Material and Methods
Based on a review of the medical literature, eight abnormalities were identified as features of EoE: fixed rings (also referred to as trachealisation), exudates (also referred to as plaques or white spots), furrows (also referred to as vertical lines and longitudinal furrows), oedema (also referred to as mucosal pallor), stricture, feline oesophagus (also referred to as transient mucosal plications), narrow calibre oesophagus (also referred to as small calibre oesophagus) and crepe paper oesophagus (also referred to as mucosal fragility). A grading scheme was developed for each of the eight abnormalities based on consensus opinion of three gastroenterologists (NG, SRA, IH) (Box 1). The primary features of rings, furrows, exudates and oedema were subcategorised into 2–3 grades. Strictures, narrow calibre oesophagus, feline oesophagus and crepe paper oesophagus were classified as present or absent.
A series of videos were selected from adult patients with EoE to include a minimum of four examples of each grade of each endoscopic characteristic with the exception of the crepe paper oesophagus where only two examples were available. The video recordings were obtained and reviewed by three gastroenterologists (NG, SRA, IH). In each case, EoE was defined in accordance with consensus recommendations to include symptoms of oesophageal dysfunction and histological evidence of ≥15 eosinophils per high power field (eos/hpf) in spite of double-dose proton pump inhibitors. Normal endoscopy videos were obtained from three patients undergoing upper endoscopy for indications who had normal oesophageal mucosal biopsies and randomly intermixed with EoE videos for analysis. One subject had dysphagia that was later identified as originating from a Zenker's diverticulum. A second control patient had dyspepsia and a third had primary laryngeal complaints. In addition, individual endoscopic features of EoE were not present in every patient with EoE.
Thirty-two endoscopists were invited to participate in a study designed to validate the interobserver agreement for the proposed classification and grading system of the oesophageal features of EoE using a series of endoscopic videos. Paediatric and adult gastroenterologists from settings that included academic medical centres, community practice and gastroenterology fellowship were included. Diversity in experience with EoE was encouraged, although the invited reviewers had clinical familiarity with the disease. Twenty-one endoscopists completed the prospective survey. Each endoscopist reviewed a DVD containing video clips from 25 patients demonstrating examples of the eight oesophageal features intermixed with normal videos. Before viewing the videos a colour pictorial atlas with representative images and written descriptions of the proposed grading scheme for EoE was provided to each reviewer (figure 1). The reviewers were blinded to the clinical and histological status of the patients corresponding with the videos. A survey form was provided to each reviewer for each video in order to document perceived mucosal abnormalities. In addition, a demographic survey was administered to each reviewer in order to obtain information regarding gender, age, level of training, practice population, years of experience after fellowship, approximate number of endoscopies performed per week and approximate number of patients with eosinophilic oesophagitis seen for consultative purposes. Expert reviewers were arbitrarily defined by endoscopists who had personally evaluated over 150 patients with EoE.
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Figure 1.
Reference pictorial atlas used for the grading system for the endoscopic assessment of the oesophageal features of eosinophilic oesophagitis. Categories for each feature are listed in Box 1. (A) Fixed oesophageal ring (trachealisation, ringed oesophagus, corrugated oesophagus). (B) Exudates (plaques). (C) Furrows (vertical lines). (D) Oedema (decreased vascular markings). (E) Transient oesophageal rings (feline oesophagus). (F) Crepe paper oesophagus (mucosal fragility).
Statistical Analysis
Numerical variables were summarised with the sample median, minimum and maximum. Agreement between endoscopists regarding assessment of endoscopic oesophageal abnormalities was assessed in two different ways. Multi-rater κ was estimated for each endoscopic abnormality along with the 95% CI. Owing to well-documented problems with the estimation and interpretation of κ—for instance, with it being highly influenced by marginal rates—the proportion of pairwise agreements between endoscopists for each endoscopic abnormality was also estimated along with the 95% CI. For a given endoscopic abnormality, the proportion of pairwise agreement results from a comparison of the grading of the endoscopic abnormality between each endoscopist and the remaining 20 endoscopists (210 total pairwise comparisons between endoscopists for one video) for each of the 25 videos (5250 total pairwise comparisons between endoscopists across all videos); the proportion of all pairwise comparisons where the grading of the endoscopic abnormality was exactly equal for the two endoscopists is reported. Interobserver agreement was interpreted based on a combination of estimates of κ and the proportion of pairwise agreements. Statistical analyses were performed using SAS V.9.2.