A Pap test is used to detect abnormal changes in the cells of your cervix that could mean you have cervical cancer or are at increased risk of developing cervical cancer. Cervical cancer begins in the cells that form the lining of the cervix. It can be prevented if precancerous cells are caught by the Pap smear. A Pap test is a screening test, not a diagnostic one which means that if abnormal cells are found, additional exams, such as a colposcopy, may be recommended to further evaluate the cervix. In addition to cancer and precancerous cells, a Pap test can detect changes in cervical cells that may be caused by infection, irritation and hormonal changes. Your health care professional will discuss with you how often you need a Pap smear.