Biopsy timing and Oxford classification variables in childhood/adolescent IgA nephropathy

Although the Oxford classification of IgA nephropathy appears valid, we found crescents were significantly related to renal outcome in our cohort, whereas segmental glomerulosclerosis (S) was not. The timing of renal biopsy may significantly affect the variables in the Oxford classification.

The relationship between biopsy timing and pathological variables (mesangial hypercellularity score [M], endocapillary hypercellularity [E], S, tubular atrophy/interstitial fibrosis [T], crescents, and global glomerulosclerosis [G]) was analyzed retrospectively in 250 children with IgA nephropathy.

The median time from disease onset to renal biopsy was 5.1 months (interquartile range, 2.7-15.4). M (ρ = -0.26, P < 0.0001), E (ρ = -0.34, P < 0.0001), and crescents (ρ = -0.14, P = 0.023) showed significant negative correlations, and S (ρ = 0.15, P = 0.018) and G (ρ = 0.25, P < 0.0001) showed significant positive correlations with time to biopsy (Spearman test). M, E, and crescents differed significantly in renal biopsies obtained before and after 3 years from onset (Wilcoxon test). Most crescents (92.9 %) were cellular/fibrocellular and were acute lesions. As crescents formed early after disease onset and decreased over time, they may be prognostic for acute phase, but not for chronic phase disease.

Renal biopsy timing may alter the significance of variables used in the Oxford classification.