Pap Test

September 20, 2011

The Pap test, also called “Pap smear,” was developed over fifty years ago. This test, in which cells are removed from the cervix and evaluated through a microscope, has dramatically decreased the number of cervical cancer deaths in this country. The Pap test can detect precancerous and cancerous changes of the cervix, allowing early detection and prevention of cervical cancer. How often women should be screened depends on age, history, and risk factors. Screening should start no later than age 21 years, and no later than 3 years after starting sexual activity. Cervical cancer is rare under age 25. Women who have had a total hysterectomy (removal of uterus and the cervix) may not require Pap smear screening if the surgery was for a benign condition. The Pap smear is currently our best screening test for cervical cancer.

The actual test itself can be performed during any part of the menstrual cycle, except during active (heavy) menses. A small brush and spatula are used to scrape cells from the inside and outside of the cervix. Usually this is not painful. The sample is then either placed in a glass slide or in a small jar. The cells are then looked at under a microscope (or by a computer). There are several new technologies that help improve the accuracy of the Pap test. One is the liquid-based, thin-layer slide preparation in which the cells are placed into a vial and the Pap smear is read from the slides that are prepared from this medium. This helps eliminate some of the air-drying artifact that can occur with a traditional slide preparation. There are also automated readers that utilize a microscope that sends images to a computer, which analyzes the slide for abnormal cells, eliminating some of the human error.

Pap smear results may be reported as normal, “ASCUS” (atypical squamous cells of undetermined significance), “AGUS” (atypical glandular cells of undetermined significance), low-grade SIL (squamous intraepithelial lesion), high-grade SIL, or cancer. Sometimes vaginal infections such as yeast, trichomonas, and bacterial vaginosis can be identified by Pap test.

Of all the Pap tests performed in this country, approximately 6% will be abnormal and require further evaluation. Significant abnormal results require evaluation with colposcopy. A colposcope is a tool that helps magnify the cervix and will usually demonstrate the area of the cervix where the abnormal cells are coming from. After visualization with a colposcope, abnormal areas are biopsied, which involves removing a small pinch of tissue from the cervix. This procedure can usually be done in the office, with minimal discomfort. An ECC (endocervical curettage), or scraping from the cervical canal, is often performed at this time. Mild abnormalities on Pap (including some cases of ASCUS) can be followed with frequent Pap testing, rather than immediate colposcopy. Recurrent abnormal findings should be evaluated with colposcopy.

The treatment depends on the biopsy results. Sometimes after the biopsy is performed, more frequent Pap smears are the only necessary follow-up. More serious abnormalities may require a minor surgical procedure to remove the abnormal cells. There are several ways in which this can be achieved. One method of treatment is a LEEP, or loop electrosurgical excision procedure, where a wire loop acts as a scalpel and removes the abnormal cells from the cervix. Another method called “cryotherapy” involves freezing the abnormal tissue and laser therapy involves using light beams to destroy the abnormal cells. Sometimes a procedure called a “conization,” or cone biopsy, is required to remove a larger cone-shaped wedge of abnormal tissue with a scalpel or laser.

Many Pap smear abnormalities, particularly SIL or dysplasia, are related to a virus called human papillomavirus (HPV). HPVs are a family of hundreds of viruses that may also cause genital warts or warts on the hands and feet. There are hundreds of serotypes of HPV, but only a few are associated with cervical cancer. Most cervical cancers are preventable with regular screening.

Because the Pap smear is a screening test, it is not 100% accurate. Both “false-positive” and “false-negative” results may occur. A false-positive Pap smear means that a Pap test appears abnormal, but there is actually no underlying abnormality. A false-negative Pap test occurs when there is actually an abnormality and the Pap smear is reported as normal. One of the benefits of regular screening with Pap tests is that an abnormality that may initially not be detected can be identified with a subsequent test.

SEE ALSO: Cervical cancer, Colposcopy, Human papillomavirus, Pelvic examination, Trichomoniasis, Yeast infection


Category: P