Variability in small bowel histopathology reporting between different pathology practice settings: impact on the diagnosis of coeliac disease

Background and Aims Coeliac disease (CD) diagnosis requires the detection of characteristic histological alterations of small bowel mucosa, which are prone to interobserver variability. This study evaluated the agreement in biopsy interpretation between different pathology practice types. Methods Biopsies from community hospitals (n = 46), university hospitals (n = 18) and commercial laboratories (n = 38) were blindly assessed by a pathologist at our institution for differences in histopathology reporting and agreement in diagnosis of CD and degree of villous atrophy (VA) by kappa analysis. Results Agreement for primary diagnosis was very good between this institution and university hospitals (kappa = 0.888), but moderate compared with community hospitals (kappa = 0.465) or commercial laboratories (kappa = 0.419). Diagnosis differed in 26 (25%) cases, leading to a 20% increase in CD diagnosis after review. Among those diagnosed with CD by both institutions (n 49), agreement in degree of VA was fair (kappa = 0.292), with moderate agreement between the authors and commercial laboratories (kappa = 0.500) and fair with university hospitals (kappa = 0.290) or community hospitals (kappa = 0.211). The degree of VA was upgraded in 27% and downgraded in 2%. Within different Marsh score categories, agreement was poor (kappa < 0.0316) for scores 1 and 2, both missed at other centres, and fair or moderate for scores 3a and 3b. Information regarding degree of VA and intraepithelial lymphocytosis was lacking in 26% and 86% of reports and non-quantifiable descriptors, eg, 'blunting' or 'marked atrophy' were prevalent. Conclusions CD-related histological changes are underdiagnosed in community-based hospitals and commercial pathology laboratories. Because incorrect biopsy interpretation can cause underdiagnosis of CD, greater CD awareness and uniformity in small bowel biopsy reporting is required among pathologists.