are good that the cells will be detected the next time.

17. What methods are being developed to improve the accuracy of Pap tests?

In April 1996, the Consensus Development Conference on Cervical Cancer, which was convened by the National Institutes of Health (NIH), concluded that about half of false negative Pap tests are due to inadequate specimen collection. The other half are due to a failure to identify or interpret the specimens correctly. Although the conventional Pap test is effective in the majority of cases, the conference made it clear that new methods of collecting and reading specimens are needed to reduce the number of false negatives.

The Bethesda System requires laboratories to determine whether there are enough cervical cells in the specimen to make a proper evaluation. This requirement helps improve the quality of samples and sample collection. The Bethesda System requires a sample to be categorized as "satisfactory for evaluation" or "unsatisfactory for evaluation."

One new method of collecting and analyzing samples is called liquid-based thin-layer slide preparation. This method may make it easier to screen for abnormal cells. Cervical cells are collected with a brush or other collection instrument. The instrument is rinsed in a vial of liquid preservative. The vial is sent to a laboratory, where an automated thin-layer slide device prepares the slide for viewing. Results of this method suggest that it is comparable to, or more sensitive than, standard Pap tests for the detection of significant abnormalities.

Computer automated readers are also being used to improve the reading of Pap tests. This technology uses a microscope that conveys a cellular image to a computer, which analyzes the image for the presence of abnormal cells.

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