The catheter flushing method increases the diagnostic yield of brushing cytology for biliary strictures

Abstract

Background and Aim: Endobiliary brushing is usually performed in the diagnosis of indeterminate biliary strictures; however, in this setting, brush cytology is limited by a low diagnostic yield and sensitivity. Here, we evaluated whether the catheter flushing method (CFM) could improve cellularity and diagnostic performance compared with the conventional cytologic method (CCM). Methods: Endobiliary brushings were obtained during endoscopic retrograde cholangiopancreatography (ERCP) from patients with biliary strictures enrolled at six tertiary hospitals. Additional CFM was performed after brushing. Using liquid-based cytologic preparations of samples, we assessed the diagnostic performance of the CCM using Pap staining and the CFM using methionyl-transfer RNA synthetase 1 (MARS1) immunofluorescence staining. Results: From a total of 399 patients (malignant, 253; benign, 146), 374 CCM samples and 361 CFM samples contained adequate cells, with no significant difference in diagnostic yield (93.7% vs. 90.5%, respectively, P = 0.721). The sensitivity of the CFM (90.3%) was significantly higher than that of the CCM (75.1%; P < 0.001), with no significant difference in accuracy between methods (81.2% vs. 82.6%, respectively; P = 0.608). Conclusions: Diagnostic yield was equivalent between CCM and CFM. Also, the high sensitivity and similar accuracy of the CFM compared with the CCM indicates that the CFM could be an additional brush cytology method for detecting malignancy in patients with indeterminant biliary strictures. Further prospective studies are needed to validate these findings.