Pap Test Health Article

Definition

The Pap test (Pap smear) is the microscopic examination of cells scraped from the both the outer cervix (ectocervix) and the cervical canal (endocervix). It is called the "Pap" test after its developer, Dr. George N. Papanicolaou, who described a procedure for staining vaginal and cervical cells that gives clearly defined detail to the nuclear chromatin. Using the Papanicolaou stain, he developed a classification system for abnormal cervical cells. Before the application of the Pap test in the 1940s, cervical cancer caused approximately 26,000 deaths in the United States each year. The death rate from cervical cancer since the use of the Pap test has become widely accepted has been reduced by 70%.

Purpose

The Pap test is a screening test used to detect abnormal growth of cervical cells at an early stage, so that if necessary, treatment can be started before the cells become cancerous and invasive. The test helps physicians identify women who are at increased risk of cervical dysplasia (abnormal cells) or cervical cancer. Only an examination of the cervix, and samples of cervical tissue (biopsies) can diagnose precancerous and cancerous changes in the cells that line the uterus, called squamous epithelium.

This microscopic analysis of cells can detect cervical cancer, precancerous changes, inflammation (called vaginitis), infections, and some sexually transmitted diseases (STDs). The Pap test can sometimes detect endometrial (uterine) cancer or ovarian cancer, although it was not designed for this purpose.

Women should begin to have Pap tests at the age of 18 years or whenever they start having sex. Young people are more likely to have multiple sex partners, which increases their risk of certain diseases that can cause cancer, such as human papillomavirus (HPV). The American Cancer Society recommends that a Pap test be done annually for two consecutive negative examinations, then repeated once every three years until age 65 for women without symptoms of gynecologic problems. Many other doctors, however, recommend annual Pap tests for all their patients.

Women with certain risk factors should always have yearly tests. Those at highest risk for cervical cancer are women who started having sex before age 18; those with many sex partners (especially if they did not use condoms, which protect against STDs); those who have had STDs such as genital herpes or genital warts; and those who smoke. Women older than 40 also should have the test yearly, especially in the event of bleeding after menopause. Women over age 60 account for 25% of new cases of cervical cancer and 40% of deaths from this disease. Women who have had a hysterectomy (removal of the uterus) may need to have Pap tests, if the surgery was for cancer, or if the cervix was left in place. Pregnant women should have a Pap test as part of their first prenatal examination.

Women who have a positive test result should be retested more frequently. If atypical squamous cells or low-grade lesions are found they should be tested every four to six months until they have three consecutive normal results. The test should be repeated within two to three months if severe inflammation, infection, or post-menoposal atrophy is found. If atypical cells or low-grade lesions persist, or high-grade lesions are found, colposcopy (examination of the cervix with a magnifying lens) should be performed, and treatment initiated as indicated.

Precautions

The Pap smear is a microscopic evaluation of individual cells, a process that requires interpretation. Differentiation of inflammatory, reactive, and atrophied cells from atypical cells is difficult and cannot always be performed with complete certainty. The test is not 100% sensitive and between 5–10% of cervical abnormalities may be missed. Most false negatives result from poor sample collection (insufficient cervical cells) or poor smear preparation. The finding of abnormal cells on a Pap smear does not mean that the cells were present on previous exams.

The Pap test should be performed in the middle of the menstrual cycle to prevent interference from blood. Sexual intercourse, douching, or the use of vaginal suppositories may affect results. Other factors that can affect test results include: water or lubricant on the specimen from the speculum; blood, mucus, or pus on the slide that obstructs the view of epithelial cells; cell damage during collection; and improper slide fixation. An acceptable smear is one that is correctly labeled with the patient's name, age, and last menstrual period; contains squamous cells covering at least 10% of the slide; and demonstrates the presence of cells from the endocervix and transformation zone. The transformation zone is the area where the squamous epithelium of the ectocervix meets the glandular epithelium of the endocervix.