Frequency of unsatisfactory cervical cytology smears in cancer screening of Japanese women: A systematic review and meta-analysis

Abstract

The Bethesda system (TBS) has been used for cervical cytological diagnosis in Japan since 2008. Evaluation of specimen adequacy is the most important aspect of quality assurance and for precise diagnosis in TBS. A systematic review and meta-analysis were performed to assess the unsatisfactory specimen rate in the primary cervical cancer screening setting in Japan.

Ovid MEDLINE and Ichushi-Web were searched from inception through May 2017. Prospective and retrospective studies that reported the proportion of unsatisfactory specimens in healthy asymptomatic Japanese women in a cervical cancer screening program were eligible for inclusion; 17 studies were included in the meta-analysis.

The random-effects model meta-analysis calculated summary estimates of the unsatisfactory rate of 0.60% (95% CI: 0.18 – 1.96%; I² = 99%) for conventional cytology and 0.04% (95% CI: 0.00 – 0.35%; I² = 99%) for liquid-based cytology (LBC). However, comparative results between conventional and liquid-based cytology, based on 4 direct and 9 comparative studies, showed no significant difference (summary odds ratio = 3.5×10^-2 favoring LBC [95% CI: 6.9×10^-4 – 1.7]; I² = 98%). In the subgroup analyses and meta-regressions, use of non-cotton devices for conventional cytology and use of a particular platform for LBC were associated with lower unsatisfactory rates. Meta-regression also suggested chronological improvement in unsatisfactory rates for both tests.

In Japanese cervical cancer screening programs, conventional cytology remains prevalent. Future research needs to focus on evaluating the impact of screening programs using LBC by comparing the accuracy, performance, and cost-effectiveness with conventional cytology in the Japanese population.

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