Development and Validation of Confocal Endomicroscopy Diagnostic Criteria for Low-Grade Dysplasia in Barrett's Esophagus

Abstract

Objectives: Low-grade dysplasia (LGD) in Barrett's esophagus (BE) is generally inconspicuous on conventional and magnified endoscopy. Probe-based confocal laser endomicroscopy (pCLE) provides insight into gastro-intestinal mucosa at cellular resolution. We aimed to identify endomicroscopic features and develop pCLE diagnostic criteria for BE-related LGD.

Methods: This was a retrospective study on pCLE videos generated in 2 prospective studies. In phase I, 2 investigators assessed 30 videos to identify LGD endomicroscopic features, which were then validated in an independent video set (n = 25). Criteria with average accuracy >80% and interobserver agreement κ > 0.4 were taken forward. In phase II, 6 endoscopists evaluated the criteria in an independent video set (n = 57). The area under receiver operating characteristic curve was constructed to find the best cutoff. Sensitivity, specificity, interobserver, and intraobserver agreements were calculated.

Results: In phase I, 6 out of 8 criteria achieved the agreement and accuracy thresholds (i) dark nonround glands, (ii) irregular gland shape, (iii) lack of goblet cells, (iv) sharp cutoff of darkness, (v) variable cell size, and (vi) cellular stratification. The best cutoff for LGD diagnosis was 3 out of 6 positive criteria. In phase II, the diagnostic criteria had a sensitivity and specificity for LGD of 81.9% and 74.6%, respectively, with an area under receiver operating characteristic of 0.888. The interobserver agreement was substantial (κ = 0.654), and the mean intraobserver agreement was moderate (κ = 0.590).

Conclusions: We have generated and validated pCLE criteria for LGD in BE. Using these criteria, pCLE diagnosis of LGD is reproducible and has a substantial interobserver agreement.

Figure 1.

Schematic representation of study flowchart. In phase I (left), 2 investigators (one pathologist and one probe-based confocal laser endomicroscopy (pCLE)-experienced endoscopist) identified recurrent endomicroscopic features in low-grade dysplasia by blinded assessment of pCLE video sequences. Three investigators (one pathologist and 2 pCLE-experienced endoscopists) performed the initial validation of the criteria for the selection of the final diagnostic panel. In phase II (right), 6 endoscopists with different level of experience in pCLE performed the external validation on an independent video set (n = 57). The diagnostic accuracy and the interobserver agreement were calculated.

Figure 2.

Final probe-based confocal laser endomicroscopy (pCLE) diagnostic panel, with pCLE view (top) and histological finding from the same endoscopic area (bottom). (a) dark nonround glands, (b) irregular gland shape, (c) lack of goblet cells, (d) variable degree of darkness with sharp cutoff (yellow arrowhead indicate transition points), (e) variable cell size (yellow arrowheads indicate the site of cellular pleomorphism), and (f) cellular stratification (yellow arrows indicate the 2 levels where cells are located). Although precise correspondence between glandular elements showed in the confocal and pathology image is difficult to be ascertained, similar features were observed on pCLE and histology.