(HealthDay News) -- A Pap test (Pap smear) collects a sample of cells from the cervix to look for any abnormalities or changes. It's often used to help diagnose infections or cervical cancer.

The National Women's Health Information Center offers these guidelines for whom should have a Pap test, and how often:

• Women younger than age 30 should get an annual Pap test.
• Women age 30 and older with three consecutive annual Pap tests with normal results should get a new test every two-to-three years, with their doctor's approval.
• Women aged 65 to 70 with no abnormal Pap tests in the last 10 years may no longer need the test, but should confirm this with their doctors.
• An annual Pap test is needed for any woman regardless of age who has a compromised immune system, is HIV-positive, or whose mother was exposed to a chemical called DES (diethylstilbestrol) during pregnancy.