The Test Sample
What is being tested?
A Pap test is a screening test for cervical cancer. It is used to detect abnormal or potentially abnormal cells from the vagina and uterine cervix. Various bacterial, fungal, and viral infections of the uterus may also be detected using this test.
Cervical cancer is caused by the uncontrolled growth of cells in the cervix, the narrowed bottom portion of a woman's uterus. Cervical cancer begins slowly. The earliest, precancerous changes cause the cells lining the inside or outside of the cervix to appear different from normal cervical cells. These changes, when present on a Pap test, are called "atypical cells." However, atypical cells are not entirely specific for a precancerous condition and can temporarily appear in response to infections or irritation of the cervix lining. If precancerous, the atypical cells can become more abnormal in appearance over time and are more likely to progress to cancer if left untreated.
Pap tests, when performed routinely, have been a great help in the detection and treatment of areas of precancerous cells, which help to prevent cervical cancer from developing. In addition, the test can help detect cervical cancer in the early stages, when it is most treatable. The Pap test is also used to monitor any abnormalities or unusual findings. In many cases, these findings are part of the body's repair process and often resolve themselves without any further treatment.
Almost all cases of cervical cancer are caused by persistent infections with certain types of human papilloma virus (HPV). HPV types 16 and 18 account for about 70% of cervical cancers in the U.S. HPV DNA tests detect the high-risk HPV types and are currently recommended along with a Pap test every 5 years for women age 30-65. HPV tests are not recommended for younger women because HPV infections are common in this age group and usually resolve without treatment. However, if a young woman has an abnormal Pap test, then HPV testing may be done.
In 2015, a panel of experts representing several major health organizations developed interim guidelines that say that HPV testing without a Pap test may be offered as an option for cervical cancer screening to women age 25 and older. (For more on this, see Common Questions #2 and the news item "Experts Offer Advice on hrHPV Testing as a Primary Screen for Cervical Cancer.")
How is the sample collected for testing?
The Pap test consists of sampling cells from the cervical area. For the more common liquid-based methods, the sample is obtained using a type of "spatula" swab or brush. The specimen is put into a special liquid preservative and sent to a laboratory, where the cell suspension is processed onto a glass slide, stained, and examined by a cytotechnologist and/or pathologist. An advantage of this liquid-based sample is that the cell suspension may also be used for HPV testing. For the older, traditional method, the sample is smeared on a glass slide and sent to a laboratory to be stained and examined under a microscope.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
You may be instructed not to douche or tub bathe for 24 hours before the Pap test is to be performed. You may also be asked to refrain from sexual intercourse for 24 to 48 hours before the test. Do not use any vaginal creams or foams for 48 hours prior to the exam and do not schedule the test during your menstrual period.