Vol. 12, 815–823, September 2003 Cancer Epidemiology, Biomarkers & Prevention 815 A Comparison of Single and Combined Visual, Cytologic, and Virologic Tests as Screening Strategies in a Region at High Risk of Cervical Cancer1 Catterina Ferreccio, Maria C. Bratti, Mark E. Sherman, cytology or cervicography. Paired tests incorporating Rolando Herrero, Sholom Wacholder, Allan Hildesheim, either liquid-based cytology or HPV DNA testing were Robert D. Burk, Martha Hutchinson, Mario Alfaro, not substantially more accurate than either of those two Mitchell D. Greenberg, Jorge Morales, Ana C. Rodriguez, test strategies alone. However, a possibly useful synergy John Schussler, Claire Eklund, Guillermo Marshall, and was observed between the conventional smear and Mark Schiffman2 cervicography. Consideration of age or behavioral risk Departamento de Salud Publica, Universidad Catolica de Chile, Santiago, profiles did not alter any of these conclusions. Overall, we Chile [C. F., G. M.]; Proyecto Epidemiologico Guanacaste, San Jose, Costa conclude that highly accurate screening for cervical Rica [M. C. B., R. H., M. A., J. M., A. C. R.]; Division of Cancer cancer and CIN 3 is now technically feasible. The Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland remaining vital issue is to extend improved cervical 20852 [M. E. S., S. W., A. H., M. S.]; Albert Einstein College of Medicine, Bronx, New York 10461 [R. D. B.]; Womens and Infants’ Hospital, cancer prevention programs to resource-poor regions. Providence, Rhode Island 02905 [M. H., C. E.]; US Health Connect, Blue Bell, Pennsylvania 19034 [M. D.]; and Information Management Services, Silver Spring, Maryland 20904 [J. S.] Introduction Increased understanding of the pathogenesis of cervical cancer should permit improved prevention methods. We now under- Abstract stand that ϳ15 oncogenic types of HPV3 infection cause vir- Increased understanding of human papillomavirus (HPV) tually all cases of cervical cancer and its immediate precursor, infection as the central cause of cervical cancer has CIN 3 (1). Vaccination might ultimately prevent or treat onco- permitted the development of improved screening genic HPV infections and/or the lesions they produce but, in the techniques. To evaluate their usefulness, we evaluated the shorter term, screening will be required for prevention. The performance of multiple screening methods concurrently challenge is to develop screening strategies, consistent with our in a large population-based cohort of >8500 nonvirginal understanding of the natural history of HPV infection and women without hysterectomies, whom we followed cervical cancer, which balance the need for sensitive detection prospectively in a high-risk region of Latin America. of CIN 3 and cancer with acceptable specificity. Specificity is Using Youden’s index as a measure of the trade-off an issue, because infections with the oncogenic types of HPV between sensitivity and specificity, we estimated are very common (2). Despite their oncogenic potential, most the performances of a visual screening method infections typically resolve within 1–2 years, and only a mi- (cervicography), conventional cytology, liquid-based nority progress to CIN 3, which poses a high risk of invasion if cytology (ThinPrep), and DNA testing for 13 oncogenic left untreated (3, 4). HPV types. The reference standard of disease was Screening tests can be categorized as visual (e.g., colpos- neoplasia > cervical intraepithelial neoplasia grade 3 copy and its proxies), microscopic (cytology), or molecular. (CIN 3), defined as histologically confirmed CIN 3 Visual screening methods rely on the identification of patterns or invasive of abnormal blood vessels or tissue whitening on application of (90 ؍ detected within 2 years of enrollment (n We analyzed acetic acid (5). The distinction between acute HPV infection .(20 ؍ cancer detected within 7 years (n and precancer (CIN 3) can be estimated roughly using grading ؍ each technique alone and in paired combinations (n 112 possible strategies), and evaluated the significance of of the same and additional visual criteria. differences between strategies using a paired Z test that Cytology, specifically the conventional Pap smear, has equally weighted sensitivity and specificity. As a single been the mainstay of cervical cancer prevention for Ͼ50 years. test, either liquid-based cytology or HPV DNA testing The spectrum of cervical cytologic abnormalities ranges from was significantly more accurate than conventional equivocal changes to the pathognomonic nuclear and cytoplas- mic effects of HPV infection (“koilocytosis”) to severe cyto- logic neoplastic changes that