Background. Standardized histological grading of transplant kidney biopsies has become a primary criterion for diagnosis of rejection in immunosuppression clinical trials. Methods. A consortium of 19 transplant centers from North America, Europe, and Australia convened in 1995 to examine kidney transplant rejection. Data from the 1995 Efficacy Endpoints Conference were examined for frequency of adoption of Banff schema. Biopsy grading was correlated with clinical parameters of rejection and therapy response. Results. Histological confirmation of rejection episodes occurred in 73% of 953 cases, with Banff criteria adoption increasing in frequency between 1992 and 1995. Banff grading significantly correlated with clinical rejection severity (rejection creatinine: grade I, 2.8 ± 0.2 mg/dl; grade II, 3.5 ± 0.2 mg/dl; grade III, 4.1 ± 0.3 mg/dl; P<0.001), although nadir creatinines were similar. Response rates of Banff grades I and II to steroid therapy were not different, but only 42% of grade III rejections responded to steroids (P<0.003. Banff grading also correlated with postrejection creatinine, day 15: grade I, 2.2 ± 0.2 mg/dl; grade II, 3.0 ± 0.2 mg/dl; grade III, 3.8 ± 0.4 mg/dl (P<0.001), and day 30: grade I, 2.1 ± 0.1 mg/dl; grade II, 2.2 ± 0.2 mg/dl; grade III, 2.7 ± 0.2 mg/dl (P<0.06). Banff grade III correlated with reduced graft survival at 1 year: grade I, 86%; grade II, 88%; grade III, 70% (P<0.01). Conclusions. This multicenter review of rejection severity confirms that standardized histologic classifications such as the Banff schema provide a reliable means for stratifying patient risk of treatment success or failure. These data support the use of Banff criteria in clinical trial design.
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