Pap Smear (Pap Test)
- For average-risk women ages 21 to 29, every 3 years
- For average-risk women ages 30 to 65, co-testing with an HPV test every 5 years (preferred) or Pap smear (Pap test) alone every 3 years (acceptable)
- For women with risk factors: you may begin screening at a younger age and more frequently
- When you have signs and symptoms, such as abnormal vaginal bleeding and/or pelvic pain
A sample of cells is taken from the cervical area during a pelvic exam using a swab or small brush. For the more common liquid-based methods, the sample is put into a special liquid preservative and sent to a laboratory, where the cells are 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.
It is typically recommended that you refrain from having vaginal sex, douching, or using vaginal products such as creams, deodorants, or medications for 24 hours before the test. Follow any instructions you are given. Reschedule the test if you are having your period (menstruating). You may be asked to empty your bladder before the examination. The American Cancer Society has recommendations on how to prepare for the test.
A Pap smear (Pap test) is primarily a screening test for cervical cancer. It is used to detect abnormal or potentially abnormal cells from the vagina and the cervix, the narrow bottom portion of a woman's uterus.
Cervical cancer is caused by the uncontrolled growth of cells in the cervix. Almost all cervical cancers are caused by persistent infections with high-risk types of human papillomavirus, also called HPV (16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66 and 68). Two HPV types,16 and 18, cause 80% of all cervical cancers.
HPV is a very common infection and may be spread by sexual contact (sexually transmitted disease). Many HPV infections resolve without treatment—the body is able to clear the infection—but infections with high-risk HPV types that do not go away can lead to cervical cancer. It can take many years for an HPV infection to develop into cancer.
An HPV infection can cause changes in the cells lining the inside or outside of the cervix. However, these changes can also occur temporarily in response to infections or irritation of the cervix lining and may not be related to cancer. On a Pap smear, the cells with these non-specific changes are reported as "atypical." Further testing may be necessary to determine the significance of the atypical cells. If they are precancerous, they can become more abnormal over time and may progress to cancer if left untreated.
Pap smears, when performed routinely, improve the detection and treatment of precancerous cells, which helps to prevent cervical cancer from developing. In addition, the test can help detect cervical cancer in the early stages, when it is most treatable.
A Pap smear may be used either alone or along with an HPV molecular test for cervical cancer screening every 5 years for women 30 to 65 years of age. HPV tests are not recommended before age 30 because HPV infections are common in younger, sexually active women and usually resolve without treatment. However, if a woman between the ages of 21 through 29 has an abnormal Pap smear, then HPV testing may be done.
How is the test used?
A Pap smear is primarily used to screen for cervical cancer. It is used to look for cervical and/or vaginal cells that are cancerous or that may be precancerous. It may be used along with a test for high-risk types of HPV that can cause cervical cancer.
The Pap smear can also be used to help determine the underlying cause of abnormal vaginal bleeding, pain, sores, discharge, or itching.
Abnormal cells and infections can be present without causing any noticeable symptoms. In some cases, further testing and/or treatment may be required. The Pap smear may be used in follow-up to monitor any abnormalities or unusual findings on an initial Pap smear.
When is it ordered?
Several health organizations have recommendations on when to get screened for cervical cancer.
The following is a summary for women ages 30 to 65 with average risk:
Screening Strategy Timing Pros Cons Co-testing with a Pap smear (Pap test) and HPV test (preferred) Every 5 years Will likely detect more precancers and cancers; done less frequently than Pap smears alone More false positives than Pap smear alone, leading to unnecessary anxiety and follow up Pap smears alone (acceptable) Every 3 years Fewer false positives Not as sensitive as co-testing (may miss some precancers and cancers); Done more often HPV tests alone (alternative) Every 5 years Done less frequently than Pap smears alone Finds HPV infections that may not cause problems; misses uncommon cancers that are not caused by HPV
You should have a discussion with your healthcare provider about the pros and cons of these screening strategies, so you can decide which approach is best for you.
Recommendations for average-risk women in other age groups:
- Ages 21 to 29— have a Pap smear every 3 years. HPV molecular testing also may be performed when a woman in this age group has abnormal changes on a Pap smear.
- Younger than 21—do not have screening, regardless of sexual activity, because cervical cancer is not common in your age group.
- Over age 65— do not have screening if you have no history of abnormal cervical changes and either of the following is true:
- You have had three consecutive negative Pap smears or
- You have had two consecutive negative co-tests (Pap smears plus HPV tests) in a row within the past 10 years, with the most recent co-test performed within the past five years.
You should still undergo regular cervical cancer screening even if you have been vaccinated against HPV.
Screening at a younger age and more frequent screening is advised if you have risk factors such as:
- A previous diagnosis of a high-grade precancerous cervical lesion or cervical cancer
- HIV infection
- A weakened immune system
- Exposure to DES (diethylstilbestrol) before birth
A healthcare practitioner may also order a Pap smear when a woman is pregnant or has signs and symptoms, such as abnormal vaginal bleeding. Other screening tests may be done at the same time as a Pap smear. For details, see the screening recommendations for Young Adults, Adults, and Adults 50 and Up.
