EVALUATION OF PANCREAS TRANSPLANT NEEDLE-BIOPSY - REPRODUCIBILITY ANDREVISION OF HISTOLOGIC GRADING SYSTEM

Background. Tissue samples for the diagnosis of pancreatic allograft r ejection are now obtained routinely through the application of the per cutaneous needle biopsy technique. The availability of biopsy material (89% adequate for diagnosis in our setting) presents a challenge for pathologists who are asked to provide a fast and accurate diagnosis of rejection and its severity, while at the same time being able to diff erentiate rejection from other causes of graft dysfunction. Methods. T o differentiate rejection from other pathologic processes, 26 histolog ic features were assessed in 92 biopsies performed for confirmation of clinical diagnosis of rejection and the results were compared with 31 protocol biopsies, 12 allograft pancreatectomies with non-rejection p athology, and 30 native pancreas resections with various disease proce sses. Results. Based on these comparisons, a constellation of findings relating to the vascular, septal, and acinar inflammation was identif ied for the diagnosis of rejection. Application of these features led us to revise our scheme for grading rejection (ranging from O-normal t o V-severe rejection) to include the categories of ''inflammation of u ndetermined significance'' and ''minimal rejection.'' The scheme was u sed by five pathologist to grade 20 biopsies independently of any clin ical data and the interobserver level of agreement was highly signific ant (kappa=0.83, P<0.0001). This grading scheme was applied blindly to all (183) biopsies from 77 patients with 6-52 months of follow-up. Th e correlation of the highest degree of rejection on each patient and u ltimate graft loss (0% for grades 0-I, 11.5% for grade II, 17.3% for g rade III, 37.5% for grade IV, and 100% for grade V) was highly statist ically significant (P<0.002). The fraction of grafts lost due to pure immunologic causes increased proportionally to the grade of rejection (0, 50, 66, and 100% for grades II, III, IV, and V, respectively). Con clusions. This study provides strong support for the proposed pancreas rejection grading scheme and confirms its potential for practical use .