The Saskatchewan Cancer Agency is changing its guidelines and says most women should have a cervical screening test, commonly known as a Pap test, only once every three years.

Previously, the agency had been recommending annual Pap tests.

In addition to calling for less frequent tests, the agency says most women should start getting tested at age 21, rather than at 18, as was recommended previously.

"There's been a lot of research done that shows there's actually very little benefit to having screening tests before age 21 and that having a pap test every two or three years is better than having a pap test every one year," said Jenny Colin, who manages the agency's cervical cancer prevention program.

The new guidelines, and the province's system of sending out reminder letters, are supposed to take effect in January. Because they're just recommendations, a woman can continue to be tested more often if that's what she and her doctor decide.

While the new guidelines call for women to get tested once every three years, the agency says women can start with tests every two years until they get a clean bill of health three consecutive times.

With Pap tests, cells from the cervix are collected and examined for abnormalities.

About 80 per cent of cervical cancers can be prevented with regular Pap tests, the agency says.

About 116,000 tests are done annually in the province.