Solez K et al. (2008) Banff 07 classification of renal allograft pathology: updates and future directions. Am J Transplant 8: 753–760

Solez et al. have reported the conclusions of the 9th Banff Conference on Renal Allograft Pathology, held in La Coruña, Spain in June 2007. At this conference, the Banff criteria for renal allograft rejection were updated to include peritubular capillaritis scoring, complement degradation component C4d scoring, the reporting of C4d deposition in the absence of morphological evidence of active allograft rejection, and application of the criteria to biopsy samples taken at the time of transplantation. Other additions to the classification, the use of which remains optional pending 2 years of testing, are the scoring of total interstitial inflammation ('ti') and an alternative scoring system for hyaline arteriolar thickening. All existing scoring categories are unchanged.

In accordance with the updated classification, peritubular capillaritis should be scored from ptc 0 to ptc 3, on the basis of the percentage of inflamed capillaries in the sample and the number of inflammatory cells present. The composition of the inflammatory cell population (monocytes vs neutrophils) and the extent of capillaritis (focal 10–50% vs diffuse >50%) should be noted. C4d staining is scored from C4d0 (negative) to C4d3 (diffuse >50% of the sample). The current system for scoring arteriolar hyaline thickening ('ah') was reported to have very poor reproducibility (κ = 0.18); therefore, an alternative system ('aah'), in which the severity of arteriolopathy is quantified by the presence of circular or noncircular involvement and the number of affected arterioles, will be tested. Improved reproducibility with the new system (κ = 0.67) has already been reported.

Finally, working parties have been set up to explore the potential role of new gene-expression technologies in the diagnosis of graft rejection.