Performance of a semiautomated papanicolaou smear screening system: Results of a population-based study conducted in Guanacaste, Costa Rica

BACKGROUND. Automated cytology devices have utility in quality assurance applications, but the effectiveness of these devices in primary screening is unknown. METHODS. Enrollment smears obtained from 7323 women participating in a population-based study sponsored by the National Cancer Institute were screened manually in Costa Rica and then evaluated independently in the U.S. with the PAPNET system (Neuromedical Systems, Inc., Suffern, NY), a semiautomated, neural network-based device. Smears with abnormal PAPNET images were microscopically rescreened and then diagnosed by a U.S. cytopathologist. ThinPrep slides (Cytyc Corporation, Boxborough, MA), prepared from rinses of the cytologic sampler, and cervigrams (National Testing Laboratories, Fenton, MO) were also evaluated. Women with any abnormal cytologic diagnosis or a positive cervigram were referred for colposcopy with biopsy and definitive therapy if indicated. RESULTS. Based on the U.S. cytotechnologist's review of the PAPNET images, 1017 (13.9%) of 7323 smears were selected for manual screening, resulting in the selection of 492 (6.7%) possibly abnormal slides for referral to the U.S. pathologist. Ultimately, 312 smears (4.3% of the total) were diagnosed as containing squamous cells of undetermined significance or a more severe abnormality (≥ASCUS), resulting, hypothetically, in the referral of 66.5% of women with a final diagnosis of a squamous intraepithelial lesion or a more severe abnormality (≥SIL) and 86.0% of patients with ≥high grade SIL. Conventional microscopic screening performed in Costa Rica resulted in the hypothetical referral of 6.5% of patients with ≥ASCUS for colposcopy, including 69.5% of patients with ≥SIL and 79.8% of those with ≥high grade SIL. CONCLUSIONS. In this study, PAPNET-assisted cytologic screening accurately identified smears obtained from women with high grade SIL or carcinoma. Determination of the clinical cost-effectiveness of PAPNET-assisted screening in routine practice awaits future study.