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What is a Pap Smear?

By Liji Thomas, MD

A Pap smear, (also called Papanicolau test, Pap test, cervical smear, or smear test) is a screening test used in gynecology that checks for cancerous or precancerous conditions of the cervix. The cervix is the lowermost part of the uterus, which protrudes slightly into the vagina and is attached to it all around by the cervical ligaments. From below, it looks somewhat like a small pink washbowl with a minute hole in the center.

The benefits of the Pap test are its ability to screen for cancer of the cervix. This is one of the most common female cancers, but can be caught early, by a Pap test, while still curable. The Pap test has been credited with a more than 50% reduction in new cases of cervical cancer, as well as mortality from this disease, in the US.

Pap test screening

Screening for cancer of the cervix usually starts at the age of 21, and is continued every 3-5 years. If an HPV (human papilloma virus) test is also done, the optimum screening frequency can be better decided on. Some high-risk variants of this virus boost the risk of developing this cancer.

After the age of 65 years, and if the last 3 Pap tests within the preceding 10 years have been normal, screening may be discontinued if desired. Following a total hysterectomy, when both uterus and cervix are removed surgically, continuing Pap tests may not be necessary provided the patient had normal tests before the surgery, and has no history of pelvic or cervical cancer.

The Pap test procedure

The test is done by microscopic examination of the cells obtained by a gentle scraping of the cervix with a special curved wooden or plastic scraping tool, or a tiny brush. In order to visualize the cervix, the patient needs to lie on her back, with the legs spread apart a little, so that a speculum can be used to stretch the vagina very gently.

This brings the cervix into view at the top of the vagina, in most cases, and the spatula is used to scrape it lightly. The cells in the scraped sample are then fixed in a preservative solution after being spread on a slide, or deposited in a special cytology liquid, and sent for examination. The procedure is quite painless and brief.

A few precautions must be taken before the test is done. Douching, sexual intercourse, and the use of vaginal tampons, foams, and creams, are all to be avoided for the 24 hours before a Pap test, since they may disturb the cervical epithelium.

Recent testing technology includes liquid-based cervical cytology. This makes testing easier, because both HPV and suspicious cervical cell changes can be tested for with the same specimen.

Pap test results

A negative Pap test means no cells with signs of cancerous changes were found on examination. The test is not foolproof, but repeating the test at regular intervals means that almost all cancers of the cervix will be picked up, because they are mostly slow-growing tumors.

The results of the test are categorized as:

  • Negative
  • Atypical cells which are classified as significant or of unknown significance.
  • Dysplastic cells of low or high grade.
  • Carcinoma-in-situ, which is a precancerous condition.
  • Carcinoma of the cervix.

The next step will therefore be either follow-up testing, or a repeat Pap test after 6 months to a year. The selection of follow up depends on the presence of any abnormality, the detection of high-risk HPV, and the presence of any high-risk factors for cancer cervix.

References

Further Reading

Last Updated: Dec 1, 2015

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