- Pap test: the Papanicolaou (Pap) test is widely used to screen for precancerous or cancerous changes in cervical cells. 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 termed "atypical cells." Atypical cells are not entirely specific for a precancerous condition, however, and can temporarily appear in response to infections or irritation of the cervix lining. Precancerous cells can become more abnormal in appearance over time and are more likely to progress to cancer if left untreated. In Pap tests, these more abnormal (intermediate) cellular changes are called low-grade or high-grade squamous intraepithelial lesions [see the sidebar on Pap test terminology].
- HPV DNA test: There are multiple DNA tests that can detect human papillomavirus (HPV) infections before cell abnormalities are evident, according to the National Cancer Institute. These tests work by screening for the DNA of different types of high-risk HPV in cervical cells. Some HPV DNA tests detect high-risk HPV without identifying the specific type of HPV. Others detect specific HPV types known to cause most HPV-related cancers.
Current guidelines from various organizations, including the American College of Obstetricians and Gynecologists (ACOG), the U.S. Preventive Services Task Force (USPSTF) and the American Cancer Society (ACS), on cervical cancer screening recommend the following:
- Screening with a Pap test for women ages 21 to 29 every 3 years
- Screening with a Pap test and HPV DNA test for women ages 30 to 65 every 5 years (preferable), or every 3 years with Pap test alone (also acceptable)
Significant changes to these recommendations may be on the horizon, however. The Food and Drug Administration (FDA) approved an HPV DNA test as a primary screening tool for cervical cancer, meaning it may be used without a Pap test. Individual health organizations have yet to update their screening recommendations, but an expert panel issued interim (temporary) guidelines in 2015. (Read "Experts Offer Advice on hrHPV Testing as a Primary Screen for Cervical Cancer.") These guidelines say that:
- The HPV test may be offered to women aged 25 and older without a Pap test.
- If initial results are negative, women should be screened again no sooner than 3 years.
Women interested in this new option should talk to their healthcare provider. The interim guidelines acknowledge that more studies are needed to further evaluate the HPV test and its role in cancer screening. For example, there are still questions about whether age 25 is the best age to start offering it as a primary screening option and how often women should be screened.
ACOG, USPSTF and ACS guidelines recommend more frequent screening for women with risk factors such as exposure to DES (diethylstilbestrol) in utero, previous diagnosis of a high-grade precancerous cervical lesion or cervical cancer, HIV infection, or a compromised immune system.
Cervical cancer screening for women younger than 21, regardless of sexual activity, is not recommended because the incidence of cancer in this age group is very low. False-positive results may occur due to normal cell changes and are somewhat common. The false-positive results may generate unnecessary and costly treatment as well as emotional anxiety.
These guidelines recommend against screening for cervical cancer for women over the age of 65 who have had negative results on adequate prior screening and do not have a history of cervical cell abnormalities known as CIN2+ or dysplasia within the last 20 years. Guidelines define adequate prior screening as 3 consecutive negative Pap tests or 2 consecutive negative HPV and Pap co-test results in the prior 10 years, with the most recent within 5 years.
If a woman has positive screening results, the health practitioner may use one or both of the following tests:
- Colposcopy: this follow-up test involves putting a vinegar-like solution on the cervix and checking it for abnormalities using a bright light and magnifying instrument. The colposcopy may include a Schiller test, which involves placing iodine on the cervix, causing normal cells to turn brown and abnormal cells to show up as white or yellow.
- Biopsy: if abnormal areas are found on the cervix during colposcopy, the health practitioner will remove small pieces of tissue for examination by a pathologist. A biopsy and microscopic evaluation are the only way to tell for sure whether abnormal cells are cancerous, precancerous, or reactive for some other reason.