Classification of probe-based confocal laser endomicroscopy findings in pancreaticobiliary strictures^[*]

Background and study aims: The accurate diagnosis of indeterminate pancreaticobiliary strictures presents a clinical dilemma. Probe-based confocal laser endomicroscopy (pCLE) offers real-time in vivo microscopic tissue examination that may increase sensitivity for the detection of malignancy. The objective of this study was to develop and validate a standard descriptive classification of pCLE in the pancreaticobiliary system.

Patients and methods: A total of 102 patients undergoing endoscopic retrograde cholangiopancreatography (ERCP) with pCLE to assess indeterminate pancreaticobiliary strictures were enrolled in a multicenter registry; 89 of these patients were evaluable. Information and data on the following were collected prospectively: clinical, ERCP, tissue sampling, pCLE, and follow-up. A uniform classification of pCLE findings (“Miami Classification”) was developed, consisting of a set of image interpretation criteria. Thereafter, these criteria were tested through blinded consensus review of 112 randomized pCLE videos from 47 patients, and inter-observer variability was assessed in 42 patients.

Results: A consensus definition of the specific criteria of biliary and pancreatic pCLE findings for indeterminate strictures was developed. Single-image interpretation criteria did not have a high enough sensitivity for predicting malignancy. However, combining two or more criteria significantly increased the sensitivity and predictive values. The characteristics most suggestive of malignancy included the following: thick white bands (> 20 µm), or thick dark bands (> 40 µm), or dark clumps or epithelial structures. These provided sensitivity, specificity, positive predictive value, and negative predictive value of 97 %, 33 %, 80 %, and 80 % compared with 48 %, 100 %, 100 %, and 41 % for standard tissue sampling methods. Inter-observer variability was moderate for most criteria.

Conclusion: The Miami Classification enables a structured, uniform, and reproducible description of pancreaticobiliary pCLE. Combining individual characteristics improves the sensitivity for the detection of malignancy.

^* This paper is dedicated to Yang K. Chen and Peter D. Stevens who both sadly passed away after courageous battles against cancer.

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