SIGNIFICANCE OF THE BANFF BORDERLINE BIOPSY

In the Banff classification of kidney transplant pathology the ''borde rline changes'' category falls short of a diagnosis of mild acute reje ction, with the recommendation that no treatment is a possible clinica l approach. We reviewed the clinical course of patients whose renal al lograft biopsies showed ''borderline changes'' to determine how often these histologic findings actually represented acute rejection. Betwee n January 1992 and June 1994, 351 biopsy specimens were obtained from 170 renal allografts and graded according to the Banff criteria. Eight y-one biopsy specimens were classified as ''borderline changes'' (23%) . Of these, 59 had Banff scores of i1, t1, and v0; the remaining 22 ha d scores of i2, t1, and v0 (i = interstitial infiltrate, t = tubulitis , and v = vasculitis). Medical record review showed that nearly all th e ''borderline'' biopsies had been performed because of an elevated cr eatinine (Cr; 78 of 81 [96%]), with a mean increase of 1.1 +/- 0.1 mg/ dL (+/-SE) over baseline. Most of the patients with ''borderline chang es'' and elevated Cr were treated for acute rejection (61 of 78 [78%]) ; some with pulse steroids alone (29 of 61 [48%]), the rest with antil ymphocyte antibody (32 of 61 [52%]). Among all 61 patients with ''bord erline'' biopsies treated for rejection, 26 had a complete response (4 3%), 17 had a partial response (28%), and 18 had no response (30%). In terpretation of these changes in Or, however, was confounded by interc urrent conditions in 28 of the patients. A group of 33 patients was th erefore identified in whom a ''borderline changes'' biopsy was obtaine d, who were treated for rejection, and in whom all other identifiable causes of elevated Or other than possible acute rejection had been sys tematically eliminated from consideration. In this group the mean Or w as 2.0 +/- 0.1 mg/dL at baseline, 3.3 +/- 0.2 mg/dL at the time of bio psy, and 2.2 +/- 0.1 mg/dL 1 month after treatment (P < 0.001 Cr at bi opsy v Cr 1 month later). Among these 33 patients, 19 had a complete r esponse (58%), 10 had a partial response (30%), and four had no respon se (12%). Therefore, the Or in 88% of the patients in this group was l ower 1 month after treatment for rejection than it was at the time of the biopsy. Follow-up biopsies were performed within 1 month of the '' borderline'' biopsy in 24 cases; these showed ''borderline changes'' ( five of 24 [21%]), mild acute rejection (eight of 24 [33%]), or modera te to severe acute rejection (11 of 24 [46%]). We conclude that in the clinical setting of deteriorating renal graft function with mild elev ation of serum Cr, the ''borderline changes'' biopsy frequently repres ents acute rejection. Antirejection treatment is therefore appropriate in the majority of cases. The reader should bear in mind that the cur rent study is retrospective, with no control group. The risk of loosel y interpreting these data is that some patients will be treated withou t due cause. Banff ''borderline changes'' should be used as part of an algorithm, but not the sole criterion, for therapeutic decision makin g. (C) 1996 by the National Kidney Foundation, Inc.