Diagnostic Performance of Bile Duct Brush Cytology with Risk of Malignancy of Standardized Categories in the Wake of World Health Organization Reporting System for Pancreaticobiliary Cytopathology: An Updated Systematic Review and Meta-Analysis

Introduction: The WHO Reporting System for Pancreaticobiliary Cytopathology revised the Papanicolaou Society of Cytopathology guidelines in alignment with the WHO classification of digestive system tumors, 5th edition. The current systematic review and meta-analysis have been conducted to accurately assess the performance of bile duct brush cytology and report the risk of malignancy (ROM) of each standard category by following the guidelines of diagnostic test accuracy meta-analysis. Methods: Medline/Pubmed and Cochrane databases were searched till June 8, 2023, with a strategy that included target site (pancreaticobiliary and related terms), diagnostic method (bile duct brushing and related terms), and keywords for diagnostic performance (for Cochrane database). Inclusion criteria included studies that have assessed bile duct cytology (BDC) for pancreaticobiliary duct stricture with a sample size of over 50, provided cytological diagnoses similar to the WHO system with details to deduce true positives, true negatives, false positives, and false negatives through subsequent final diagnoses (benign vs. malignant). The exclusion criteria were the fewer sample size, assessment through other cytological categories, limited data, and clinical setting. Two authors independently reviewed the result of the search strategy. The quality of the selected articles was assessed by the QUADAS-2 tool. Bivariate random-effects model was used to get the pooled sensitivity and specificity. Heterogeneity across studies was assessed using I-squared statistics, and potential sources were found using meta-regression. Pooled and a range of ROM in each category was analyzed. Results: Thirteen studies were included with 4,398 bile duct brushings. The pooled sensitivity is 0.437 (95% CI: 0.371–0.504), and the pooled specificity is 0.972 (95% CI: 0.943–0.987). The ROM in various categories are as follows: inadequate/nondiagnostic: 23–100% (pooled: 50.15%), benign/negative for malignancy: 22–70% (38%), atypical: 0–95% (66%), suspicious for malignancy: 74–100% (89%), malignant: 91–100% (98%). Conclusion: Even with standard cytological categories, the sensitivity of BDC remains low. The review has analyzed and discussed potential causes of heterogeneity that will be helpful for future diagnostic studies.