A test that looks for the virus found in 99 percent of cervical tumors is far more effective than a Pap smear for detecting the early stages of cervical cancer, Canadian researchers said on Wednesday.


The test for the human papillomavirus, or HPV, found 95 percent of cases in which women had potentially pre-cancerous changes in the cervix. This compared to 55 percent of Pap smears, the team at McGill University in Montreal found.

"We're proposing to go straight to the HPV test," said team leader Eduardo Franco.

They studied 10,154 women in Montreal and St. John's, Canada, using both the Pap smear -- in which doctors use a little paddle to scrape some cells off the cervix -- and the Qiagen virus test.

Pap tests are examined by pathologists for signs of abnormal cells that could be on their way to becoming tumors. The HPV test looks for two strains of the virus that cause most cases of cervical cancer, which is diagnosed in about 11,000 U.S. women each year, killing nearly 4,000.

Writing in the New England Journal of Medicine, Franco's team said while the HPV test found more cases of active infection and of precancerous lesions, it gave a false positive report in 6 percent of the women.

This is because an HPV infection can disappear without causing cancer, or it may take time for it to produce abnormalities in a cell.

In contrast, the false positive rate is just over 3 percent for a Pap smear.

Franco said that one advantage using the HPV test would be that technicians would probably be more vigilant about reading Pap smears from women already found to be HPV-positive.

A second study, also published in the New England Journal of Medicine, found that combining both types of tests increased the detection rate by 51 percent.

The Swedish study, led by Pontus Naucler of Lund University in Malmo used an HPV test in 12,527 Swedish women in their 30s.


Using two tests to look for cancer "raises the initial cost, which may limit the applicability of widespread screening in resource-poor countries," Carolyn Runowicz of the University of Connecticut Health Center wrote in a commentary.

Franco said an HPV test costs about $90 compared to $10 to $20 for a pap test.

Mass production could bring down HPV test costs. If it did, giving that test first and using the Pap smear as a follow-up test "would be a much more cost-effective way of doing screening, and for most women you would only be doing one test instead of doing both," Franco said in a telephone interview.

Women can now be vaccinated against HPV with the Gardasil vaccine from Merck & Co. GlaxoSmithKline has developed its own vaccine, called Cervarix, which has been approved in Europe and Australia.

"Vaccination will not, however, eliminate screening," Franco and his colleagues said.

Gardasil only covers two types of HPV -- numbered 16 and 18 -- responsible for three quarters of tumors. Screening will still be necessary to look for the growths caused by other types of HPV.

And none of the vaccines help women who have already been infected with HPV, which is passed during sexual intercourse.