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The Papanicolaou test (abbreviated as Pap test, known earlier as Pap smear, cervical smear, or smear test) is a method of cervical screening used to detect potentially pre-cancerous and cancerous processes in the cervix (opening of the uterus or womb). Abnormal findings are often followed up by more sensitive diagnostic procedures, and, if warranted, interventions that aim to prevent progression to cervical cancer. The test was invented by and named after the prominent Greek doctor Georgios Papanikolaou. A Pap smear is performed by opening the vaginal canal with a speculum, then collecting cells at the outer opening of the cervix at the transformation zone (where the outer squamous cervical cells meet the inner glandular endocervical cells). The collected cells are examined under a microscope to look for abnormalities. The test aims to detect potentially pre-cancerous changes (called cervical intraepithelial neoplasia (CIN) or cervical dysplasia; the squamous intraepithelial lesion system (SIL) is also used to describe abnormalities), which are caused by sexually transmitted human papillomaviruses. The test remains an effective, widely used method for early detection of pre-cancer and cervical cancer. While the test may also detect infections and abnormalities in the endocervix and endometrium, it is not designed to do so. In the United States, Pap smear screening is recommended starting around 21 years of age until the age of 65. Guidelines on frequency vary from every three to five years.〔〔〔American Cancer Society. (2010). (Detailed Guide: Cervical Cancer. Can cervical cancer be prevented? ) Retrieved August 8, 2011.〕 If results are abnormal, and depending on the nature of the abnormality, the test may need to be repeated in six to twelve months. If the abnormality requires closer scrutiny, the person may be referred for detailed inspection of the cervix by colposcopy. The person may also be referred for HPV DNA testing, which can serve as an adjunct to Pap testing. Additional biomarkers which may be applied as ancillary tests with the Pap test are evolving.〔Shidham VB, Mehrotra R, Varsegi G, D'Amore KL, Hunt B, Narayan R. p16 INK4a immunocytochemistry on cell blocks as an adjunct to cervical cytology: Potential reflex testing on specially prepared cell blocks from residual liquid-based cytology specimens. CytoJournal (online ) 2011 (2011 Apr 17 );8:1. Available from: http://www.cytojournal.com/text.asp?2011/8/1/1/76379〕 ==Medical uses== Screening guidelines vary from country to country. In general, screening starts about the age of 20 or 25 and continues until about the age of 50 or 60. Screening is typically recommended every three to five years, as long as results are normal.〔〔 Women should wait a few years after they first have intercourse before they start screening, and should not be screened before age 21. American Congress of Obstetricians and Gynecologists (ACOG) and others recommend starting screening at age 21 (since that is a few years after initial sex for most American women). Many other countries wait until age 25 or later to start screening. For instance, some parts of Great Britain start screening at age 25. ACOG's general recommendation is that people with uteruses age 30-65 have an annual well-woman examination, that they not get annual Pap tests, and that they do get Pap tests at three-year intervals.〔, which cites * * * *〕 Most people who contract HPV do so soon after becoming sexually active.〔 It takes an average of a year, but can take up to four years, for a person's immune system to control the initial infection. Screening during this period may show this immune reaction and repair as mild abnormalities, which are usually not associated with cervical cancer, but could cause the person stress and result in further tests and possible treatment. Cervical cancer usually takes time to develop, so delaying the start of screening a few years poses little risk of missing a potentially precancerous lesion. For instance, screening people under age 25 does not decrease cancer rates under age 30. There is little or no benefit to screening people who have not had sexual contact. For example, United States Preventive Services Task Force (USPSTF) recommends waiting at least three years after first sex.〔 HPV can be transmitted in sex between female-assigned people, so those who have only had sex with other female-assigned people should be screened, although they are at somewhat lower risk for cervical cancer. Guidelines on frequency of screening vary—typically every three to five years for those who have not had previous abnormal smears.〔〔 Some older recommendations suggested screening as frequently as every one to two years, however there is little evidence to support such frequent screening; annual screening has little benefit but leads to greatly increased cost and many unnecessary procedures and treatments.〔 It has been acknowledged since before 1980 that most people can be screened less often. In some guidelines, frequency depends on age; for instance in Great Britain, screening is recommended every 3 years for women under 50, and every 5 years for those over. Screening should stop about age 65 unless there is a recent abnormal tests or disease. There is probably no benefit screening people aged 60 or over whose previous tests have been negative. If a person's last three Pap results were normal, she can stop at age 65, according to the USPSTF, ACOG, ACS and ASCP;〔〔 England's NHS says 64. There is no need to continue screening after a complete hysterectomy for benign disease. Pap smear screening is still recommended for those who have been vaccinated against HPV,〔 since the vaccines do not cover all of the HPV types that can cause cervical cancer. Also, the vaccine does not protect against HPV exposure before vaccination. Those with a history of endometrial cancer should discontinue routine Pap tests.〔 Further tests are unlikely to detect recurrence of cancer but do bring the risk of giving false positive results, which would lead to unnecessary further testing.〔 More frequent Pap smears may be needed to follow-up after an abnormal Pap smear, or after treatment for abnormal Pap or biopsy results, or after treatment for cancer. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pap test」の詳細全文を読む スポンサード リンク
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