A comparison of liquid-based and conventional cytology using data for cervical cancer screening from the Japan Cancer Society

Objective: Liquid-based cytology has replaced conventional cytology in cervical cancer screening in many countries. However, a detailed comparison of liquid-based cytology with conventional cytology has not been reported in Japan. Therefore, the aim of the study is to evaluate efficacy of liquid-based cytology in Japan. Methods: We first evaluated the prevalence of use of liquid-based cytology and then examined the efficacy of liquid-based cytology and conventional cytology for detecting CIN and the rate of unsatisfactory specimens using data from cancer screening collected by the Japanese Cancer Society from FY2011 to FY2014. A Poisson regression model with random effects analyses was used to classify histological outcomes and unsatisfactory specimens using liquid-based cytology compared to conventional cytology. Results: A total of 3 815 131 women were analyzed in the study. The rate of liquid-based cytology increased from approximately 8% in FY2011 to 37% in FY2014. Compared to conventional cytology, the detection rates with liquid-based cytology were significantly higher (1.42 times) for CIN1+ [detection rate ratio (DRR) = 1.42, 95% confidence interval (CI) 1.35-1.48, P < 0.001] and CIN2+ (DRR = 1.16, 95% CI 1.08-1.25, P < 0.001). Positive predictive value ratios of CIN1+ and CIN2+ were also significantly higher for liquid-based cytology than for conventional cytology. However, there was no significant difference between liquid-based cytology and conventional cytology for detection rates and positive predictive values of CIN3+ and cancer. The rate of unsatisfactory specimens was significantly lower with liquid-based cytology compared to conventional cytology (DRR = 0.07, 95% CI 0.05-0.09, P < 0.001). Conclusions: In order to avoid the unsatisfactory specimens in cervical cancer screening, the results of this study did indicate that liquid-based cytology was more useful than conventional cytology in practical standpoints.