[1506] Immunostaining Findings in IgA Nephropathy: Correlation with Histology and Clinical Outcome in the Oxford Classification Patient Cohort

S Bellur, S Troyanov, HT Cook, ISD Roberts. John Radcliffe Hospital, Oxford, United Kingdom; Hôpital du Sacré-Coeur de Montréal, Montreal, Canada; Imperial College, London, United Kingdom

Background: IgA nephropathy is defined by the presence of IgA-dominant glomerular deposits. Within this definition there is variation in the location of IgA and the presence of other immunoglobulins. The Oxford Classification of IgA nephropathy identifies 4 histological features that are independent predictors of clinical outcome but does not include immunostains. Here we investigate the potential clinical significance of immunostaining data.
Design: Original biopsy reports from patients in the Oxford Classification study were reviewed. The location of IgA deposits (mesangial vs mesangial + capillary wall) and the presence of IgG >trace were correlated with histological and clinical features.
Results: Original biopsy reports were available for 211 of 265 patients in the Oxford Classification cohort. Of these, 175 included sufficient detail to subclassify immunostaining findings. The presence of capillary wall IgA deposits was associated with a higher mesangial cellularity score (1.28 ±0.65 vs 0.89 ±0.51 for mesangial-only IgA, p=0.004) and more endocapillary proliferation (% of glomeruli 12.2 ±16 vs 5.3 ±12.1, p=0.003). Similarly, the presence of IgG, was associated with a trend to higher mesangial cellularity score (1.16 ±0.64 vs 0.91 ±0.54, p=0.059) and more endocapillary proliferation (10.4 ±14.1 vs 5.1 ±12.1, p=0.005). Capillary wall IgA and the presence of IgG were associated with younger age at diagnosis and greater immunosuppression (IS). The % of patients who received IS was 35% of those with capillary wall IgA vs 23% with mesangial-only IgA, and 37% of those with IgG vs 21% with no IgG. These differences did not reach statistical significance but are a potential source of bias when interpreting the impact of immunostaining findings on clinical outcome. Analysis of follow-up data revealed no significant association between the location of IgA or presence of IgG and rate of loss of renal function, and no association between the location of IgA and renal survival. There was a trend towards poorer renal survival in those patients with glomerular IgG (p=0.055).
Conclusions: We conclude that the location of glomerular IgA and the presence of IgG correlate with mesangial and endocapillary cellularity but do not independently predict clinical outcome. These findings do not support the inclusion of immunostaining data in the Oxford Classification.
Category: Kidney (does not include tumors)

Wednesday, March 24, 2010 1:00 PM

Poster Session VI # 235, Wednesday Afternoon


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