suggest progression to CIN 3 (6, 7). New cytologic techniques might offer increased accuracy at Received 11/25/02; revised 6/2/03; accepted 6/5/03. increased cost, particularly liquid-based cytology produced in The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1 Supported by a series of National Cancer Institute contracts. In addition, this work was supported in part by Grant CA78527 (to R. D. B.) from the NIH. 3 The abbreviations used are: HPV, human papillomavirus; CIN, cervical intra- 2 To whom requests for reprints should be addressed, at Division of Cancer epithelial neoplasia; Pap, Papanicolaou; ASCUS, atypical squamous cells of Epidemiology, National Cancer Institute, NIH, Department of Health and Human undetermined significance; LSIL, low-grade squamous intraepithelial lesion; Services, Room 7066, 6120 Executive Boulevard, Rockville, MD, 20852. Phone: HSIL, high-grade squamous intraepithelial lesion; HC2, Hybrid Capture 2; (301) 496-1691; Fax: (301) 402-0916; E-mail: [email protected]. TaqGold, AmpliTaq Gold polymerase; CI, confidence interval. Downloaded from cebp.aacrjournals.org on September 29, 2021. © 2003 American Association for Cancer Research. 816 Comparing Screening Strategies for Cervical Cancer standard, automated fashion relying on cells collected into After collection of the materials listed above, the cervix preservative buffers (8, 9). was rinsed twice with 5% acetic acid, and two photographic Molecularly, HPV DNA of known oncogenic types can images of the cervix (cervigrams) were taken (15). The ex- now be directly measured, as can viral RNA, proteins, and posed, undeveloped film was sent to National Testing Labora- related antibodies produced against viral antigens by some tories, Worldwide (Fenton, MO) for developing and evaluation. exposed individuals. At present, HPV DNA detection is the Interpretation of Enrollment Screening Tests and Colpo- most accurate molecular technique for the detection of current scopic Referral. The conventional smears were stained and HPV infection. The combination of HPV DNA testing and initially interpreted in Costa Rica by a team of cytotechnolo- cytology for cervical cancer screening, particularly among gists and one experienced pathologist. The staining process was Ն women 30 years of age, is under evaluation by several groups reviewed and improved in mid-enrollment because of early including the American Cancer Society (10) and has been variability. We had conventional cytologic interpretations for approved by the Food and Drug Administration. Screening 8481 of the 8551 women. After the Costa Rican conventional using a combination of methods, although more expensive per interpretation, a cytotechnologist/pathologist team reinterpreted screening, might be cost effective if the increased sensitivity the smears using PapNet, a computer-assisted technology that permits lengthening of the screening interval. added to the sensitivity of the overall enrollment screening but In short, there is an increasingly large research literature is no longer available (and thus not evaluated here; Ref. 16). on possible applications of new visual, microscopic, and viro- The PreservCyt vials were sent to the United States where logic screening methods for prevention of cervical cancer. ThinPreps were prepared using a prototype of the ThinPrep However, few if any investigators have examined the relative 2000 Processor, and a third cytology interpretation was made. performance of new techniques, and combinations of tech- During the early part of enrollment, the preparation of many niques, in systematic surveys of whole populations where a ThinPreps was repeated to optimize the automated slide prep- broad and representative spectrum of cervical lesions is ex- aration technique, which was not yet standardized at that time. pected. A few international shipments of PreservCyt vials were lost The present article summarizes the project experience and, thus, we had results for 8082 of the 8551 women. related to performances of a visual screening method, conven- All three of the cytologic methods used the 1991 Bethesda tional cytology, liquid-based cytology, and DNA testing for 13 System (17) for reporting, which included the following: nor- oncogenic HPV types in a large cohort study in Guanacaste, mal including reactive changes, ASCUS, LSIL, HSIL, or car- Costa Rica. cinoma. With regard to visual screening, during the enrollment Materials and Methods examination, the nurses referred women to colposcopy if the Population. The enrollment (11, 12) and follow-up (13) direct visual appearance without acetic acid or magnification phases of the Guanacaste Project have been described in detail