Frequency of cervical smear abnormalities within 3 years of normal cytology

Objective: To compare cervical screening outcomes associated with age and t hree screening intervals, 1, 2, and 3 years. Methods: We did a prospective cohort study comprising 128,805 women at comm unity-based clinics throughout the United States who were screened for cerv ical cancer within 3 years of normal smears through the National Breast and Cervical Cancer Early Detection Program. We determined the incidence of cy tologic abnormalities defined as atypical squamous cells of undetermined si gnificance (ASCUS), low-grade squamous intraepithelial lesion (SIL), high-g rade SIL, and suggestive of squamous cell cancer. Results: Over the 3 years after normal smear results, the incidence of new smears interpreted as high-grade SIL or suggestive of squamous cell cancer (high-grade SIL or worse) was 66 of 10,000 for women under 30 years old, 22 of 10,000 for those 30-49 years, 15 of 10,000 for those 50-64 years, and 1 0 of 10,000 for those over 65 years. Age-adjusted incidence rates of high-g rade SIL or worse were similar for women screened at 9-12 months (25 of 10, 000), 13-24 months (29 of 10,000), and 25-36 months (33 of 10,000) after no rmal smears (P = .46). Age-adjusted incidence rates of ASCUS, the most comm on cytologic abnormality, did not change (P = .36). Incidence of smears int erpreted as low-grade SIL increased as time from the normal smear increased (P = .01). Conclusions: Within 3 years after normal cytology results, cervical smears interpreted as high-grade SIL or worse are uncommon, and the incidence rate is unrelated to the time since last normal smear. Optimal screening strate gies for women with recent normal cytology results should be based on compr ehensive modeling studies that incorporate the true risks and benefits of r epetitive screening. (C) 2000 by The American College of Obstetricians and Gynecologists.