The test checks for the human papilloma virus (HPV), also known as human wart virus. The virus, which causes genital warts, is the main cause of cervical cancer in women.

Researchers at a conference on the subject in Montreal said 26% of Americans are infected with the virus. About 1% of them have genital warts, 5% have pre-cancerous lesions and 20% have latent infections which have no symptoms at all.

More sensitive

Attila Lorinez and colleagues at Georgetown University in Washington said a new HPV test, called Hybrid Capture, was more sensitive than the Pap smear in catching cervical cancer and the pre-cancerous changes that can develop into cancer.

His team reviewed tests of more than 10,000 women in Costa Rica whose average age was 37. They had the Pap test that most adult women now have every year or so, plus the new HPV test.

The Pap test detected 92% of the cancers and 78% of pre-cancerous cases, Lorinez told the International Conference of Human Papillomavirus Infections and Cervical Cancer.

But the Hybrid Capture test, made by US company Digene Corp, detected all the cancers and 90% of pre-cancerous lesions, known as dysplasias.

Better for older women

"The HPV test was 10 to 15% more sensitive than Pap smears," Lorinez said in a statement. The older the woman, the better it worked, he said.