INTERNATIONAL STANDARDIZATION OF CRITERIA FOR THE HISTOLOGIC DIAGNOSIS OF RENAL-ALLOGRAFT REJECTION - THE BANFF WORKING CLASSIFICATION OF KIDNEY-TRANSPLANT PATHOLOGY

A group of renal pathologists, nephrologists, and transplant surgeons met in Banff, Canada on August 2-4, 1991 to develop a schema for inter national standardization of nomenclature and criteria for the histolog ic diagnosis of renal allograft rejection. Development continued after the meeting and the schema was validated by the circulation of sets o f slides for scoring by participant pathologists. In this schema intim al arteritis and tubulitis are the principal lesions indicative of acu te rejection. Glomerular, interstitial, tubular, and vascular lesions of acute rejection and ''chronic rejection'' are defined and scored 0 to 3+, to produce an acute and/or chronic numerical coding for each bi opsy. Arteriolar hyalinosis (an indication of cyclosporine toxicity) i s also scored. Principal diagnostic categories, which can be used with or without the quantitative coding, are: (1) normal, (2) hyperacute r ejection, (3) borderline changes, (4) acute rejection (grade I to III) , (5) chronic allograft nephropathy (''chronic rejection'') (grade I t o III), and (6) other. The goal is to devise a schema in which a given biopsy grading would imply a prognosis for a therapeutic response or long-term function. While the clinical implications must be proven thr ough further studies, the development of a standardized schema is a cr itical first step. This standardized classification should promote int ernational uniformity in reporting of renal allograft pathology, facil itate the performance of multicenter trials of new therapies in renal transplantation, and ultimately lead to improvement in the management and care of renal transplant recipients.