A Pap smear is an examination under the microscope of cells scraped from the tip of the cervix. The cervix is the lower part of the uterus (womb) that opens at the top of the vagina.
How the test is performed
The Pap smear is done as part of a gynecological exam. You will lie on a table and place your feet in stirrups to position your pelvis for examination. The health care provider will insert an instrument (speculum) into your vagina and open it slightly to see inside the vaginal canal.
The health care provider will take a sample of cells from the outside and just inside the opening of the cervix (cervical canal) by gently scraping the outside of the cervix with a wooden or plastic spatula, then inserting a small brush that looks like a pipe cleaner into the canal.
The cells are placed on a glass slide, or put in a bottle containing a preservative, and then sent to the lab for examination.
How to prepare for the test
Tell your health care provider if you:
- Are taking any medications or birth control pills
- Have had an abnormal Pap smear
- Might be pregnant
Within 24 hours of the test, avoid:
- Having intercourse
- Taking a tub bath
- Using tampons
Avoid scheduling your Pap smear while you have your period (are menstruating), because blood and cells from the uterus may affect the accuracy of the Pap smear. Empty your bladder just before the test.
How the test will feel
You may have some discomfort, similar to menstrual cramps, and a feeling of pressure during the procedure. You may bleed a little bit after the test.
Why the test is performed
The Pap smear can detect cancerous or precancerous conditions of the cervix. Most invasive cancers of the cervix can be detected early if women have Pap tests and pelvic examinations.
Screening should start within 3 years after first having vaginal intercourse or by age 21. After the first test:
- Woman should have a Pap smear ever 2 years to check for cervical cancer.
- If you are over age 30 or your Pap smears have been negative for 3 times in a row, your doctor may tell you that you only need a Pap smear every 3 years.
- If you or your sexual partner have other new partners, then you should have a Pap smear every 2 years.
- After age 65-70, most women can stop having Pap smears as long as they have had three negative tests within the past 10 years.
- If you have a new sexual partner after age 65, you should begin having Pap smear screening again.
Women who have had a total hysterectomy (uterus and cervix removed) and have not had any previous history of cervical dysplasia (abnormal cells), cervical cancer, or any other kind of pelvic cancer, may not need to have Pap smears.
A normal value is negative, meaning there are no abnormal cells present.
Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
What abnormal results mean
The current system divides the abnormal results into these main areas:
- ASCUS or AGUS (atypical cells of uncertain significance): These changes may be due to infection with HPV but may also mean there are precancerous changes present.
- LSIL (low-grade dysplasia) or HSIL (high-grade dysplasia): This means precancer changes are likely to be present; the risk of cancer is greater if the result is HSIL.
- Carcinoma in situ (CIS): This usually means the abnormal changes are likely to progress to cancer.
- Atypical squamous cells (ASC–H): This means abnormal changes have been found and may be HSIL.
- Atypical glandular cells (AGC): Cell changes are seen that suggest precancer of the upper part of the cervical canal or inside the uterus.
When a Pap smear shows abnormalities, further testing or follow-up is needed. The next step depends on the results of the Pap smear, your previous history of Pap smears, and risk factors you may have for cervical cancer.
This may include:
- Colposcopy-directed biopsy
- An HPV test to check for the presence of the HPV virus types most likely to cause cancer
For minor cell changes, doctors usually recommend having a repeat Pap smear in 3-6 months.
What the risks are
There are no risks involved.
The Pap smear test is not 100% accurate. Cervical cancer may be missed in a small number of cases. Fortunately, cervical cancer develops very slowly in most women and follow-up Pap smears should identify worrisome changes in time for treatment.
The following drugs may affect Pap smears:
- Compounds in cigarettes
- Silver nitrate
ACOG Practice Bulletin No. 99: management of abnormal cervical cytology and histology. Obstet Gynecol. 2008;112(6):1419-1444.
ACOG Committee on Gynecological Practice. ACOG Practice Bulletin No. 109: Cervical Cytology Screening. Obstet Gynecol. 2009 Dec;114(6):1409-1420.
Noller KL. Intraepithelial neoplasia of the lower genital tract (cervix, vulva): etiology, screening, diagnostic techniques, management. In: Katz VL, Lentz GM, Lobo RA, Gershenson DM. Comprehensive Gynecology. 5th ed. Philadelphia, Pa: Mosby Elsevier; 2007:chap. 28.
Reviewed By: David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc., and Susan Storck, MD, FACOG, Chief, Eastside Department of Obstetrics and Gynecology, Group Health Cooperative of Puget Sound, Redmond, Washington; Clinical Teaching Faculty, Department of Obstetrics and Gynecology, University of Washington School of Medicine.