Background & Aims: Ancillary cytologic tests including digital image analysis (DIA) and fluorescence in situ hybridization (FISH) have been developed to improve the sensitivity of routine cytology (RC) for the diagnosis of malignancy in pancreatobiliary strictures. The goal of this study was to retrospectively compare the performance of RC, DIA, and FISH on clinical brushing specimens. Methods: Endoscopic retrograde cholangiopancreatography brushings were obtained from 498 consecutive patients with pancreatobiliary strictures and analyzed by RC, DIA, and FISH as per standard practice. RC diagnostic categories included negative, atypical, suspicious, or positive. Aneuploid/tetraploid histograms were considered positive for DIA. FISH was performed using UroVysion (Abbott Molecular, Inc, Des Plaines, IL) and classified as negative, trisomy, tetrasomy, or polysomy. Results: The sensitivity of polysomy FISH (42.9%) was significantly higher than RC (20.1%) when equivocal RC results were considered negative (P < .001) with identical specificity (99.6%). There was a significant difference in time for diagnosis of carcinoma between FISH diagnostic categories (P < .001) and between RC diagnostic categories (P < .001). Logistic regression analysis revealed that polysomy FISH, trisomy FISH, suspicious cytology, primary sclerosing cholangitis status, and age were associated with carcinoma (P < .05). Conclusions: Polysomy FISH had high sensitivity without compromise to specificity. DIA was not a significant independent predictor of malignancy. Multivariable modeling using RC, FISH, age, and primary sclerosing cholangitis status can be used to estimate the probability of carcinoma for an individual patient. We recommend including FISH as a routine test where available, along with RC, in the evaluation of indeterminate pancreatobiliary strictures.
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