When cryosurgery has been used to treat precancerous cells in the cervix, a Pap smear should be done every 3 to 4 months after that for one year. During the second year, Pap smears should be done every 6 months. A Pap smear is done to test for cancer of the cervix. If a Pap smear is abnormal, a biopsy of the cervix may be needed to check the cells of the cervix more closely. A biopsy involves taking a small piece of tissue from the cervix with a special needle. The tissue can then be sent to the lab for analysis.