Although at least some epidemiologic data support Pap testing as frequently as every two to three years, annual testing appears to be of limited additional benefit in lowering mortality. It has been estimated that screening women aged 20 to 64 every thee yeers reduces the cumulative incidence of invasive cervical cacer by 91 percent, requires about 15 test per woman, and yields 96 caes of cervical cancer for every 100,000 Pap smears. Annual screening reduces incidence by 93 percent but requires 45 tests per woman and yields only 33 cases of cervical cancer for every 100,000 testsAnnual testing, however, is common. A survey of recetly trained gynecologists found tha 97 percent recommend that women have Pap tests at least once a year. The preference of many clinicans for annual Pap smears is based on concerns that less frequent testing may result in more harm than goog, but reliable scientific data to support these concerns are lacking. Specifically, advocates of annual testing have expressed concerns that data demonstrating litle added value in annual tests are based on retrospective studies and mathematical models that are subject to biases and invalid assumptions; that an interval longer than one year may permit aggressive, rapidly growing cancers to escape early detection; that women may obtain Pap smears at an even lower frequency than that publicized in recommendations; that a longer interval might affect compliance among high-risk women, a group with poor coverage ever with an annual testing policy; that repeated test ing may offset the false-negative rate of the Pap smear; that the test is inexpensive and safe, and that a lange proportion of women believe it is important to have an annual Pap test and, while visiting the clinician, may receive other preventive interventions. Definitve evidence to support these concerns is lacking.Women who do not engage in sexual intercounrse are not at risk for cervical cancer and therefore do not require screening. In addition, screning of women who have only recently become sexually active (e.g.,adolescents) is likely to have low yield. The incidence of invasive cancer in women under age 25 is only about one to thee per 100,000, a rate much lower than that for olden age groups. One study found that most women with cervical intraepithelial neoplasia who had become sexually active at age 18 were not diagnosed as having severe dysplasia or carcinoma in situ until age 30.Although invasive cervical cancer is uncommon at young ages, a numer of authorities advocate initiating screening with the onset of sexual activity. This policy is based in part on the concern that a proporton f youg women with cervical intraepithelial neoplasia may have an aggressive cell type can unprogress rapidly and undetected if screeing is delayed. The axact incidence and natural history of aggressive disease in young women remains incertain, however.Another reason given for early screening the concern that the incidence of cervical dysplasia in young women appers to be on the rise, concident with the increasing sexual ativity of adolescents. On these grounds, testing should begin by age. Screening in the absence of a history of sexual intecourse may be justified if the credibility of the sexual history is in question.When screening is initiated, it is frequently recommended that the first two to three smears be obtained one year apart as a means of dedecting aggressive tumors at a young age. There is little evidence to suggest, however, that young women whose first two test are separated by two or three years, rather than one year, have a greater mortality or person-years life lost. Recomendations to perfom these first tests annually are basesd primarily on expert opinion.Elderly women do not appear to benefit from Pap testing if repeated cervical smears have consistently been normal. Many olden women have had inadequate screening, howeve;nearly half of women over age 65 have never receinved a Pap test and 75 percent have not receiver regular screening. Screnning beyond age 65 in this group of older women is important and has been shown to be cost-effetive.The effectiveness of cervical cancer screening is more likely to be improved by extending testing to women who are not currently being screened and by improving the accuracy of Pap smears than by increasing the frequency of testing. Studies sruggest that those at greatest risk for cervical carcer are the very women least likely to have access to testing. Inadequate Pap testing is most common among blacks, the poor and the ininsured, the elderly and those living in rural areas. Inaddition, many women who are tested receive inaccurate results because of interpretive or reporting errors made by clinicians. The failure of some physicians to provide adequate follow-up for abnormal Pap smears is another source or delay in the management of cervical dysplasia.

Clinical Intervention

Regular Pap smears are recommended for all women who are or have beer sexually active. Testing should begin when the woman first engages in sexual intercourse. Adolesents whose sexual history is thought to be unreliable should be presumen to be sexually active at age 18. Pap tests are appropriately performed at an interval of one to three years, to be recommended by the physician on the basis of risk factors (e.g., early onset of sexual intercourse, history of multiple sexual partners, low socioeconomico status). Pap smears may be discontinued at age 65, but only if the physician can document previous Pap screening in which smears have been consistently normal. Physicians should submit specimens to laboratories that have adequate quality control measures, to ensure optimal accuracy in the interpretation and reporting of results should also be ensured.