Usefulness of Oxford Classification in Assessing Immunoglobulin A Nephropathy After Transplantation

Background. We explored the efficacy of the Oxford classification for assessing native immunoglobulin A nephropathy (IgAN) in posttransplantation patients compared with the glomerular injury score and Haas classification. Methods. A total of 125 renal allograft biopsies obtained from 114 patients diagnosed with IgAN regardless of original disease were assessed. Results. The average time to biopsy was 70.5+/-45.3 months after transplantation. Glomeruli showed normal histology in 18.4%. Mesangial hypercellularity (M1), endocapillary hypercellularity (E1), segmental glomerulosclerosis (S1), and tubulointerstitial fibrosis (T1-2) were present in 12.8%, 6.4%, 45.6%, and 20.8% of the samples, respectively. There was a significant correlation between Oxford-MEST scores and glomerular injury score or Haas subclass. S1 and T1-2 were correlated with elevated serum creatinine level, proteinuria, and decreased estimated glomerular filtration rate, and E1 was correlated with decreased estimated glomerular filtration rate at the time of biopsy. The 10- and 15-year graft survival rates were 62.9% and 34.3%, respectively. The graft survival rate was significantly lower in the presence of S1 and T1-2. Endocapillary hypercellularity, segmental sclerosis, and tubulointerstitial fibrosis predicted graft survival and endocapillary hypercellularity and tubulointerstitial fibrosis also predicted serum creatinine doubling. Conclusions. The Oxford classification scheme is useful for evaluating chronic graft dysfunction in patients with posttransplantation IgAN. In addition to tubulointerstitial fibrosis, the presence of endocapillary hypercellularity and segmental sclerosis should be included in the pathology report.