Diagnoses and outcomes in cervical cancer screening: a population-based study.

OBJECTIVE: This study was undertaken to examine routine cervical cancer screening diagnoses and outcomes on an age-specific basis in a US population.

STUDY DESIGN: We conducted an observational cohort study using 1997-2002 health plan administrative and laboratory data for women enrolled at Kaiser Permanente Northwest (Portland, Ore) in 1998.

RESULTS: Across all female enrollees (n=150,052), the annual rate of routine cervical cancer screening was 294.7 per 1,000, with cytologic abnormalities detected at a rate of 14.9 per 1,000. The annual incidence of cervical intraepithelial neoplasia (CIN) 1 was 1.2 per 1,000 with a rate of 1.5 per 1,000 for CIN 2/3. CIN 1 incidence peaked among women aged 20 to 24 years (5.1 per 1,000), with CIN 2/3 rates highest among those 25 to 29 years (8.1 per 1,000). From among 44,493 routine cervical smears, results were normal for 94.5%, with abnormal diagnoses of atypical squamous cells (3.3%), atypical glandular cells (0.2%), low-grade squamous intraepithelial lesion (1.2%), high-grade squamous intraepithelial lesion (0.3%), and inconclusive/inadequate (0.5%). Of women with abnormal routine smears, CIN or cancer was detected on follow-up in 19.4% of cases, 51.5% were found to have had a false-positive smear, and 29.0% incomplete follow-up as defined by published management guidelines.

CONCLUSION: These are the first comprehensive age-specific estimates of routine cervical cancer screening diagnoses and outcomes to be reported within a US general healthcare setting. Overall, 5% of routinely screened women were found to have an abnormal cervical smear with an annual incidence of CIN across all female enrollees of 2.7 per 1000.