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Do any kidney biopsy findings predict outcome in immunoglobulin a nephropathy?
Yes. Several variables have been found to correlate with a poor renal outcome.
The Oxford classification shows that histopathology has a predictive value—independent of the clinical parameters of hypertension, proteinuria, and GFR—related to the degree of mesangial proliferation, presence of endocapillary proliferation, segmental glomerulosclerosis, the degree of tubular atrophy/interstitial fibrosis, and the percentage of crescents.
This classification has been validated in many different countries and in cohorts comprising a wider variety of presentations and degrees of progression than the original studies.
Although uncommon and not part of the original MEST classification, crescent formation also points to a poor renal prognosis.
Extension of the IgA deposits into the subendothelial location of the capillary wall has also been associated with a worse prognosis, but this has been somewhat inconsistent.
The Oxford Classification MEST Criteria
| PATHOLOGIC FEATURE | Score | ||
|---|---|---|---|
| 0 | 1 | 2 | |
| Mesangial hypercellularity (M) | <50% of the glomeruli showing hypercellularity | >50% of the glomeruli showing hypercellularity | Not applicable |
| Endocapillary hypercellularity (E) | No endocapillary hypercellularity | Any glomeruli showing endocapillary hypercellularity | Not applicable |
| Segmental sclerosis (S) | No segmental sclerosis | Any glomeruli showing segmental sclerosis | Not applicable |
| Tubular atrophy/interstitial fibrosis (T) | ≤25% tubular atrophy/interstitial fibrosis | >25%–50% tubular atrophy/interstitial fibrosis | >50% tubular atrophy/interstitial fibrosis |
| Crescents (C) a | No cellular/fibroceullar crescents | 10%–25% of glomeruli having cellular/fibrocellular crescents | >25% of glomeruli having cellular/fibrocellular crescents |
a Crescents were studied in addition to the MEST score in 2016 and were validated.
