Predictors of outcome in paediatric IgA nephropathy with regard to clinical and histopathological variables (Oxford classification)

There has been a lack of international consensus on the classification and the predictive value of the histopathology findings in IgA nephropathy (IgAN). Recently, the International IgA Nephropathy Network has developed the Oxford classification in which four histological variables with the most prognostic importance are identified (MEST score). Our objective was to validate these findings and to assess their predictive power in our cohort and to compare them to identified clinical predictors. Ninety-nine children with a follow-up time > 5 years were included and investigated with clearances of inulin or iohexol for glomerular filtration rate (GFR), proteinuria and blood pressure at biopsy and during follow-up. Biopsies (90/99) were re-evaluated and scored according to the Oxford classification. Eighteen patients progressed to a poor outcome [end-stage renal disease (ESRD) or GFR reduction > 50%]. In the univariate analysis, we found that mesangial hypercellullarity score > 0.5, presence of endocapillary hypercellularity or tubular atrophy/interstitial fibrosis of > 25% were each associated with a poor outcome, and also presence of cellular or fibrocellular crescents and of global glomerulosclerosis, but segmental glomerulosclerosis did not reach statistical significance. The clinical predictors of a poor outcome were a low GFR, a high mean arterial blood pressure and a high amount of albuminuria (log Ualb/c) at time of biopsy and low GFR and a high log Ualb/c during follow-up. We found that three of the four histology lesions identified in the Oxford classification, as well as presence of crescents, were valid in predicting a poor outcome in our cohort of patients.