If you have had a total hysterectomy (surgical removal of the uterus and cervix) and you have no history of cervical cancer or cervical changes, guidelines suggest that you may discontinue cervical cancer screenings. However, if you have a history of cervical cancer or moderate to severe cervical changes, then it is recommended that you continue to be tested for cancer for 20 years after your surgery. If you had a partial hysterectomy (removal of the uterus but not the cervix), then you should continue to have regular cervical cancer screenings as recommended above.
What does the test result mean?
A "negative" Pap smear means the cells appear normal or there is no identifiable infection.
In some instances, a Pap smear may be reported as "unsatisfactory" for evaluation. This may mean that there were not enough cells present to be examined or that cells could not be clearly identified. In this case, a repeat Pap may be recommended in about 2 to 3 months, but it does not necessarily mean that there is a significant problem.
Other reported Pap smear results, such as infections or atypical cells, are explained in detail in the next section: Understanding Your Pap Smear (Pap Test) Report.
If a Pap smear is performed without an HPV test, the presence of abnormal cervical cells may indicate the need to perform an HPV test to determine whether HPV infection is the cause of the cellular changes.
Pap and HPV test results go hand-in-hand when determining a woman's risk for cervical cancer. Results from a Pap smear and HPV test (typically reported as negative or positive) can help determine whether cervical cells are infected with a high-risk type of HPV and identify abnormal changes in cervical cells.
The following chart summarizes the meaning of some common co-testing results and includes the American Cancer Society (ACS), American Society for Colposcopy and Cervical Pathology (ASCCP), and American Society for Clinical Pathology (ASCP) recommendations for follow up. Remember, co-testing is currently recommended for women aged 30 to 65 years.
Co-testing Results What Results Might Mean Recommended Follow Up HPV test negative, Pap smear normal Cervical cancer risk is low at the present time. Repeat co-testing in 5 years (or Pap test alone in 3 years) HPV test positive, Pap smear normal Cervical cells are infected with a high-risk type of HPV, but no abnormalities found in cervical cells. Option 1: Repeat co-testing in 12 months
Option 2: Test for HPV-16 and HPV-18
- Positive: colposcopy recommended to examine the cervix for abnormal areas, to take samples for biopsy, and/or treat as indicated
- Negative: repeat co-testing in 12 months
HPV test negative, Pap smear result unclear (ASCUS) No HPV infection; changes in cervical cells may be the result of infection, inflammation, or hormonal changes and are likely to clear up without treatment. Repeat co-testing in 3 years HPV test positive, Pap smear result unclear (ASCUS) Cervical cells are infected with a high-risk type of HPV. The infection is the likely cause of abnormalities in your cervical cells. Colposcopy recommended HPV test negative, Pap smear abnormal [low- or high-grade lesion (LSIL, HSIL)] No HPV infection; cause of abnormal cervical cells unknown Option 1: Repeat co-testing in 12 months
Option 2: Colposcopy recommended
HPV test positive, Pap smear abnormal [low- or high-grade lesion (LSIL, HSIL)] Cervical cells are infected with a high-risk type of HPV, which is the likely cause of abnormal cell growth. Colposcopy recommended
For more information about high-risk HPV and Pap co-testing, see the Human Papillomavirus (HPV) Test article.
Understanding Your Pap Smear (Pap Test) Report
In 2014, a task force updated the classification system for reporting Pap smear (Pap test) results, called the Bethesda System. The Bethesda System terminology was originally developed in 1988. The 2014 review of the system incorporated minimal changes to the earlier version but refined some positions and content.
Bethesda System Terminology:
Important Sections of the Report and the New Terminology
Specimen Adequacy: Each laboratory must report if the cervical sample obtained for the test was adequate (that is, if enough cells were present on the slide to be examined) and if the quality of the slide was satisfactory for examining under the microscope. Before looking at the results, one should always check to see if the specimen was marked "Satisfactory." If "unsatisfactory," the reasons will be given and the test will have to be repeated in 2 or 3 months.
Interpretation/Results: This is where the important findings from looking at the cells are reported. There are four different sections:
- Negative for intraepithelial lesion or malignancy
- Other: Endometrial cells present in a woman age 40 or more
- Epithelial Cell Abnormalities
- Other Malignancies
Negative for intraepithelial lesion or malignancy:
This is where a "normal" result is reported, as well as abnormal findings not related to the risk of cancer. There are two important subcategories:
- ORGANISMS: This is where evidence of an infection is reported. Examples include a fungal (yeast) infection (e.g., Candida), Trichomonas, and herpes.
- OTHER NON-NEOPLASTIC FINDINGS: This is where evidence of injury and response to injury, previously termed "Benign Cellular Changes," is reported. (Non-neoplastic means the findings are not related to abnormal growth of cells.)
