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DNA Test Recommended after Abnormal Pap Test

By Nancy Touchette

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Ovarian Cancer

Electron micrograph of human papilloma virus, a major cause of cervical cancer.
Pap tests have been used for routine screening of cervical cancer for more than 70 years, but experts are divided over the best way to treat women whose initial Pap test appears ambiguous. Options include repeated Pap tests or a DNA test for the virus that causes cervical cancer, human papilloma virus (HPV).

A new study, based on data collected over 10 years, reports that the DNA test is the best approach for women who need a follow-up.

“We found that the [HPV DNA] test is more sensitive in diagnosing precancerous lesions than repeat Pap tests,” says Marc Arbyn of the Scientific Institute of Public Health in Brussels, Belgium, and lead author on the recent study. “It’s also more specific.”

Arbyn says the DNA test is better at finding precancerous cells without introducing false positive results. He cautions, however, that the DNA test should not necessarily replace the Pap test. Nor should it be used to screen the general population because the virus is prevalent in younger women, but usually clears up on its own without causing cancer.

If negative, the DNA test can spare women from having to undergo a colposcopy, in which a doctor looks at the cervix directly through a microscope, and possible biopsy. In some cases, the HPV test can be conducted on samples collected when the original Pap test is done.

The study was commissioned by the European Network of Cervical Cancer Screening, which, based on the study results, is going to update its guidelines for European physicians. The findings are reported in the Journal of the National Cancer Institute.

In the United States, the guidelines of the American Society for Colposcopy and Cervical Screening call for following ambiguous looking Pap tests with a colposcopic exam, repeat Pap tests, or a DNA test for the HPV virus.

Pap tests observed under a microscope enable the technologists to detect abnormal looking cells from the cervix. The cells are graded according to their appearance.

For cells that look highly abnormal, the treatment is relatively straightforward. Most women have a colposcopy and a cervical biopsy, in which a tissue sample is removed for further evaluation.

But for women with cells that are ambiguous—those that look abnormal but not cancer-like—the approach is less clear. Abnormal looking cells could be the result of a local irritation or inflammation, or they could be precancerous.

Until recently, physicians recommended a colposcopic exam or follow-up Pap tests every three months. But some women fail to show up for the second exam and their potential cancers could go undetected.
Arbyn, M. et al. Virologic versus cytologic triage of women with equivocal Pap smears: A meta-analysis of the accuracy to detect high-grade intraepithelial neoplasia. JNCI 96, 280-293 (February 18, 2004)
Solomon, D. and Schiffman, M. Have we resolved how to triage equivocal cervical cytology? JNCI 96, 250-251 (February 18, 2004)

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