No gold standard test exists for gastroesophageal reflux disease (GERD). Diagnostic difficulties are greatest when reflux symptoms occur without visible esophageal mucosal damage at conventional endoscopy. However, two thirds of such patients do have microscopic esophageal lesions. This study aimed to develop and standardize criteria for recognizing these microscopic esophageal lesions in GERD. Draft histologic criteria were developed and tested by an international group of 5 independent gastrointestinal pathologists using 167 biopsy specimens from GERD patients and healthy controls (phase I). Draft criteria were refined and reassessed using 250 photographs of biopsy specimens (phase II). Histologic lesions evaluated were basal cell hyperplasia, papillary elongation, intraepithelial eosinophil, neutrophil and mononuclear cell number, necrosis/erosion, healed erosion, and dilated intercellular spaces. Interobserver agreement and kappa values increased significantly from phase I to II. When tested in annotated photographs (phase II), mean pairwise agreements were 74%, 89%, 93%, 97%, 81%, 97%, 94%, and 74%, respectively. Mean pairwise kappa estimates (+/-SD) were 0.49 (0.16), 0.81 (0.05), 0.87 (0.05), 0.84 (0.09), 0.60 (0.09), 0.90 (0.04), 0.73 (0.14), and 0.61 (0.08), respectively. Estimated intraclass correlation coefficients for basal cell layer thickness and papillary length increased from 0.38 and 0.56 to 0.69 and 0.95, respectively, when revised criteria were used. The draft criteria achieved promising levels of agreement when assessed independently by 5 pathologists. Further steps include evaluation of lesions without indicating the area to be assessed and exploring the correlation of microscopic esophagitis with symptoms and esophageal acid exposure.
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