A Follow-up Study of Atypical Squamous Cells in Gynecologic Cytology Using Conventional Papanicolaou Smears and Liquid-Based Preparations: The Impact of the Bethesda System 2001

We evaluated the impact of the Bethesda System (TBS) 2001 in cytology reporting of atypical squamous cells (ASC) when using conventional Pap smears and liquid-based cytology preparations (LBC). Follow-up information for all ASC cases encountered in Queen Mary Hospital, Hong Kong, China, from July 2000 to June 2004 (using TBS 1991 in the first 2-year period and TBS 2001 in the second) was analyzed. Among 4,089 ASC cases studied, more than 50% had negative follow-up; this percentage was lower with TBS 2001. The percentage of ASC cases with a low-grade cervical intraepithelial neoplasia (CIN) end point was higher with TBS 2001, especially after application of LBC. There was also a decreasing trend of having this low-grade CIN end point with advancing age. Most clinically significant outcomes occurred after 6 months and before 1 year post-ASC diagnosis. With TBS 2001, more than 50% of ASC, cannot exclude high-grade squamous intraepithelial lesion (ASC-H) were associated with high-grade CIN on follow-up. TBS 2001 improves the positive predictive value of ASC for clinically significant lesions. Introduction of dichotomous subcategorization of ASC is relevant, with ASC-H associated with a much higher risk of subsequent high-grade squamous lesions.