Similar Risk Patterns After Cervical Screening in Two Large U.S. Populations: Implications for Clinical Guidelines.

OBJECTIVE: To compare the risks of histologic high-grade cervical intraepithelial neoplasia (CIN) or worse after different cervical cancer screening test results between two of the largest U.S. clinical practice research data sets.
METHODS: The New Mexico Human Papillomavirus (HPV) Pap Registry is a statewide registry representing a diverse population experiencing varied clinical practice delivery. Kaiser Permanente Northern California is a large integrated health care delivery system practicing routine HPV cotesting since 2003. In this retrospective cohort study, a logistic-Weibull survival model was used to estimate and compare the cumulative 3- and 5-year risks of histologic CIN 3 or worse among women aged 21-64 years screened in 2007-2011 in the New Mexico HPV Pap Registry and 2003-2013 in Kaiser Permanente Northern California. Results were stratified by age and baseline screening result: negative cytology, atypical squamous cells of undetermined significance (ASC-US) (with or without HPV triage), low-grade squamous intraepithelial lesion, and high-grade squamous intraepithelial lesion.
RESULTS: There were 453,618 women in the New Mexico HPV Pap Registry and 1,307,528 women at Kaiser Permanente Northern California. The 5-year CIN 3 or worse risks were similar within screening results across populations: cytology negative (0.52% and 0.30%, respectively, P<.001), HPV-negative and ASC-US (0.72% and 0.49%, respectively, P=.5), ASC-US (3.4% and 3.4%, respectively, P=.8), HPV-positive and ASC-US (7.7% and 7.1%, respectively, P=.3), low-grade squamous intraepithelial lesion (6.5% and 5.4%, respectively, P=.009), and high-grade squamous intraepithelial lesion (53.1% and 50.4%, respectively, P=.2). Cervical intraepithelial neoplasia grade 2 or worse risks and 3-year risks had similar trends across populations. Age-stratified analyses showed more variability, especially among women aged younger than 30 years, but patterns of risk stratification were comparable.
CONCLUSION: Current U.S. cervical screening and management recommendations are based on comparative risks of histologic high-grade CIN after screening test results. The similar results from these two large cohorts from different real-life clinical practice settings support risk-based management thresholds across U.S. clinical populations and practice settings.