Current guidelines recommend initiating Pap testing three years after first intercourse and no later than age 21 years, continuing every one to two years until age 30, and then screening at one- to three-year intervals until age 65–70 or indefinitely (4
). Despite recommendations to the contrary, most U.S. practitioners continue to screen at annual intervals (8
). Models suggest that annual screening of women with extensive prior screening is not cost effective (9
). The risk of cancer in young women is quite low, and assessment of changes in cervical cancer rates where comprehensive screening has been initiated suggests that screening has little impact on rare early-onset cancers, especially those presenting before age 25 (10
). Screening after hysterectomy for benign indications also is not cost-effective, though still commonly done (11
). Overscreening can result in patient harms, including missed work, travel and child care costs, anxiety, stigmatization, and obstetric and surgical complications from treatment of lesions that would not have progressed to cancer (13
While some women are over-screened, the absence of an organized screening program in the United States results in a substantial proportion of women falling outside the prevention system. Underscreened women account for some 50% of cervical cancers diagnosed in the U.S. (15
). Regrettably, with cost a barrier to care, increasing the intensiveness of screening among women in regular care to compensate for this not only has minimal impact, but the resulting cost increases also may raise barriers to access, decreasing the screening of at-risk women.
In addition, medicolegal concerns likely promote excessive screening, both by increasing the frequency of screening and by driving the development of more sensitive but less specific screening tests, as missed lesions on Pap specimens ranks third among the common causes of medical negligence claims against U.S. pathologists (16
). Most findings identified by cervical screening, including carcinogenic HPV infections, atypical and low grade cytology results, and grade 1 cervical intraepithelial neoplasia (CIN) are in fact not premalignant but rather clinical manifestations of transient HPV infections. A minority of these abnormalities may progress to cancer, and distinguishing these requires longitudinal observation. When patients or clinicians find observation burdensome, needless treatment may result.
Increasing evidence suggests that testing for carcinogenic HPV infection may be a useful replacement or adjunct for conventional cytologic screening in cervical cancer prevention programs (17
). However, barriers to adoption of HPV screening are multiple. Appropriate follow-up for a positive stand-alone test, an approach that is currently investigational, is unclear and may include interval repeat HPV testing, reflex cytology, colposcopy, or other interventions. HPV testing requires patient education. Some consider HPV exclusively as a sexually transmitted disease whose diagnosis results in stigmatization, anxiety, and anger (18
). Others overestimate the cancer risk underlying the diagnosis of a carcinogenic HPV infection, driving overtreatment. Also, extending screening intervals using HPV testing may pose a financial disincentive to some clinicians.
Cytology is limited by human error, fatigue, and subjectivity, by sampling errors, and by lesion biology (19
). Specimen collection requires technical skill in obtaining samples to ensure assessment of the full transformation zone. As a triage test, colposcopy appears to miss a quarter of CIN3 lesions identified during two years of observation of women with ASC-US cytology (20
). Clinician interpretations of colposcopic findings are limited; reproducibility of colposcopic diagnosis is problematic even among experts, and lesion detection and eradication require training to develop skills in performing colposcopy and treatment. Problems maintaining proficiency in cytologic and colposcopic interpretation will likely increase as vaccination results in a decline in the prevalence of serious abnormalities. Some patients fail to understand that these processes are imperfect, that a single negative test does not mean no cancer risk, and that even with annual lifetime screening some cancers will be missed. These unrealisticially high expectations of screening increase medicolegal hazard and drive overscreening (19