Prognostic Value of Endocapillary Proliferation in IgA Nephropathy Patients with Minimal Immunosuppression
Aron Chakera, Clare MacEwen, Shubha S Bellur, La-or Chompuk, Daniel Lunn, Ian SD Roberts. Sir Charles Gairdner Hospital, Nedlands, Australia; Churchill Hospital, Oxford, United Kingdom; John Radcliffe Hospital, Oxford, United Kingdom; University of Oxford, Oxford, United Kingdom
Background: Interpretation of the Oxford Classification study of IgA nephropathy (IgAN), and subsequent validation studies, is confounded by immunosuppression (IS) bias. In these studies, a median of 38% of patients have received IS. In no study does endocapillary proliferation (E score) independently predict outcome. This may reflect bias from higher levels of IS in patients with endocapillary proliferation that is reported in these studies. In order to determine the true value of E score, retrospective analysis of patient cohorts that have received little or no IS, irrespective of histology, is required.
Design: We performed a retrospective single centre study of patients diagnosed with IgAN. Our unit takes a conservative approach to IS in IgAN and steroid/cytotoxic therapy is rare. Biopsies were reviewed and scored according to Oxford Classification (MEST) criteria. The primary outcome was rate of loss of renal function, dichotomised to slow and fast loss (< and >5ml/min/year), the secondary outcome development of end-stage renal disease (ESRD; CKD stage 5).
Results: 237 patients with IgAN were identified, mean follow up 82 months. 200 had biopsies available for review, of which 44 were inadequate for scoring (<8 glomeruli), leaving 156 patients with a clinical & histological dataset that were included for analysis. Summary of clinical data, expressed as mean (standard deviation): age at diagnosis 42 (15) years, initial eGFR 50 (25) ml/min/1.73m2, uPCR 250 (281), MAP 107 (16) mm/Hg, delta-eGFR -2.8 (23.5). Only 8/156 patients (5%) received steroid/cytotoxic therapy. In multivariate analysis, including histology & clinical data at diagnosis, the only independent predictors of subsequent ESRD were eGFR (p=0.018) & proteinuria at the time of diagnosis (p=0.004); histology scores did not provide additional prognostic information. Independent predictors of fast loss of eGFR were proteinuria (p=0.008), E (p=0.034) & T scores (p=0.007).
Conclusions: We conclude that in a cohort of IgAN patients receiving little immunosuppression, endocapillary proliferation and tubular atrophy/interstitial fibrosis are independent predictors of rate of loss of renal function. The lack of predictive value of E score in all other clinicopathological studies is most likely a result of IS-associated bias. Our findings provide additional evidence to support IS treatment of endocapillary-pattern IgAN.
Category: Kidney (does not include tumors)
Monday, March 4, 2013 1:00 PM
Poster Session II # 237, Monday Afternoon