The Papanicolaou (Pap) test involves scraping cells from the cervix (the lower narrow portion of the uterus that connects to the vagina) and examining them under a microscope for signs of cervical cancer or abnormal cells that could lead to cancer.
Pap tests, also referred to as cervical smears or cervical/vaginal cytology, can detect abnormal cervical cells before they develop into cancer cells. Pap tests also detect cervical cancer in its early stages when it is easier to treat, as well as noncancerous conditions such as infection and inflammation. Most cases of invasive cervical cancer can be prevented by regular Pap tests. Since 1950 new cases of and deaths from cervical cancer have declined sharply due to widespread screening with the Pap test. Deaths from cervical cancer are as of 2008 rare in women of any age who have regular Pap tests. Of American women diagnosed with cervical cancer, 60% had not had a Pap test in the previous five years.
Almost all cervical cancers are caused by persistent infection with the human papillomavirus (HPV), which is spread through sexual contact. However, temporary HPV infections and insignificant cervical cell changes are very common, and it takes years for significant abnormalities or cancer to develop. Therefore, Pap tests should be performed at least once every three years, starting about three years after a woman begins having sexual intercourse but no later than age 21.
If Pap tests between the ages of 55 and 65 are normal, women are often advised that no further screening is necessary. Women who have a negative Pap test at age 60 or older are very unlikely to have a subsequent abnormal Pap. Women aged 65 and over who have never had a Pap test are advised to have two tests one year apart: if both tests are normal, no further testing is necessary.
Pap tests are not useful in women who have had a total hysterectomy in which the uterus and cervix were removed unless the surgery was for cervical pre-cancer or cancer. These women should be tested annually for vaginal cancer until they have had three normal test results.
Pap tests miss up to 20% of cervical cell abnormalities. Such false-negative results may delay treatment even in the presence of symptoms of cervical cancer. However, since changes in cervical cells occur very slowly, abnormalities should be detected in a subsequent Pap test within the next three years.
False-positive results occur when cells appear abnormal although no cancer is present. Some abnormal cervical cells never become cancerous. False-positive results can cause anxiety and lead to more tests and procedures which have their own risks.
Pap tests are performed in doctors' offices, clinics, local health departments, and hospitals, usually in the course of a pelvic examination. The woman lies on an exam table with a sheet over her legs and stomach, her feet in holders called stirrups, and her knees open. A female staffer is always present. A plastic or metal instrument called a speculum is used to widen the vagina so that the upper part of the vagina and cervix are visible. Cells are scraped from the surface of the cervix and vagina using a piece of cotton, a small cervical brush, or a small wooden scraper or stick.
The cells are placed on a microscope slide, treated with fixative, and sent to a laboratory. The cells are examined under a microscope to look for abnormalities. With a new liquid-based, thin-layer slide preparation, the brush or other collection device is rinsed in a vial of liquid preservative and the vial is sent to the lab where an automated device prepares the slide. This eliminates background material and provides a thin layer of cells for analysis. Studies suggest that this procedure is more sensitive than the traditional Pap smear. Computer-automated readers can send the image to a computer for analysis. Sometimes an HPV DNA test to detect strains of HPV associated with cervical cancer is performed at the same time as the Pap test.
Pap tests should not be performed during menstruation. The best time for a Pap test is 10 to 20 days after the first day of the last menstrual period. Women should avoid douching or using vaginal medicines or deodorants, spermicidal foams, creams, or jellies, or tampons for about two days before a Pap test since these products can disguise or wash away abnormal cells. Women should avoid sexual intercourse for 48 hours before a Pap test to avoid inconclusive results that may require retesting.
Following a Pap test a woman may immediately resume her normal activities.
Some Pap tests are unreadable and need to be repeated due to the following:
too few cells in the specimen
obscuring by blood or mucus.
