Liquid-based cytology versus conventional Papanicolaou smear in an organized screening program

Abstract

The objective of this study was to evaluate whether liquid-based cytology (LBC) can improve high-standard cervical cancer screening cytology further. The primary endpoint was histopathologic high-grade lesions in current and subsequent screening rounds. The secondary endpoints were cytologic diagnosis and inadequate samples. Women were randomized to smear taking by conventional Papanicolaou (Pap) smear or LBC according to the time of appointment. Eight thousand eight hundred ten conventional Pap smears and 4674 LBC samples were included. Evaluations of atypical cytology and referral to colposcopy and treatment were performed as routine procedures. Histopathologic diagnoses were retrieved from a regional database 8 months after the study was closed. The mean follow-up was 2 years and 9 months. Inadequate samples were observed in 0.3% of LBC samples versus 0.7% of Pap smears (P = .002). The total fraction of nonbenign diagnoses in cytology was 4.5% versus 3.5%, respectively (P < .001). Histopathologic evaluation was made on 570 patients constituting 4.6% of the LBC samples and 4% of the Pap smears. Forty percent more high-grade lesions were identified as a result of LBC sampling (1.20% vs 0.85%; P = .05). The influence of the sampling method was significant for all variables (odds ratio [OR], 1.60; 95% confidence interval [95% CI], 1.12-2.28) for high-grade lesions that were identified by histology when adjusting for age and screening unit in a logistic regression model. At the second follow-up 2 years and 1 month later, the OR was decreased only slightly (1.51; 95% CI, 1.13-2.01). In the ongoing cervical screening program of western Sweden, liquid cytology produced a significantly higher yield of histologic high-grade lesions compared with conventional Pap smears.