Investigation of Factors Affecting the Sensitivity of Bile Duct Brush Cytology

Objectives While bile duct brush cytology during endoscopic retrograde cholangiopancreatography (ERCP) is a well-established procedure for detecting malignant biliary stricture, its sensitivity is reportedly low. We aimed to determine the pre-ERCP factors affecting brush cytology sensitivity. Methods We retrospectively analyzed 185 patients who underwent brush cytology during the first ERCP for undiagnosed biliary stricture at our institution between January 2014 and December 2016. We analyzed the relationship of age, sex, final diagnosis, stricture location, tumor size, stricture length, total bilirubin level, white blood cell count, and C-reactive protein level with brush cytology sensitivity. Results The following conditions were established as final diagnoses: benign disease, 19 cases (10.3%); intrahepatic cholangiocarcinoma, 10 cases (5.4%); hilar cholangiocarcinoma, 38 cases (20.5%); extrahepatic cholangiocarcinoma, 44 cases (23.8%); pancreatic cancer, 55 cases (29.7%); other malignant tumors, 19 cases (10.3%). The sensitivity and specificity of brush cytology were 60.8% and 94.7%, respectively. The stricture length, total bilirubin level, and white blood cell count in true-positive cases were significantly higher than those in false-negative cases. Furthermore, a stratified analysis of the bilirubin levels demonstrated that sensitivity was highest in patients with moderate jaundice (80% for a total bilirubin level of 10-20 mg/dL), but significantly lower in patients with severe jaundice (total bilirubin level ≥20 mg/dL). Conclusion While the sensitivity of brush cytology increases with bilirubin levels of up to 20 mg/dL, severe jaundice has a negative effect on sensitivity, warranting additional pathological examinations according to the pre-ERCP bilirubin level.