Usefulness of Liquid-Based Cytology in Diagnosing Biliary Tract Cancer Compared to Conventional Smear and Forceps Biopsy

Background/Aims: Liquid‐based cytology (LBC) has been shown to improve the diagnostic efficacy of brush cytology for thyroid, cervical and pancreatic cancer. To evaluate the diagnostic performance of LBC for biliary tract cancer, we compared it with conventional smears and forceps biopsies. Methods: A retrospective study was conducted of all consecutive patients who underwent brush cytology under ERCP from January 2010 to April 2020. The primary outcome was the diagnostic efficacy of conventional smears and LBC. The difference between the two groups was corrected using inverse probability weighting (IPW). The secondary outcome was the sensitivity and specificity of brush cytology and forceps biopsy. The secondary outcome was evaluated in patients who underwent both methods. Results: Among 162 patients, conventional smears were performed in 70 patients and LBC was performed in 92 patients. In the primary analysis using IPW, the sensitivity of conventional smears and LBC was 56.00% and 78.26% respectively (P = 0.009). The specificity was 100% for both methods. The accuracy was 66.15% for conventional smears and 83.33% for LBC (P = 0.012). In the secondary analysis, the sensitivity of conventional smears versus forceps biopsies was 62.16% versus 78.38% (P = 0.034) and 81.16% for both LBC and forceps biopsies. The specificity of both cytological examination and forceps biopsies was 100%. Conclusions: Liquid-based cytology demonstrated better sensitivity and accuracy than conventional smears. Moreover, its diagnostic performance was close to that of forceps biopsies.