Prospective, Blinded Assessment of Factors Influencing Accuracy of Biliary Cytology Interpretation

Abstract

Background: There is little published data assessing factors which influence the accuracy of biliary cytology interpretation. The aim of this study was to: a) prospectively compare inter-observer variability among two blinded pathologists interpreting biliary cytology specimens, b) describe the predictors of inter-pathologist agreement, and c) characterize the predictors of accurate cytology interpretation. Methods: In total, 113 consecutive patients undergoing ERCP with brushing of suspicious biliary tract strictures were prospectively enrolled to assess routine cytology (RC) accuracy. Initial RC interpretation was performed by the pathologist on duty with the benefit of the patients clinical information. Subsequent interpretation was performed by 2 independent pathologists blinded to the patients clinical details. Strictures were classified as benign on the basis of surgical confirmation or cancer-free clinical course for at least 6 months or malignant if confirmed by histology or progressive disease on subsequent imaging studies. Results: Of 113 patients, 67 had malignant strictures and 46 had benign strictures. Between the three pathologists the sensitivity of RC varied significantly from 9% to 24% (p=0.02), while the specificity varied from 61% to 100% (p<0.001) (see table). Overall accuracy however did not vary significantly (39% to 51% p = n.s.). The rate of equivocal readings was significantly lower when interpreted by the pathologist who had the clinical information (2%) compared to those pathologists blinded to clinical information (p<0.001). Overall correlation of both blinded pathologists interpretations was only moderate, r = 0.51. Cytology accuracy declined with increasing patient age, OR = 0.18 (95% C.I., 0.07 to 0.39; p<0.0001) for >59 years vs <59 years (median age). Neither cytology accuracy nor inter-pathologist agreement improved with increasing specimen cellularity. Conclusions: Inter-pathologist variation for biliary cytology interpretation is high. Knowledge of the patients clinical information appears to clarify cytology interpretation resulting in fewer equivocal results. Reliable predictors of cytology accuracy, including a more cellular specimen, were not detected.