Pap test results come back from the laboratory in one to two weeks. Most U.S. laboratories use the Bethesda System for reporting Pap test results:
“Negative for intraepithelial lesion or malignancy” is a normal result meaning that no abnormal cells were found on the surface of the cervix.
Atypical squamous cells of undetermined significance (ASC-US) indicates that the squamous cells—the flat thin cells that line the surface of the cervix—do not appear completely normal, perhaps due to HPV infection, but the significance of the abnormality is unknown.
Atypical squamous cells-H (ASC-H) indicates that the cells are atypical, and although the significance is unclear, a precancerous high-grade squamous intraepithelial lesion (SIL) cannot be excluded.
Atypical glandular cells (AGC) indicates that the mucus-producing cells in the endocervical canal (the opening at the center of the cervix) or in the lining of the uterus do not appear normal, but the significance of the change is unclear.
Endocervical adenocarcinoma-in-situ (AIS) means that precancerous cells are found in the glandular or mucus-producing tissue.
Low-grade squamous intraepithelial lesion (LSIL) indicates early changes in the size and shape of the squamous cells caused by HPV infection.
High-grade squamous intraepithelial lesion (HSIL)indicates markedly abnormal or precancerous cells with a higher probability of progressing to invasive cervical cancer.
Cancer cells are present.
Healthcare providers may use slightly different terms to describe abnormal Pap test results:
Dysplasia indicates the presence of abnormal cells which could develop into very early cervical cancer. It is categorized as mild, moderate, severe, or carcinoma-in-situ (CIS) (cancer cells confined to the surface of the cervix) depending on the degree of abnormality; mild dysplasia is a LSIL and moderate to severe dysplasia or CIS is an HSIL.
Cervical intraepithelial neoplasia (CIN) indicates abnormal growth of cells on the surface of the cervix. It is categorized as CIN-1 to 3 depending on the severity; CIN-1 is equivalent to a LSIL or mild dysplasia; CIN-2 and -3 are HSIL, moderate to severe dysplasia, or CIS.
Cervical cancer indicates that cancer cells have spread deeper into the cervix.
Invasive cervical cancer means that cancer cells have spread to other tissues or organs.
Cervical cells can undergo changes for many reasons other than cancer, including the following:
bacterial, viral, or yeast infection
growths such as benign polyps or cysts
hormone changes due to pregnancy or menopause.
Of about 55 million Pap tests performed annually in the United States, about 3.5 million or 6% are abnormal and require medical follow-up. The Pap test may be repeated, particularly if the results are ambiguous or indicate only a minor abnormality, since abnormal cervical cells often disappear without treatment. Cell changes are often caused by low hormone levels. An ACS-US result in a woman who is near or past menopause can often be cleared up with the application of an estrogen cream to the cervical surface for a few weeks. Following two normal Pap results women can return to routine Pap tests every three years.
ASC-US, ASC-H, LSIL, or HSIL Pap results are often followed by colposcopy, in which the cervix is coated with a dilute vinegar solution that turns abnormal cells white and a lighted magnifying instrument called a colposcope is used to examine the vagina and cervix.
An HPV DNA test may be performed to determine whether the abnormal cells are the result of infection with an HPV that is linked to cervical cancer. A large clinical trial has indicated that testing a cervical sample for HPV is more efficient than colposcopy or a repeat Pap test for identifying ASC-US abnormalities that require treatment. It was expected as of 2008 that HPV tests may replace Pap tests for routine cervical cancer screening.
If colposcopy reveals abnormal cells, the cervix may be examined with a LUMA Cervical Imaging System, which shines a light on the cervix. Normal and abnormal cells respond differently to the light and the system produces a colored map that distinguishes between them.
If these procedures indicate the presence of cells that may be precancerous, various additional tests and procedures may be utilized to diagnose and treat the condition.
Pap tests are performed by the following:
women's healthcare specialists
Apathologist supervises the examination of the Pap smear for abnormalities.
See also Cancer; Cancer therapy, supportive; Cervical cancer; Chemotherapy; Oncology.
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