Multi-institutional development and validation of a novel histologic grading system for colonic graft-versus-host disease.

Graft-versus-host disease (GVHD) remains a major complication for patients who have undergone hematopoietic stem cell transplantation. The Lerner system is the most widely used histologic grading score for gastrointestinal GVHD but its clinic utility is debated. The aim of our study was to develop a novel histologic grading system for gastrointestinal GVHD that incorporates independent evaluation of both apoptotic counts and crypt destruction. Colonic biopsies taken to assess for GVHD were retrospectively assessed for: Crypt damage (No crypt dropout or ulceration-0; crypt dropout without ulceration-1; ulceration-2) and crypt apoptotic counts (No apoptosis-0; 1-6 apoptotic bodies per 10 contiguous crypts-1; >6apoptotic bodies per 10 contiguous crypts-2). The two scores were added together to get an overall grade (0-4). Alternative apoptotic cutoff points were examined. An apoptotic cutoff of >9 apoptotic bodies per 10 contiguous crypts marginally improved the area under the curve (AUC), but the AUCs from the resulting novel grade calculations were not significantly different (p = 0.10). Lerner grading was also applied. The study group consisted of an initial analysis cohort (n = 191) and a second validation cohort from a separate institution (n = 97). In the initial analysis cohort, our histologic grading system provided prognostic stratification for GVHD-related death within 6 months (p = 0.0004, AUC = 0.705). The Lerner system performed similarly in terms of providing prognostic stratification for GVHD-related death (p = 0.0001, AUC = 0.707). In the external validation cohort, our histologic grading system was not associated with GVHD-related death (p = 0.14, AUC = 0.621), but the Lerner system was associated with GVHD-related death (p = 0.048, AUC = 0.663). While our grading system may have some advantages compared to the Lerner system, due to lack of reproducibility we do not currently recommend widespread adoption of this system. Nonetheless, we present a standardized tool for assessing both apoptosis and crypt damage. Future studies assessing alternative histologic grading systems with external validation and further examination the lower apoptotic threshold for GVHD diagnosis are warranted.