A single test that looks for the virus that causes cervical cancer cut the death rate from the tumor in half, researchers in India reported on Wednesday.

Qiagen NV's human papilloma virus, or HPV, test was also more effective than Pap smears or an inexpensive method that uses a mild acid to detect tumors, the researchers reported in The New England Journal of Medicine.

A commentary on the study said tests for the virus should become widely used.

"The implications of the findings of this trial are immediate and global: international experts in cervical-cancer prevention should now adapt HPV testing for widespread implementation," wrote Drs. Mark Schiffman and Sholom Wacholder of the National Cancer Institute in Bethesda, Maryland.

The test could eventually replace the Pap smear as the primary method for cancer screening, and women uninfected by the virus could wait much longer between tests, they said.

Netherlands-based Qiagen believes its HPV product could be worth $1.1 billion annually.

The company said it plans to donate a million units of the $30 test over the next five years to encourage its use in developing countries, and it is working on a version of the test for regions with few resources that does not require electricity or running water.

The researchers, funded by the Bill and Melinda Gates Foundation, studied 131,746 women in rural India for eight years.

Only 34 of the women who received HPV testing died of cervical cancer. In contrast, 54 of the women who got Pap smears died, 56 visually examined using acetic acid died and 64 women who got no screening died of cervical cancer.

In addition, the women who received the HPV test were found to have far fewer cases of advanced cervical cancer.

A Pap smear is a scraping of the cervix which is then examined for irregular cells that may be on the way to becoming a tumor. The acetic acid test is used to directly look at the cervix for potentially cancerous cells, while the HPV test looks for the virus in cells taken from the cervix.

Medical diagnostics company Hologic Inc also has a screening test for HPV.

CATCHING MORE TUMORS

"The significant reduction in advanced cancers and cervical cancer deaths following a single HPV test is due to the possibility that HPV screening detected more precancerous lesions with a high potential of becoming cancer than those detected by visual screening or Pap smear," Dr. Rengaswamy Sankaranarayanan of the International Agency for Research on Cancer said in a statement.

Cervical cancer strikes about 493,000 women worldwide each year and kills 273,000. Eighty percent of the cases are in underdeveloped countries, where access to Pap smears may be limited or followup treatment may be inadequate.

HPV causes warts as well as mouth, penile, and anal cancer. It is the most common sexually transmitted disease in the world, infecting about 20 million Americans alone, according to the U.S. Centers for Disease Control and Prevention.

Schiffman and Wacholder said the new findings mean that "a single HPV test that is performed 15 to 20 years after the median age of first sexual intercourse will detect many easily treatable, persistent infections and precancers while limiting overtreatment." All of the women in the study were over 30.

The Indian findings come at a time when vaccines against two strains of the virus hold the potential for dramatically lowering the cancer rate in developed countries.

Both Merck and GlaxoSmithKline make vaccines against some of the strains of HPV most strongly linked with cervical cancer.

"Even when HPV vaccines are affordable and widely used, they will not substantially decrease rates of cervical cancer for decades because of the long latency between infection and cancer," said Schiffman and Wacholder.

The Indian findings show HPV testing "can lower the death rate from cervical cancer within 5 to 10 years," they said.