Costa Rican Natural History Study of HPV and Cervical Neoplasia

A population-based study was initiated in Costa Rica in June 1993 to investigate the natural history of human papillomaviruses (HPV) and cervical neoplasia. Over a period of 18 months, ending in December 1994, 10,080 women were recruited into our study, after informed consent was obtained. At the initial recruitment visit, all women were administered a brief risk factor questionnaire, had 15ml of blood collected and, if sexually active, were given a pelvic examination. At the time of the pelvic examination, a Pap smear was collected, as were additional cervical cells which were then used for additional monolayer smears (ThinPrep) and for human papillomavirus and other testing. Pictures of the cervix, known as cervigrams, were also taken as a third screening test. Based on these screening tests, women were referred to colposcopy, at which time a more detailed risk factor questionnaire was administered, additional cervical cells and blood (15ml) were collected, and histological specimens were obtained, if indicated by the colposcopy. Women diagnosed with a high-grade cervical lesion (HSIL) or cervical cancer were treated by Social Security Administration clinicians using standard local protocols.

Women without evidence of HSIL or cancer at enrollment comprise the group of subjects who have been followed as part of our longitudinal study. Three distinct groups of women of approximately equal size (about 3,000 women each) exist within our longitudinal cohort. The first group consists of women who at enrollment had evidence of low-grade cervical lesions (LSIL) or equivocal lesions and a sample of the remaining cohort members. This group is being followed actively at 6-12 month intervals through their seventh anniversary in the cohort. The second group consists of women who were cytologically normal at enrollment but randomly selected for active follow-up. This second group will be seen once after enrollment, at their fifth anniversary in the cohort. Women in this group with evidence of LSIL at the fifth anniversary visit will be added to the first group described above and followed at 6-month intervals. The final group consists of the remaining women in our cohort (all cytologically normal at enrollment). These women are being followed passively via linkage to the cytology and tumor registries in Cost Rica.

Clinical visits conducted during follow-up consist of a brief personal interview that collects information on exposures since enrollment, the collection of 15ml blood, and a pelvic examination. Pap smear is prepared during the pelvic examination, and additional cervical specimens are collected and used to prepare a monolayer smear (ThinPrep) and for human papillomavirus and other testing. Similar to the enrollment visit, cervigrams are also collected from each participant at the time of their follow-up visits.

During follow-up, women with any evidence of progression to HSIL or cancer (by Pap smear, ThinPrep, cervicography, or by visual inspection) are referred to colposcopy, censored from the study, and treated by Social Security Administration clinicians using standard local protocols.