Other: Endometrial cells present in a woman age 40 or more:
This section is used to alert the healthcare provider that endometrial cells (cells from the lining of the uterus) are present when they normally should not be. This is a check on the status of the uterus and endometrium and not the cervix. When a woman is having monthly periods, endometrial cells are often present near the time of a period. After menopause, however, they should not be present. If you are still having periods even though you are over age 40, you and your healthcare practitioner may choose to disregard this part of the report.
Epithelial Cell Abnormality:
This section is where abnormalities that are associated with the risk of developing cancer are reported. The abnormalities range from changes that are only slightly abnormal to definite cancer. There are two types of epithelial cells in the cervix (squamous and glandular) and changes in each are listed.
The lists below are arranged so that the potential for cancer increases as you move down the list, with the last bullets listing invasive cancers.
Squamous Abnormalities (cells that cover most of the external part of the cervix)
- Atypical Squamous Cells: Unknown Significance (ASC-US)
- Atypical Squamous Cells: cannot exclude HSIL or high-grade changes (ASC-H)
- Low-Grade Squamous Intraepithelial Lesion (LSIL)
- High-Grade Squamous Intraepithelial Lesion (HSIL); one subcategory: "with features suspicious for malignancy"
- Squamous Cell Carcinoma
Glandular Abnormalities (cover the lining of the uterus opening and canal)
- Atypical cells, not otherwise specified (AGC)
- Atypical cells, favor neoplastic
- Adenocarcinoma in situ is a cancer limited to the surface that has not invaded.
- Adenocarcinoma can be endometrial (uterus), endocervical (cervix), extrauterine (origin from outside uterus and cervix), or the site of the malignancy cannot be determined based on the Pap smear.
Glandular abnormalities are much less common than squamous abnormalities.
Malignant tumors other than primary squamous carcinoma and glandular adenocarcinoma are occasionally seen on a Pap smear and they are reported here.
Note: There are over 28.5 million Pap smears done in the US each year and approximately 13,000 new cancers are reported. The odds of a positive Pap smear for cancer are quite small.
It is important that if you do not understand your Pap smear results, you ask your healthcare practitioner for clarification. Many of the abnormal findings reported on a Pap smear are either benign, resolve on their own, or are treatable. However, regular cervical cancer screening remains important to ensure that any potentially serious problems are detected promptly.
Does an abnormal Pap test always mean cancer?
In a small percentage of cases it may mean cancer, but in general a single "abnormal" Pap smear does not necessarily indicate that cancer is present. The lining of the cervix undergoes constant changes and repair. You may have additional testing and/or procedures to help determine whether the abnormal Pap smear is significant.
Depending on your age and medical history, you may be monitored more closely (e.g., a repeat Pap smear in a year) to see if the abnormal cells are cleared, or you may have an HPV test if it has not already been done. Depending on those results, additional tests, procedures, and/or treatment may be done.
Do I need a Pap smear if I have an HPV test done?
Current guidelines state that HPV tests alone may be an adequate cervical cancer screening tool for some women. You should have a discussion with your healthcare provider about the pros and cons of HPV testing with or without Pap smears, so you can decide which approach is best for you based on your lifestyle and health history.
Do I need cervical cancer testing even if I've had the HPV vaccine?
You should continue to undergo regular cervical cancer screening even if you have been vaccinated against HPV because the vaccine does not offer protection against all HPV types and not all cervical cancers are a result of HPV infection. Additionally, the vaccine does not provide protection against cervical cancer and other HPV-related diseases if you have already been exposed to one or more HPV types at the time of your vaccination.
For more information about the HPV vaccine, see the Human Papillomavirus (HPV) Test article.
Why do I need regular Pap smears or HPV tests?
Cervical cancer is a slow, progressive disease and may take years to advance beyond the cervix. Because of this fact, regular gynecologic examinations and screening tests are necessary to detect precancerous cells and allow removal of affected tissue. Regular exams can also detect cervical cancer early if it does develop. With early detection, cervical cancer is easier to treat. Left unchecked, however, it is almost always fatal.
What are the risk factors for cervical cancer?
The most important risk factor for cervical cancer is infection with high-risk types of human papilloma virus (HPV). That is why HPV tests are now recommended in conjunction with a Pap smear for women who are 30 to 65 years of age.
According to the National Cancer Institute, additional factors can further raise cervical cancer risk after an HPV infection. These include having given birth to more than 3 children, long-term oral contraceptive use, and cigarette smoking.
Increased risk is also associated with beginning sexual intercourse at an early age, having multiple sexual partners, exposure to a drug called diethylstilbestrol (DES) before birth, a previous diagnosis of cervical cancer or precancerous changes to the cervix, and a weakened immune system, for example after an organ transplant or from HIV infection.
Is there anything else I should know?
The Pap smear is generally used as a screening test. A certain percentage of abnormalities may go undetected with a single Pap smear, which is why it is important to have Pap smears done regularly. A significant limitation of the test has to do with sample collection. The Pap smear represents a very small sample of cells present on the cervix and in the vaginal area. Even for the most experienced healthcare practitioner, the sample collection may not provide enough cells to be examined and a repeat Pap may be required.
Certain drugs (such as digitalis and tetracycline) may affect results.