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 cancers 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
were 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 was
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 was seen once after enrollment, close to
fifth anniversary in the cohort. Women in this group with evidence of LSIL at the fifth
anniversary visit were 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 were followed passively via linkage to the cytology and
tumor registries in Costa Rica.
Clinical visits conducted during follow-up consisted of a brief personal interview that
collects information on exposures since enrollment, the collection of 15ml blood, and a
pelvic examination. A Pap smear was prepared during the pelvic examination, and additional
cervical specimens were collected and used to prepare a monolayer smear (ThinPrep) and for
human papillomavirus and other testing. Similar to the enrollment visit, cervigrams were
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) were referred to colposcopy, censored from
the study, and treated by Social Security Administration clinicians using standard local
Allan Hildesheim, Ph.D.
National Cancer Institute (NCI)
United States: Federal Government