Your doctor or health provider performs a Pap smear to look for cervical and/or vaginal cells that are cancerous or could be potentially pre-cancerous. The smeared cells or cell suspension is placed on a glass slide, stained with a special dye (Pap stain), and viewed under a microscope by a cytotechnologist or pathologist. The Pap test can also be used to detect vaginal or uterine infections. This allows infections to be treated promptly, thus avoiding further discomfort or more serious complications. When a Pap smear is ordered, an HPV DNA test also may be requested for women over the age of 30.

Different organizations have varying opinions on the appropriate frequency of Pap testing (see Screening: Cervical Cancer (ages 18-29), (ages 30-49), (ages 50 and up). For example, the American Cancer Society recommends that women over the age of 18 and/or those sexually active have an annual Pap smear. In other situations, a Pap smear may be ordered if a woman has frequent sexual partners, is pregnant, or has abnormal vaginal bleeding, pain, sores, discharge, or itching. After three consecutive normal Pap smears, it may be performed less frequently or as your doctor deems appropriate. The American College of Obstetricians and Gynecologists (ACOG) issued guidelines in August 2003 recommending that women 30 years of age or older be offered the option of having an HPV DNA test along with the Pap smear. If both are negative, testing may be performed less frequently.

A "negative" Pap smear means the cells obtained appear normal, or there is no identifiable infection. In some instances, the conventional Pap smear may be reported as "unsatisfactory" for evaluation. This may mean that cell collection was inadequate or that cells could not be clearly identified. A summary of other reported results follows. [See also the sidebar on the 2001 Bethesda System for classification of Pap smear results.]

• Unsatisfactory: inadequate sampling or other interfering substance.
• Benign: non-cancerous cells, but smear shows infection, irritation, or normal cell repair.
• Atypical cells of uncertain significance: Abnormal changes in squamous cells (ASCUS) or glandular cells (AGCUS) for which the cause is undetermined. An ASCUS test result is frequently followed-up with DNA testing to identify the presence of a high-risk infection with Human Papilloma Virus (HPV).
• Low-Grade changes: infection with HPV, which in some instances can be a risk for cervical cancer. This test result may sometimes be followed-up with DNA testing to identify the presence of a high-risk HPV infection.
• High-Grade changes: very atypical cells that may result in cancer.
• Squamous cell carcinoma: cancer is evident and requires immediate attention.

The Pap smear is generally used as a screening test. A small percentage of abnormalities in women may go undetected with a single Pap smear, which is why it is important to take Pap smears regularly. The most common errors are those made in collecting the sample. The Pap smear represents a very small sample of cells present in the vaginal area. Even for the most experienced physician, sample collection can be occasionally inadequate and a repeat Pap may be required.

The Pap smear, when performed routinely, has been a great help in the early detection of cervical cancer, which is treatable if caught at an early stage. The Pap smear is also used to monitor any abnormalities or unusual findings. In many cases, these findings are part of a body's repair process and often resolve themselves without any further treatment. If you douche, tub-bathe, or use vaginal creams 48 - 72 hours prior to the examination, your test results might be "unsatisfactory." Other factors that may alter results include bleeding (menstruation), infection, drugs (such as digitalis and tetracycline), or having sexual relations within 24 hours prior to examination.

In these cases, a repeat Pap smear may be necessary but does not necessarily mean there is a significant problem. In some instances, the use of the liquid-based techniques may eliminate some of the obscuring materials (blood and mucus) that may prevent a clear and uncluttered presentation of cervical cells. A second advantage is that the same sample may be used to perform additional testing for HPV if appropriate.