Check Up: DNA test endorsed as alternative to Pap smear

An expert medical panel has endorsed using a DNA test as an alternative, not just an add-on, to the venerable Pap smear for cervical cancer screening.

But the American College of Obstetricians and Gynecologists, which had a representative on the panel, says the new screening approach is premature. The ob/guns' group continues to recommend either Pap smears or "co-testing" using the Pap and DNA tests.

The DNA test, called cobas and made by Roche, detects two strains of the human papillomavirus (HPV) that causes cervical cancer. Cobas was approved by the FDA last May as a primary screening test for women 25 and older.

The new guidance was published last month by Obstetrics and Gynecology and two other journals.

An editorial by two California ob/guns lamented that the latest advice adds "more information, but little clarity, to the shifting landscape of cervical cancer screening."

An annual Pap smear is no longer recommended by any groups, but surveys suggest that many women and doctors are clinging to that strategy amid confusion over their increasingly complicated options.

The Pap smear, named for Georgios Papanikolaou, the pathologist who developed it more than 70 years ago, examines a scraping of cervical cells under a microscope to spot precancerous changes that can then be treated to prevent cancer.

The cobas test also requires a sample of cells, but it uses molecular technology to identify infection with HPV 16 or 18, which cause about 70 percent of cervical cancer. The test also looks for 12 other HPV strains that occasionally trigger cancer, but a positive result does not specify which strain.

Although studies show the DNA test can reliably detect infection with cancer-causing strains, such infections are common in young women and often clear up without treatment. Thus, some experts worry that using the HPV test as the primary screening tool will flag too many women for diagnostic exams and treatment, without saving more lives.

Cervical cancer deaths have plummeted thanks to Pap screening. About 12,100 cases a year are now diagnosed, and 4,200 women die.

The Society of Gynecological Oncology and the American Society for Colposcopy and Cervical Pathology convened the 13-member panel that published these new guidelines:

Starting at age 25, women should undergo screening using the cobas DNA test.

If the DNA test is negative, women should not repeat the test sooner than three years, given that precancerous changes take years to progress to cancer.

If women test positive for HPV 16 or 18, they should undergo a colposcopy, a procedure that visually examines the cervix with magnification. If the cobas test is positive for any of the 12 other dangerous strains, it should be followed up with a Pap test to decide whether a colposcopy is needed.

Women who want to be screened starting at age 21 should follow existing guidelines for Pap testing or co-testing.

Primary HPV testing "is an important scientific and clinical advance in cervical cancer screening, since it offers better reassurance of low cancer risk compared with [Pap screening] at the same interval," the panel concluded.

As for insurance coverage, Roche's website says that Medicare and most private insurers cover medically necessary lab tests, so they "are likely to cover diagnostic HPV testing." In addition, the Affordable Care Act expanded coverage for women's preventive services, including coverage of HPV testing.

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