Crypt apoptotic count reproducibility in small bowel allograft biopsies

Enumeration of crypt apoptotic bodies (AB) is used in the diagnosis of acute cellular rejection (ACR) in small bowel allografts. Due to differing definitions, there is a potential for variation in AB numbers between pathologists that may affect diagnosis. Thirty biopsies from allografts were obtained: 10 negative for ACR, 10 indeterminate, and 10 with mild ACR. Three pathologists blindly reviewed each case twice and counted the maximal AB number per 10 crypts. Intraobserver kappa ranged from 0.423 to 0.913 and interobserver kappa from 0.478 to 0.686 depending on AB definition. Intraobserver diagnosis agreement based on classical AB number occurred in 81 of 90 instances (90%) and in 77 of 90 using the liberal definition (85%), P < .01). There was substantial intraobserver and moderate to substantial interobserver agreement in crypt AB counts. However, both intraobserver and interobserver variability would have led to diagnostic discrepancies in a small subset of cases.