Men who engage in receptive anal sex have been urged by medical researchers to undergo regular anal Pap smears to screen for early cellular changes that could indicate the development of anal cancer due to research showing that men who have a risk of anal cancer more than 30 times higher than those who don't, The New York Times reports.

An anal Pap smear, which involves taking a swab of cell tissue from the rectum, is similar to the Pap tests that women receive to screen for precancerous cells in the cervix.

Researchers from UC San Francisco, Stanford, the Harvard School of Public Health and elsewhere have also reported that gay men with HIV are at even more significant risk.

Anal cancer, which can be fatal if not diagnosed in its early stages, can be caused by the human papillomavirus (HPV). Most sexually active gay men carry the virus, with as many as 90% of HIV-positive gay men also co-infected with HPV.

HPV is a widespread, though often asymptomatic, sexually transmitted disease. More than 20 million Americans are believed to be infected with it.

"This is something we really need to be paying attention to," said Joel Palefsky, a professor of medicine at the University of California, San Francisco.

"We've decided as a society that it's important to spend billions of dollars to test for and treat cervical dysplasia before it turns into cancer. And we should also be testing for and treating anal dysplasia in high-risk populations."

Palefsky recommends anal Pap smears every two to three years for HIV-negative gay and bisexual men and annually for those who are infected with HIV.