Federal health regulators have cleared a genetic test from Roche as the first U.S.-approved alternative to the Pap smear, the decades-old mainstay of cervical cancer screening.

The Food and Drug Administration approved cobas, a test from Roche to detect the human papillomavirus, or HPV, in women 25 or older. HPV causes nearly all cases of cervical cancer.

Doctors already use such DNA-based tools as a follow-up to confirm Pap test results. But Thursday’s decision means Roche can now market its test as a stand-alone option for cervical cancer screening, ahead of the Pap test.

Roche supported its bid for expanded marketing with study results suggesting that genetic testing is more accurate and objective in identifying cancerous growths than the Pap smear, which requires doctors to examine cervical cells under a microscope for signs of cancer.

The FDA approval comes despite resistance from a number of women’s health groups, which warned regulators that approving the DNA test as an alternative to Pap testing could lead to confusion, higher costs and overtreatment. More than a dozen patient groups raised those concerns in a letter to the FDA last week. They said HPV-only testing could lead to overtreatment of younger women who carry the virus but have little risk of developing actual cancer. Most sexually active young people contract HPV, but their bodies usually eliminate the virus within a few months. Only years-long infections develop into cancer.

FDA officials said in a statement Thursday that they approved the test because “Roche Diagnostics conducted a well-designed study that provided the FDA with a reasonable assurance of the safety and effectiveness.” The trial included more than 47,000 women who underwent cervical screening using either Pap or HPV screens. The test results were then checked for accuracy against final biopsy results that confirmed whether they had cancer.

For decades, the Pap test was the only screening option for cervical cancer, and it has had a remarkably successful track record. The number of cervical cancer cases reported in the United States has decreased more than 50 percent in the past 30 years, primarily due to increased Pap screening. Still, an estimated 12,000 cases of cervical cancer are expected to be diagnosed this year, a fact that has spurred development of HPV tests such as those from Roche, Qiagen and others. HPV tests generally cost between $80 and $100, about twice as much as a $40 Pap screen.

Medical guidelines have been evolving rapidly in an attempt to incorporate both techniques. Under the latest guidelines from the American Cancer Society, a Pap test is recommended every three years for women 21 to 29 years old, while women 30 and older should have both a Pap test and an HPV test every five years, or a Pap test alone every three years. HPV screening is not recommended for women in their 20s because it increases the odds of more invasive testing that can leave the cervix less able to handle pregnancy later in life.

The FDA approval allows Roche to market its test to women as young as 25. Women who test positive for the most high-risk strains of HPV will be referred directly to colposcopy, an invasive test in which doctors view the cervix with a magnifying device and often collect a tissue sample for testing.

Groups including the Cancer Prevention and Treatment Fund, American Medical Women’s Association and Our Bodies Ourselves questioned why the FDA would approve labeling that goes against medical society recommendations, which recommend HPV screening only for women 30 and older.

In its statement approving the test, the FDA staff suggested that its decision would not change how doctors use HPV screening.

— Associated Press