Original contribution Development of consensus guidelines for the histologic recognition of microscopic esophagitis in patients with gastroesophageal reflux disease: the Esohisto project ☆,☆☆ Roberto Fiocca MD a, ⁎ , Luca Mastracci MD a , Robert Riddell MD b , Kaiyo Takubo MD c , Michael Vieth MD d , Lisa Yerian MD e , Prateek Sharma MD f , Paula Fernström MSc g , Magnus Ruth MD g a Department of Anatomic Pathology, University of Genoa, Genoa, Italy b Department of Pathology, Mount Sinai Hospital, Toronto, Canada c Department of Clinical Pathology, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan d Institute of Pathology, Klinikum Bayreuth, Bayreuth, Germany e Department of Anatomic Pathology, Cleveland Clinic, Cleveland, OH f Division of Gastroenterology and Hepatology, University of Kansas School of Medicine, Kansas City, KS, USA g AstraZeneca R&D, Mölndal, Sweden Received 26 March 2009; revised 18 July 2009; accepted 23 July 2009 Keywords: Consensus development; Esophageal histology; Esophagitis; Gastroesophageal reflux disease Summary 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 κ 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 κ 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 ☆ AstraZeneca R&D, Mölndal, Sweden, provided economic support for travel arrangements, logistics, biopsy specimens/photos and statistical analyses. ☆☆ Conflicts of interest: None declared: R. Fiocca, L. Mastracci, R. Riddell, K. Takubo, M. Vieth, L. Yerian, P. Sharma. Employees of AstraZeneca: P. Fernström, M. Ruth. ⁎ Corresponding author. Division of Anatomical Pathology, University of Genoa, Via De Toni 14, 16132 Genoa, Italy. E-mail address: fiocca@unige.it (R. Fiocca). www.elsevier.com/locate/humpath 0046-8177/$ – see front matter © 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.humpath.2009.07.016 Human Pathology (2010) 41, 223–231