Indication for corticosteroids in IgA nephropathy: validation in the European VALIGA cohort of a treatment score based on the Oxford classification
Abstract
The Oxford classification of immunoglobulin A (IgA) nephropathy (IgAN) was established in 2009 to predict progression using a standardized pathology reporting method. Mesangial (M) and endocapillary (E) hypercellularity, segmental glomerulosclerosis (S) and interstitial fibrosis/tubular atrophy (T) were found to be associated with kidney outcomes independently of the estimated glomerular filtration rate (eGFR), blood pressure and proteinuria at renal biopsy and during the follow-up.
Crescents were subsequently added following a large collaborative study, forming the MEST-C score [1, 2]. The new 2021 Kidney Disease: Improving Global Outcomes (KDIGO) glomerular disease guidelines recommend determining the MEST-C score in each patient with IgAN but do not support the use of the Oxford classification to guide immunosuppressive therapy [3].
Part of this uncertainty stems from the impact of immunosuppressive treatments on the predictive value of each lesion. A European Validation Study of the Oxford Classification of IgAN (VALIGA) found that corticosteroids (CS), mostly used in monotherapy, blunted the predictive ability of the score, especially for the E, C and S lesions [2, 4].
Repeat kidney biopsies have shown a reduction in endocapillary hypercellularity after CS [5]. In childhood, a study showed a reduction in mesangial, endocapillary and extracapillary hypercellularity in the second biopsy after treatment with CS [6].