The main reason why a pap test or pap smear is done is to screen for cancerous and precancerous cells of the cervix.
There is actually a recommendation to do the test from the onset of sexual intercourse to age 65. Pap test should be done every 1 to 3 years for women without risk factors for cervical cancer. For women who have had hysterectomy because of precancerous or cancerous changes in the cervix, a continuous regular pap smear must be observed. But for women who have had hysterectomy with the cervix removed for non-cancerous or benign reasons do not need to continue Pap test. While women who have had weakened immune system may need to test more often than once a year.