Papanicolaou (Pap) smears are used to screen for cervical cancer before a person has symptoms. To perform a Pap smear, doctors use a swab during an internal examination of the vagina to take a sample of cells from the cervix to examine under a microscope. In conventional Pap smears, samples are smeared directly onto a microscope slide. In liquid-based cytology Pap smears, the sample is put in a bottle of preservative and is then smeared onto the slide. If abnormal cells are found, the patient is sent for colposcopy, which allows doctors to look at the cervix with magnification and take larger samples of abnormal areas.