Analysis of the Differences between Bethesda Groups according to Conventional Smear and Liquid-Based Cytology Methods in Cervicovaginal Cytology: A Single-Center Experience with 165,915 Cases

<b><i>Introduction:</i></b> Liquid-based cytology (LBC) has replaced conventional smear (CS) in the world. In this study, through a series with a large number of cases, we aimed to make a comparison and general evaluation in all groups, primarily epithelial abnormalities, according to LBC and CS methods. This study was carried out in a private pathology laboratory located in a metropolitan city, where cytological materials sent from many clinics were examined. <b><i>Material and Methods:</i></b> There were 165,915 cases whose smears were examined between 2012 and 2020, most of them conventional (131,224 CS, 34,691 LBC). Cases were evaluated on the basis of the Bethesda 2014 classification and divided into sub-diagnostic categories after they were divided into two main groups as “with epithelial abnormalities” and “without.” χ² and Fischer’s precision statistical tests were conducted using SPSS 23.0 package. In the CS process, cervical samples were obtained using an endocervical brush and a spatula. Cells were directly spread onto the slides and promptly fixed in 95% ethanol, followed by staining with the standard Papanicolaou stain. For LBC ThinPrep, cervical specimens were gathered using a cervix brush. The brush was washed in a vial and discarded. Finally, cells were isolated through vacuum filtration and transferred to the slide using air pressure. <b><i>Results:</i></b> Squamous cell abnormalities (atypical squamous cells of undetermined significance [ASC-US], atypical squamous cells – cannot exclude high-grade squamous intraepithelial lesion [ASC-H], low-grade squamous intraepithelial lesion [LSIL], high-grade squamous intraepithelial lesion [HSIL], squamous cell carcinoma, atypical glandular cells of undetermined significance) were reported in 5,696 (3.43%) cases. ASC (ASC-US + ASC-H)/SIL ratio (1.36/2.04) was found to be 0.67 (recommended Bethesda ratio is &lt;3). ASC-US (<i>p</i> &lt; 0.001), ASC-H (<i>p</i> &lt; 0.001), and HSIL(<i>p</i> &lt; 0.001) detection rate of LBC was found to be significantly higher than CS. ASC-US (1.8/1.2), ASC-H (0.08/0.008), and HSIL (0.6/0.3) case ratios of LBC/CS were found to be significantly higher in LBC. LSIL (1.72/1.66) rate was similar. <b><i>Conclusion:</i></b> LBC is superior to CS in detecting epithelial lesions. In addition to being used as a screening method, it is clear that it makes a great contribution to reducing cervical carcinomas due to HPV typing. Definitive comments regarding comparison of methods on reactive changes and microorganism detection are challenging. Preanalytical factors might account for these situations.