Background. The Banff classification for assessment of renal allograft biopsies was introduced as a standardized international classification of renal allograft pathology and acute rejection. Subsequent debate and evaluation studies have attempted to develop and refine the classification. A recent alternative classification, known as the National Institutes of Health Collaborative Clinical Trials in Transplantation (NIH-CCTT) classification, proposed three distinct types of acute rejection. The 1997 Fourth Banff meeting appeared to move towards a consensus for describing transplant biopsies, which incorporated both approaches. Patients who received a renal allograft at the Oxford Transplant Centre were managed by a combination of protocol and clinically indicated biopsies. We have undertaken a retrospective analysis of the biopsies correlated with the clinical outcome to test the prognostic value of the original Banff (Banff 93-95) and NIH-CCTT classifications. Methods. Three hundred and eighty-two patients received renal allografts between May 1985 and December 1989, and were immunosuppressed using a standard protocol of cyclosporine, azathioprine and steroid. Adequate 5-year follow-up data were available on 351 patients, and of these, 293 had at least one satisfactory biopsy taken between days 2 and 35 after transplantation, the latter patients forming the study group. The D2-35 biopsies taken from these patients, which were not originally reported according to the Banff classification, were re-examined and classified according to the Banff 93-95 protocols. For each patient the biopsy found to be the most severely abnormal was selected, and the Banff and NIH-CCTT grading compared with the clinical outcome. Results. Seven hundred and forty-three biopsies taken from 293 patients between days 2 and 35 after transplantation were examined and the patients categorized on the basis of the 'worst' Banff grading as follows. Normal or non-rejection, 20%; borderline, 34%; acute rejection grade I (AR I), 18%; AR IIA, 6%; AR IIB, 14%; AR III, 1%; AR IIIC, 3%; widespread necrosis 3%. The clinical outcome for the last two groups combined was very poor with 18% of grafts functioning at 3 months and 6% at 5 years. The other groups with vascular rejection (AR IIB and AR III) had an intermediate outcome, graft survival being 78% at 3 months and 61% at 5 years. The remaining four groups (normal, borderline, cellular AR I and AR IIA) had the best outcome: graft survival 95% at 3 months and 78% at 5 years with virtually no difference between the four groups. Three forms of acute rejection, namely tubulo-interstitial, vascular and transmural vascular, were identified, but only the latter two categories were associated with a poor outcome. Conclusions. The eight sub-categories of the Banff classification of renal allograft biopsies are associated with three different prognoses with respect to graft survival in the medium term. These three prognostic groups correspond to the three NIH-CCTT types. The data provide support for the consensus developed at Banff 97 separating tubulo-interstitial, vascular and transmural vascular rejection (types I, II and III acute rejection).
